thought it was a bad MAF but...

[HYBRIDxS13]

i've tried researching already but here is my problem...

a couple days ago my 89 240sx hatch w/ a sr20det red top would not idle with the MAF plugged. it would die unless i gave it some gas but even then it would idle like crap and would sputter and spit black smoke out of the exhaust when i tried to rev it up.

i had to unplug the MAF to make it idle normally. i couldn't rev it pass 2500 rpm (safe mode kicking in i believe) and had to drive it like that on side street all the way home for about 15 miles.

so after some research i thought it was a bad MAF. so i picked up an extra MAF that my friend had and it acted the same. i then double checked the MAF wiring where it was lengthened. it all looked ok. i then disconnected the battery to try resetting the ECU.

after about an hour w/ the battery disconnected, i reconnected it and tried starting it w/ the MAF plugged. now it seems to idle ok but i still can't go pass 2500 rpm. running as if its still in safe mode even with the MAF plugged in.

so what is it now? bad injector, fuel pump, ECU, etc. did driving it for about 15 miles in safe mode mess something else up?

[SRdave240]

So you are saying it idles OK now? but won't rev over 2500?

Check your ECU for codes then reset it via the small philips head on the side instead of just unpluging it..

[HYBRIDxS13]

i tried checking for codes on the ECU but the LED doesn't flash or anything. am i even checking for codes correctly? this is what i did...

i put the key on the ON position. i then located a plastic philip screw on the side of the ECU. i turned it a few times COUNTER clockise then a few time CLOCKWISE. i then looked at what looks like the LED through a little oval circle on the same side of the ECU where the screw was. no red flashes or anything. i also tried this with the key on the accessory position.

did i check for codes correctly? does no LED flashes mean the ECU had no codes to report or is my ECU bad?

[SRdave240]

no - turn it clockwise all the way. Hold for 2 seconds then turn it back CCW all the way. Then the LED will flash your codes. 55 means everything is OK.

[HYBRIDxS13]

ok i will do that... but am i turning the correct screw? it looks like a flat plastic philip head that u have to access through a hole on the side of the ECU. when i was turning it earlier it just kept turning and turning. felt like it had no end clockwise or counter-clockwise. which screw is it exactly?

thanks for tryin to help!

[HYBRIDxS13]

well i tried again. and that 1 screw i mentioned above is the only one i can find. still no LED flashes. so do i have to get a new ECU now? it seems to idle and start up fine still... just can't get over 2500rpm. the ECU must still be thinking it has to operate in safe mode i'm assuming.

any other suggestions or help please?

[NY S13 SR]

Check your MAF wiring again, I've never seen an ECU stuck in limp mode. 99% of the time if you can't rev over 2500 it is the MAF or MAF wiring.

Use a multimeter to check continuity from MAF wires to ECU pin, and also check from all wires to ground - only one should be grounded.

__________________Jeff Hheavythrottle.com

[180fan]

Yes, it's most likely the MAFS or MAFS wiring. If you could rev past 2500, then you're in the same boat as I am.

[SRdave240]

I'd swap ECU's witha friend and see what happens. Maybe your LED is bad but I doubt it. You might need a new ECU.

[Luke]

I had the same problem as you, i had switched the mafs and checked my extensions. I found the problem when I started following the harness back to the firewall. The white wire and black wire were cut by one of those ziptie things that hold the harness to the body of the car. Soldered those together and she started running. 2-3 weeks lost to figure that out, check the wiring again.

[unfrgivn]

Try flipping your mafs plug upside down. I had the exact same problem.