Neverending engine troubles 2.3 AAR

Niklas.L · 04-12-16, 02:13 PM

Hi,

My name is Niklas and I'm from Sweden. I own a 1992 Audi 100 2.3 quattro with close to 360.000km on the clock. I have been having trouble getting the engine to run properly since the day I bought it, bought it knowing it didn't run as it should. Have been writing on a swedish forum, but they are giving me the silent treatment at the moment. So I thought I would see if you guys could help me sort out the issues.

Have been replacing and troubleshooting quite a bit so I thought I would give you a quick run through of what I've been doing.

When I bought the car it ran like shit more or less. It was misfiring and hesitating on full throttle, ran 10x worse when cold. Had to keep the pedal to the metal for it to pick up speed, which it did eventually. After 1km or so it started to run better, on half throttle or less.
Changed the spark plugs, rotor/distributor cap and the ignition cables. Cleaned the throttle body and air flow meter. The car ran better, but still had its issues.

Changed the oxygen sensor and the knock sensor. Again the car ran better, but with its issues.

Changed the fuel pressure regulator, the black plastic thing attached in front on the fuel pump. It started running better when cold. Didn't drop revs when idling if cold. Before it went from 1100rpm down to 200rpm and slowly worked its way up again. Also didn't hesitate as much when giving it the beans. Almost nothing.

Changed the o-ring for the vacuum pump because it was leaking oil. After this I started getting problems with it going between 1100-1400rpm when warm on idle. Found out it was the air flow meter so I change the whole package on top of the air filter box. The idle was ok again, but the car is still hesitating/out of power at full throttle and once again started running like shit when cold, not as much as before though.

Other issues with the car that I havn't had the time or motivation to fix is the head gasket. It leaks both oil and coolant. Not that much coolant, but I have filled roughly 6-8 liters of oil during the 18.000 something km I've drove with it. Also leaks a bit breaking fluid.

Right now I am out of ideas and more or less motivation as well. Hope you can help me sort out the issues I'm having!

Niklas

mikes2 · 04-12-16, 03:13 PM

How old are the fuel filter and pump ?

Hanuman · 04-12-16, 03:14 PM

http://www.sjmautotechnik.com/troubl...g/100ecuf.html

I can't offer any specific insight on this model, however, a starting point might be pulling the codes, if they are available. Hence the link above; which may provide a little help, even if the specific engine isn't listed.

I borrowed a cheap code reader from a neighbour, and with an adaptor lead, pulled the codes on my 100-V6 not so long ago. (£30 for a VAG reader. I don't think it had any specific reset capability, though)

AdrianH · 04-12-16, 03:25 PM

How is the fuel metered on this model?

jimh · 04-12-16, 05:02 PM

If you suspect that you have a problem with the head gasket anyway, I would start by checking compression.
If you have poor compression on one or more cylinders, no amount of swapping fuel & ignition parts will help you.
This is what my head gasket looked like when I pulled the head (Urq):-

See the nice gap in the gasket between cylinders 3 & 4?
I measured compression at 10bar, 10bar, 5 bar, 5bar, 10 bar, so the gasket looked just like I thought it would.
The engine did not run very well in that state...

Niklas.L · 04-12-16, 05:28 PM

mikes2: I don't know how old they are. The pump could very well be the original pump. The fuel filter is changed at one stage, different fabricator.
The thing that confuses is that the symptoms change as I change the parts. Before I changed the whole air flow meter and fuel distributor it ran okey when cold. It wasn't a speed demon, but it didn't flutter and hesitate as it does now.

The Real MSH!: I did check the error codes before I changed the air flow meter/fuel distributor and it showed no error codes.

AdrianH: It is all vacuum controlled. The more you accelerate the more the air flow meter flap opens and it sends a signal to the fuel distributor/fuel pump to supply more fuel. I have checked for vacuum leaks and all leaks are fixed.

jimh: I will check the compression before proceeding to changing more parts.
A followup question regarding the head gasket. Do you have to disassemble the front in order to get the timing belt of? Looks extremely tight between the front of the engine and the radiator.

Thanks for all your answers!

AdrianH · 04-12-16, 05:37 PM

Assuming it's a K–Jet type derivative, have you checked that the pipes from the warm up regulator are connected correctly? My urQuat was running as you describe until it was noticed that the control pressure / warm up regulator pipes (I can't remember exactly which) had been transposed at some time before I got the car –*such an obvious thing that no one noticed for ages (not that I'd have known anyway!)

Val · 06-12-16, 01:21 AM

You need to check air flow potentiometer in fuel distributor. 3 pin connector. It mechanically worn out inside track and resistance is no more smooth as it should be. It's most stupid invention from VAG except Audi A2 and TT.

Check google how it can be diagnosed. And it's more like KE-jetronic than K-jetronic. You will need ohmmeter and ampere meter.

There's 4 little screws under plastic of potentiometer body if you want to see how bad it looks. Beware that it will need to be aligned to put it back.

