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Discussion Starter · #1 ·
I've been having this problem for a while. Car was running fine when I got it. Now I will cruise fine at 14.7, but once I let off the throttle (and leave it in idle) my AFs will immediately go lean, as normal, then a second later jump back down to rich, like 10.5/11, and slowly climb back up, and be back to stoich about 15 seconds later. If I get back on the throttle while it's doing this, it'll be fine at stoich again.

If I'm getting on it, it's stoich until I get to higher RPMs (usually past 4K, where the SAFC starts) then it gets SUPER rich, 10s at first, then out of the range of my wideband past 5000 or 5500. My wideband was tuned a few months ago on a dyno, and all the A/F correction settings are the same as it was before. It should also be noteworthy that my car doesn't seem to be as fast as it was before.

Noteworthy:
1. I'm in TTC electronically, and have the 12v and EGR mods done.
2. The VPC MAP sensor (which requires the vaccum nipple facing down) was facing mostly up when I got the car, and during and after the tuning. Since then I have pointed it downwards, shortened all the vaccum lines, and limited how many T fittings are on the same vaccum source.
3. I have gotten NO ECU codes.
4. I have checked the VPC MAP sensor voltage with the engine off and it is normal.
5. The problem was worse (took longer for the A/Fs to climb back up) when the battery terminal was loose. This makes me think the problem is electrical.

What's my problem? Thanks a bunch in advance. PayPal $10 to whoever gives me a solution.
 

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What are your knob settings on the VPC ? Are you running with o2 sensor plugged in ?
 

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Troux said:
I've been having this problem for a while. Car was running fine when I got it. Now I will cruise fine at 14.7, but once I let off the throttle (and leave it in idle) my AFs will immediately go lean, as normal, then a second later jump back down to rich, like 10.5/11, and slowly climb back up, and be back to stoich about 15 seconds later. If I get back on the throttle while it's doing this, it'll be fine at stoich again.

If I'm getting on it, it's stoich until I get to higher RPMs (usually past 4K, where the SAFC starts) then it gets SUPER rich, 10s at first, then out of the range of my wideband past 5000 or 5500. My wideband was tuned a few months ago on a dyno, and all the A/F correction settings are the same as it was before. It should also be noteworthy that my car doesn't seem to be as fast as it was before.
I took my car out for a spin yesterday afternoon and my a/f's do the same thing as your car except mine doesn't go as rich over 5k rpm. My throttle set points for the s afc is 20% low and 94% high. Take your spark plugs out and look at them. If they are real black put a new set in, there not expensive. I have ngk 6097's. Try reseting your ecu and drive the car around slowly, keeping an eye on a/f ratio.

What fuel system do you have? Did you recently make any changes to your car that could have caused your issue?
 

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Ever since I changed from 680 to 880 injectors, my car does the same thing - goes rich when I let off, then gradually climbs back up. The problem is worse right after an ECU reset. Seems to get gradually better over time.

I also get a lean spot off idle after a battery disconnect. I usually reset the ECU one more time with the car warm to help clear it up.

The symptoms seem like something the RESPONSE button should fix by turning it up a couple clicks, but it doesnt! I have not found a solution to the problem.

I cannot comment on the high RPM richness cause I dont have stock twins. Do you have the correct VPC chip for you injector size? I did not have this issue at all when I was running 680's.

Al
 

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Discussion Starter · #6 ·
Well the car was running fine before. I'm not sure about the chip, but I don't think it has the wrong one. (Needs an A chip, right) It very suddenly started happening. Ran fine a few months ago.
 
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