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Discussion Starter · #1 ·
Need a little help here. Our Supra is breaking up in the upper RPMs. When on the dyno it showed that it was going stupid rich during this time. We ended up correcting out ~-33% on the SAFC to get it to run properly, and this is on stock injectors.

A little history -

Car ran great. 112 MPH traps on 100 octane and ~18 PSI. We wanted to fine tune her a little more so we purchased the SAFC. We had the SAFC installed (at the time I was too afraid of messing something up doing it myself) and put the car on the dyno to get a few more RWHP. The car immediately began breaking up in the high RPMs. It was fine prior to the SAFC install, however.

We made numerous pulls on the dyno and finally got it to stop breaking up, but as noted above, that was with a ~-33% correction. Car made terrible power once the stuttering stopped.

We assumed at this point that maybe the SAFC was bad / hooked up wrong. So, to test the theory we pulled the SAFC out of the car totally. It still broke up in the upper RPMs.

My only guess at this point is maybe the airflow signal from the MAS is not getting to the ECU cleanly thanks to the snip, splice, and then patch job that has been done to the wire going to the ECU. Does this sound reasonable??? What would be the symptoms of a car running without an air flow signal or with a poor signal? Shouldn't it throw a CEL if that were the case? I'm going to be going back in this weekend to see if I can't get a better connection for the air signal wire, and I'm open to any suggestions you guys can offer to point me in the right direction.

We have done a boost leak test, and the system holds fine, with a small leak around the EGR that we plan on taking care of. Other than that, it's pretty much solid.

Thanks for any help you guys can offer.
 

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I smell C-16 ;D
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Probably just put a new set of plugs in it NGK 3330's or 6097's gapped down to .028" This should cure your problem. Typically once you get our cars into an overly rich condition once or twice the plugs are pretty much trash. Just my $.02 Drew
 

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yep i would also say check the spark plugs and put new ones in. my car was bogging out at high rpm and it just started trying to go but it wasn't going if you understand me correctly. but i am pretty sure it is your spark plugs. put new ones is and then floor it. get rid of the apex and go with the HKS. just my opinion.
 

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Discussion Starter · #4 ·
OK, we'll try the spark plugs again. I failed to mention in the original post that we have changed the plugs twice. Once with NGK coppers, then followed with OEM NGKs. Bot sets of plugs netted the same result, but this was prior to the SAFC removal.

Does anyone know if the car would still run without a CEL if the air flow signal was weak and / or not getting to the ECU at all???
 

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Definitely change the plugs. Check the plastic connectors that connect to the top of the coil packs, make sure that they are on tight and on the inside of these connectors, there are some white (seperators??) Make sure that none of them are missing because you could get a spark between the two metal leads inside. Also check for oil in the gully next to the plugs.
 

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Discussion Starter · #6 ·
Something else I forgot to mention...

We also changed out the coil packs prior to pulling the SAFC from the car.

I'll be changing out the plugs this weekend to see if we get a miracle out of it, but I'm not holding my breath. Thanks for the suggestions. I'm all ears if you have any more. :D
 

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No Ego or Arrogance!!!!!!
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RE:

Yeah I got the same problem my car was fine even after we installed the afc 3 months. later the car stared with the problem in first gear and when and I down shift.but if just in first gear right about 5800 rpms,If I shift around 5000rpm to second I can take it to redline and no problem third and so on its just first gear its frustraring,so far this is what I change :check afc connections,new 3 sets of plugs gap at 32,30,28, a hks twin power dli,new coil packs,new gas pump and filter,check the coil clips they seen ok but going to change them anyway I have swap a maf with my friends and nothing, have a vpc that will get installed to see what happens,it has got be something stupid its not the plugs trust me,if anybody had this problem please help.:mad:
 

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Had the same problem when making pulls from high gear/low rpm. Turned out to be the coil pack connectors.
 

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No Ego or Arrogance!!!!!!
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RE:

Are you sure when you checked them did they look normal,just eye ispection I mean.I got a new connectors and the wires,they look ok I guess but lets see what happens when I put new ones I have had this problem 6 months now.and it sucks.
 

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RE:

This is what is keeping me from running 11's my best run so far is 12.0 at 120mph with 2.0 60 ft. bpu++ I can't get my 60ft. because of this stupid problem.
 

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Discussion Starter · #11 ·
Small update -

Checked the coil pack connectors. All have the white spacers in them. Pulled the plugs and they were very black. Obvious the car is running way rich. Local parts stores don't stock the plugs, so I just cleaned the ones we have and gapped them down from 31 to 29. I put the car back together and it's even worse now. I think trying to salvage the plugs was a bad idea. A new set gapped at 29 will be going in this weekend.

