rb20 running badly, event next weekend... help!

[Gavin Johnson]

the car:90 s13 with rb20 swap. stock injectors, bcpr6eix plugs gapped at .27 and yellow jacket coil packs,safc (w/ sock settings) blitz dual sbc(at 15psi, turned it down and no difference) and front mount.

the issue:car will start when cold, then when hot it will crank for a few seconds then hit a wall and then start cranking again but wont start, i have to bomb start it. starts perfect when cold. also has a high rpm miss that just came up. when i try to drive through it itll keep missing and my a/f starts to go lean, initially when it starts missing its about 11.8-12.3 or so

what ive tried:spark plugs re-gapped, starter, alternator,battery, ignitor, o2 sensor( just for maintenance), all replaced. ecu shows no codes.

dynoed it last week at 265whp and it ran flawlessly, then went on about a 1500 mile trip and the starting problem came up and then the miss, only mods since dyno are the safc and it worked fine for most of my trip. ive got a payed demo on the weekend so i need to figure this out, thanks guys!

[rb25det250sx]

idk bout the rb20, but .27 sounds a bit close... i had a problem like this. my coil packs were grounding out. so i had to coat them with a expoxy, or flexane 94. that will help a bunch

[Gavin Johnson]

mine are brand new, ill try stock coils tommorow and see if it changes. any other ideas to try? coils wouldnt effect hot starting woul;d they?

[Sil240]

That's what I'm thinking. Either Coils or your ignitor.

If its your ignitor you can either use a J30 or a Z32 one.

Where are your coils mounted?

Also Turn down the BOOST!!!Your gonna blow that stock turbo.keep it BELOW 14psi. Your gonna shatter your wheels.
Modified by Sil240 at 5:29 PM 5/21/2009

[Carl H]

remove the iriduiums and replace with standard bcpr6es-11 plugs gapped to .8mm.check base timing.and 265whp on STOCK turbo and injectors is bs, dunno what dyno you did that on but its definately lying.

[Gavin Johnson]

i just used another rb20 one that i had kicking around. coils are mounted in stock position, going to try stockers tonight. yea boost is a little high, ill turn it down a bit

remove the iriduiums and replace with standard bcpr6es-11 plugs gapped to .8mm.check base timing.and 265whp on STOCK turbo and injectors is bs, dunno what dyno you did that on but its definately lying.

will do carl, i can scan the sheet for you if it will please you, i meant 256 also, typo sorry. but it was on a mustang dyno that was working fine with everyone elses car that day and was accurate so im not sure why you dont think so.

[Gavin Johnson]

also, just started it cold, ran perfect, except when revving it its building 10-11 pounds of boost reving to 7 or so?! wtf causes that?? unplugged coolant temp sensor for the engine and it didnt make a difference, so im going to replace that too

[Gavin Johnson]

ok, did new plugs carl recommended at .8mm, stock coil packs and a new temp sensor, runs a bit better and found out my ignition switch is screwed, have to turn it and just about let off for it to start . still misses at high rpm. also my ignition start circuit is wired up from pin 43 to the orange dash wire. when i removed this it cranked alot better.

[Sil240]

Dunno what it could be.If its not the Coils, the ignitor, the coolant temp sensor.

Maybe the MAF- but doesn't make sense that it would be affected by temp.

Do you have good grounds?I know that was a problem for me getting the car started.

[Gavin Johnson]

ok, tried a new ign switch and still same problem, cant fiugre out what would cause it to not work only when hot, im looking at my harness and its rubbed a few times before and just been taped up so im fixing that properly and trying a new cas. any more ideas?

[Gavin Johnson]

ok went through the harness that runs down the side and removed everything that i didnt use, left with fuel pump wire, white with black, red with black and purple with white, now it starts when hot but its in limp mode, traced back all wires removed and they where for ps pressure, abs, and other stuff thats unrelated, no codes at all, but itll rev and stay at 2500 like its a limiter. what causes limp mode? everythings plugged in and hooked up afm and o2 are for sure hooked up, any ideas? i need it running! thanks anyone who can help i spent the whole day and found nothing. also swapped my cas as well, i think that was the hot start problem.

