ALH compression numbers: Seeking advice.

After a long hiatus, its time to invest some time into my parked Golf...


The car seems to run well when its warm. It starts easily and has seemingly good power. The car misfires and smokes at every cold startup, eventually clears up. Smoke is greyish and smells of unburned diesel. It will occasionally throw a cylinder #3 Misfire code. I swapped injectors and have checked a few other things. At the point I was pretty sure there was a mechanical problem i bought a cheap compression tester that turned out to be complete garbage. I have a higher quality one now that I trust. Numbers: (taken slightly warm, not at temp)
#1 - 485psi
#2 - 440psi
#3 - 410psi
#4 - 480psi

I have no history on this car. I suspect the car may have a partially bent #2/3 conrod from an "incident" of some sort? I also suspect that the previous owner possibly drove said car "awhile" like this. What are the chances the block may have scored up cylinder walls? If i pull oil pan, with these numbers any chance i could see a bent rod and/or check cyl wall. I realize this will likely end with pulling head off! If bent rods only, I'd like to fix with engine in car.

Chance of valve issues possible? Head is gunky looking on intake side. IF a rod(s) are bent I would be very interested in using Franko6's services for reassembly and parts. Another thought was installing a set of used rods and pistons and measuring for proper head gasket.

Your opinions and/or experiences greatly appreciated!

Some crud may have broke loose in the Intake Manifold and entered those two center cylinders. Crud on top a piston could possibly bend a rod. Or, crud could have been smashed under a valve(s), thus, compromising the sealing around the circumference of the valve contact with the valve seat (exhaust or intake valve).

If it was a previous Valve to Piston Contact due to a Timing Belt incident, I sort of doubt the two cylinders affected would have been adjacent to one another.

If those lower compression numbers are due to bent rods, I seriously doubt you would be able to visualize the difference if they were laying on a work bench beside perfect rods. And, it would definitely be impossible to recognize a bent rod (in this case), especially in what appears to be very small difference, by looking up from the bottom with the oil pan off.

Yes, Franko6 is an excellent source for rebuilt heads and parts.

I would suggest having a leak-down test done for cylinders 2 & 3. That should tell you if it's valves not sealing, or something else.

Although it does appear there might be something going on with cylinders 2 and 3, they are both well within specification and should not cause any noticeable engine performance, idling or otherwise. All of my TDI engines (and IDIs) have done or do stumble a bit on cold mornings or when fired-up after sitting for several days which generally results in some smoking. I've never given it much thought to be a major problem. But, getting the mis-fire DTC indicates something is amiss for sure.

Several years ago, I installed an 01 ALH in my brother's 03 Jetta. There is a difference in the electrical connector on #3 Injector (I now own the car). So, I cut and spliced the wires. Occasionally, it will hiccup for an "instant" as if the ignition has been cut off and back on. And, occasionally the hiccup will result in a mis-fire DTC on #3 cylinder. I suspect it (ECU) doesn't like the info/data coming and going through the splice.

So, maybe there's something going on with the #3 Injector circuit.

Here is link to 1.9 TDI engine compression info at My Turbo Diesel..
https://www.myturbodiesel.com/wiki/how-to-do-compression-test-on-vw-audi-tdi-engine-results/

#3 rod is bent, almost guarantee it. 410 PSI is way too low.

AndyBees said:

Although it does appear there might be something going on with cylinders 2 and 3, they are both well within specification...

Click to expand...

In the link that you posted, it clearly states no more than 73 psi difference between cylinders. The difference between cylinders 1 and 3 is 75 psi. So clearly, something is wrong.

I agree that you need to do a leakdown test, and a compression test cold and hot with oil on the rings cold and without.
It might seem that there is a mechanical problem but I never diagnose something unless I have done all the testing I can. Your going to be right pissed off if you pull the head or oil pan to find out that the issue was not internals.
Rule it out. Before you start spending $ and time chasing a wild goose

Well, as stated above you have no history on the car.
I would at least get a 100k timing belt kit.
At this point I would pull the head and do a piston protrusion check.
It’s only gonna cost you some additional time, a head gasket and head bolts ( that’s just my opinion).
I went through this with my last project car that was supposed to go to my older daughter.
I ordered a TB kit and when I pulled the cam I didn’t like what I was seeing so I pulled the head.
I found #1 piston was beat ,dinged and gouged........no damage to the head......
Car ran well slightly hard to star when cold but fine when warm.
Come to find out that the PO mechanic pouched the TB job, it dropped a valve and he had the balls to tell the PO that the head failed......
They put a used head on and kept on trucking till he sold it.

