223 replies to this topic

[DaveyC]

Misfire at 2000rpm I thought I'd start a new thread to condense all the information I've had so far on this issue from my LSJ throttle body thread and thanks to everyone who offered suggestions and help there. I've now just about run out of ideas. Symptom: when sitting out of gear or cruising steadily I got a consistent misfire at around 2000rpm. Gently increasing the revs causes it to go away. I've never had any misfires higher up the rev range. The car: it's a 2.2 that is supercharged. I'll cover the spec a little more later on. It started off as stage two on a standard engine with remapped ECU and VXT injectors, standard manifold and milltek cat and silencer. What I've tried: Engine - it's had a completely new bottom end, lower compression pistons, comp cams, forged rods, original cylinder head has been cleaned and valves replaced with supertech ones. In the process the timing chain was replaced and balancer shafts removed. Injectors - I've had the VXT injectors cleaned and flow tested and I've since replaced them with Siemens 650cc injectors. Spark plugs - it's had many sets of plugs, the three electrode kind as well as single electrode ones, I've tried a variety of different gaps from 1mm down to 0.5mm. Coil pack - it's had two different coil packs. Throttle body - thanks to nick I was able to try out his TB as well as the one currently on the car. Exhaust - on the suggestion that the cat might be blocked, I've removed it. Oxygen sensors - I've replaced both O2 sensors. Crank sensor - I have also replaced this. Fuel pump - I believe it is the standard pump, though this is confusing because the access hatch has been widened as per the guide on here. I cleaned the pump filter and refitted it. ECU - I've replaced this with one that has OBD tuner and had a number of base maps from Peter to try but there is only so much he can do from viewing data logs hundreds of miles away. Tuning - I've had the car on the rolling road with a very experienced tuner who tried everything tune based to stop the misfires, fuelling and ignition timing. Electrical noise - on the assumption that there might be some noise we've hooked up additional suppressors to the ECU power feeds. Earthing - when I took ownership of the car, the ECU case wasn't earthed, the earth strap between cam cover and cylinder head was also missing. I have since replaced these and checked all the earth points (chassis front, chassis rear and engine) I've also added an attritional earth point to the rear, thoroughly cleaned the existing earths, replaced the earth cables and run additional cables between the cylinder head and rear chassis earth. Nothing I've tried has made even a tiny bit of difference, does anyone have any other ideas?

[CocoPops]

Scan gauge or other obd reader plugged in?

[DaveyC]

I've had an OBD reader and laptop with Peter's OBD software and there are no codes.

[pete-r]

So you have the Dutch ecu map? If so do a log file and send it to Peter. Have you done a fuel learn? Again if not do one and smooth it before saving to the permanent ecu. I though I'd don't mine properly but I hadnt. Chill helped me set the car up and while I didn't have any issues like your having the car runs much smoother and cleaner now.

[Ormes]

Scan gauge or other obd reader plugged in?

Think the question was less about codes and more about the way having a scangauge plugged in with refresh rate too high causing issues.

[DaveyC]

Scan gauge or other obd reader plugged in?

Think the question was less about codes and more about the way having a scangauge plugged in with refresh rate too high causing issues.

Ahhh! It does it even with nothing plugged in.

[DaveyC]

So you have the Dutch ecu map? If so do a log file and send it to Peter. Have you done a fuel learn? Again if not do one and smooth it before saving to the permanent ecu. I though I'd don't mine properly but I hadnt. Chill helped me set the car up and while I didn't have any issues like your having the car runs much smoother and cleaner now.

Yes I do have a Dutch map. I'm on about my 5th map from Peter based on log files I've sent over to him. I've done several fuel learns but even holding the car on the rolling road at 2000rpm and gradually adjusting the fuelling and ignition specifically for the cell being used at the time does not get rid of the misfires. Peter and my tuner are now of the opinion that it is not a tune based problem.

[CHILL Gone DUTCH]

What condition have the plugs been in when you have removed them ?

[CHILL Gone DUTCH]

I would look closer at the fuel system Kinked fuel line Fuel filter (inline filter in engine bay ) And if all else fails change the pump Fuel regulator or the vacuum pipe to it from manifold could also be issue

Edited by CHILL Gone DUTCH, 03 May 2015 - 09:57 AM.

[Nev]

Cracked head possibly ?

[Kieran McC]

Does the eml or any faults occour at the same time as the misfire ?

