R32 Gtr Stumbling On Acceleration

[ZED X]

Hey Guys,

I'm just fishing for some ideas at this point. Starting to run out of ideas myself on what could cause this issue.

Abit of a background.

I've owned the car for around 4 years now, up until around 8 months ago it had been pushing around ~250awkw at ~14psi on a set of standard twins, tuned by turbo tune ~3 years ago. Around the same time i started noticing that on hard acceleration the blow off valves would actuate whilst under load and on full throttle. Seemed to come and and go i only noticed this a couple of times and thought nothing of it. When this happens there is a huge jerking motion seeming like a miss fire however only really seems to happen when on boost.

If i attempt to drive around off boost, everything is fine and normal. As soon as it begins building around ~5 PSI upward this issue occurs. If i attempt to hold the throttle around half way to maintain ~5>6psi the blow off valves sound as if they are shuffling and i fail to maintain forward momentum. Similar to what you might hear when under load (ie up hill) partial throttle release.

This is now occurring all the time. I'm also running a wide band to monitor AFR's whilst this is occurring however im seeing around 14-15 on low throttle which seems to me to be a little bit lean considering this is using a stock map. Generally the japs tended to run these fairly rich? no?

I should note that up until a couple of months ago, this would only occur whilst under load. However its now developed on idle, when free reving up to around ~3000rpm.

To me that seems to rule out an ignition fault, as AFR's would be lower if there was unburnt fuel being expelled? However ive also tried the following:

- re flashed my ECU to a stock/base map with the help of Pete from Nistune

- Replaced plugs and gapped to 0.8 - BCPR6ES also tested with a set of BCPR7ES.

- Replaced Coil pack harness with a brand new item. The original had some damaged clips.

- Tested for air leaks, there was a MASSIVE one on the BOV return pipe. I've since repaired this and no more leaks occurring.

- Replaced CAS with one that is known to work.

- Injected a large amount of injector cleaner into the top of the fuel filter just before the fuel rail.

- Replaced AFM's & also re soldered.

- Ran a Fuel pressure gauge just after the filter. I'm getting around ~40 whilst priming and ~35 whilst engine idle. I also drove up and down my driveway with the bonnet off and it sits around the same under load.

- Pulled the fuel pump (standard) and checked for any crap in the fuel tank. Couldn't see anything there.

- Pulled both BOV's apart and can confirm they are both working, both seals are fine and springs move freely.

- Replace standard twins with a set of GT2860-7.

I haven't tested another set of coil packs yet, kind of hesitant to throw more money at this until i know what the cause is. I haven't been able to find a spare set i could borrow to eliminate this either..

Ive got a fairly standard 32R with the following:

Apexi Power Intake

3.5" Exhaust

HKS Front Pipes

Larger Front Mount Inter-cooler (specs unknown)

HKS Adjustable Cam Gears

Nistune

GT2860-7 (Recently installed)

I'll see if i can get a recording of this tonight but any suggestions would be welcome!

[scotty nm35]

If the BOV's are opening on boost I would be checking the vac hose that actuates them. There should be boost pressure holding them shut.

[R.3.2.G.T.R]

what bout temporarily blanking off the pipe connecting to the bovs and see if it behaves the same way?

[Ben C34]

As Scott said something seems wrong with the bovs.

Also light throttle is meat to be 14.7 to 1, so nothing to worry about there. The stock maps run rich when on boost.

Are there any error codes on the ecu?

How hard did you load it up in your driveway to check fuel pressure? Would have to be a pretty serious driveway to be able to rule out fuel pressure as a problem.

It seems like replacing the fuel pump might help as it's something you haven't done.

I'm not sure how well injector cleaner works, but by putting it in the fuel rail is kinda a waste of time, as once the pump primes it would have pumped it all back to the tank.

So actually cleaning the injectors would be the better option.

Looks like you have done a lot and must be frustrating.

I would look at your valve clearances also as they will cause serious issues if out of spec.

All the best

[Lrs94]

I had similar problem, car would run fine, on low boost around 7psi right the way up to redline, but above 14psi, the the whole car would shake violently and hard back and forth, and would not go past 7psi. Like I hit a rev limit/ speed limiter. I was sure it was not a boost leak as both my gauges read 7psi, I was sure it would be my ignition system breaking down somewhere along the line or fuel system. I plugged laptop in ecu, and everything was working fine, coil packs checked out fine, all my sensors worked fine on laptop.

In the end it turned out one of the welds my Intercooler had a big split 150 mm, got it welded up, runs like new again. Am still puzzled to why both of my boost gauges read 7 psi, when I had such a huge leak

Hope that can be of some help.

[ZED X]

Thanks for the feedback guys.

I've checked the coilpacks again, they are not arking from beneath the coilpack boot. So they seem ok... However i may go further and check the loom as its not a factory one. One of those justjap copies, ive got the old loom somewhere but the clips are all "crispy" ie falling apart. It was replace along time ago way before this issue presented itself.

what bout temporarily blanking off the pipe connecting to the bovs and see if it behaves the same way?

I honestly cant believe its the BOV's to be honest, i've blocked them off completely in the past and no change overall..

