PaintItBlack

To start,

I have a 94 ex z6 bottom end.. y8 head... web stage 2 cam ported and polished... arp rod bolts and head studs, obd2 dis housing, with obd 1 internals. fresh rebuild... running a converted and chipped po6.. had msd on it with external coil... ran fine after everything was completed... 2 weeks later went out to start my car and now it wont rev over 3500 rpm... acts like it hits a rev limiter... changed msd boxes... didnt change... went back to stock honda ignition... didnt change.. have brand new ngk wires, cap, rotor, etc....thought maybe fuel pressure reg... changed it.. didnt help. i have a cel but when i try the jumper... my cel wont flash... but the srs light flashes constantly... possible bad ecu? also have erratic idle.... any help would be great

thanks

Former User

Likely a bad ECU or a short in the CEL/service connector circuit.

PaintItBlack

would running no o2 sensor have that effect on the ecu's adjustments or is it just pretty much doing what its told since its an obd1 ecu

angel_i

You need the primary(before the cat. conv.) oxygen sensor for it to run above 3500.

killa4lyfe

did it go above 3500 after u swapped?.. or did it do it later on..if it did it right after check your thermostat sensor and ur oil pressure sensor (under your vtec solenoid) try to switch it and see what happens because they are the same i believe. I did my y8 swap in my 98 coupe and i mixed those 2 and it didnt go past 5500 rpm. put them back and it goes all the way to 7 now. goodluck with it man hope u find out wuhs wrong.

trustdestruction

Had the same problem, it was because I messed up my ECU. You can't go over 3.5k because you're in limp mode. I replaced my ECU and everything went back to normal.

PaintItBlack

everything that im being told seems to be pointing to the ecu... and yea it cranked up and ran great went all the way to the 7200 rpm rev limit...no idle problems or anything.... then about 2 weeks later went out to crank it up and i couldnt rev over 3500rpm.... ive got someone letting me borrow a stock p28 today to test with.... ill repost later and let everyone know how that goes

PaintItBlack

and as far as the o2 sensor goes... im running a jg edelbrock tri y header and a test pipe... i have no place to put an o2 sensor.... so when we chipped the po6 we tried to compensate for running without the o2

trustdestruction

What you should do is get an O2 bung welded into the header.

If you really don't want to do that to that header, what you can do is since you have a test pipe you can get an O2 bung (if there's not already one there... they usually have one) welded into the test pipe and get an O2 sensor wire harness extension from Password:JDM and put the O2 sensor in the test pipe.

I would definitely consider either of these if I were you, running without an O2 sensor is not good.

Former User

No, but you should install an O2 sensor, as mentioned by others.

PaintItBlack

ok so i found out what my problem was.... bad chip in the po6. i removed the red jumper just above the chip to revert it back to a stock po6 map...runs fine....no vtec but will go over 3500 rpm without trouble.... thanks for all the input

trustdestruction

Ah, that's exactly what happened to me. I messed up the area of the board where the chip goes.
Removed the jumper and it worked, but I got a new ECU anyway. Sold the old one to someone else (I told them about the problem and that it will only work on the stock map).

PaintItBlack

yea im sourcing a p28 from a buddy of mine....we are going to chip it and hope for the best...