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Miss fire - Need some input


T2 MSW

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Sorry to post a thread outside the project one but I need some input as this issue is doing my head in.

 

The problem is the car wont idle. It sits at about 950 rpm once its warmed up and hunts for an idle between 900 and 1000 rpm, you will every so oftern get a pop through the exhaust. When the car is driven it feels like its holding back then its ok and over and over, then it will run fine. When it holds back the AFR's go from anywhere between 11.5 and 16.

 

So far its had the below, none of which have made any difference :-

 

New Injectors

New coil packs

New plugs

New coil pack clips

changed the cam sensors

changed the CPS sensor

changed the ingnitor pack

Check and wiggled every wire for the sensors, coil pack connectors, injectors, ECU injector wires. Nothing makes it better or worse.

 

Looking for other sugestions etc.

 

Currently waiting for the engine to cool down so I can take the plugs out and get some pictures up of them.

 

Any input greatly received as im getting fed up with this now :(

Edited by T2 MSW (see edit history)
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Icv?

 

Ive taken it off and cleaned it, did not really seem to make any difference at all. Not sure if this would cause the holding back when being driven though?

 

Firstly is it VVTI (97 plus model), if so; you may want to consider checking the MAF (Mass Airflow Meter), if its pre 97 TT then check the MAP sensor (Mass Air Pressure...i think), also check for boost/Vac leaks thoroughly.

 

 

Its a 94 but its got a brand new 3.5 bar AEM MAP sensor on it and this issue occured before the AEM was put on the car :(

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Its a 94 but its got a brand new 3.5 bar AEM MAP sensor on it and this issue occured before the AEM was put on the car :(

 

In that case, I would focus on possible Vac/Boost leaks, check the pipe work for kinks, wear and tear etc.

 

You seem to be running lean when you say the car is holding back, north of 12.0 AFR's on WOT is running pretty lean, if this is what is happening then I would check the Vac/boost lines for any wear or kinks around the top of the engine wear alot of the smaller pipe work is located.

Edited by wkdtime (see edit history)
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Dont think its a spark issue as every spark plug is identical, the electrode is a dark white and the rest of the plug is a sooty black. Certianly cant attirbute any one plug to an issue.

 

I'm not up to speed on your project thread, but what ECU do you have fitted? Has the o2 sensor been replaced? When you say holding back, it that while it's in closed loop?

 

Its an AEM and yes its a new UEGO O2 sensor, it is in closed loop but it had this issue before all the work was done and that was BPU with stock auto ECU

 

I had a similar problem with a miss fire and replaced all the coil packs and coil pack connectors and it was still miss firing but when i put new rocker cover gaskets on it stopped

 

New gasket set throughout :(

 

has it got a RLTC fitted.

 

It used to but its all been taken out and wireing put back to stock. Ive double and tripple checked every soldered wire too.

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In that case, I would focus on possible Vac/Boost leaks, check the pipe work for kinks, wear and tear etc.

 

You seem to be running lean when you say the car is holding back, north of 12.0 AFR's on WOT is running pretty lean, if this is what is happening then I would check the Vac/boost lines for any wear or kinks around the top of the engine wear alot of the smaller pipe work is located.

 

Its not on WOT as the car has not been run in yet, its when cruising say betwen 2-3.5 k.

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good point rob, be worth checking all earth connections, seen this many times before on peoples cars, suprising what effect it does have on the idle and overall running

 

Especially the ones that bolt to the intake manifold underneath ;)

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Send it back to be fixed by the person thats done the rebuild and single install? Surely you should have had the car back in full working order? Not meaning to have a dig, i like Paul and he clearly knows what he is doing and turned out some top cars so why not send it back?

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Earth points?

 

Vibration at those specific revs causing intermittent contact on either earth or live side of a contact somewhere.

 

When you replaced coil pack clips did you 'close them up'?

 

What sort of AFRs showing when the missfire occurs?

 

What am I looking for when checking the earth points? Just thay they are clean and tight?

 

Where are they all too?

 

If it was a positive feed I would be able to see the voltage changes through the AEM software wouldnt I??

 

Did think about closing them up when I was putting the plugs back in, Assume Paul has already done this as they are quite a tight fit. Can check that tomorrow night though.

 

AFR's when the missfire occurs basically can go round the clock from 11 right to 16/17 they just go wild then settle on 14 ish again.

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Send it back to be fixed by the person thats done the rebuild and single install? Surely you should have had the car back in full working order? Not meaning to have a dig, i like Paul and he clearly knows what he is doing and turned out some top cars so why not send it back?

 

Im sure Paul will not take it that way and they have done an excellent job of the engine rebuild and im very happy with that part just need to get these teething issues sorted out :)

 

Paul has offered loads of help with the AEM issues and talked me through sorting that out. Has also supplied the CPS and cam sensors free of charge. Its the distance thats the issue and I wanted to try all the obvious things myself before having the conversation with Paul.

 

considering you have done most of the checks. i would first of all check the coolant sensor as that can play havoc with fuelling, then check fuel pressure.

 

Just put the car away and was thinking about the fuel pump, was going to take the top off the tank tomorrow and check its all ok, unfortunatly I dont have a spare pump to test or a fuel presure guage on the car which could make checking the pressuer difficult :( Good idea though and something I need to check.

 

Coolant sensor - would that be the one in the elbow or the one in the lower part of the rad? The one in the rad has been changed but I was under the impression thats something to do with the air con and the one in the elbow is the coolant sensor, is that correct?

Edited by T2 MSW (see edit history)
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Send it back to be fixed by the person thats done the rebuild and single install? Surely you should have had the car back in full working order? Not meaning to have a dig, i like Paul and he clearly knows what he is doing and turned out some top cars so why not send it back?

 

I have to agree, were none of these issue present when they did the 30 odd miles when the MOT was done? The car has issues the same day you picked it up, i would have sent it back, even on a tow truck.

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I have to agree, were none of these issue present when they did the 30 odd miles when the MOT was done? The car has issues the same day you picked it up, i would have sent it back, even on a tow truck.

 

I appreciate your comments but thats not the object of this thread, just after some input to try and get the issue resolve. Please dont take it the wrong way. Just want to get it resolved :)

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