When I had the head off I’d did the piston protrusion check, I found the dinged up piston (#1) and #4 to be at the correct height for the #2 holed gasket, however the #2 and #3 pistons were below the specs for a #2 gasket set up by a lot.

I called Franko6 and he recommended I pull all 4 pistons and connecting rods and I sent them to him.
He called me a few days later and asked me the history, I told him what I stated here.
He was puzzled as yes two rods were bent slightly , a third rods weight was way out of specs compared to the other three.
In the end he replaced a piston, matched lengths and weights with all 4pistons, new rings ,
New connecting rod bolts, new main bearings .
I balled honed the cylinders and she is purring like a kitten with no smoke issues and actually fires up better than my other TDI’s.
Again it’s just my .02 on pulling the head.....not much more time to do that, at least pull the cam and check the followers, see if any are spider cracked.

Blacktree said:

In the link that you posted, it clearly states no more than 73 psi difference between cylinders. The difference between cylinders 1 and 3 is 75 psi. So clearly, something is wrong.

Click to expand...

I tend to agree........ but, 2 psi off would call for more testing.

Thus, before I did anything further, I'd do a follow-up Compression Test.. maybe two or three more! If the same results are there, then move to the next thing.

I'm not sure what a leak down test would benefit. Maybe if it leaked off slowly the culprit could be rings, which I doubt. If it leaks off rather fast, then the issue is likely a burnt valve or crud under a valve (Intake or Exhaust).

If it were mine, I'd do the TB job as someone has suggested and drive it for a while. If it is a burnt valve, the described issues will likely get worse. If it is worn rings or stuck rings (could have be used as a grease car since the OP has no history) nothing is going to be hurt.

AndyBees said:

I tend to agree........ but, 2 psi off would call for more testing.

I'm not sure what a leak down test would benefit.

Click to expand...

First of all, it's not 2 psi off. It's 75 psi off. That is significant, and it indicates a problem.

Second of all, a leak-down test can tell a lot about the condition of the engine. For example, if pressure is venting out the intake tract, you have a leaky intake valve. Ditto for the exhaust valve. And if pressure is venting (rapidly) out the crankcase, the piston rings aren't sealing. If none of that is happening, then it's probably a bent rod.

Thanks for the replies. I do not suspect any piston to valve contact history. I don't think the head has ever been off. The timing belt was replaced at some point before I bought the car and was in fair shape. (200k on odo) I personally have already replaced the timing belt and all components. I am positive the mechanical and injection timing is spot on. Swapping and cleaning injectors seemed to not change symptoms at all. Swapped used with used, not known good. The Inter-cooler did initially have an excessive amount of oil in it. Since cleaning out the I/C and driving the car awhile oil accumulation seems normal. Turbo shaft play seems ok. I may consider replacing turbo, at the very least I will keep an eye on oil in the I/C...

At this point I will try to do a leakdown test on hole #3 IF I can fit the right adapter on my leakdown tester. I will likely also do a cold compression test or two. I had to pull the fuel lines off injectors to fit my compression adapter. Also I broke the connector off the fuel shut off valve and also removed it in an attempt to hold spinning stud...so fuel system is full of air now and won't start. Have a new fuel-shut valve ordered.


I'm going to re-use new timing belt/components if pulling head. I've read conflicting information regarding O.K. to mark belt and pullies and put together VS you must use setup tools and procedure as you would if installing new belt. Thoughts?

There is one right way to set the belt and components and a lot of wrong ways, whether you're re-using components or not.

Genesis said:

There is one right way to set the belt and components and a lot of wrong ways, whether you're re-using components or not.

Click to expand...

That is what I thought. Thanks.

Genesis said:

There is one right way to set the belt and components and a lot of wrong ways, whether you're re-using components or not.