As Scott said something seems wrong with the bovs.

Also light throttle is meat to be 14.7 to 1, so nothing to worry about there. The stock maps run rich when on boost.



Are there any error codes on the ecu?

How hard did you load it up in your driveway to check fuel pressure? Would have to be a pretty serious driveway to be able to rule out fuel pressure as a problem.



It seems like replacing the fuel pump might help as it's something you haven't done.


I'm not sure how well injector cleaner works, but by putting it in the fuel rail is kinda a waste of time, as once the pump primes it would have pumped it all back to the tank.
So actually cleaning the injectors would be the better option.



Looks like you have done a lot and must be frustrating.
I would look at your valve clearances also as they will cause serious issues if out of spec.


All the best

I've checked for codes using my ECUTalk, nothing has come up yet. However i'll check the ECU manually as i've been told that not all errors will appear via consult. Good call Ben thanks

Yep pretty frustrating, I've been tempted to take it to a proper mechanic in the past to just a professional opinion. However its completely undrivable and to be honest i wouldn't risk driving it in its current state. Dont really want a rod through the block.

Haha.. its actually not a very long drive way, i really only got upto maybe 5000RPM in first then hard on the brakes. Had no other way to do this as unregistered... The gauge has a max reading pin which can be reset.

I've wanted to clean the injectors properly, just waiting on a new set of orings to arrive. As it doesn't look like they have ever been removed. Assuming many of them will perish on removal.

I had similar problem, car would run fine, on low boost around 7psi right the way up to redline, but above 14psi, the the whole car would shake violently and hard back and forth, and would not go past 7psi. Like I hit a rev limit/ speed limiter. I was sure it was not a boost leak as both my gauges read 7psi, I was sure it would be my ignition system breaking down somewhere along the line or fuel system. I plugged laptop in ecu, and everything was working fine, coil packs checked out fine, all my sensors worked fine on laptop.

In the end it turned out one of the welds my Intercooler had a big split 150 mm, got it welded up, runs like new again. Am still puzzled to why both of my boost gauges read 7 psi, when I had such a huge leak

Hope that can be of some help.

Hmm interesting, i did hit a parking cone a couple of years ago. Pushed the intercooler in abit. However i sealed it up with resin and it held around.. 40PSI without bursting. So i'dd say its all good!

Yea actually now that you mention it.. that's actually what it feels like It's as if im hitting rev limit but of course im not..

Mines much worse then what you've described though. It's so bad that i had to roll down my street in neutral once because any application of the throttle would cause this extreme misfire.

[Sustained Loss Of Traction]

I pulled my Afms out at one stage when my R34 was playing up, saw the thread on soldering, opened them up. To my great satisfaction there were dry joints, thought to myself "yip, Nailed it". Anyway, soldering it didn't fix the stumbling issues I was having while driving. To cut a long story short. Sometimes AFMs are stuffed, sometimes intermittently. Be careful of swapping another used set in because the replacement set might be even older than the ones you are taking out. Could it still be the AFMs? Im running a map sensor now because I got driven insane by AFMs.

[JDM33R]

The same thing happened to me. This might sound ridiculous but

I replaced my turbos with N1 upgrades and i forgot to take out a rag that i had used to plug up the intake pipes with (to stop dust getting down there) When i had finished replacing the turbos the car ran 1 bar boost for about 2 weeks.

Then one day on my way to work i couldn't boost it past 10 psi. Then the next day Max psi was around 5-6psi and i got massive BOV shuffle on load.

It was like that for 3 months before i figured out the rag had made it down to the intercooler and was blocking the air from the turbos.

If that doesn't work for you Vacuum test your waste gates.

That is all. Lol!

[ZED X]

I'll admit i thought i had fixed this after re soldering my AFM's but alas continues.

The same thing happened to me. This might sound ridiculous but

I replaced my turbos with N1 upgrades and i forgot to take out a rag that i had used to plug up the intake pipes with (to stop dust getting down there) When i had finished replacing the turbos the car ran 1 bar boost for about 2 weeks.

Then one day on my way to work i couldn't boost it past 10 psi. Then the next day Max psi was around 5-6psi and i got massive BOV shuffle on load.

It was like that for 3 months before i figured out the rag had made it down to the intercooler and was blocking the air from the turbos.

If that doesn't work for you Vacuum test your waste gates.

That is all. Lol!

I did think this might be the cause, however i've pulled all of the piping off on the turbo side, nothing found.

I've checked my coilpacks over the weekend. I'm seeing some leakage on 5/6 of them at extreme distances from ground. So cleaned the boots and bottom of the coilpacks with an electrical circuit board cleaner, hammered them with a wirebrush and covered them with an RTV Silicone (just the base of the coilpack around the boot)

Tested 3/6 of them (the others are still drying) much better so far, arking down to the ground plate as opposed to leaking onto the coilpack bracket.

Test:

http://youtu.be/fwxKhTM_dKE

Looks much better now, whether or not this was the cause. However i can confirm that at a gap of around 15mm (from the tip of the plug) the coilpacks would ark from directly between the coil boot/bottom of the coilpack across to the mounting bracket. Now im seeing no leakage at around 25mm distance.

