Why can't my supra run right?

[gixxer750]

I just don't understand. No matter what I do to it, I just can't get a good idle...ever. It's always random misfire, Idle bouncing around bullshit. Its been like this as long as I've had it. Its on the second rebuild now. The IAC has been changed, coils, CPS, TPS, O2, AFM, coolant temp, and FPR.... and it still does this same bullshit. It will run smooth for a minute, and then you get a stumble, it goes rich for a second, and then smooth back out.

Mods are

Lex Afm, RC 5550's. NGK 3330's gapped at .026, AFPR, Walbro 255(hardwired 10 gauge, 12 volt mod), Ported Head, Wiseco pistons, Race prepped stock rods, full balance job, Cometic 2.0mm, ARP hardware, UR cam gears, Hardpipes, 62-1 Turbonetics turbo, NGK wires, Custom air intake, Greddy Emanage Blue with Additional injector harness, KS rewire, Electric Fans, Mr2 alternator, Optima Redtop, Ported exhaust manifold, BIC DDP, custom 3.5 inch exhaust, koyo radiator, 180 TRD thermostat, and some stickers under the hood.

WTF? I've got great, even compression numbers. 175 per cylinder. Leakdown came out 89/100 on all cylinders. I've got good engine grounds. Valves don't leak. Coil packs are within spec. CPS shaft is not loose, and air gap is correct.

Any ideas.... it just bugs me. I have always had this problem and dealt with it, but have never had a clue on the cause.

 

[bigaaron]

I just don't understand. No matter what I do to it, I just can't get a good idle...ever. It's always random misfire, Idle bouncing around bullshit. Its been like this as long as I've had it. Its on the second rebuild now. The IAC has been changed, coils, CPS, TPS, O2, AFM, coolant temp, and FPR.... and it still does this same bullshit. It will run smooth for a minute, and then you get a stumble, it goes rich for a second, and then smooth back out.

Mods are

Lex Afm, RC 5550's. NGK 3330's gapped at .026, AFPR, Walbro 255(hardwired 10 gauge, 12 volt mod), Ported Head, Wiseco pistons, Race prepped stock rods, full balance job, Cometic 2.0mm, ARP hardware, UR cam gears, Hardpipes, 62-1 Turbonetics turbo, NGK wires, Custom air intake, Greddy Emanage Blue with Additional injector harness, KS rewire, Electric Fans, Mr2 alternator, Optima Redtop, Ported exhaust manifold, BIC DDP, custom 3.5 inch exhaust, koyo radiator, 180 TRD thermostat, and some stickers under the hood.

WTF? I've got great, even compression numbers. 175 per cylinder. Leakdown came out 89/100 on all cylinders. I've got good engine grounds. Valves don't leak. Coil packs are within spec. CPS shaft is not loose, and air gap is correct.

Any ideas.... it just bugs me. I have always had this problem and dealt with it, but have never had a clue on the cause.

I feel your pain...
I'm in the same poor idle club. :cry:

 

[mattjk]

remove your 12v mod.

is your honeycomb straight and clean?

do you use an oiled k&N? check for oil contamination in for AFM system

is your tps in spec? have you tried to adjust it?

 

[Yellow 13]

RC 5550's

I think 5550cc injectors would make you run just a wee bit rich.

 

[fiyota]

lmfao yellow 13 that clip in your sig is great!

(sorry to go off topic man, I feel your pain on the poor idle.. well my problem is a high warm idle..)

 

[gixxer750]

I use an AEM dryflow filter. The fins in the AFM are straight and clean. I can't see where the 12 volt mod would be a problem, but walbros don't like the 9 volt setting. I've tried multiple afm's. The TPS is brand new from toyota and calibrated to TRSM specs.

I just don't understand why it does this when everything is perfect. It doesn't idle rich except when it stumbles. The emanage has the idle taken care of.

 

[figgie]

gixxer

a rough ilde.. it start to surge (ie rev up and down)?

if so, you want to look at timing, You are probably at 10 right now might want to lower that to 8 to see if takes care of that. That is a common problem especially on stand alone cars when timing is too advanced.

 

[gixxer750]

it doesn't really surge. it will idle smooth for 20-30 seconds at 850 rpm, and then it will go to 10.0 afr for half a second, bog to around 300 rpm and come back up to 850. It's so rich I get a little black smoke out the exhaust when it happens. It keeps repeating this about every 20 seconds to a minute. Also the cold idle SUCKS.

 

[figgie]

ahh


might be two problem

cold start injector is bad.. disconect it see if it takes care of that. Check the cold start injector sensor in the temp housing

 

[gixxer750]

maybe the cold start intermittenly(sp) coming in even when the car is warm?

That would make sense. I'll unhook both and look for a change.

 

[mattjk]

maybe the cold start intermittenly(sp) coming in even when the car is warm?

That would make sense. I'll unhook both and look for a change.

sometimes they go bad and start to leak

 

[Facime]

have you considered the possibility of a bad ECU? I had a pontiac GP that had a mind of its own when it came to idle...sometimes it would just jump up to 2000 sitting at a stoplight...used to have to stay way back from people in front of me so I didnt rear end anyone on accident. Anyways, turned out the ECU had gone bad. Replaced it and all my problems when away