[smiley]

Fuel pump - I believe it is the standard pump, though this is confusing because the access hatch has been widened as per the guide on here. I cleaned the pump filter and refitted it.  

 

By the sound of your specs, you're at stage 3 or higher. (which is dangerous area for a standard pump)

Lift that hatch and look what you have, and see if there are any damages to the hosing.

 

The hatch has been made for a reason. Somebody did something, and you'd better find out what exactly.

 

[DaveyC]

Does the eml or any faults occour at the same time as the misfire ?

 

No, no EML occurs and no codes are reported.

 

 

Fuel pump - I believe it is the standard pump, though this is confusing because the access hatch has been widened as per the guide on here. I cleaned the pump filter and refitted it.  

 

By the sound of your specs, you're at stage 3 or higher. (which is dangerous area for a standard pump)

Lift that hatch and look what you have, and see if there are any damages to the hosing.

 

The hatch has been made for a reason. Somebody did something, and you'd better find out what exactly.

 

 

 

Currently on the standard stage 2 pulley and lower than standard compression so the standard pump should be fine.

It will be replaced before I reduce the pulley size, as will the exhaust, but I'm trying not to throw money at something that is currently not working properly.

 

Googling the numbers on the side of the pump didn't return any relevant hits.

 

Surely the pump is either working or it isn't? It's always just pumping the same amount of fuel, if it can supply enough for full boost, why would it be causing a problem at 2000rpm and hardly any load? The same goes for the filter and send lines. Perhaps if the return line was kinked or regulator was dodgy it might be chucking in far too much/little fuel but on the rolling road we were getting reasonable AFRs through a wideband but still getting a misfire.

[smiley]

I can't remember who it was exactly on here (not so long ago), but also had weird problems, which were pump hose related.

 

Lifting the pump to take a look costs nothing, and by the huge list of all the other things you allready checked, this is what my gutt feeling is telling me.

 

The pump with number 25226034 / 0171-1 is oem (NA).

 

 

[CHILL Gone DUTCH]

Was chrisPduck he changed his pump and hoses within the housing all fine now

[CHILL Gone DUTCH]

http://www.vx220.org...for-help/page-4

[NickB787]

very strange this, wonder if it's worth hooking up a temp swirl pot just to check if it's starvation? I my old one here if you want to try.

[Arno]

You already changed/swapped a lot, so what remains of the original?

 

Did it have the misfire pre-SC conversion initially? I guess not?

 

If no then I'd tak a very good look at the state and quality of the loom modifications that have been done for the SC.

 

The 'left un-connected' grounds and such seem to indicate that the initial SC conversion was perhaps not done with too much attention to detal. Perhaps one of the injector wires is only so-so connected/extended..

 

Or scrounge up a different 'known good' harness and convert that for the SC and install on the car.

 

You'd need to hook up a scope or signal analyser to various lines, but it smells like an interference or bad connection issue that rears it's head at certain frequencies.

 

Bye, Arno.

[DaveyC]

You already changed/swapped a lot, so what remains of the original?

 

Did it have the misfire pre-SC conversion initially? I guess not?

 

If no then I'd tak a very good look at the state and quality of the loom modifications that have been done for the SC.

 

The 'left un-connected' grounds and such seem to indicate that the initial SC conversion was perhaps not done with too much attention to detal. Perhaps one of the injector wires is only so-so connected/extended..

 

Or scrounge up a different 'known good' harness and convert that for the SC and install on the car.

 

You'd need to hook up a scope or signal analyser to various lines, but it smells like an interference or bad connection issue that rears it's head at certain frequencies.

 

Bye, Arno.

 

This is the sort of thing I expect it to be.

 

I bought the car already converted and it has always had the problem during my ownership. The previous owner didn't do the conversion, I believe it was the chap before him.

 

Reckon it is worth getting an auto electrician to take a closer look at it? I can use a multimeter, but don't have access to a scope or know what to look for.

[DaveyC]

I can't remember who it was exactly on here (not so long ago), but also had weird problems, which were pump hose related.

 

Lifting the pump to take a look costs nothing, and by the huge list of all the other things you allready checked, this is what my gutt feeling is telling me.

 

The pump with number 25226034 / 0171-1 is oem (NA).

 

 

I've just had the pump out in the last hour, the number is:

25236034

0171-1

 

Any idea of what else to look for whilst I've got it apart? None of the internal hoses are visibly split or damaged.