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EightyWay
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Joined: Jul 17, 2014
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Location: Ireland

PostPosted: Wed Sep 20, 2017 8:11 am Reply with quote Back to top

Hi, I have a recurring problem with the running of my Audi 80 2.0 16v ACE engine. It ended up in a no-start condition and ended up at the garage. The garage correctly diagnosed a worn distributor rotor, replaced it and sent me on my way.

After a few days my original symptoms have returned - Easy to start but hard to keep running from cold. If I let t cut out before it reaches (say) 90 degrees then it will cut out. Then the hard will be very hard to start!. If I can keep it running at 2k rpm for 15minutes then the car suddenly runs well! It really seems like it is temperature dependent or that the engine is warm enough to expel moisture.

I am going to take a look at the rotor and cap again. And potentially replace as a set from BERU.

What (temp) sensors kick in at warmer temps that may have an impact on running?

Other notes:
- Repaired Cyl 1 spark plug lead that had corroded
- Vagcom say 00537 Lambda sensor intermittent error (but I have had this code for years and replacement didn't change anything)
- I have adjusted the MAF with the 3mm hex key. Basically to smooth out idle, I did this with Vaccom live data running -> seems to work well.
 
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Mikes2
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PostPosted: Wed Sep 20, 2017 11:09 am Reply with quote Back to top

I'm guessing no fault codes ?

ecu temp sender is possible but failure is rare

too much fuel possibly when cold ?

what colour are the spark plugs ?

If it has a cold start valve, try disconnecting it

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EightyWay
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Joined: Jul 17, 2014
Posts: 113
Location: Ireland

PostPosted: Wed Sep 20, 2017 5:57 pm Reply with quote Back to top

Codes:
00537 - lambda (oxygen sensor) regulation
08-10 - Control limit surpassed - Intermittent
---------------------------------------------------------
Which sensor does the ECU use - I am getting decent readings on Vagcom and on the instrument dials (oil temp & coolant temp).
---------------------------------------------------------
Spark plugs are about 18 months and are correct NGK. They are sooty if the engine is cold/barely starting. From memory the cyl 4 was sootiest - same as csv...They are light brown when running well/engine warm.
---------------------------------------------------------
All injectors are "new" (18 months) with new seals. The cold start injector is old. I disconnected it on the way home from work slightly harder to start but it ran with no hesitation, smoother power delivery. I will try this again tomorrow morning when the engine is properly cold.
---------------------------------------------------------

Thanks so much, I will report back.
 
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EightyWay
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PostPosted: Thu Sep 21, 2017 7:55 am Reply with quote Back to top

Update: Removing the cold start connector did not have any effect other than making the car harder to start. The car cut out as it did before. I got it running by keeping it at 1500rpm until warm/hot then it was fine.

I am curious about the ECM temp sender and associated systems. It seems like the car runs ok when it hits closed loop 75(?) but the cold start setup isn't quite right.

I will take a look at the new distributor rotor to see if it has mangled itself within a week. The mechanic says the cap is ok (otherwise it would have been replaced). Timing was adjusted from 8 BTDC to 6 BTDC which he said was better - but that has made no difference to the cold start issue.

Regarding the ECU Temp sender: I cleaned the connectors (at 6AM!) - I am thinking that Vagcom can see these values and be able to see if the data is off or inconsistent when cold. Or would disconnecting the ECM temp sender bypass that part of the system?
 
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Mikes2
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PostPosted: Thu Sep 21, 2017 8:16 am Reply with quote Back to top

It was worth a try with the csv. It eliminates it as a possible problem. Harder to start and still running like a dog from cold - do you have the facilities to measure the fuel pressures ?

the G62 sender is on the rear of the cyl head on 5 cylinders. Not sure on the 16v, would have to dig out the manual.

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EightyWay
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Joined: Jul 17, 2014
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PostPosted: Thu Sep 21, 2017 8:56 am Reply with quote Back to top

I can get the mechanic to take a look at fuel pressures - I think he has a kit. The G62 is also at the rear of the head on the 16v, white connector. This is the one I cleaned.

Regarding the fuel system. These parts are relatively new (A-Branded parts)
-Fuel pump
-Fuel filter
-Injectors

The fuel system has two accumulators AFAIK. One in the tank and another before the metering head.
 
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Mikes2
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PostPosted: Thu Sep 21, 2017 9:22 am Reply with quote Back to top

one will be a fuel pressure regulator

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EightyWay
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PostPosted: Thu Sep 21, 2017 9:36 am Reply with quote Back to top

Yes, the one on the airbox.
 