Click to expand...

the correct way to do anything to any car is via the manufacterurs spec
AKA, feed the money beast
the best way is to use common sense and expert advice.
so i did a timing belt ages ago and i messed up the vacuum pump shaft seal on my AHU, LOTS of oil all over everything, i tor it back apart and slapped on a new seal and a new belt, all other parts in there were new so im not going to replace everything! no point.

the reality is that the TB usually dont fail first. its the crap connected to it and around it that fail more often.

ALH compression specs:

"new" is 25-31 bar

Wear limit (lowest permissible) is 19 bar.

The maximum difference between cylinders is 5 bar.

So all the cylinders are above the wear limit.

The difference in the highest to lowest is right at 5 bar.

Most healthy ALHs will tag 30 bar easily, I rarely ever see one low. So chances are very good that *something* is not right in #3, but based on the numbers alone I am not sure I'd do anything unless you are ready and willing to "do it all", meaning pull the head, pull the oil pan and oil pump, and pull the rods/pistons out and give it all machine shop level scrutiny. If not, then chances are it will continue to operate just as it is for a good long time.

A severely gunked up intake part can also alter the cranking compression readings, as the air cannot get into the cylinder as quickly as it should. So can a lifter that is not pumping up completely (you will hear this as a ticking after cold start though).

oilhammer said:

So chances are very good that *something* is not right in #3, but based on the numbers alone I am not sure I'd do anything unless you are ready and willing to "do it all", meaning pull the head, pull the oil pan and oil pump, and pull the rods/pistons out and give it all machine shop level scrutiny. If not, then chances are it will continue to operate just as it is for a good long time.

Click to expand...

Just as it is = misfires badly while warming up (even longer in MN cold) and lots of stinky smoke I'm sure the neighbors/bystanders hate. I don't really want to but I'm pretty sure I need to "do it all" or bust. Thanks for the reply oilhammer, i have always appreciated your posts!


I just did a leakdown on #3. Only 3-4% leakage past the rings @ 100psi. To me, this really supports a bent rod...

I also did another half-ass compression test (just trying to avoid stinky mess with my high profile adapter) cold on cylinders 1 and 3 only several times back and fourth:
#1: 500psi
#3: 410psi


So 6 bar difference cold. Not sure why #1 went up, maybe there is a little oil that leaked down whilst sitting.

eh, bent rod, not a big deal, its not that much bent, i would just drive it and forget about it. probably from your cold AF nights up where you live. condensate can send a slug of water into the engine and typically nails #3, its not too uncommon so im told.
i would just drive it till it dies, get a AAA membership, it will pay for its self when you have to have it towed, or just call an uber!

Thanks for your opinion Mongler. Anyone else?

What are your long term plans for it? Do you know how long it's been like this? Is the car in good enough shape to spend the money for the rebuild?

I would think running bent rods for a long time would damage the cylinders requiring boring when you decide to rebuild it. If you rebuild it now, assuming it hasn't been like this too long, you will probably only require the new rods, pistons and rings.

I assume standard practice in this situation is to replace the two pistons that hit along with the rods. I wouldn't trust them to be undamaged.

KLXD said:

What are your long term plans for it? Do you know how long it's been like this? Is the car in good enough shape to spend the money for the rebuild?

I would think running bent rods for a long time would damage the cylinders requiring boring when you decide to rebuild it. If you rebuild it now, assuming it hasn't been like this too long, you will probably only require the new rods, pistons and rings.

I assume standard practice in this situation is to replace the two pistons that hit along with the rods. I wouldn't trust them to be undamaged.

Click to expand...

I just want to be able to drive or sell the car. The current smoke-show and wait for misfires to stop doesn't work for me. Unfortunately, I don't know how long its been like this. The car is in fair shape, not all rotted out like most around here. It is an auto most unfortunately, shifts fine. I've dumped a lot of new parts and money into the car. If I can get away without boring the block and honing cylinders in car I think its worth fixing. The labor doesn't scare me. My lack of time does. I realize parts costs will add up. I would need to buy a couple measurement tools...


Someone please tell me to fix this?!

