This is topic '90 GT rough idle, check engine on and off SOLVED in forum Tech Talk at Northern California Ford Owners  .


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Posted by 90GT510 (Member # 9199) on :
 
My 5.0 manual idles rough, revs when it feels like it and dies. Throughout this the check engine light will go on and off, sort of blinks. It runs fine then out of no where a hesitation starts and light comes on. It dies when I get to a stop. I changed out the 02's and the same thing keeps happening. Any ideas on what could be causing this?

On a side note when the key is in the on position or when the car is running there is this buzzing noise that sounds like it comes from the firewall area intermittently. Don't know if this could be related.

[ 2014-05-04, 05:38 PM: Message edited by: 90GT510 ]
 
Posted by 70stang351w (Member # 9948) on :
 
did you clean the MAF? or replace fuel filter?
 
Posted by Wht86drop (Member # 12104) on :
 
I think the buzzing might be your IAC going bad
 
Posted by 90GT510 (Member # 9199) on :
 
quote:
Originally posted by Wht86drop:
I think the buzzing might be your IAC going bad
Yes this is what is buzzing. I disconnected both connections from it and same symptoms continued.
 
Posted by 90GT510 (Member # 9199) on :
 
quote:
Originally posted by 70stang351w:
did you clean the MAF? or replace fuel filter?
no I have not
 
Posted by Wht86drop (Member # 12104) on :
 
Did you disconnect and then start or start then disconnect? And the IAC should only have one plug to it. The other in that area is only the EGR and TPS. The buzzing is a for sure bad. Never have I heard them do that unless if it's an incorrect unit for the car or just going bad
 
Posted by 90GT510 (Member # 9199) on :
 
quote:
Originally posted by Wht86drop:
Did you disconnect and then start or start then disconnect? And the IAC should only have one plug to it. The other in that area is only the EGR and TPS. The buzzing is a for sure bad. Never have I heard them do that unless if it's an incorrect unit for the car or just going bad
I started it then disconnected it while running. nothing changed.

Its the correct unit most likely just going bad.
 
Posted by Wht86drop (Member # 12104) on :
 
Yup just replace the unit and disconnect the battery for like 15min before restarting the car
 
Posted by 90GT510 (Member # 9199) on :
 
quote:
Originally posted by Wht86drop:
Yup just replace the unit and disconnect the battery for like 15min before restarting the car
Just put a new iac waiting 15 minutes before reconnecting batt and starting lets see if this works.
 
Posted by 90GT510 (Member # 9199) on :
 
I actually unplugged the wrong thing earlier this time before I installed the new iac I unplugged the original one and the car died so I'm assuming the original one is doing it's job.

The new iac valve makes the car run worse than it was already
 
Posted by 90GT510 (Member # 9199) on :
 
The car runs like shit with this new iac I guess I'm going to return it to get a fuel filter and some maf cleaner.
 
Posted by Wht86drop (Member # 12104) on :
 
Damn that freaking sucks. Check fuel pressure too if you think it's choking from little fuel getting to it. Chances are if the filters clogged pressure would be low. That buzzing that the IAC is doing isn't normal though.. Oh and did you even check for codes?
 
Posted by 90GT510 (Member # 9199) on :
 
It does suck oreilly fuckers won't take it back
 
Posted by Wht86drop (Member # 12104) on :
 
Is it a special Order part? Wtf??
 
Posted by 90GT510 (Member # 9199) on :
 
quote:
Originally posted by 90GT510:
It does suck oreilly fuckers won't take it back
I went across town and dude was chill as shit saying " there's evidence it's been installed" but took it anyways.
 
Posted by Cstang5.0 (Member # 4925) on :
 
Have you tried to run the codes to see what comes up??
 
Posted by 90GT510 (Member # 9199) on :
 
Just clean maf runs smooth now! Strange thing is now engine light decides to show itself. I'll be back with the code.
 
Posted by diablounicorn (Member # 13033) on :
 
when you did the IAC did you check the readings? i know i messed with mines a bit set it on .98v it solved it for me. then i cleaned my maf it runs smooths. but i have an auto with stock gears and tf1 cam
 
Posted by 90GT510 (Member # 9199) on :
 
quote:
Originally posted by diablounicorn:
when you did the IAC did you check the readings? i know i messed with mines a bit set it on .98v it solved it for me. then i cleaned my maf it runs smooths. but i have an auto with stock gears and tf1 cam
Stock iac was good no buzzing the buzzing was coming from elsewhere. I used maf cleaner and that solved my problem.
 




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