# VRT Missfiring at 5500 rpms



## 98rzvr6 (Nov 12, 2005)

Hey guys i have a 92 gti vrt with stock bottom end, tt 288 cams, running e85, and lugtronic. The car runs amazing up until i get into boost and it pulls really hard up to 5200 rpms and then slowly bogs down, you can tell it starts to break up. Ive asked Kevin and hes been helping me but nothing has worked yet. I have purchased brand new Bosch wires, brand new ngk 5671a-9 plugs, tried gapping them at .25 amd .20 amd nothing worked. Changed out the coilpack with one that i know is in good condition with no help. Did a compression check, 120 in 4 cylinders and 125 in the other 2. Kevin suggested to do a compression check to see if the valves are bent or maybe cracked ringlands but nothing showed with the compression check. I changed the dwell time to 4 amd 4.5 and it did get better, it actually let me rev past 6k rpms bu its still breaking up. Anybody else got any other suggestions??


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## bonesaw (Aug 8, 2004)

Did you do a leak down test?


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## 98rzvr6 (Nov 12, 2005)

No not yet, that was going to be my next step if i didnt figure it out in couple of days.


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## 98rzvr6 (Nov 12, 2005)

How exactly do you do a leak down test? Correct me if im wrong but i think you're supposed to take the cams out, take out plugs, and hook up the tester on each cylinder and put air in it to see if it leaks, right?


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## BlownGinster (Jun 23, 2002)

Does it do this at all boost levels, or just when you turn up the wick?


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## 98rzvr6 (Nov 12, 2005)

Well right now i have it set at 12 and ive turned it up to 15 and still same thing no matter, pulls really really hard but then just starts to die out after 5200ish rpms and pretty much become a rev limiter at like 5800 or 6k rpms


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## 98rzvr6 (Nov 12, 2005)

And i should add, it doesnt lean out, the afrs are around 11.2 and dip a little bit to 10.5 or so but pretty much stay on the richer side a little bit


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## VEE-DUBBER (Nov 22, 2000)

I just went through something very similar. Over 5500rpm my compressor wheel was contacting the housing giving a misfire/studder sensation. Check your shaft play. Under 5500 it was fine.


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## MarcoVR6SC (May 3, 2003)

And if you lessen the boost, does it still ‘misfire’?

If it still does, then you may have sensor interference or a bad crank sensor, if not it may be valve float, did you change the valve springs? 

Does the engine riv freely past 6000rpm with no load(in neutral)?


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## 98rzvr6 (Nov 12, 2005)

The car does rev freely if no load is put on it. I have not tried with a smaller spring, im running wastegate pressure right now. Im also thinking jts valve float, i put some brand new autotech heavy duty valve springs in it last year, they literally maybe have a 2k miles on it tops. I just dont get it. I trued running some more grounds, didnt help


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## leebro61 (Nov 7, 2001)

I recently resolved crank sensor issues that showed up as ~5000 RPM misfires... I mentioned this in your other post a month or so ago... but I'll mention it again because I know you recently put a new short block in your car because of crank sensor/trigger wheel problems. Does your car REALLY rev smoothly in neutral? When my car was misfiring it felt much, much better in neutral (probably because you don't get the 'jolt' of the car missing when its driving), but it still wasn't clean. Do you have some videos of the car revving in neutral and/or some datalogs? Any crank sensor signal errors? I know how frustrating this was on my car, so hopefully you can get it resolved soon. :thumbup:


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## 98rzvr6 (Nov 12, 2005)

Well i added another short block in it with the same head i had last year in it so the trigger problem got fixed. This is really frustrating man, it seems to run really smooth up until the 5k mark, i have a bunch of logs but none of them have a trigger error at all.


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## radoman57 (Jan 16, 2007)

I have had lugtronic for a while now. Mine also seems not rev as high as it used to on chip tune but I'm getting closer to getting it cured.
It's all in the fueling. Take some fuel out of the 6k and higher on your map. Do some logs and try to get the higher range closer to the requested fuel
around 11.9 afr.


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## Wishing on a Vr (Feb 7, 2003)

What plugs are you using? I had the same issue. Fouled plugs, and a FPR that wasnt set properly was cause to my issues.


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## 98rzvr6 (Nov 12, 2005)

Im using NGK r5671A-9 amd they always look a little black when i take them out but not horrible i guess. I havent touched my for since last year, i set it last year and i havent touched it since


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## Wishing on a Vr (Feb 7, 2003)

For basic troubleshooting. I Disabled my launch control to make sure that it wasnt staying locked in. Have you tried that?


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## Wishing on a Vr (Feb 7, 2003)

Also make sure your tps is calibrated.


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## Yareka (Mar 5, 2002)

Based on the crank sensor theory, have your watched your rpm logs at that rpm to see if it drops out at all? And yeah 10.5 is a bit on the rich side and might be something to look into as well


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## 98rzvr6 (Nov 12, 2005)

Tps is calibrated. As far as the launch control theory, kevin did mention that he noticed that the channel 7 was flickering which was used for launch control and gas/e85 fuel trim so he disabled the gas part and i hooked up my launch control on a switch cause he thought maybe the wires were touching each other but still same thing. I just boufht some Msd coils so im gonna hook those up on thursday i believe so we will see. Thanks for all the suggestions guys, i really appreciate it. I ordered a brand new CHRA for my turbo so im gonna hook and the msd so hopefully we will an improvement. I havent tried completely disabling 2 step so i'll try that this week once i get everything


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## 98rzvr6 (Nov 12, 2005)

A little update guys, I added some NGK BRK7e plugs and I gapped them at .25 and it is definitely better, it seems to raise up to 6k now and above where it really starts to break up really bad, I upped the dwell time and it did help but definitely not enough. Any other ideas at all guys? im at like 12.0 now on the fueling so i am definitely good there.


