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View Full Version : rough idle during cold start condtion

paul91gt
04-10-2005, 03:24 PM
has anybody seen or heard of surging problems at idle when cold. I have to
hold about 2000 rpms for it to stay running when its cold and if i do this for 2 minutes. As i let off and let it idle it begins to surge real bad until it gets warm.The funny thing is when its warm it wants to surge a little bit but not anywhere as bad when cold. I've replaced the iac motor already but I'm leaning more towards a bad mass air flow sensor.any ideas?
thanks
Paul
BlackLX
04-15-2005, 11:56 AM
Are you pulling any codes? Is the check engine light on at all?

Could be another sensor, but you need a scan tool to figure it out for sure.
upngo50
04-15-2005, 12:31 PM
How many miles on the o2 sensors?
paul91gt
04-19-2005, 01:32 PM
i think they have 100,000 on them.when i pulled them to change my exhaust they were extremely lean! why?
quietflow
04-19-2005, 01:59 PM
Sounds like a vacum leak maybe
MILLERTIME5.0
04-19-2005, 04:26 PM
What year is your car? Is it a 5.0?
upngo50
04-19-2005, 06:10 PM
100,000 spells time for some new o2 sensors. Whether that is your problem or not is another story. Check for vacuum leaks and clock you mass air meter.
TheRealStubot
04-19-2005, 07:09 PM
I had a similar problem, and I traced it to the throttle position sensor. It was so far off, I had to file both slots to get it to read .97 at idle.

On a side note: Never buy someone elses unfinished project car! Even though the deal may be sweet, you'll spend the next year working all the bugs out.
upngo50
04-19-2005, 07:37 PM
On a side note: Never buy someone elses unfinished project car! Even though the deal may be sweet, you'll spend the next year working all the bugs out.


But save thousands of $$...
paul91gt
04-20-2005, 09:55 AM
it's a 91 gt 5.0
MILLERTIME5.0
04-22-2005, 02:17 PM
Try and check your intake air temp sensor. Sometimes they get all gummed up and cause a poor idle condition when cold.
paul91gt
04-29-2005, 10:27 AM
there isn't a air charge temp sensor on 89-93 mustangs
TheRealStubot
04-29-2005, 12:40 PM
there isn't a air charge temp sensor on 89-93 mustangs
There isn't? That's bizarre, I'm getting an ACT too low error from my Auto X-Ray... I better look at my VIN again, I may have put the wrong letter in there.