VW Corrado Loss of Power
Discussion
2.0 16 Valve 9 A Engine.
This issue has been going on for weeks now and I'm running out of ideas?
Mainly appears after about 20mins to an hour of running, although I've noticed it's particularly bad in damp conditions.
It's never stopped completely or left me at the side of the road, and it does tend to clear after more running - for instances I've just done a round trip of 200 miles motorway running. Very bad on the way down (wet conditions) not as bad on the return - dry..
The engine response is down on power as if restrained, but it does not seem a fuel or electrical issue. The power delivery hesitant, but if you floor the accelerator after initial hesitation you get full power. But the throttle response is not smooth at all. Strangely turning the ignition off/on clears the fault for a few minutes, but the fault returns.
I've replaced cap/rotor/leads as a matter of course, and the throttle position sensor as I'd had advice this could be the issue.
I've also had advice that it could be the Lambda sensor, or Catalytic Converter (it is on its last legs CAT rattling) someone said it could be the honeycomb breaking up and restricting flow. I was going to go ahead and replace them next, but some very rough running in damp conditions this afternoon has made be question that logic..
Any advice would be welcome
This issue has been going on for weeks now and I'm running out of ideas?
Mainly appears after about 20mins to an hour of running, although I've noticed it's particularly bad in damp conditions.
It's never stopped completely or left me at the side of the road, and it does tend to clear after more running - for instances I've just done a round trip of 200 miles motorway running. Very bad on the way down (wet conditions) not as bad on the return - dry..
The engine response is down on power as if restrained, but it does not seem a fuel or electrical issue. The power delivery hesitant, but if you floor the accelerator after initial hesitation you get full power. But the throttle response is not smooth at all. Strangely turning the ignition off/on clears the fault for a few minutes, but the fault returns.
I've replaced cap/rotor/leads as a matter of course, and the throttle position sensor as I'd had advice this could be the issue.
I've also had advice that it could be the Lambda sensor, or Catalytic Converter (it is on its last legs CAT rattling) someone said it could be the honeycomb breaking up and restricting flow. I was going to go ahead and replace them next, but some very rough running in damp conditions this afternoon has made be question that logic..
Any advice would be welcome
So you have replaced cap/rotor & leads but what about plugs?
Pardon my ignorance but what age is that engine/car combination?
Had similar symptoms with cat as you mention, but that doesn't explain the wet/dry as you also say.
Also had similar symptoms with a bit of debris floating around in a carb bowl being occasionally picked up & then dropping back into suspension when stopping the engine, but I would imagine this is FI so that won't be the issue.
Have you had any codes from it?
Pardon my ignorance but what age is that engine/car combination?
Had similar symptoms with cat as you mention, but that doesn't explain the wet/dry as you also say.
Also had similar symptoms with a bit of debris floating around in a carb bowl being occasionally picked up & then dropping back into suspension when stopping the engine, but I would imagine this is FI so that won't be the issue.
Have you had any codes from it?
Edited by E-bmw on Saturday 20th October 12:51
It's a Dinosaur 1994, I'm led to believe the engine management is fairly rudimentary and does not give good feedback on codes (I've had it in a garage)... And when it was in the garage it was running perfectly (at the time)
No I've not changed the plugs, as I'd only realistically expect failure on one maybe? And the issue is nothing like running on 3 pots.. I suppose it's a cheap try at least and something to rule out..
No I've not changed the plugs, as I'd only realistically expect failure on one maybe? And the issue is nothing like running on 3 pots.. I suppose it's a cheap try at least and something to rule out..
I assume this uses the KE Jetronic system. Not the easiest things to tinker with. It may be worn tracks on the air flap potentiometer which are giving a bad fuel signal to the ecu in some throttle positions. Obviously they wear out first in the positions the air flap spends most of its time at i.e. cruise so if you open the throttle to take the air flap past that point you get a clean signal again. Have a look at the relevant section here.
https://mbworld.org/forums/e-class-w124/400937-ke-...
You didn't mention changing spark plugs. I assume you're at least going to check and gap these though.
If your car has fault codes then get those read. It might show up a problem with long or short term fuel trims.
https://mbworld.org/forums/e-class-w124/400937-ke-...
You didn't mention changing spark plugs. I assume you're at least going to check and gap these though.
If your car has fault codes then get those read. It might show up a problem with long or short term fuel trims.
Simple answer, replace them.
Personally I don't bother with such fandangled things.
Just find the old-school NGK single copper cored plugs & replace every year.
Pretty much the only reason these things are used is to extend service intervals and cost £40+/set as opposed to £9/set & chuck every year.
Personally I don't bother with such fandangled things.