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EightyWay
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PostPosted: Sat Sep 23, 2017 9:16 pm Reply with quote Back to top

Ok, the mechanic said it was the ISV, but the car was behaving in his presence. Fortunately, I had a spare with me when I went to collect the car, tried it, and, no improvement. But, now we could reproduce the problems. After some testing on the ignition/spark system we concluded we did have spark but not as strong as it should be. Fortunately i had a spare coil, fitted it and still the no-start issue continued, but with a stronger spark.

The spark plugs weren't wet after cranking which got him thinking of fuel. With the 3mm hex key in the airflow meter we were able to move the airflap to invoke a start.

My focus is now in 3 areas:
1. The multifunction sensor/thermo - apparently the ECU gets a signal from this one and may be used as part of the cold start fueling system. If the ECU gets its feed from G62 I would consider that too. I have a spare so I test the multifunctional first running a live data feed from vagcom.
2. The metering head may have some internal issue. The Airflow meter is fairly new with a new potentiometer. - possible rebuild using new seals or 2nd hand replacement. I may do measurements on the potentiometer to see if ti falls within spec.
3. The differential pressure regulator sensor on the metering head may also be a culprit. I will research how to diagnose this. I am not sure if it can be replace or if I can get the part.

I think I have something to work with. The problem can be reproduced and manually fixed (by pulling up the air flap). We need this to work automatically as part the cold start system.

Any comments or thoughts/questions are welcome!


Last edited by EightyWay on Mon Sep 25, 2017 8:24 am; edited 1 time in total 
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EightyWay
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PostPosted: Mon Sep 25, 2017 8:22 am Reply with quote Back to top

This morning he car was very rough until it hit 90. Any throttle input would cause it to stall. Then, as it reached 90 it smoothed out. I was running a live feed. I think I need to get a full understanding of the cold start systems on the 16v ACE engine.

After warmup this morning I got this code. I cleared it but it came back immediately. Maybe I have 2 duff ISVs - but they work fine when the engine is warm I've tested them with a multimeter and a 9v battery and they work fine.

00533- Idle Speed Regulation
10-00 - Adaptation Limit Not Reached
 
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Mikes2
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PostPosted: Mon Sep 25, 2017 7:16 pm Reply with quote Back to top

That's the controller for the idle. Sounds like it's operating outside it's normal range so it can't regulate.

Are you able to measure the current draw on the circuit ?

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EightyWay
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PostPosted: Thu Sep 28, 2017 11:08 am Reply with quote Back to top

It hasn't thrown up any codes since with respect to the idle. It may be something that is happen only on the cold start cycle.

It has become clear that it is going to find someone with the diagnostic expertise to troubleshoot the Motronic. I have seen many forum threads describing the same symptoms unfortunately users never came to a resolution.

I believe it is possible to diagnose it, with time. With a (oldtimer mercedes) specialist on the other side of the country quoting 70 per hour labour I feel that it will cost more than 500 to diagnose (based on the amount of tests that need to be performed). I could swap a load of parts for that!

As it is my only car I need it running so my plan is to get something else and repair it in my own time. I am determined to get to the bottom of this!

Let me know if you know of any CIS/Bosch diagnosis experts in Ireland!
 
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EightyWay
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PostPosted: Mon Oct 02, 2017 8:04 am Reply with quote Back to top

Update: From what I can gather CIS systems which use sensors also have a "limp mode" when the sensors are disconnected. As mentioned earlier in thread I disconnected the CSV with no effect, I also had the car running without the ECM coolant sensor connected. The differential pressure regulator is last on the list.

My current thinking is that the seals in the metering head are shot. I had been plagued by a Lambda error for year as soon as the engine reaches closed loop. There has been a notable degradation in the running of the car since April.

My initial thought was to get/buy another metering 2nd hand unit. But, there are seal kits available, or even refurbished units. I'm inclined to go for the seal kit.

Any thoughts on this approach? `it is unscientific but after viewing this series: https://www.youtube.com/watch?v=WnAKa3RW5HE
-> it may be the best step I can take...
 
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K_KID
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PostPosted: Mon Oct 02, 2017 11:36 am Reply with quote Back to top

Watching your thread with interest as i also have an ACE engine in my coupe. Ref your comment on the limp home mode. I found this in my Bentley Bosch fuel injection & engine management. Hope it helps with your KE Motronic CIS.
Limp home mode.
"The actuator plate is designed to rest at a limp home position if the control unit current is interrupted. the engine will continue to run , but slightly leaner than normal. in this circumstance mixture is determined solely by the mech. metering of the air-flow sensor and control plunger. the uncontrolled plate in the pressure actuator allows just enough pressure drop to keep a warm engine running. the engine may not start but if its running , will get you home. you can simulate the limp home home condition on a running warm engine by disconnecting the pressure actuator connector."
Tried to attach a PDF of the page but would not work!
 