So the quick and dirty explanation (not procedure) to fix this in your driveway properly (properly enough)
pull the head and the oil pan, timing belt, and misc parts to do so.
you will need parts once its apart, (personally i would upgrade to BEW rods and pistons and get a piston and rod scale and balance them (not a difficult task, new ring set and get a ring grinder and feeler gauges and size them to the bore
general set of sockets and what not and a good torque wrench, no reason to go nuts, a harbor freight will work for 99% of your tools for this job
big Rubbermaid bin with holes drilled in the bottom to match the cylinders, dinglebearry hone, diesel fuel as hone lube and a drill with a slow speed setting
no need to measure the bore as its not been over heated and your compression speaks that there is no massive egg or warp
and possibly lower bearings
you need a new timing belt kit (its worth it, jut do it!)
fluids
If it looks and feels ok, it is, TDI's are tough (cylinder wall, and crank journals)
basically take the head off, the pan off, pull the pistons and rods out
Put the tub over the block and mark where the holes are, cut them out and hold the tub down with magnets, this keeps all the hone fluid (diesel fuel) from making a massive nasty mess, run the hone up and down moderately fast at a slow drill setting with plenty of lube. your looking for a very light hone, basically to help the new rings seat, not looking to make it look new in there.
clean everything with a air compressor chemical sprayer with mineral spirits, i mean clean as clean is, use coffee filters for rags to clean the journals on the crank and everything you can reach, no lint!
spray with wd40 to stop rust
now push the new rings down with the piston to the middle or 1/3 down the cylinder, use a feeler gauge and grind the rings down till its right, using a proper conrod and piston combo scale, make them balanced by taking off a little bit at a time on the bottom of the conrod, dont chase the lowest number to much!
clean and assemble
you will need new conrod bolts and a bunch of parts.
thats not all there is to it but thats 20% of what you need to know, its not an easy task and a mistake can be costly and or devastating if done wrong.
i could do this in a garage with a lift in probably 3 days, 2 if it was a job!

all these techniques are on youtube,
you can do this at your own pace and order parts as you find you need them. all in all i would say about $500 in parts if you get them used (rods and pistons), another 200 in tools, probably by the time your done i think you could get this done in parts and tools for about $1,100 but its going to take a few weeks of down time.

honestly i would go find a running donor car for $500 bucks and just do the swap, just as much work but less fuss over internals, i would rather swap an engine than rebuild one in the car, probably about the same price either way, maybe cheaper.
OR just go buy a used car and swap your good parts to it instead.
plenty of crapmobiles floating around with good engines, bad trans that is not worth pulling as a seller.

If you're planning on selling, you'd be silly to fix a possible bent rod. You won't recoup what you've put into it.

Just for fun, have you hosed down the injector and glow plug with soapy water to see if they're leaking compression when the engine is running?

I might suggest the internals are O.K, but worn. The smoky start, misfires, are engine management. Sensor, IP, worn out injectors and on and on. But I'm guessing you've been thru all that.

Mongler98 said:

So the quick and dirty explanation (not procedure) to fix this in your driveway properly (properly enough)
...

Click to expand...

Good post. Thanks! That was pretty much my understanding. Doesn't seem to be a ton of these cars around here on the cheap. Also, I don't have much room currently. Not opposed to making something like that work (swap) temporarily. I agree an engine swap might be somewhat easier.

Nero Morg said:

If you're planning on selling, you'd be silly to fix a possible bent rod. You won't recoup what you've put into it.

Just for fun, have you hosed down the injector and glow plug with soapy water to see if they're leaking compression when the engine is running?

Click to expand...

I know. It would be silly to think I could recoup all I have into this thing at this point. I bought the car with the intention of driving it. I may have to sell due to lack of time? My house needs tlc. Yes, I have checked glow plug and injector for leaks previously.

BobnOH said:

I might suggest the internals are O.K, but worn. The smoky start, misfires, are engine management. Sensor, IP, worn out injectors and on and on. But I'm guessing you've been thru all that.

Click to expand...