Just find the old-school NGK single copper cored plugs & replace every year.
Pretty much the only reason these things are used is to extend service intervals and cost £40+/set as opposed to £9/set & chuck every year.
It has a diagnostic socket under the gear shift gator, but I'm told it's a 3 pin type and the info given is not that reliable.. The garage that informed me of this have a good reputation and for honesty and specialise in VW.. It's rare I take any of my vehicles to a garage as I normally try to repair myself - but I was at loss this time and hoped they'd be able to go right to the fault rather than me faff about..
I'll give the plugs a change, but I'm not that sure it explains the symptoms between dry and damp running.. I'd expect a duff plug or more to give bad performance from cold start and all of the time - rather than after a duration of time.
I'll give the plugs a change, but I'm not that sure it explains the symptoms between dry and damp running.. I'd expect a duff plug or more to give bad performance from cold start and all of the time - rather than after a duration of time.
If you're up for a little fault finding, add some instrumentation so you can see what's changing when the problem occurs. I'd start with simple things like fuel pressure and injector duty cycle - both easy to measure remotely using cheap DIY parts (remote mechanical fuel pressure gauge and remote NOID lamp).
Fuel pressure tells you whether you have a fuel supply problem unrelated to the ECU, and injector duty cycle tells you whether the ECU is demanding the wrong amount of fuel - which might suggest sensor related problems.
It could equally be an ignition problem, but that's harder to diagnose. I have a passive strobe light that I can wire in series with a plug lead but this relies on being able to position the lamp where it can be seen from the driving seat, and I don't know how easy that would be in your case. I don't know if that engine uses CoP but if so it would make things even more awkward - but maybe still possible with a little ingenuity.
Fuel pressure tells you whether you have a fuel supply problem unrelated to the ECU, and injector duty cycle tells you whether the ECU is demanding the wrong amount of fuel - which might suggest sensor related problems.
It could equally be an ignition problem, but that's harder to diagnose. I have a passive strobe light that I can wire in series with a plug lead but this relies on being able to position the lamp where it can be seen from the driving seat, and I don't know how easy that would be in your case. I don't know if that engine uses CoP but if so it would make things even more awkward - but maybe still possible with a little ingenuity.
Single coil.intresting question though??
When the problem first appeared I spoke to the prop at the aforementioned garage, he suggested it sounded like the coil breaking down. This is my second Corrado, my first was written off but I kept some spares. I fitted the old coil of that and the problem settled down for a couple of weeks - it's still fitted.. It's obviously a now very old item and that too is now failing after being sat for a long time. I guess that would also be a reasonably cheaper item to replace new and rule out..
When the problem first appeared I spoke to the prop at the aforementioned garage, he suggested it sounded like the coil breaking down. This is my second Corrado, my first was written off but I kept some spares. I fitted the old coil of that and the problem settled down for a couple of weeks - it's still fitted.. It's obviously a now very old item and that too is now failing after being sat for a long time. I guess that would also be a reasonably cheaper item to replace new and rule out..
I did once, many years ago have an old 320 I which did something similar, but it was related to the coil "breaking down" in hot conditions, but rather than on/off fixed it, the bonnet had to be lifted & the engine bay had to radically cool down for around an hour before it would run at anything other than tick over off-load again.
AA man had a spare for £5 in his car.
AA man had a spare for £5 in his car.
GreenV8S said:
If you're up for a little fault finding, add some instrumentation so you can see what's changing when the problem occurs. I'd start with simple things like fuel pressure and injector duty cycle - both easy to measure remotely using cheap DIY parts (remote mechanical fuel pressure gauge and remote NOID lamp).
Fuel pressure tells you whether you have a fuel supply problem unrelated to the ECU, and injector duty cycle tells you whether the ECU is demanding the wrong amount of fuel - which might suggest sensor related problems.
It could equally be an ignition problem, but that's harder to diagnose. I have a passive strobe light that I can wire in series with a plug lead but this relies on being able to position the lamp where it can be seen from the driving seat, and I don't know how easy that would be in your case. I don't know if that engine uses CoP but if so it would make things even more awkward - but maybe still possible with a little ingenuity.
It's mostly mechanical injection.Fuel pressure tells you whether you have a fuel supply problem unrelated to the ECU, and injector duty cycle tells you whether the ECU is demanding the wrong amount of fuel - which might suggest sensor related problems.
It could equally be an ignition problem, but that's harder to diagnose. I have a passive strobe light that I can wire in series with a plug lead but this relies on being able to position the lamp where it can be seen from the driving seat, and I don't know how easy that would be in your case. I don't know if that engine uses CoP but if so it would make things even more awkward - but maybe still possible with a little ingenuity.
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