VR6 Periodic misfire

[Atki 0]

Hi all. My Vr6 Corrado is not well! Every now and again it suddenly decides to stutter and run lumpy then for awhile bursts back into all cylinders firing. I've changed the plugs and leads and had the ignition coil checked. All seem to be well. I have also run some injector cleaner through. I have noticed that on idle there is a small misfire but others have not been able to detect it. Timing chains are quiet too.

Any thoughts ? please. oooo just remembered, the oil is clean and there is no sign of white sludge and the water has no sign of oil in it.

[VW_OwneR_85 1]

Hi,i dd check out MAF sensor and its plug/conections for corrosion and wiring to it. Also worth looking at ISV idle stability valve if your symptoms only happen when idling. also worth looking at the rubber breather hose off the cam cover to intake hose as they do split,

[easypops 8]

I had a similar, occasional misfire. Turned out the back middle lead wasn't seated on the plug correctly. Worth a look, and free too :)

[robrado974 1]

As above , as easy pops said . This happened to me , I kangarooed all the way home . And two of the leads were not seated correctly .

[Atki 0]

Hi all. My Vr6 Corrado is not well! Every now and again it suddenly decides to stutter and run lumpy then for awhile bursts back into all cylinders firing. I've changed the plugs and leads and had the ignition coil checked. All seem to be well. I have also run some injector cleaner through. I have noticed that on idle there is a small misfire but others have not been able to detect it. Timing chains are quiet too.

Any thoughts ? please. oooo just remembered, the oil is clean and there is no sign of white sludge and the water has no sign of oil in it.

 

 

Hi again. I checked the leads and they are all seated as they should be. The stutter only happens when she's running at around 2000 rpm. it's brief normally. I'll have a look and a fiddle with the MAF tomorrow and check the breather hose too. Thanks so far. I'll keep you updated.

[Atki 0]

Well, checked the MAF plug and conections. Checked the breather hose ( no splits ) checked the plug leads just to be sure. Fired her up and all was well until at about 80 degrees temp she started to miss fire, stutter and then run fine again.....Is there a sensor that pops in to control warm running?

Took her for a run and this time only once did she perform the stutter. However, whilst running her up on the drive i noticed what i can best describe as a burbling note after releasing the throttle, almost to the point of a small backfire but not giving the actual bang!!! She idles at 800 rpm and is steady at that. at 1100 rpm the burbling starts.

[Jim 1]

Doesn't the lambda only come into play once the car has warmed up? Think it's the same with the MAF too..?

[Gti_Jamo 10]

Yes oxygen sensor doesn't cut in until upto temp. Try disconnecting then running it, connector is situated on top of the rear engine mount.

[Dox 22]

https://en.wikipedia.org/wiki/Oxygen_sensor

 

"The probe[edit]

 

The sensor element is a ceramic cylinder plated inside and out with porous platinum electrodes; the whole assembly is protected by a metal gauze. It operates by measuring the difference in oxygen between the exhaust gas and the external air, and generates a voltage or changes its resistance depending on the difference between the two.

 

The sensors only work effectively when heated to approximately 316 °C (600 °F), so most newer lambda probes have heating elements encased in the ceramic that bring the ceramic tip up to temperature quickly. Older probes, without heating elements, would eventually be heated by the exhaust, but there is a time lag between when the engine is started and when the components in the exhaust system come to a thermal equilibrium. The length of time required for the exhaust gases to bring the probe to temperature depends on the temperature of the ambient air and the geometry of the exhaust system. Without a heater, the process may take several minutes. There are pollution problems that are attributed to this slow start-up process, including a similar problem with the working temperature of a catalytic converter.

 

The probe typically has four wires attached to it: two for the lambda output, and two for the heater power, although some automakers use the metal case as ground for the sensor element signal, resulting in three wires. Earlier non-electrically-heated sensors had one or two wires."

[Atki 0]

Me again!!

Had a new Lambda fitted less than 3000 miles ago, Very recently had and passed the MOT.

 

Further

Up-date.

Took her out again today and apart from a brief moment she performed much much more like her old self. I ran her through varying temperatures and all seemed to be well. Much appreciate the advice and comments. Many thanks to you guys. FYI she's done 286250 miles. Want to make the 300.000 before an engine rebuild. My scirroco storm made it to 320.000.