On the inside of the car I did find a few wires going to the ECU that had the sheilding nicked down to the wire. I taped them off to be safe and double checked the BCC and O2 sim install. It all seems to be OK.

One interesting note... The SAFC was hooked up to a couple of the wires running to the BCC (note - the SAFC was not installed by me). I know this isn't correct, so now I wonder if maybe the connection to the BCC has been compromised, and is causing this problem??? Does that sound possible? I'm going to have to go over the wiring again to make sure none of the wires were severed by the inline splices used to install the SAFC.

Still open for ideas and suggestions. Thanks for the help thus far. :)
 

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No Ego or Arrogance!!!!!!
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RE:

One of my friend took a look at afc connection and he said that they were hook to bcc, so when we have time we'll take a better look, let me know on what you find.:(
 

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I would read www.mkiv.com to check S-AFC wiring. If your car is running "stupid rich" and it's not the plugs or coil packs, the next logical thing is to make sure AFC is wired and tuned correctly IMHO.

Joe
 

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Discussion Starter · #14 ·
LLCoolJ94 said:
I would read www.mkiv.com to check S-AFC wiring. If your car is running "stupid rich" and it's not the plugs or coil packs, the next logical thing is to make sure AFC is wired and tuned correctly IMHO.

Joe
The SAFC is no longer in the car. We took it out because the car started running poorly just minutes after the install. Bad thing is, the car did not go back to normal once the unit was removed. I guess it is possible that the SAFC was never part of the problem, but it's a weird coincidence that the problems started right after it was installed.

Still searching for the cure...
 

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How much boost are you running and on what octane fuel? I have seen cars break up like this on the upper RPMs due to timming being pulled. Just another thing to consider. Drew
 

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This may sound Stupid, but have you tried resetting your ECU after you Took Out the SAFC? Im just getting into the tech stuff but sometimes its the simplest things.
 

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Discussion Starter · #17 ·
It's running on 93 octane from the same station I get fuel for all 3 cars. My VR-4 (upgraded turbos running 18.5 PSI) and GSX (upgraded turbo running 17 PSI) run fine off the gas, so I don't think it's a bad gas situation.

The car isn't making much boost. Just under 1.0 KG/CM2, so what... roughly 13 PSI? It used to be higher than that with the same settings on the EBC. We did a boost leak test and the system held fine with only a slight leak from one of the EGR units (we're going to install blockoffs here soon).

I'm running out of ideas, and I again thank you guys for the suggections and if there are more I'm all ears.
 

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Discussion Starter · #18 ·
SupraTT85 said:
This may sound Stupid, but have you tried resetting your ECU after you Took Out the SAFC? Im just getting into the tech stuff but sometimes its the simplest things.
Doesn't sound stupid at all. All options are welcome! :)

I actually unplugged the battery for the SAFC uninstall, so that should have reset the ECU. I'll pull the fuses on the car today when I get home and see if that method of resetting does anything different.
 

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SupraTT85 said:
This may sound Stupid, but have you tried resetting your ECU after you Took Out the SAFC? Im just getting into the tech stuff but sometimes its the simplest things.
Check resetting the ECU and maybe the fuel rail and injectors? Possibly an injector seal is broken? Though, usually that leads to breaking up on the lower end.

Joe
 

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Discussion Starter · #20 ·
Minor update -

I had a brainstorm that told me maybe the BCC was causing the issue. I checked the ground wire that the SAFC was tapped into to make sure it was not compromised. It looked like it was still getting a clean signal. I taped it back up and removed the BCC. I could hear something rattling inside the BCC and a screw fell out of the bottom of it once I pulled it from it's mount. I opened it up to find that one of the little brass nuts had been free inside the unit. Who knows if it was bridging something inside of not.

Once I got the BCC to a 12V source the reading on the voltmeter said it was at ~3.80V. For a '97 Supra the voltage should be close to but not greater than 4.10V. We set it to 4.08V and put it back in. Cranked the car up and took her for a spin. Ran great until 6K RPM when it politely broke up again. DAMN! I thought I was on to something...

Now I'm not so sure the plugs aren't the problem. I was going to replace them this weekend, but we did the fuel filter instead. No change with the new fuel filter either, but it needed to be done anyway.

Next step is another new set of plugs @ .028 to see if the problem goes away. I hope it does, but I'm not holding my breath. Will update soon.

P.S. Still accepting advice. :)
 
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