Misfire and stumbles at around 4k rpm.

[IronMonkey]

Hey guys, Im having some problem with my rb25det. Car runs ok until it hits around 4k rpm, then it just starts popping,misfire, and stumbles. It have greddy intake manifold, q45 t-body, gt35r, 550cc, nismo fpr, and power fc for tuning, all running at 7psi. I checked the fuel pressure, and its right on. Changed out plugs to BKR7E. Timing is right at 15. I havent gotten the chance to check the resistance between the coilpacks yet though. Tach is right on as well, as I use power fc and r33 cluster. Any suggestions?

Also, has anybody tried putting series 1 coilpacks/ignitor on a series 2 motor?

[Shocker]

might be knocking and pulling timing on you. Who tuned the car? and what were the a/fs when they did it? Did the weather get cooler since the tune?

[Darius]

PFC does not pull timing like the stock ECU does. It will let you blow the thing sky high. You setup the MAF and injectors in the PFC, correct?

With it stumbling at 4000 rpm it sounds MAF related, but it is also where it starts to hit boost. Do you know what the AFRs are when this happens?

[mello88]

I would suggest boost leak or bad coilpack(s). You didn't address those in your post and they are easy to check for.

[Joe]

what MAF are you using?

and boost leak check the system

[eh?]

Post a data log , Verify plug gaps and verify pfc timing agrees with base timing.

[d356bud]

Also, has anybody tried putting series 1 coilpacks/ignitor on a series 2 motor?

Yes, I have and it works

[IronMonkey]

how was the wiring for the coilpacks conversion? im using a tune from a guy on datalogit group. also, my aem wideband is dead and i havent hooked up my lc-1 yet...

and by 4500rpm, i have already built full boost (wastegates opens up). i dont have this problem in 1st/2nd gear, but itll do that after i shift into 3rd....my laptop just took a dump....

ill check for boost leak this weekend.....
Modified by IronMonkey at 8:33 PM 1/30/2008

[Cameron]

Im having the same problem with my car.. Cept its on the KA. Iron Monkey you live in GA right? i think it may just be the colder weather.. cause i did a 100$ tune up on it today, New spark plugs, wires, new fuel filter, and when i took off the coil wire on the distributor, it was broke so i got a new distributor top, and then took it for a test drive and it still did it. i think its the cold weather.. cause whenever i get back pressure from my exhaust then step on the gas it like sputters. but it also could be a valve, cause ive been running the Single Cam pretty hard lately.. god i hope its not...

[d356bud]

The coil pack conversion is quite simple, just get the s1 coil packs, coil pack harness and a igniter chip with the plugs and your all set. just have the incoming signal from the ecu go to the base of each of the transistors on the igniter chip

[Cameron]

I know this Probably wont help you none, but i found out the problem on my KA. I was having similar problems, like when would gas it, whether it be at idle, or on a rev match on a down shift, air was getting into the Engine, but fuel was delayed, so it made my AFR go haywire, and it would pop, stutter, and go almost dead, until it realized that it needed fuel then it would rev up. When it first started happening, i thought up many scenarios. First I thought it was MAF Related, but then i realized that it wasnt, cause once it got past the fist couple thousand rpms, it revved up fine til redline. Then i thought i just got some bad gas or something. Then i filled up another tank and realized that wasnt the problem. Then i thought, well hey maybe it has to do with ignition! So i changed the Spark Plugs, Wires, and while i was changing them, i popped the Distributor cap off, and saw that the plug for the coil wire was roasted, and white powdery plastic everywhere. so i replaced the Cap, in hopes of it working. It Didnt Help.. Then I Replaced the Fuel Filter, took it for a test drive, and still no. So today i was all bummed, and started thinking that my baby was finally dying, and thought it was a Bad TPS, Bad Valve, because i have ran her hard lately, and i didnt want to admit to it, that its life was about to be over, so i blamed it on the weather , and even a vacuum leak. And today i was out piddling around with it, and was revving with the throttle Cable, and Noticed this little plug right here.

This plug for you:

This Plug for me:

it was wiggling around. So i pushed it down and held pressure on it, and revved it, and all of a sudden things cleared up. Pulled up on it a little bit, and things went back bad. So i Found the Problem, took it off, readjusted a little bit where it would stay plugged in. And now shes running fine and dandy, with a good $100 tune up. I knew the end of her life wasnt quite here yet!

So just for the sake of dumb luck, go out there and check that plug, wiggle it around and hold pressure on it, then rev it, see if it changes how its acting..

Cameron.

Sorry For the ThreadJack..