Strange idle problem

Hi

My grandfather has a '92 2 litre Passat which we recently did a lot of work on as detailed in the last post.

We now have a problem with idle speed.

When we start the engine it will idle happily at 1000 rpm. However, if we blip the accelerator, the speed will rise with the blip and then stay at the speed it revved to. If the speed it below about 2000 it will then very gradually fall back to 1000. If the speed is above about 2000 then it will continue to rise by itself to about 3500. Putting a load on the engine causes it to come back down again, and switching it off and on also resets it.

We changed the "Idle stabalisation valve" because we had one lying around and it was easy to change, but it made no difference. We cant think what we might have done to cause this.

Any help would be very much appreciated.

Cheers!

I'm not familiar with UK spec cars, does this have CIS-E fuel injection w/16 valve engine?

I'm not familiar with UK spec cars, does this have CIS-E fuel injection w/16 valve engine?

No, this is the 8 valve engine with fuel injection. I have forgotten the name of the ECM/fuel injection/electronic ignition system but it begins in d!

The problem has now become more severe, with it refusing to start on a regular basis when left standing for more than a few hours. The only way to get it to start is to hold the accelerator down right to the floor and crank it, which makes eventully fire and gradually pick up RPM.

We think we have a mixture problem. What could be causing this?

Thanks

Probably Digifant, it wouldn't have braided steel fuel lines to the injectors then. There should be an air flow meter attached to the air filter housing, I would start with that. It has a 5-pin electrical connector (only four pins are used). Resistance beween pins #3 & #4 should be 500-1000 Ohms. Resistance between pins #2 & #3 should smoothly rise & fall as you open & close the air flow flap. Also, check for air leaks at the intake rubber hose.

Probably Digifant, it wouldn't have braided steel fuel lines to the injectors then. There should be an air flow meter attached to the air filter housing, I would start with that. It has a 5-pin electrical connector (only four pins are used). Resistance beween pins #3 & #4 should be 500-1000 Ohms. Resistance between pins #2 & #3 should smoothly rise & fall as you open & close the air flow flap. Also, check for air leaks at the intake rubber hose.

Yeah, thats the one, Digifant :)

Thanks, I will relay this information to the car owner.

Yeah, thats the one, Digifant :)

Thanks, I will relay this information to the car owner.

Do you have any idea what could be causing the car to flood about 20% of the time at startup? (it just turns over and wont fire until you put your foot on the accelerator and hold it there for a while, and then when it does fire it runs lumpy and takes a while to build up RPM.

Actually it runs lumpy almost every time its started.

Also our central locking/clock fuse blows on a regular basis and the battery flattens itself every now and then?

Cheers!

That kind of sounds like an EGR valve problem to me, if you have to keep your foot on the gas for a while to keep it running.

A rich running Digifant system is often the coolant temp sensor or a bad ECM.

A rich running Digifant system is often the coolant temp sensor or a bad ECM.

What is an EGR valve?

I checked the impedance of the coolant temp sensor when the engine was cold, and it measured about 17k Ohms which I believe is not right.

Exhaust Gas Recirculation valve. That is way out of spec on the temp sensor.

Exhaust Gas Recirculation valve. That is way out of spec on the temp sensor.

Firstly am I correct that the blue sensor in the rubber tube at the front of the engine, is the coolant sensor?

Secondly, would this cause the problems we are having with the darned thing?

Cheers

That sounds like it, it should have brown/white & violet/black wires on it's harness. 17K Ohms across the sensor would cause the engine to run extremely rich.

Thanks Boschman,

Do you have any idea what could be causing the idle speed problem? It wasnt happening before we replaced the exhaust system, and whilst we were doing that we also cleaned the plugs, took the distributor apart and put it back, and we removed the big thick air intake pipes and put them back (we were trying to get to the fuel pressure regulator which we thought might have been causing our problem).

We think we must have damaged a vaccum line or something, but we have checked it all over and it looks fine.

Any ideas would be very much appreciated!!

Cheers,

Have you replaced the sensor first?

Have you replaced the sensor first?

Im not sure what you mean by sensor, but we have replaced the "idle stabalisation valve" that connects to the air intake, and it made no difference

The blue coolant temp sensor that has the wrong readings.

The blue coolant temp sensor that has the wrong readings.

Boschman, you are absolutely right. My grandfather disconnected the blue sensor and it solved the starting problem and the idle speed problem. For some reason it seems to be working fine with the sensor disconnected!!

We will try and source a new one.

Thanks Boschman for all your help! Us novices would be lost without experts like you giving up your time to help us, so Cheers!!

did you change the o2 sensor?

Im not sure what you mean by sensor, but we have replaced the "idle stabalisation valve" that connects to the air intake, and it made no difference

Guys, I have too an idlle problem. Can somebody help?
The car is a Passat 1992, automatic, 2L, 16 Valves, all equiped.
Idelle is OK at cold start-up for about 1 min. Then, it becomes more and more oscilating while the motor warms-up.
Also black smoke starts to come out from exhaust at idlle.
When the motor is hot, the idlle dies.
Another symptom is that the automatic transmissin, after reaching 100Km/h and going down, it does not change up unless I reach 4000 rpm.
Recently I have found the oxigen sensor wires broken. I have re-connected them, but no improvement. Did not check the fuse.
The exhaust system is not in a very good condition.
I do not feel the switch at the throttle valve, as I feel at my 1991 scraped Passat.
I have lots of parts from my 1991 Passat