Injectors, including #3 have been swapped with no change. I have not been through IP but I suspect its ok. Again, car runs well warm. I suspect this is when the #3 cyl starts starts firing normally?

eh, my AHU will explode in a hydrolock mess if i WOT the sombish when its still cold, i hydrolocked it 3 times already with fuel lol its a crazy stupid build, i had the head off, i had a small deviation but im sure all the rods are bent now, like all the rods, my compression is still ok 420 low on #3 and 440 high on #1 but thats due to a 2 hole gasket vs the 3 hole that came stock, bent rods = shorter pistons and i found that on mine after my messy build. , poor little ahu rods!
still runs like a bat outa hell though.
have you tried cleaning the injectors or changing the fuel filter for water content? there are things that can cause the miss fire, im fairly sure, like 85% that your miss fire issue is NOT related to a bent rod. seeing as your still within spec and that your leak down seems good, i would look else wear
there is a chance that you have a issue with the #3 injector harness or with the IP getting the data. It is my understanding (someone correct me if im wrong) but even if you swap the injectors around, the #3 injector and nozzle are still connected to the same wire harness and thus you will still get the same misfire data regardless where you swap it to. I think you have a leaking nozzle or bad injector or possibly that the pop pressure is off. who knows, more info needed.

any chance you moved the crank when you did a leak down. you defiantly want to move it but only within the range that the cam does not move the valves, this is a second step in diagnosing egg limit or wall scuffing issues, try it at TDC, and at BDC

if you get a really bad leak down issue at BDC, well then were talking a different story.

anyways, i would not right it off yet. what is your QA set at in vcds? have you tried starting it cold with liquid molly in a closed loop? there are some quick things like that to test to see if you can isolate the missfire.

Mongler98 said:

.....
have you tried cleaning the injectors or changing the fuel filter for water content? there are things that can cause the miss fire, im fairly sure, like 85% that your miss fire issue is NOT related to a bent rod. seeing as your still within spec and that your leak down seems good, i would look else wear
there is a chance that you have a issue with the #3 injector harness or with the IP getting the data. It is my understanding (someone correct me if im wrong) but even if you swap the injectors around, the #3 injector and nozzle are still connected to the same wire harness and thus you will still get the same misfire data regardless where you swap it to. I think you have a leaking nozzle or bad injector or possibly that the pop pressure is off. who knows, more info needed.

any chance you moved the crank when you did a leak down. you defiantly want to move it but only within the range that the cam does not move the valves, this is a second step in diagnosing egg limit or wall scuffing issues, try it at TDC, and at BDC

if you get a really bad leak down issue at BDC, well then were talking a different story.

anyways, i would not right it off yet. what is your QA set at in vcds? have you tried starting it cold with liquid molly in a closed loop? there are some quick things like that to test to see if you can isolate the missfire.

Click to expand...

Thanks again for the post Mongler! I did a half assed leakdown. I think I confirmed valves/head not likely issue. I'm honestly not sure if I was BDC or TDC. I will try to do a better leak-down bdc. I basically found one or the other using air pressure... The fact that you guys are telling me this thing may be mechanically okish gives me hope.

If an injector is leaking down. Would it likely only dump a fixed amount of fuel into a cylinder before it stops? This thing has always started, never hydrolock with fuel situation. I would be a happy camper if all I need is another set of injectors/rebuilt injectors! Not sure what QA is in VCDS now! I have the larger nozzle USED/UNKNOWN manual injectors in now with the 11mm pump. If they are an issue I'm sure it is possibly exaggerated by more fuel? I think i wrote it down previously at some point but not finding it. I will try to report back.

Original 200k auto injectors and these manual injectors were soaked in diesel friendly solvent and cleaned with diesel purge (running). I never opened them. Performance ok, but maybe one or two leak? Pulling strings...

a quick breakdown of the lingo for you
The IP ( injection pump) has 2 parts the main pump body, and the QA ( quantity adjuster) that sits on top, the box bit that the return hose comes out of. You can "hammer mod" move it sideways either way to manually adjust how the little cam needle sits in relationship to the body and thus increasing or decreasing the IQ (injection quantity) higher the number the less fuel is delivered over the map that is set in the ECU (electronic control unit) usual range on ahu and alh is 3 to 6. 1 to 9 being the total range it can go. Anything less than 3 is a bit aggressive on fuel economy and anything past 5 or 6 is a bit lack luster on power. I still can get 50+mpg on a 1.4 and if you dont modify much but only the nozzles you need to up the number to like 6 to combat too much fuel so you dont increase egt (exhaust gas temperature)

you need VCDS its a software you can get here https://www.ross-tech.com/vag-com/ and a cable, you can also get here, or buy used. you NEED that cable or a hacked ebay version to connect to the ECU to read the car. you can see the QA value here and you have to adjust it manually, not in the software.

