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1989 Mustang GT rough idle and no acceleration, after sitting about a month

10K views 21 replies 8 participants last post by  dynawideglide01 
#1 ·
My car is a project car first. The car ran fine when I parked it about a month ago. Now I start it and it will surge badly and then shut off, runs rich, and will not accelerate quickly, slow steady acceleration until about 3k then pops and sounds like it is missing. Changed FP regulator and no luck. I bought this car as a work in progress, ran fine before parking, quite a few mods.:confused:

Already cleaned IAC, checked TPS, not sure of correct readings (mine ranges from 1.2+/- to 4.6+/- ohms with key off, TPS unplugged) not sure if MAP sensor can be checked.
 
#5 ·
How do you know if the voltage is correct going to the ECM with no power to the sensor?

Test should be done with with the Key on engine off, and TPS hooked up.

Tp properly test the MAP/BP sensor, you would need to use a DVOM that has a hertz reading capability.

First off, you need to check the codes from the ECM.
 
#7 ·
You pierce the black and green wires, probe them with a digital voltmeter and check it with the key on engine off. At closed throttle, it should be between .6 and .99 volt and not go over 5.0 volt at wide open throttle. If at anytime the voltage drops to zero, there's a problem with it.

Checking your mass air meter would be a good idea.

89coupe can tell you how to check the codes without a code reader.
 
#9 ·
It could be corrosion on the mass air element. Get some brake cleaner, take the mass air meter off the car, and then lightly spray the element inside the meter housing. The brake cleaner leaves no residue behind, and be careful when spraying the element because it's fragile and can be easily broken. Let the element dry completely then reinstall the meter and see if it helps.

TPS voltage sounds fine.
 
#16 ·
Adding new gas is on my list, I may add some race fuel to it since there is about a half tank already there. The other problem is that I cannot run the code test while running because it will not run at an idle long enough, as of now I get no response from the throttle.
 
#18 ·
Unhooking it made it shut off. The gas is another option I will try later, I wouldn't think that it could be a problem because it is only been in there about a month or so also, possibility though, the place I got the gas from is in question for having watery gas (who would of guessed!) Just getting tired of fuel injection problems, too many things to act ghostly in a moments notice.
 
#21 ·
Thanks for all the input, NO LUCK YET, Changed the cap and rotor, bought new blaster 3 coil, changed fuel filter, dropped and cleaned tank out and changed screen, still same problem, stomp on it and it will cut out spit and NOT accelerate. I am trying to sell or trade this car, but I would like to fix and have running decent before then, any input would be appreciated
 
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