16 V 9A loss of power / missing when warm

[Jim H 10]

Hi All,

This started a few weeks ago and is fairly intermittent .. I've had it in a garage and they could find nothing!

Basically at low revs (when it's been idling in 4th gear it struggles to pick up, it's like it's got no power and missing on all four cylinders. It almost seems electrical because the power can come back suddenly, then fall just as suddenly.

It never stops completely and when you get it up in the revs, it clears a bit..

Strangely turning the ignition off and back on seems to clear it.. Like I say it only does it when warm, and on two occasions going up hill seems to make it worse..

 

EDIT:What is really frustrating, I've just been out in the car and covered about 20 miles, up to temperature etc and it never missed a beat - it was perfect.

I have noticed the symptoms do appear more often when the car is low on fuel and strangely - when the weather is damp (raining)..Perhaps the latter unconnected?

Bauhaus, I have a fuse box and relays from my last Corrado, I'll look into that.

Edited September 9, 2018 by Jim H
Update

[Bauhaus 3]

I'm not familiar with the fuse /box relay positions of your car or the injection system you have, but If you suspect its electrical then consider replacing the fuel pump relay.

Turning the ignition off then back on and it clears is a classic sign of a intermittent relay fault.

[Jim H 10]

Any takers for Throttle Position Switch? I was talking to a chap who used to be a member on here and he suggested this.. I was out in the car before and although fine to begin with the problem appeared.. I was trying to induce it my modulating the throttle around the idle and first opening stage and it resulted in the symptoms. Reluctance to rev and no power, lumpy "poppy" tick-over and rich smell from exhaust as if not receiving correct air/fuel mix.

 

Are the switches still available and if so where, I've tried VW Heritage and they can't source.. Main dealer? I've done a quick search on eBay and not a lot showing, I'm a bit reluctant to go the second-hand route for obvious reasons.

[Sanj 0]

This used to happen to mine when I first got my car. I tried everything i.e. spark plugs , ignition coil, leads, disc cap, etc, it turned out to be the Lambda Sensor. Essentially the car would be fine when cold, but when it got up to speed and warm on the motorway I would get loss of power and stuttering. Turning the engine off and then back on seemed to rectify the prob until a few miles later it would happen again.

Hope this helps.

[Jim H 10]

Many thanks Sanj,

 

I replaced the plug leads, dizzy, and rotor arm at the weekend ( the leads were original 1994!) and annoyingly it's not missed a beat of late. However I'm not convinced I've fixed the real problem..

 

I've managed to source a new throttle position switch today (expensive at £130 + VAT).. I'm going to get quotes for Lamda Probe replacement at the weekend and then decide which to replace next.. I've got a long motorway trip coming up soon and I really don't want it causing me a problem then!!

[Sanj 0]

Jim hope you got the prob sorted. I would be interested to know if the throttle position sensor sorted the issue.

[Jim H 10]

Sanj, sorry for late reply. I'm struggling loggiing on so this reply may appear twice.. Did plugs and leads etc - no joy..

I was going to go down your route and replace the Catalyser and Lambda, but I've had conflicting advice against???

I've ordered a throttle position sensor and hope to receive and fit soon.. I was out in the car last night and the problem appeared, OK to begin with, then when warm the throttle response became unresponsive, mild back firing and lumpy erratic tick- over. So bad I struggled to reverse the car up the drive.. Turned ignition off/ on and the problem cleared.. I didn't drive the car any further.. I guess if the TPS doesn't fix It, I'll go down the Cat/Lambda route

[1200 bandit 10]

Check the 3 wires that go to the throttle body,has a similar fault found the wiring had snapped inside but looked ok on the outside of the wiring

[Jim H 10]

Well at £168 that was an expensive experiment that didn't work! Fitted TPS and felt the throttle response was better, but within minutes of the engine getting up to temperature, the problem returned..

Switched off ignition and back on, drove perfectly all the way home..

I'm not convinced the wires from the TPS are the issue, surely by jiggling them about whilst the engine is running would induce an symptom? Which I've tried and it didn't ..

It might be worth mentioning the catalytic converter has been rattling for most of this year - and getting worse.

[vw rule 19]

I'm not saying this is your problem,

but some years back I was working on a early MK1 Ford Mondeo, and it had exactly the same issue it was fine from cold but once up to temperature it had no power, basically the fault was the honeycomb inside the catalyst had broken away, and was floating freely which was ok from cold but once hot it would expand due to the hot exhaust, which caused it to partly block the exhaust pipe resulting in no power.

 

To me though your problem sounds like fuel related, the fuel metering head has the fuel distributor, fuel Governor, and the air flow metre, unfortunately on the 16v Corrado's you can't link up a diagnostic scanner for the engine, I believe you have to use a multimeter and test each sensor in turn the old school way.

So if your Corrado is missing / down on power, but then it clears it's self once ignition is switch off, then this definitely suggests that something is resetting it's self.

I wouldn't of thought it's a vacuum leak as it would be doing it all the time.

 

Possibly the resistance in one of the above sensors is changing enough, to cause you problems once the engine is up to temperature.

 

The coolant temp switch can play up,

plus they communicate with the fuel Governor on the metering head.

 

As you've already mentioned it could be the Lambda sensor, these can cause a lack of power and poor throttle response.

 

But to be honest the only real way to check most engine sensors on the 16v Corrado's is like I say with a multimeter, and the bible for the Corrado i.e (the Bentley manual)

 

Si

[vw rule 19]

Also the 16v Corrado's don't have a crank sensor, but they do have a pickup sensor,

this is the Hall sensor in the distributor,

as long as the ECU can see the signal from Hall sensor, otherwise again this can cause a lack of power and very poor throttle response, but it wouldn't reset it's self unless a possible fault with the control unit (ECU)

 

Si

[vw rule 19]

Plus as mentioned by other people in this thread, it could also be a wiring fault,

but then there must be something else as the system resets it's self once you've turned your engine off ??

 

Si

[Bauhaus 3]

I still say it’s your relays, either the one for the fuel pump and or the one for the ECU the contacts these relays are probably a bit worn / pitted if their the original ones and will give a poor voltage to power the fuel pump and ECU.

 

Also check your battery is in good condition and delivers at least 13.4v, the electrical system gets a bit flaky if not supplied with a good voltage and relays don’t latch properly causing the same intermittent problems as dodgy relays, also it goes without saying check all your earth connections.

[vw rule 19]

I think your fuel relay is the bottom right one, if it's the original relay from new then it should have on the back of it number 167 plus is possibly grey in colour.

Then to the left of this fuel relay still on the bottom row, is relay for ABS, relay for your horns from memory, the rest I'll have to look up to remind my self.

 

Si

[Jim H 10]

Guys, I feel very stupid! I went back to have a fiddle with it yesterday evening, to my shock I saw te TPS was unplugged - I'd simply forgotten to connect it in my haste.

How the car ran with it disconnected I'd love to know, does it only come in when the engine is up at temperature?

Plugged it back together, went for a spin and all is well..

I'll put some more miles in over the weekend and report back.

[Cressa 43]

Congratulations on sorting it. That is a great fix.

[Sanj 0]

Glad it sorted mate.