Idle air control for 87 gt

[Kuwait Fox Body]

Hello guys

So with my 87 GT

Since I had it, in idle engine speed is around 2000 and some times engine cut off while shifting in low speed. I was thinking that i need to replace the Idle Air Control, so I've ordered that and im still waiting for it.

Couple of days ago, it started to cut off more even while driving in the highway.

I just replaced the IAC and now its better in idle but when ever I press the gas paddle it feels like the engine wants to cut off and then rpm rise again

You can see that in this video ( my Mustang GT 87 )

Thanks

 

[broncojunkie]

What you're describing could be caused by a number of things, unfortunately. But to start, since the car is over 30 yrs old, you should check the fuel tank (if you haven't already).

My 88 had the same issue. After dropping the tank, I found some rust and varnish buildup inside. The sock filter was getting clogged up with gunk.

You could also try just changing the fuel filter.

 

[broncojunkie]

Throttle position sensor can also cause these issues and is a common problem. There is a way to test it, which I would suggest doing before replacing it. Simply throwing a new one on can cause more problems.

 

[Kuwait Fox Body]

What you're describing could be caused by a number of things, unfortunately. But to start, since the car is over 30 yrs old, you should check the fuel tank (if you haven't already).

My 88 had the same issue. After dropping the tank, I found some rust and varnish buildup inside. The sock filter was getting clogged up with gunk.

You could also try just changing the fuel filter.

Your saying "number of things" what do you think i need to check more?

Also I'm thinking about vacuum hoses but i need a map or guide for all vacuum hoses and valves
Or maybe one of the sensors

 

[Kuwait Fox Body]

update

Checked TPS and all vacuum hoses

Noticed that while the vehicle is cool everything is fine

 

[broncojunkie]

You say you checked vacuum hoses? Did you just look them over or did you go through a process to check for leaks? You can hook up a smoke machine to it and check that way, but that involves some work and expense. Quick way is to spray some starting fluid around the engine while idling. Use your own judgement on whether or not that's a good idea. Obviously, you don't want to do this if you have, for instance, some bad plug wires causing electrical arcs. Speaking of which, you can also check that fairly easily. Just look under the hood at night. Spray a light mist of water over the engine while it's running and you'll see arcing, if you have a problem. Back to the vacuum leaks...if you're spraying something flammable around the engine, the vacuum should suck it in and the idle will go up. There are other ways to check, but I've found this is the quickest way.

You say it doesn't show symptoms when cold, so that makes me suspect an ignition problem. Electrical parts often break down with heat. Unfortunately, it's a bit tricky to narrow it down. I would suggest NOT just replacing ignition parts till it's fixed. You'll very likely find that you're introducing multiple problems that way. The current market for aftermarket ignition parts has flooded the parts stores with garbage. I could tell you stories you wouldn't believe. Whenever I pick up an ignition part from the local parts store, I give it about a 30% chance of being bad right out of the box. So you'll probably be better off trying to test each part. Common problems are pick-up coil in the distributor, tfi module, maf, o2 sensors, and the ecm itself. Of course, plugs/wires/cap/rotor should all be checked first.