still having cut out problem

[twisted99s10]

i have an 89 s13 with a s1 rb25 swapped in. i have a walbro 255 with a z31 fuel filter. i have a front mount intercooler, and a 3 inch downpipe and straight back 3" exhaust.

at around 5000 rpm the engine breaks up and i get clouds of black smoke out the exhaust. so i know its not a fuel cut. this leads me to believe it is maf or ignition related. the timing is set to 15* off top dead center. the ignition chip, and all of the coil packs pass the ohm tests. the spark plugs are ngk iridiums with a 6 heat range, and gapped to .80. i cleaned the maf with some spray contact cleaner today, and it didnt make a difference. i adjusted the tps into place. .45 when closed 4.5 at WOT. no noticeable difference. i am out of ideas. if any one has any ideas on how to fix this so i can enjoy my rb swap i would be eternally grateful.

thank you so much in advance.

[Kansei240sx]

Try coating your coil packs with flexane 94 hardening agent, you might be getting coil pack bleed off into the head causing a stutter or hesitation in that RPM range.

Check for POST maf air flow leaks, make sure your knock sensors are torqued properly and have a good connection.

Make sure the Coolant Cylinder temperature sensor has a good range reading and is corrosion free on its connector.

If all else fails, and ITS a long shot, but you might try balancing your front tires as well. Some vehicles have tires that go out of balance and the resonant frequency of the tire vibration is almost the same as a engine ping or knock and can cause a random multiple misfire and retard timing and cause it to run rich in a one trip detection logic. I work at Toyota and this happens more frequently on the 2GR-FE motors as well.

[twisted99s10]

thank you so much for the ideas. i'll give them a shot as soon as i get otu of work tomorrow and post up the results.

[a31nismo]

probly stock ecu i heard they do this on the 25 u need a chip

[Kansei240sx]

probly stock ecu i heard they do this on the 25 u need a chip

Thats not quite how it works.

[twisted99s10]

it is the stock ecu... but its also just a stock motor with no real power adders. i wouldnt think i would need a chip to run the motor in stock form?

[spikee306]

i had the same cutting out problem myself at about 5000 rpm. i did a lot of checks and it just came out to be a restriction in my intake after the MAF but before the turbo. didn't realize it before this, but my flexible intake pipe was a bit kinked. so the computer was seeing an amount of air at the maf, but that amount of air wasn't making it to the intake manifold because of the restriction after the maf. a good thing to do is go through and make sure you don't have any restrictions through out your piping and make sure you don't have any boost leaks. the best way to do that is to pressure check your all your piping and intercooler. good luck!

[bmadd2402]

search for rich and retard. also try to see what your maf voltage is when the stutter happens. when you open up the 25 with the stock ecu with stuff like intake, exhaust, fmic, some dont like it too much. Rich and retard.

[a31nismo]

have u had this motor runin proply before, how much boost u pulln

[twisted99s10]

i'll give all of these a shot tonight when i get out of work. i am running the stock 7psi, and no i have never had it run correctly.

[DustinZ]

I have the same issue going on with one of my cars. I cranked it up in the dark with the coil pack cover off and it looked like christmas lights. I have recoated the coil packs but havent had a chance to check it out from there.

Dustinz

[twisted99s10]

this is an ooold thread, but figured i would update it for search purposes. For what ever reason it needed to be slightly tuned. i leaned it out with an safc. later i swapped over to a q45 maf and it runs perfectly with no tune.