HTH

RIP Jetronic.

Niklas.L · 07-12-16, 08:30 PM

The Real MSH!: I really hope it's not there that the problem lies. Will do the compression test first and see what results I get.

jimh: Okey, then it shouldn't be that much work to get access to the timing belt. Thanks!

Val: I just changed the whole air flow meter and fuel distributor. The car I took it from ran okey, so the problem is not in the air flow potentiometer. Thanks anyway!

Val · 07-12-16, 09:10 PM

Good to hear.

One local used audi part seller made stats about these parts in year 2008.
He said that only 15% of flow meters are still usable. Right now it should be even less.

04-12-16, 03:13 PM	#2
mikes2 4 ring whore! Classic Audi Club Member Join Date: Nov 2007 Location: Polmont Posts: 2,617	How old are the fuel filter and pump ? __________________ 1991 90 quattro 20v sport 1991 90 quattro

04-12-16, 03:14 PM	#3
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,026	http://www.sjmautotechnik.com/troubl...g/100ecuf.html I can't offer any specific insight on this model, however, a starting point might be pulling the codes, if they are available. Hence the link above; which may provide a little help, even if the specific engine isn't listed. I borrowed a cheap code reader from a neighbour, and with an adaptor lead, pulled the codes on my 100-V6 not so long ago. (£30 for a VAG reader. I don't think it had any specific reset capability, though) __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

04-12-16, 03:25 PM	#4
AdrianH Grown up member Join Date: Jan 2014 Posts: 218	How is the fuel metered on this model?

04-12-16, 05:02 PM	#5
jimh Grown up member Classic Audi Club Member Join Date: Dec 2008 Posts: 122	If you suspect that you have a problem with the head gasket anyway, I would start by checking compression. If you have poor compression on one or more cylinders, no amount of swapping fuel & ignition parts will help you. This is what my head gasket looked like when I pulled the head (Urq):- See the nice gap in the gasket between cylinders 3 & 4? I measured compression at 10bar, 10bar, 5 bar, 5bar, 10 bar, so the gasket looked just like I thought it would. The engine did not run very well in that state...

04-12-16, 05:28 PM	#6
Niklas.L Newbie! Join Date: Dec 2016 Location: Sweden Posts: 9	mikes2: I don't know how old they are. The pump could very well be the original pump. The fuel filter is changed at one stage, different fabricator. The thing that confuses is that the symptoms change as I change the parts. Before I changed the whole air flow meter and fuel distributor it ran okey when cold. It wasn't a speed demon, but it didn't flutter and hesitate as it does now. The Real MSH!: I did check the error codes before I changed the air flow meter/fuel distributor and it showed no error codes. AdrianH: It is all vacuum controlled. The more you accelerate the more the air flow meter flap opens and it sends a signal to the fuel distributor/fuel pump to supply more fuel. I have checked for vacuum leaks and all leaks are fixed. jimh: I will check the compression before proceeding to changing more parts. A followup question regarding the head gasket. Do you have to disassemble the front in order to get the timing belt of? Looks extremely tight between the front of the engine and the radiator. Thanks for all your answers!

04-12-16, 05:37 PM	#7
AdrianH Grown up member Join Date: Jan 2014 Posts: 218	Assuming it's a K–Jet type derivative, have you checked that the pipes from the warm up regulator are connected correctly? My urQuat was running as you describe until it was noticed that the control pressure / warm up regulator pipes (I can't remember exactly which) had been transposed at some time before I got the car –*such an obvious thing that no one noticed for ages (not that I'd have known anyway!)

06-12-16, 01:21 AM	#8
Val Grown up member Join Date: Dec 2012 Location: 5vtq gte Posts: 177	You need to check air flow potentiometer in fuel distributor. 3 pin connector. It mechanically worn out inside track and resistance is no more smooth as it should be. It's most stupid invention from VAG except Audi A2 and TT. Check google how it can be diagnosed. And it's more like KE-jetronic than K-jetronic. You will need ohmmeter and ampere meter. There's 4 little screws under plastic of potentiometer body if you want to see how bad it looks. Beware that it will need to be aligned to put it back. HTH RIP Jetronic.

07-12-16, 08:30 PM	#9
Niklas.L Newbie! Join Date: Dec 2016 Location: Sweden Posts: 9	The Real MSH!: I really hope it's not there that the problem lies. Will do the compression test first and see what results I get. jimh: Okey, then it shouldn't be that much work to get access to the timing belt. Thanks! Val: I just changed the whole air flow meter and fuel distributor. The car I took it from ran okey, so the problem is not in the air flow potentiometer. Thanks anyway!

07-12-16, 09:10 PM	#10
Val Grown up member Join Date: Dec 2012 Location: 5vtq gte Posts: 177	Good to hear. One local used audi part seller made stats about these parts in year 2008. He said that only 15% of flow meters are still usable. Right now it should be even less.