I guess we shall see..

Also pulled the FMIC off completely and pressure tested it to around 30 PSI it was holding perfectly. I didnt have any leakage at all and i left it charged for 30 mins..

Tested the rest of the piping turbo side and there is a small drop in pressure around 1psi per second. So the same as the last time i checked.

[JDM33R]

Either coil packs or O2 sensors. Try unplugging an O2 sensor 1 at a time and taking it for a spin. Could be doing something weird.

[XGTRX]

I agree with the 2nd post Scotty. A vac line...BOV not working correctly therefore air running back to your afms causing a rich mixture. You will probably be getting blow off and turbo shuffle sounds at the same time.. good luck

[ZED X]

I agree with the 2nd post Scotty. A vac line...BOV not working correctly therefore air running back to your afms causing a rich mixture. You will probably be getting blow off and turbo shuffle sounds at the same time.. good luck

Thats pretty much exactly what its doing.

I was mucking around replacing the fuel filter around the same time as this occurred. Pretty sure the BOV Vac line joins beneath the intake manifold yea? Possible it may have been pulled on.

I'll check that out tonight

Either coil packs or O2 sensors. Try unplugging an O2 sensor 1 at a time and taking it for a spin. Could be doing something weird.

Yea already tried O2's, i disconnected them completely with no change. To be honest i cant see how this could be the cause. The O2 sensor reading is irrelevant under acceleration anyway.

Still waiting for the silicone to dry and ill see if the "Repaired" coil packs fix the issue.

Thanks for the input

[XGTRX]

Yep underneath the intake plenum, but check the whole line to be sure, they are fairly old. Good luck.

[Emrarrr]

I am having a similar problem at the moment, misfires under boost. When was your timing belt changed? Do you hear any tapping coming from the timing belt cover when idling? Just a thought! Also could the BOV be stuck open? Cylinder pressure? Boost controller? My car improved heaps since rerouting some vac lines to BOV, fixing some shitty hoses, removing crappy manual boost tee and changing AFM. I'm going to change the coil packs tonight but if that fails I am going to look into getting the timing belt done as there is a bit of a tap and it's coming up to change time!

Hope you sort it soon

[ZED X]

Yep underneath the intake plenum, but check the whole line to be sure, they are fairly old. Good luck.

Took a look the other night, had to pull the fuel filter and pressure gauge out of the way. However it looks fine as far as i can tell. I blocked off the BOV end and pushed ~40psi through it and i couldnt hear any leaks

Thanks for the suggestion though, man its a pain in the arse to get your hands under the intake side! Need smaller hands..

I am having a similar problem at the moment, misfires under boost. When was your timing belt changed? Do you hear any tapping coming from the timing belt cover when idling? Just a thought! Also could the BOV be stuck open? Cylinder pressure? Boost controller? My car improved heaps since rerouting some vac lines to BOV, fixing some shitty hoses, removing crappy manual boost tee and changing AFM. I'm going to change the coil packs tonight but if that fails I am going to look into getting the timing belt done as there is a bit of a tap and it's coming up to change time!

Hope you sort it soon

I changed the belt/pump/tensioner etc around 15,000km ago myself. The belt did make a whining noise initially but i suspect it was over tensioned. I backed it off abit around 5000km ago and haven't heard that since.

I'm thinking i may also relocate my EBC Actuator as its in the factory position next to the fuse box. Then the vac lines run beneath the intake manifold and around the back of the engine across to the turbos. I did see some boost creep initially when it was tuned but worked around this by setting the warning to -2psi and it was ok.

Thinking i might put this on the turbo side to reduce some of the lines running across.

Anyway appears this was coils after all. Strange as after coating all 6 i wasn't seeing any leaks. However the issue was still present under load. So the top of the coils must have had some small micro-fractures.

i just went out and bought a set of YJ to replace my OEM ones. Seems to have cleared up for now.

Managed to get my hands on a timing light, seems timing was correctly set. Though really strange as the CAS is in the 100% anti clockwise position for 15deg tdc? That cant be right?

Well it seems drivable for now, so at least i can get it to a workshop.

Thanks for all of your help guys really appreciate it!

[Ben C34]

When you set the timing you need to disconnect the tps and use a lead in between a coil and the plug.

The loop sucks and can cause issues.

[ZED X]

When you set the timing you need to disconnect the tps and use a lead in between a coil and the plug.

The loop sucks and can cause issues.

Thank you sir! I had heard of this technique but hadn't realized this was preferred. I had no idea this would give false readings it would certainly explain some things.

Interestingly though i'dd borrowed a spare CAS from Abe last year to rule out my cas being a faulty. His could be set much closer to the middle to obtain ~20deg BTDC

Appears my exhaust cam has been advanced ~5deg when it was previously tuned by turbo tune. I'll set this back to 0deg and then set base timing using the method in the FSM and see that improves things.

Thanks for the tip!

[GH05T]

is your fuel pump noisey? could be on its way out and dropping fuel pressure, if you have already hardwired it in i would consider replacing it anyway.

[Burger]

Slightly old thread.

[GH05T]

Oh, not sure why it popped up on my feed.