Misfire/bogging after SR swap

[PMRacing532]

:help Hi, I just got an SR swap (S13 redtop into S14 body) and have a few issues... Right after the swap was done, the car was running like sh*t - misfiring, stuttering, bogging in all gears and throughout the entire rpm range. My mechanic said it was the MAF and/or ECU and he ended up replacing the ECU and maybe the MAF too (not sure - he's out of town now so I can't ask him).

Anyways after that it ran a lot better, BUT was still misfiring in 4th and 5th gear from 4-5k rpm on the fwy. I brought the car back to the shop and they replaced the crank angle sensor. Ran a whole lot better for like 15 minutes.. then started misfiring again.. this time in 3rd and 4th gear, around 3-4k rpm...

This is getting to be really frustrating and annoying, especially since the ship is a 40 minute drive from my house. I will bring it back this weekend but I'm wondering if anyone has had a similar experience or has an idea of what I should have checked out.

Also... is a compression test result of 140-145 good? How about 135? I had 140-145 in all of my cylinders except #3 was around 135...

BTW I'm running a 3" turbo outlet, 3" downpipe but completely stock exhaust from the cat out.. I know this could contribute to some of the bogging but shouldn't cause the car to misfire right??? I should be getting a 3" catback exhaust very soon...

Thanks in advance for any insights, tips, or advice...

Danny95 240SX SR20DET

[180fan]

those look to be within spec. I would check the timing for your misfire. your exhaust might cause some pops

[C-Kwik]

Does it do this only under boost? Full throttle? Part throttle? Load? No load? Does it feel like you hit a rev limitier or does it just seem to rev up slower as if one piston is misfiring. Well need to be more specific to try and get closer to the answer.

[PMRacing532]

Thanx - Well they claimed to have checked the timing when they did the swap but I'll definately have them check it out again.. or do it myself if I have the time...

[PMRacing532]

Does it do this only under boost? Full throttle? Part throttle? Load? No load? Does it feel like you hit a rev limitier or does it just seem to rev up slower as if one piston is misfiring. Well need to be more specific to try and get closer to the answer.

At both full throttle and part throttle. If I punch it in 3rd gear starting from 2k rpm it will start boosting up and pull smoothly until about 3500, at which point it will start misfiring, and losing power (revs up slower). But as long as I keep stepping on it, it will slowly accelerate. No it does not feel like it's hitting the rev limiter.

If I slowly accelerate at partial throttle from 2k rpm and keep it steady at 3500 rpms it will start misfiring and stuttering badly.

By the way I'm getting about 15pmg (about 50% fwy/city driving)... stock everything except for 3" turbo outlet and 3" downpipe.

[reds14]

I would check the ignitor chip. My friend had the same problem with is s13. First it was the coil pack harness wires were switched, then we switched them. But it started running the same. Then we figured out it was a bad connection with the ignitor chip and now it runs perfect. Hopefully this helps.

[got2b240]

what kind of bad connection? How did you go about fixing it? I have a similiar problem. Any help would be greatly appreciated.

[xatracing]

did you replace your fuel pump? It does sound like timing. Be careful, if you rev high while engine is out of time it will cause you additional problems. compression seems a little low- healthy motors usually test at about 170- 180

[240_Keyy]

it sounds like either a timing or a MAFS issue to me.

however, like xatracing said, those compression numbers are hella low. I tested mine the other day and I had 180 across the board.

A drop of 40psi per cylinder can't be a good thing, does it smoke any or burn any oil?

[got2b240]

i fixed mine, TPS was way off and Fuel Pressure Regulator and 1 injector was bad

[PMRacing532]

it sounds like either a timing or a MAFS issue to me.

however, like xatracing said, those compression numbers are hella low. I tested mine the other day and I had 180 across the board.

A drop of 40psi per cylinder can't be a good thing, does it smoke any or burn any oil?

I've heard a lot of conflicting reports on compression numbers. Some say that 130-140 is normal but now I see you guys getting 170-180. Mine was 145 across the board with 130-135 in one cylinder. Do you have a blacktop or redtop? I have the redtop. Kinda worried now.. there's not much I can do about it though right? BTW my misfiring problems seem to have gone away. The shop replaced almost everything - coils, ignitor, crank angle sensor, and checked the timing. Car's running fine but I think a little slow... hopefully I'll see a big improvement when I get an exhuast...