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## 98rzvr6 (Nov 12, 2005)

Hey guys another update, i added my Msd coils and its still the same thing, it pulls great up to 6100ish and then just slowly dies off unfornately. Any more ideas at all guys?


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## leebro61 (Nov 7, 2001)

Can you screenshot and post datalogs? Can you flip the "trigger edge" in the ecu? It shouldnt take a perfect combination of fueling and ignition components to rev out to 7k. What im saying is, im not convinced you dont still have crank sensor issues.

Edit - do you have a resistor on your VR+ wire? If the VEMS crank signal circuitry is at all like MS that might be your issue. Has your car ever revved out cleanly with any of your previous setups?


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## MarcoVR6SC (May 3, 2003)

Yes could be that, I needed also a resistor in parallel over the VR sensor for my Pectel SQ6 ECU, the problem is that the voltage get's to high at high rpm's.

It's worth to try it out, not sure of the value anymore, but something in the range of 5K or a little less will probably to it.


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## 98rzvr6 (Nov 12, 2005)

leebro61 said:


> Can you screenshot and post datalogs? Can you flip the "trigger edge" in the ecu? It shouldnt take a perfect combination of fueling and ignition components to rev out to 7k. What im saying is, im not convinced you dont still have crank sensor issues.
> 
> Edit - do you have a resistor on your VR+ wire? If the VEMS crank signal circuitry is at all like MS that might be your issue. Has your car ever revved out cleanly with any of your previous setups?



It used to rev out find last year but then i had issues this year reving to 4k cause of trigger errors and the ecu would show trigger errors so i put a new used short block in it and that fixed that issue. I can pist a data log if you guys want me to or i can send you my log through email so you can see for yourself


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## 98rzvr6 (Nov 12, 2005)

And no, i do not have a resistor for my crank signal wiring. It is a custom built harness by Kevin and as far as i know, he doesnt add one to them


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## 98rzvr6 (Nov 12, 2005)

Just tried flipping the trigger edge to falling from rising, same thing. No trigger errors light never came on


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## 98rzvr6 (Nov 12, 2005)

Alright guys so I decided to take my head off because i had a spare one. Took it off and saw this 




So i took the lifter off and saw this little piece, I have no idea what it is, does anybody know what it is??? 





Nothing looks damaged on the valve or the lifter itself, any ideas at all guys what this is? 

That piece was on cylinder 4 but there was nothing on cylinder 2 that i found out of the ordinary so why does that cylinder look the same as cylinder 4? Im just going by the top of the piston.


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## 98rzvr6 (Nov 12, 2005)

So upon further review, that little piece is from the lifter, if you look close enough at the pics, you can see it. Im just still curious about cylinder 2, any ideas there guys? Im just concerned cause it looks like the problem cylinder 4


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## 98rzvr6 (Nov 12, 2005)

I cant effin believe it but I ended up replacing all 6 lifter on the intake side just to be on the safe side, drove it around and its still doing the same effin thing, COMEEEE ONNNNNNN


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## vergessen wir es (May 12, 2010)

burning much oil? check/replace stem seals just now? losing coolant? new head gasket? 2 and 4 being so dirty and the rest so clean, is spark getting knocked out? w/m is off or on?


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## vr6swap (Aug 17, 2001)

98rzvr6 said:


> I cant effin believe it but I ended up replacing all 6 lifter on the intake side just to be on the safe side, drove it around and its still doing the same effin thing, COMEEEE ONNNNNNN


Did you ever do a leakdown? 

From looking at that lifter I'm wondering if you didn't tag a valve or two. Although it does seem like that would be more evident at idle than at one million RPM or whatever.


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## 98rzvr6 (Nov 12, 2005)

I had a machine shop check out the valves and they said they looked good, the head seems to look in great condition. I checked compression again and it looked really good


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## leebro61 (Nov 7, 2001)

vergessen wir es said:


> w/m is off or on?


This is a good point. Run your setup in the absolute SIMPLEST POSSIBLE configuration until you can rev out cleanly, then start adding features back one at a time.

W/M OFF. Disable any kind of launch control/antilag or software based rev limiter. Switch back to waste spark if you are currently running sequential ignition or fuel. Basically, try to dumb the ecu down to only the basic features needed to run the car.


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## 98rzvr6 (Nov 12, 2005)

What is w/m? Water meth? I dont even run that. Fuel trim is disabled and so is launch control


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## leebro61 (Nov 7, 2001)

98rzvr6 said:


> What is w/m? Water meth? I dont even run that. Fuel trim is disabled and so is launch control


Yeah, water/meth. By fuel trim off you mean that you are running in open loop full time (no o2 sensor feedback), correct? Are you running sequential or waste spark?

Definitely post a screen shot of a datalog with the basics (Throttle position, map, afr, rpm, ignition timing, etc. etc.).


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## 98rzvr6 (Nov 12, 2005)

Here are some pics, i pretty much took the pics where it starts to break apart


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## 98rzvr6 (Nov 12, 2005)

Here is a video, NOW i DO REALIZE ITS ON THE RICHER SIDE, I tried upping the fuel pressure and I didnt adjust my tune but the car is acting the same way so I was just trying to see if it would help at all or hurt.


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## 98rzvr6 (Nov 12, 2005)

Hey guys, so i changed out my head with a spare head i had and its still the same damn thing 😡😡😡. Any other ideas guys??


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## VEE-DUBBER (Nov 22, 2000)

You still haven't checked to see if the compressor wheel is contacting the housing. I thought "no way" too. Felt exactly like misfiring.


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## 98rzvr6 (Nov 12, 2005)

It is not touching, ive had the housing off dozen of times now and everything is in good shape


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