my 1988 mustang gt convertible usually runs great but sometimes it idles up and down and will even die. the problem stops when i accelerate but will continue at cruising speed. sometimes it does not happen for days, then when it happens it can last for a few seconds up to a day. i have replaced the cap, rotor, plugs, wires, fuel filter and egr valve. it feels like a vacuum issue, but i do not think a vacuum issue would come and go like this. i am lost! please help

Asked by Mar 11, 2015 at 06:28 AM about the 1988 Ford Mustang GT Convertible

Question type: Maintenance & Repair

my 1988 mustang gt convertible usually runs great but sometimes it idles up and down
and will even die. the problem stops when i accelerate but will continue at cruising
speed. sometimes it does not happen for days, then when it happens it can last for a
few seconds up to a day. i have replaced the cap, rotor, plugs, wires, fuel filter and egr
valve. it feels like a vacuum issue, but i do not think a vacuum issue would come and
go like this. i am lost! please help

5 Answers

107,745

Does the check engine light come on when this is happening? It could be a bad sensor or ECM ground. Sometimes the wiggle test can locate the trouble if it is a wiring or grounding issue.

15

I conquer with tennisshoes, also consider checking on the condition of your engine mountings please.

270,305

I'd clean the throttle body and IAC valve. Like tennisshoes says, pull the code or codes, maybe the TPS is suspect. BTW: the '88 doesn't have a check engine light hooked up to the ECM, wasn't till the '89 models.

107,745

Your right Tom, i just assumed it was a air density car. I forgot that 88 was the only year Ford didn't t use a check engine light.

vapor return valve stuck open causes throttle surging at idle in park. Car sucks air though vent- runs lean- idle surges- ecm compensates- rpm drops- vicious cycle.

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