the reason i want to know what it is, if its to low, 1.6 or lower, your idle is going to be rough, you can try bumping up the QA and maybe this might help, if it does change it slightly, well, we are now on the right track and know its a fuel issue with the IP.
In VCDS we cal also see each injectors injection amount, and we can also log things like boost, fuel delivery, manifold pressure, and a buch of other things. if you got us a log we can see as the car warms up, or a log of it running cold and it running hot, we could potentially find an issue that could save you a crap ton of time and money.

i suggest to you that you dont spend a dime on this in parts until you have exhausted all your options, VCDS and a VAG-COM cable is going to serve you well, its a bit pricly for a tool but its what you need.
you can hack one from ebay though, i dont recommend it at all as its limited and hit or miss on actually working and im not sure you can do logging with it.

Mongler98 said:

a quick breakdown of the lingo for you
The IP ( injection pump) has 2 parts the main pump body, and the QA ( quantity adjuster) that sits on top, the box bit that the return hose comes out of. You can "hammer mod" move it sideways either way to manually adjust how the little cam needle sits in relationship to the body and thus increasing or decreasing the IQ (injection quantity) higher the number the less fuel is delivered over the map that is set in the ECU (electronic control unit) usual range on ahu and alh is 3 to 6. 1 to 9 being the total range it can go. Anything less than 3 is a bit aggressive on fuel economy and anything past 5 or 6 is a bit lack luster on power. I still can get 50+mpg on a 1.4 and if you dont modify much but only the nozzles you need to up the number to like 6 to combat too much fuel so you dont increase egt (exhaust gas temperature)

you need VCDS its a software you can get here https://www.ross-tech.com/vag-com/ and a cable, you can also get here, or buy used. you NEED that cable or a hacked ebay version to connect to the ECU to read the car. you can see the QA value here and you have to adjust it manually, not in the software.

the reason i want to know what it is, if its to low, 1.6 or lower, your idle is going to be rough, you can try bumping up the QA and maybe this might help, if it does change it slightly, well, we are now on the right track and know its a fuel issue with the IP.
In VCDS we cal also see each injectors injection amount, and we can also log things like boost, fuel delivery, manifold pressure, and a buch of other things. if you got us a log we can see as the car warms up, or a log of it running cold and it running hot, we could potentially find an issue that could save you a crap ton of time and money.

i suggest to you that you dont spend a dime on this in parts until you have exhausted all your options, VCDS and a VAG-COM cable is going to serve you well, its a bit pricly for a tool but its what you need.
you can hack one from ebay though, i dont recommend it at all as its limited and hit or miss on actually working and im not sure you can do logging with it.

Click to expand...

Thanks! I'm familiar with this my friend. I have a VCDS/VAG-COM setup! I wasn't clear. I meant to say I'm not sure what QA/IQ values are off the top of my head. I did write some of this down previously. I will look for this info or simply get it again.

Quick update: Compression numbers seem consistent. 410PSI on #3. Other cylinders are higher. Leak-down consistent under 5% ATDC and BTDC #3.

Cylinder Balance: 1-2 min after startup:
IQ 1: -1.86
IQ 2: -1.88
IQ 3: +1.88
IQ 4: +1.81
Warm
IQ 1: 0.16
IQ 2: 0.05
IQ 3: -0.19
IQ 4: -0.09

Partially revved at 1k rpms while warming up (missing and smoking), cylinder 3 is more positive than all others.

I.Q + 3.8-4.0 mg/str colder, warmer 3.4 mg/str

Again: Injectors and nozzles are well used and NOT known good. I'm tempted to spend some $ installing/rebuilding good refurbished injectors. I really don't want to plop down the cash if lowered compression may be causing the cold miss and smoke.


Anything I can adjust/play with to possibly verify a fueling issue cold??