coupe 2.6 running cold / intermitent jumpy acceleration

[Coupe Headache]

Hi, i wonder if anyone can help me?

I have a coupe with the ABC engine, when driving from cold it struggles to warm up and sometimes the temperature will not rise above 50 degrees until in traffic.
When stationary / in traffic it will rise to 90 and the fans cut in but once driving again will drop to around 70. I have changed the thermostat and O ring but not much improvement, is it possible i have fitted it incorrectly? The car sometimes drives well but can have problems accelerating smoothly and is jumpy up to 4000rpm where it smoothes out. Are the problems related? Where can you get good quality information on this engine?

any help would be appreciated

[scotty33]

Is it possible the gauge is reading low? 90 deg seems low for the fan to come in..
If it IS running cool, it will be staying in it's cold enrichment mode for perhaps longer than it should. I'm not sure whether this would cause poor running as such, the low engine temp would justify it, but this stuation would be giving poor mpg and damaging the cat(s). Maybe try a stat that opens at a higher temp or check the new one is not in backwards?
I usually point v6 owners to www.12v.org, but it has not been up for a while now, it does not really cover the 2.6 being a US site and they only had the 2.8, but it is useful for most things.
Other than that see this thread for possible sources: https://www.vwaudiforum.co.uk/forum/s...?t=3084&page=2
It might be useful for you to get the ECU read for fault codes, I think the diagnostic connectors are in the fuse box, if you are going to do this yourself.

[Coupe Headache]

Thanks Scotty33

I Had a thought gauge might be reading low. But I didn't know what temperature the fans should kick in at. Is there a way of testing the brown temperature sender for the gauge / warning light?
Since it does cost £100 to buy from Audi, I would like to check before buying if possible. Hopefully the thermostat is operating correctly, because I would rather not disturb the timing belt again.

Should my car have an EGR Valve? As I have two blanked holes on the exhaust manifolds, but cannot see where the valve would have been situated.
Is it possible Lamba probes could be faulty/

I am sure the thermostat is in the correct way around, with the spring facing into the engine block.

[scotty33]

This link for SJM autotechnic, again it is not specifically for the V6, but the multi function temp sender seems to be used across the range, and there is some good info there. As far as I know, the two dots on the temp gauge approx 3/4 of the way around the scale, the first one should be where the fan cuts in at low speed, the second one would be high speed i think! It would be worth you trying Vagparts, eurocarparts GSf etc for the sender, as the link says, the part is made by Beru, also it says it is common for there to be problems with the connections inside the rubber boot, so you may not even need one?

http://www.sjmautotechnik.com/troubl...g/cooling.html

If you have a multimeter, you can test the lambdas yourself, they usually have 3 wires, two white (heater circuit) and one other which should be the signal wire. You need to set the meter to volts or millivolts, run the car until warmed up fully.
Leave the lambda connector plugs connected to the cars loom, but expose the signal wire, by peeling back the rubber boot.
put meter negative lead to earth, positive lead goes to the signal wire.
meter should read voltage of approx 0.2v approx rising to 0.9v approx going back down to 0.2v etc, this should happen once/second. average should be approx 0.5v if not sensor is bad, if slower than 1/sec, sensor is on it's way out and best replaced.
Should also show up in ECU fault code check as would most other sensor problems.

[scotty33]

Re the Exhaust gas recirculation?, It would not surprise me if your car does not have it and never had it, just shares the manifolds/downpipes with the same take off points for cars that do use the system.
My 20v is the same with it's lambda, it is mounted on the manifold, but the cat has a point for fitting one which is plugged.

[Coupe Headache]

Thanks for your reply. thanks for your tip on vag parts they sell the temp sender for half the price, i will order one and see if that alters the gauge reading. Have had the ecu checked twice at two different places and both times came back clean. do you know if the injectors are included in the check process? would worn / faulty injectors cause jumpy acceleration. just drove 200 miles in the car, it drove fine apart from when accelerating, very frustrating

[scotty33]

You may be onto something there, if the injectors are dirty/damaged the spray pattern could be affected, this would not show up on a fault code scan, but can give the lumpy acceleration you are getting.
You could try some injector cleaner and a few tankfuls of V power first, or get them ultrasonically cleaned by an injector specialist?

[chicy]

hello new to forum but had very similar problems with my 1994 coupe with
2 ltr 16 v engine.i tried everything and i mean everything plugs points temp
senders fuel filters and much more.audi main dealer could find nothing wrong
they had the car three times and found nothing.to cut a long story short the
lamba probe has a fuse to it number 21 i think box on bulk head this fuse had
blown which i discovered by chance .put new fuse in ,hey presto away we went
and she has driven perfect ever since .hope this may be of some help

[scotty33]

Sounds like that was the fuse for the lambda probe's heater circuit? this would affect the mixture, as the lambda needs the heater to work properly.