[craz4240]

Send your harness to someone who knows what their doing.

[Gavin Johnson]

Send your harness to someone who knows what their doing.

thanks for nothing, car has run and worked fine for 6 months. anybody else?

[rb25det250sx]

underneath the intake mani, there is two sensors on each side. crank position sensors or sumthing like that i think... anyways, i know that on my rb25 swap they weren't hooked up, and my motor was running of safe mode. so i hooked them up and i;ve been fine every since. sorry for the somewhat long post. but check those out! i think it will help.

BTW the wires that go to it on my rb25 are brown, and they have a power wire running through them then they are rapped around by a ground wire, then covered in the brown.

[craz4240]

thanks for nothing, car has run and worked fine for 6 months. anybody else?

Define what running fine is??

Not to sound harsh however my rb20det s14 I drove everyday for about a year,lots of power,never let me down,smelled a little gassy but due to the carbon canister being removed.Turns out in the end there was real wiring demons that needed to be addressed. I didn't wire the swap someone else did and I now have the whole car stripped down and am replacing all the wiring from the firewall forward.

[maryjane]

bkr7e copper ngkr plugs are the shizznat!

[kickertu]

Has no one brought up the s-afc issue?

if you just installed it and are now having a maf issue, or rev limit then it sounds to me like your s-afc isnt either hooked up correctly, or isnt set correctly.

take the s-afc totally out and fix the maf part of the harness. see where its at without the safc. also for the missing part of it, the fuel map might be messed up on that part of the afc.

good luck on figuring it out, but from what i read, sounds like the issues started happening after you put the afc in

[Gavin Johnson]

underneath the intake mani, there is two sensors on each side. crank position sensors or sumthing like that i think... anyways, i know that on my rb25 swap they weren't hooked up, and my motor was running of safe mode. so i hooked them up and i;ve been fine every since. sorry for the somewhat long post. but check those out! i think it will help.

BTW the wires that go to it on my rb25 are brown, and they have a power wire running through them then they are rapped around by a ground wire, then covered in the brown.

i dont believe the rb20 has these sensors.

Has no one brought up the s-afc issue?

if you just installed it and are now having a maf issue, or rev limit then it sounds to me like your s-afc isnt either hooked up correctly, or isnt set correctly.

take the s-afc totally out and fix the maf part of the harness. see where its at without the safc. also for the missing part of it, the fuel map might be messed up on that part of the afc.

good luck on figuring it out, but from what i read, sounds like the issues started happening after you put the afc in

ive tried unplugging the afc and jumping the 2 wires to bypass it and still no dice, afc was on stock settings and worked fine for over 600 miles. tired a new maf today and nothing, tryed another ecu and tryed my ecu in another car... nothing. tried jumping signal wires and signal ground for maf to ecu direct to theyre pins and nothing. it runs the same with maf or not, 9.0afr, and if i rev it to 2500 where it stops and let it bounce it goes straight lean to 16-20 before i stopped. im stumped ive tried everything, i bought another harness months ago but the dude hasnt had a chance to ship it. hopefully he can asap to rule that out, also bought a timing light but had to order it in, messed with timing and same thing.

[Gavin Johnson]

the dude is shipping the harness tommorow morning so i should see it before thursday. hopefully thats the problem, any other ideas while i wait for it?

[rb25det250sx]

well one of my friends had a build rb20, and it would run fine cold, for a couple of pulls, then start running safe mode and run exactly how you explained in the above post. we ended up, replacing ALL the sensors, pulling the ecu, installing a EMS and getting it tuned! then it ran great.

[Gavin Johnson]

lol ok, well maybe in the future but doubt i can make that happen in 2 days