Engine 91 Gt Running Rich Please Help

bman91gt · Apr 13, 2017

hello,i have a 91 gt running rich,it runs fine but when i stop at a traffic light idle will drop to about 500 or 600 rpms step on gas it clears up but goes right back a few seconds later it has new plugs wires cap and button new 02 sensors new air filter new fuel pump 190 lph fuel pressure set at about 38 with engine off ,it has longtubes no smog or cats h pipe flowmaster e303 cam 76mm mass air meter for 19 lb innectors 70 mm throttle body pulleys any help is greatly appreciated

jrichker · Apr 13, 2017

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 200,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

bman91gt · Apr 13, 2017

jrichker said:
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 200,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

thanks for reply

Dan02gt · Apr 13, 2017

Run through the idle surge check list like jrichner suggested.

But honestly I don't know that you will ever get that combo to idle correctly. The E cam is not known for it's idle quality and the long tubes move your O2 sensors to far away from the exhaust ports to read correctly. I have fought that fight before.

What kind of Mass Air meter is your 76mm? If it's a C&L it can be a problem also.

If it were my car I would loose the E cam for about any other cam. The Comp XE264HR would work well with your combo. I would also replace the long tubes with a good set of shorty headers. If you want to keep the long tubes, wrapping them with heat wrap can help keep the heat in and can improve the accuracy of the O2 sensors A/F metering. Running ceramic coated headers also help with that.

Dan02gt · Apr 13, 2017

Oh and if you have the stock pulleys it wouldn't hurt to put them back on so you can ensure you're getting enough voltage at idle.

bman91gt · Apr 13, 2017

Dan02gt said:
Oh and if you have the stock pulleys it wouldn't hurt to put them back on so you can ensure you're getting enough voltage at idle.

thanks for the advice cleaned mass air meter today set tps voltage seems to do better but still after sitting still a few minutes the idling drop a few hundred rpms guess i will have to deal with it.I have a 130 amp altenator ordered to take care of charging issues stock water pump pulley on there now.i pulled the codes also and all came back good code 11 only.but anyway like i said thanks for the advice

Dan02gt · Apr 14, 2017

My buddy ran a E cam about 15 years ago and before we knew any better LOL. We had the best luck with setting the idle between 750-800 RPMs. He installed one of these to set the idle with:

https://lmr.com/item/LRS-9939A/1986-93-Mustang-50L-58L-Idle-Air-Control-Iac-Adjuster

jrichker · Apr 14, 2017

See the Surging Idle Checklist and check out the base ide reset procedure after you have cleaned the IAB/IAC as described in the checklist. That will improve your idle stability greatly if you don't have vacuum leaks or other problems like codes that need to be fixed.

bman91gt · Apr 15, 2017

ok so cleaned everything i could mass air sensor,iac valve and i was doing the o2 sensor voltage check while car is idling pulled the computer but not unhooked looked and my wires are not the same color as what ive seen everyone say they are on pin 29 people say ut should be dark green / pink wire i have a gey with light blue stripe and pin 43 peoole say it should be dark blue / pink i have red with black stripe any thoughts cauae i. kinda confused

upon looking closer at the thread i was looking the color of my wires seems to match the color for wires on 94-95 5.0 but i have a 91 gt so now im really confused has anyone else seen this before do i just have a crazy mixed up harness

bman91gt · Apr 21, 2017

problem solved new 75 mm pro m mass air meter and it runs like new

Engine 91 Gt Running Rich Please Help

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