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211 Posts
Discussion Starter · #1 ·
Ok guys Im still having issues and its at that point where its now seriously pissing me right off!!!

I will start at the beginning so you all know whats happening and what I have tried.

Setup is fairly heavily modified R32 GTR with Z32 maf's, Single Turbo, 720's Cams, Pulleys, Remapped ECU etc

The car has run great since getting her and I have never had any issues other than the sticky wastegate.

One day driving to Fife from Glasgow I had been stuck in slow moving traffic and as it cleared I began speeding back up to sit at 60-70mph on the motorway. I noticed the car felt odd which it didnt before the heavy traffic.

At first I thought maybe the slow moving and start stop had coked up the iridium plugs so gave her a blast and she seemed to boost fine and pull hard as ever.

As I slowed back to cruising speed and at about 3000 rpm again it felt a little rough and each time I lifted then accelerated again it would pop and bang a fair bit then still feel lumpy trying to stay at part throttle.

This continued and through varying the throttle I determined that it was actually misfiring between about 2000 rpm and 3600ish rpm

I decided to just try and keep moving as it wasnt a good place to be pulling over. As I got near the services I hit a bump in the road and all of a sudden the mis vanished !

It never came back again at all the rest of the way to fife. It didnt come back whilst I was there over the weekend and didnt come back on the route back to Glasgow.

I used the car daily for the next few weeks and still no issues at all.

Just last weekend I done the Glasgow to fife trip again , guess what.... slow moving traffic as always then when it cleared I started to accelerate and..... misfire is back !!!

I tried varying speed but again between 2000 and 3600ish rpm missing and pops and bangs etc etc. This time though even after deliberatly hitting the same bump on the road the mis did not clear.

At this point I thought possibly the plugs were shafted so the following day I went to get new ones.

Stuck in new plugs, fired her up, increased the revs to just over 2000 and it was missing again.

I then checked all the coilpacks were secure and looked in good nick, still no joy.

I then removed and cleaned the MAF's, Still no joy

I then continuity tested the ignition loom going from ignitor to coilpacks, all checked out fine.

Tried wiggling various plugs and connectors to no avail.

SO I thought possibly I had dropped a coilpack ?

New packs arrived today which were second hand but known to be working. Fitted them but still a mis between 2000 and 3600 rpm!!!!!

I am really losing the rag.

If you hold it at around 2000 rpm where it starts to mis and unplug either coilpack 1 or 2 the misfire sounds the same indicating its cylinders 1 and 2 that are not firing properly.

If you keep the revs the same and unplug coils 3 or 4 or 5 or 6 the mis gets worse, indicating that those cylinders ARE firing.

The weird thing though is that if you do that same test at Idle unplugging any coilpack makes the car misfire. Kinda indicating that there all working !!!

Its ONLY when your between 2000 and 3600 rpm that the engine starts to mis, as soon as you get past it revs perfectly and nice and smoothly producing loads of boost as always !!

It uses no oil, always starts easily and has good even compression over all 6 cylinders. Theres no cooling issues or water loss etc and the engine doesnt breath heavy at all either.

I hope someone can shed some light on what may be the issue here.

Im running out of Ideas. Is it possible the ignitor has gone faulty ?

What are the symptoms of a faulty MAF ? I popped the MAF covers off tonight and they dont look like theres any dry solder joints etc, continuity is good between the plug and the board on both maf's too.

Please please please help me as I currently cant drive it due to it being so lumpy at the revs its at !

P.S if anyone local to glasgow has a Z32 MAF I can borrow to try checking incase one of mine has died then I would be very very grateful ! It would only take 5 mins to check.

1,883 Posts
Do you have a wideband in your car? Or one you can borrow, see what happens to the afr during the misfire. It will tell you if it is a ignition or fueling problem.

Do you still have the fuelcanister? If i remember correctly, it connects to the butterflys on cylinder 1+2, it could be sucking in excess fuel. Just a thought.

It could also be the injectors, if you can get hold of a stethoscope, you can listen to the clicking noise at that rpm (or just a long thin screwdriver and put your ear to it), and see if there is a difference on the 1+2 cylinder injectors then to the rest of them at that certain rpm.


211 Posts
Discussion Starter · #3 ·
I have one yes, not checked that yet though however I will tomorrow.

I do still have the fuel canister pish too, Ill check that.

I dont think it will be the injectors as there not very old and have been working perfectly until now. Also the fact that all 6 plugs are the same colouration would tend to imply its deffo not fuel related as far as injectors are concerned as normally you would see a variation.

Are we saying if the AFR turns out to be lean its an ignition issue and if rich its a fuel issue ?

121 Posts

my r33 gtr developed a misfire / hiccup around 3k revs off boost ever since had apexi l-jetro fitted? original ecu car ran sweet Thinking of reverting back to std ecu?
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