idle problem on fox

torque89 · Jan 22, 2011

I cant take this messed up idle anymore. I have to keep the IAC unplugged all the time just to get the rpms not to hang, and most of the time i cant keep it running on cold starts. When i had the IAC plugged it idles too high, rpms hang, idle goes up and down. Also the car runs rich all the time and gets horrible gas mileage. it has NO o2 sensor for some reason, also it is a speed density car. please help!

gt350son · Jan 22, 2011

One reason why I like carbs betters I always threads about the idle having issues in EFI mustangs.. anyway. I had the same problem as you on my SD 5.0. I did everything checked for vacuum leaks, adjusted my tps, replaced my IAC and tps, cleaned my TB, reset idle like 20 times, used sea foam in the gas tank and in the vacuum tree. I tried a lot of stuff. Then I decided to buy a timing gun and check the timing. Well turns out the person I recently bought it from who had rebuilt it I guess never set the timing on it. The timing was at 30º ATDC. Talk about bad performance. I also had other issues because of that. Only way i could get it to somewhat idle was at 1600 rpms.

torque89 · Jan 22, 2011

gt350son said:
One reason why I like carbs betters I always threads about the idle having issues in EFI mustangs.. anyway. I had the same problem as you on my SD 5.0. I did everything checked for vacuum leaks, adjusted my tps, replaced my IAC and tps, cleaned my TB, reset idle like 20 times, used sea foam in the gas tank and in the vacuum tree. I tried a lot of stuff. Then I decided to buy a timing gun and check the timing. Well turns out the person I recently bought it from who had rebuilt it I guess never set the timing on it. The timing was at 30º ATDC. Talk about bad performance. I also had other issues because of that. Only way i could get it to somewhat idle was at 1600 rpms.

well i set the timing but not sure if i did it right...pulled the spout out then started the car and set the timing then shut the car off and put the spout back in...is that right?

gt350son · Jan 22, 2011

Yeah, that's corrects. I usually like my timing around 10-12 and 14 being the highest with stock parts.

torque89 · Jan 22, 2011

gt350son said:
Yeah, that's corrects. I usually like my timing around 10-12 and 14 being the highest with stock parts.

mine should be at about 12 unless somehow something threw it off

jrichker · Jan 23, 2011

See the "Surging Idle Checklist for help with all your idle/stall problems. The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes] for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

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