sr20 runs, but big problems

[driftin'180]

ok guys i just swaped and s13 blacktop into my 1990 240. i got everything wired up and the motor starts right up and runs most of the time. it has an extremely rough idle, it sputters when it starts up then spikes up to about 2500 and falls to about 1k-1500 and it sounds like a harley (i installed a and exhaust 3 inch from the turbo back and no cat so its gonna be pretty loud). it sorta responds when u give it throttle but i cant get it to rev past 3000. the motor also shakes like crazy, and sometimes there is some misfiring. ii think it could be timing but im not sure and don't realy want to take the radiator out and go throgh all that if i don't have to. also i know the inabilty to rev past 3k can be from the maf but i checked and rechecked the wiring and i did use the shielded stuff from the ka, also the guy at the place i bought it from said the car ran fine (it was a clip) when it was dismantled. any help would be apreciated

[USsil80]

have you checked your timming.... and pulled your plugs to see if theye are still good...

[driftin'180]

yeah the plugs are still good. i think it might be the timing

[driftin'180]

but what about the 2500 rpm rev limit i heard this vould be the mafs but it should still be good

[180fan]

2500 limit = MAFS no question. check the mafs or the circuit.

[driftin'180]

i checked the mafs wiring a few times and everything seems to be good and i got a new mafs and it still doesn't work. i heard that a coolant temperature sensor could be the problem, any ideas?

[dsm007]

The coolant temperature could be the problem but I highly doubt it,it would have a hard time starting like start the engine several times and it cuts right out,if it was the coolant temperature sensor it would go away as the engine warms up,all the coolant temperature does is act the choke for our engines just like a choke did for the old carburated engines back in the day,except on out engines it detects the temperature of the coolant so the ECU can determine how rich or lean the fuel needs to be at startup....................anyways bro I am having the same problem here too as you,I just started up my SR tonight and drove her down the road,same problems as you,Im thinking its either a vacume leak or the MAF as the others said......make a boost leak tester and try her out,you will be surprised at what you will find...well room you now have two people to help on this board lol..........Levi

[Tims_240]

when it idles really rough, can you smell that it is running rich? if so, i would bet money that it is the mafs wiring. same thing happened to me when i hooked up my z32 mafs on my ka. sometimes when you wire up your mafs, you should forget about using the factory ground wire (the ground that goes to the ecu), and just ground your mafs to the chassis, this was the problem for me, maybe it will help you too.-tim

[Luke]

When i did my swap, i had this exact same problem. It WAS the MAFS wiring, 2 signal wires were cut due to a zip tie cutting into the harness. it's either the mafs or the mafs wiring connections. it was a very hard problem to find. the swap took me 1 week, diagnosing this problem took 3 weeks. Take some time with an ohmeter and let us konw. gl

[driftin'180]

when i start it up it does cut out like once or twice right when it turns over. and the engine is running pretty rich, i can sometimes smell unburnt fuel coming out.

[driftin'180]

hey luke u said a wire might be cut, im taking my harness apart right now but did u take the sheilding wire off. i just wanted to know if i did this would it screw up my wiring.

[Luke]

You're describing every problem i had. what happened to me, was the zip tie thing that would snap into the chassis, had ripped through the sheilding and cut both signal wires. therefore i had no mafs signal at all, causing those symptoms. the only thing i can say is follow the wiring from the mafs to the ecu. or take an ohmmeter, and test for continuity between the wires at the ecu and the mafs. if you have no connection, it's the wires.

i did extend the mafs wiring over using the sheilded wire from my KA harness, and i had good solder connections. hope that helps :]

oh and to answer your question, you should keep the sheilded part in-tact all the way because you won't want any interference in that wire's voltage.

[driftin'180]

yeah i am gonna borrow a ohm meter from a buddy of mine and if it is the wiring that got cut(i already went over the whole thing just looking at the outside) i guessi could snake the wires back through the sheilded part

[Luke]

If they wires are good, you swap MAFS to test if you know someone with an SR. or find a SOHC KA24E at the junkyard and wire it up with the KA plug, it's the same mafs.

[driftin'180]

yeah thats what i did my sr mafs didn't work but i kept my sohc ka mafs (worked fine when i took it off a few weeks ago) and wired that up and it still didn't work so im pretty sure its the wiring

[driftin'180]

yeah i just checked the wiring and i got nothing so i guess tomorrow im pullin it all apart. anyways thanks alot u guys.

[Luke]

you got nothign on what wire? there should be like 2 shield wires going to the ecu and a 3rd unshielded one one. it's hard to remember from memory. i remember when i got my swap, the mafs wire was also cut by the ecu, maybe someone had an safc or something.

[driftin'180]

yeah the white shielded wire was cut at the ecu. i connected and did several 6000 rpm revs. so i thought it was fixed. turned it off went inside and came back out an hour later to see if it was still good. the second time the idleing was fine, stays pegged at 1100, but i couldn't get it past 2500 again. i went over all my wiring again and found no breaks or anything.

[driftin'180]

i just checked my ecu for codes and it gave me a 55 which means its some problem thats not known to the motor. i know a 12 is the mafs. anybody got any ideas?