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Long story short, we got 91 Mustang GT with 302 HO and some bolt ons.

As far as I know the car was built and supercharged, I have no idea whats on the inside of the engine. But it has stock heads, explorer intake (which I installed), MAC long tubes (driver side might have a hole from steering shaft), CAI, Pro M 75 mm MAF, 24 LBS injectors, Stock distributor and recently SCT Chip installed.

About 2 months ago I started to replace all of the sensors on the car after our newer mustang's O2 sensors went bad after 60k miles. IAC valve ,ACT, ECT, BAP, VSS, O2's and TPS got replaced (they were as old as the car). Right before I replaced the TPS and ECT the car starts right up and dies but only when it's cold, other than that it runs fine. Starts normal when warm, only thing I can think off is lower temperature outside. It will take 2-3 startup's and it runs fine.

Today my fiancé drove the car and it died in the middle of the road, shortly before that check engine light came on. Got codes 15, 85 and 91 after I got home. The 85 code was on the car forever...

The car got tuned with SCT / BAMA chip on thursday, it was running fine until today. Other than startup issues. No codes other than 11 and 85 were present.

Thoughts? It's driving me nuts.
 

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Long story short, we got 91 Mustang GT with 302 HO and some bolt ons.

As far as I know the car was built and supercharged, I have no idea whats on the inside of the engine. But it has stock heads, explorer intake (which I installed), MAC long tubes (driver side might have a hole from steering shaft), CAI, Pro M 75 mm MAF, 24 LBS injectors, Stock distributor and recently SCT Chip installed.

About 2 months ago I started to replace all of the sensors on the car after our newer mustang's O2 sensors went bad after 60k miles. IAC valve ,ACT, ECT, BAP, VSS, O2's and TPS got replaced (they were as old as the car). Right before I replaced the TPS and ECT the car starts right up and dies but only when it's cold, other than that it runs fine. Starts normal when warm, only thing I can think off is lower temperature outside. It will take 2-3 startup's and it runs fine.

Today my fiancé drove the car and it died in the middle of the road, shortly before that check engine light came on. Got codes 15, 85 and 91 after I got home. The 85 code was on the car forever...

The car got tuned with SCT / BAMA chip on thursday, it was running fine until today. Other than startup issues. No codes other than 11 and 85 were present.

Thoughts? It's driving me nuts.

MisiekFL,

Let's see if we can trouble shoot your problem with a few steps.

Codes:

85- is generally the gas purge solenoid on the EVAP canister. Have you replaced this or even checked that is it still there? Missing the purge solenoid can make your Mustang run rough.

91- NO HEGO switching detected always lean (left side)

15- Keep Alive Memory (KAM) test failed

11- System pass / System Clear

So, I would say the first thing to check is your purge solenoid. That could easily cause all of these problems if it is malfunctioning. Once you can confirm it is good or bad, we'll take the next step from there.

Hope this helps!

Shane
 

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Discussion Starter #3
What's the procedure for EVAP solenoid test?

I tried to pick one up at local parts store but they don't have one for 91 GT.
 

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Discussion Starter #4
Shane, Thank you for your help.

I replaced the EVAP solenoid and vacuum lines that connect to it and the car runs and starts up much better! All codes are gone except of code 15, now i get code 11.

It still has hard time when it starts up when cold, but it doesn't die ever since I changed the EVAP. Drops to 500-600 rpm and than goes to 1500 and runs okay.

When it does that car makes hissing noise coming out of passenger side (seems like its in the dash), it also does that when accelerating on cold engine. - Vacuum leak?

Another minor issue is car shuts off randomly, after check eng light comes on. Only happens when my fiance is driving...

Thank you for help!
 

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You can try a base idle reset and see if it changes how the car idles when it's cold out. The car shutting off randomly could be the tfi.
 

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Code 11 is a good code. It means system pass
 

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Discussion Starter #8
Thank you guys!

I did Baseline idle reset quite few times, has some IAC Valve issues.

Funny thing is, got little warmer outside and the car runs fine.

I'm going to replace ECT, ACT; also got MSD Distributor and 6 AL box.

Got to show some love to the fox.
 

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Discussion Starter #9
So, I have replaced the distributor but kept the old cap and wires. So far so good, other than couple of glitches at WOT.

It still has difficulties at cold start - startup and either almost die or die.

But it runs without randomly shutting of so far at least. Got check engine light 3 times so far after going over some serious bumps. Pulled codes and got 41 and 91 codes with KOEO test. I can't seem to complete KOER since the car got tuned. Other than that all good.
 

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Pull the chip and see if the issues go away. If they do, you know where your issue lies. Was this dyno tuned or mail order?
 
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