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EightyWay
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PostPosted: Mon Oct 02, 2017 12:30 pm Reply with quote Back to top

Thanks, I might just have that 204 page pdf! One thing I have on my side is a working scantool. Each sensor throws a code when disconnected. I am working with the assumption that the ECM is good and that the wiring to and from the sensors is good.
 
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EightyWay
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PostPosted: Mon Oct 02, 2017 7:33 pm Reply with quote Back to top

OK, I took some measurements of the various sensors/valves on my CIS ACE engine. Some measurements were taken when the engine was warm. Yes it was a pig to start again but ran ok after 20 minutes after carefully nursing the throttle. There is something very wrong with the open loop cold start setup. Because I don't entirely understand the Motronic CIS I am reluctant to target the fuel distributor.

ISV/IAC: 7.9 Ohm, movment/click when voltage applies. No crud
Cold start valve (CSV): 10 ohms, 12.21v switched voltage, click when 12v applied.
Differential pressure regulator (DPR): 18ohms (between terminals), 2volts at start (backprobed) and +- 0 mA when running
Air flow potentiometer: U1 = 4.83v, U2 = 0.74v

As far as I can gather there is nothing wrong with these parts. I didn't try to invoke "limp mode" I read that it could be done only when the engine is running and that it may not start without it plugged in.
 
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EightyWay
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PostPosted: Tue Oct 03, 2017 8:15 am Reply with quote Back to top

OK...the accumulator. I have one in my fuel tank P/N 0438170052. There is also a fuel pressure regulator on the metering head. I assume the only way to test these is to pressure test the system.

My understanding would be that if the accumulator was not holding pressure/maintaining a pressurised system then the car may give trouble starting until the system is pressurised (in my case 20 minutes!). Does this make sense. Could I bypass the accumulator as part of my diagnosis?

Is there anything I can learn from my symptoms which could indicate an accumulator?
- long crank cold start or no start
- rough when cold
- ok when hot
 
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EightyWay
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PostPosted: Tue Oct 03, 2017 9:28 pm Reply with quote Back to top

RESOLVED:

I had a clear plan of action this evening. Definitively rule out the ECM coolant sensor and do what tests I could on the accumulator/metering head.

Oddly the car started 1st time - actually I wanted long cranking this time! I hooked up Vagcom to clear some codes. On the live data I saw no feed from the differential pressure regulator (turquoise blue in my case). I always assumed that was the unit on the metering head.

Anyway, I decided to measure the resistance of the ECM coolant temp sensor. I could get 5v control voltage from the connector. It was a challenge to get the probes in there, I thought I couldn't get a connection but I didn't know for sure. I connected and grounded the replacement sensor. It ran...with no stutter. Switched the connector back a few more times to confirm the new sensor was better. I bit the bullet and set about removing the sensor. Not to bad in the end with a deep socket 19mm, swivel and a short ratchet. Luckily the heater was off and almost no coolant came out.

Measuring the old and new sensors confused me. Both were 1720 Ohms. So the old was good.....After a bit of head scratching I measured again and again and realised that most of the readings measured 0 and I was getting reliable readings from the new sensor. So I fitted the new one.

All along Vagcom would throw a G62 code if unplugged. It did not detect a fault with the failure of this Bosch sensor.

I ran the car in open loop for a bit to check on my persistent Lambda 00537 code. Nothing so far, touch wood!

I'll bet my airflow settings are a bit off and in the future I may well need to optimise the fuel system - but measurements and test procedures first!

I'm glad I took the time to diagnose, even if it was chaotic. Thanks for the support.

Moral: Find your ECM coolant sensor (seems to vary where it is) and test it - then test it again. It's only 5!
 
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Mikes2
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PostPosted: Wed Oct 04, 2017 10:45 am Reply with quote Back to top

Glad you got there.

The old is possibly cracked and is water contaminated - that's the usual fail mode

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EightyWay
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PostPosted: Thu Oct 05, 2017 8:16 am Reply with quote Back to top

Yeah, I got stuck on a roundabout during rush hour this morning. I was pumping the throttle so hard it broke off! The car was similar to before running really rough at cold. At the roundabout I was cranking and as if it was half starting. It was also smoking from somewhere near the bellhousing! It sounded terminal. I got a tow to a nearby petrol station. I fixed throttle cable with zip ties. Got the spare battery and jumped the connection. Sprayed some starter fluid into the air intake and jiggled the engine sensitive connectors a bit, including the hall sensor under the dizzy.

It started 1st time and super smooth/no stutter.

The coolant sensor was a fix, there is no doubt in my mind about that because the car simply runs better. I have question marks about:
- Intermittent electrical connectors, Hall, Coolant temp ecu
- The settings on the metering head/mixture (hex 3)
- Fuel pressure/fuel starvation

It's looking like it won't be practical to run this car daily

Crying or Very sad
 
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