I have had this problem for a LONG TIME. I can not fiqure it out.....First I will tell you what I have. I have a 90 Ford mustang GT 5.0. It has a 302 (stock Bottom end) with AFR 185cc heads, 1.6 frpp roller rockers, trickflow stage 2 cam, BBK SSI intake with BBK TB, #24 injectors, CAI, and thats mostly it. Ok my problem is I will crank my car runs good for a second. Once I start driving I will hit probably 2 sometimes 3rd gear and it will start popping through the exhaust or the intake ( I cant tell which). Now first I thought that it was flooding out, but I dont smell fuel when it does it nor do I see smoke behind me. Now here is the weird part I know it is going to start missing when I am at a idle because will stop lopping (from the cam) and lop Really fast and when I take off it starts missing, now I can get it to stop for a few minutes by turning my igintion switch off then right back before the motor has time to completely stop and it runs good then for a few minutes then does it again... CAN SOMEONE PLEASE GIVE ME SOME IDEAS of what this could be I would be MOSTLY grateful!!!!!

 

To see my car go here www.myspace.com/90bluestreak

 

How new is your timing chain?
Doesn't sound like a fuel problem. Sounds like a timing issue of some sort.

 

I thought maybe a timing issue too, but what would explain turning ignition off then right back on and the runds great for a few minutes?

 

how new are your O2 sensors? and aren't the 185s a little big for stock displacement?

 

They are not that new but I know other 5.0s that dont even run 02s and I dont think the 185cc are too big the car runs at WOT it just normal driving where it does it. My car ran a 12.6 at 107 mph and 8.03 at 87 mph and it is stock from the bottom end back!!!

 

When it starts doing this, have you tried wiggling the TFI connector to see if it makes the car run differently? They are a known problem with these cars. That is why you can get the repair harness from most parts houses as well as Mustang suppliers.

 

What is the TFI connector?

 

is your still running an A9L and removed the oxygen sensors then the motor will not run right at all, WOT bypasses all the emissions so thats why it might seem normal then

 

Check your ignition switch....not the key but the one that is on the column activated by the key. These were recalled and known to fail and the fact that you say if you move your key it affects it tells me this is the FIRST place to look. These switches start to come apart and the electrical contacts become intermittent...it is also a fire hazzard.

 

The TFI connector is where the harness plugs into the TFI at the distributor. As they get older they, being subject to temperature changes, loose the ability to make good connection. This can cause a lot of problems and can cause a miraid of peoblems.

 

The first thing that comes to mind is an experience I had long ago with a Chevy Van. There was a carbon-core wire that (part of the ignition system) that ran across the exhaust manifold. When the engine was cold this wire had a certain tension and would not touch the manifold or anything else, but when it warmed up and was exposed to the engine heat then it moved and fell up against the exhaust manifold. What this caused was the wire to kind of "melt" due to the heat. Since it was ignition system-only it was not needed to keep the engine running while started but was needed to start the engine up every time I cranked it over.

If I drove somehwere and turned the engine off briefly (like you're only going in to a convenience store, for example) then came back and started the engine it wouldn't start until the engine had cooled down. Needless to say I looked for a cooling problem for the longest time.

After several frustrating days I finally figured out that the wire would not allow current to flow through it until it had fused back together (once the engine and the wire had cooled off that is). Once it cooled and the melted part of the carbon core fused back together then electrical current could/would flow and I could crank the engine and run on down the road.

I'm taking the long way around the barn to explain this to you; you might want to check your wires by closely following them back from one point to the other to see if this might be a possibility, otherwise you may never think this could occur until you start tearing things down only to realize later that it was just a simple wire (???)

Otherwise, let me ask you this ... do you have a stick or auto?

 

Repling to txbluoval....as far wiring begin an issue it could be an issue but I am pretty sure that it isnt touching any metal cause this does it when the engine is cold and when it is hot doesnt matter.... so I am not sure about it....It is an stick but use to be a Automatic. I convert it, but that was a long time ago. My problem started missing just a little bit and I would floor the gas pedal ( like to clear out the engine) and it fix my problem temporarly, but gradually it got worst to where if it was missing I would get on it and it would barely accelerate and pop and miss as it did accelerate. So I am really lost. What would cause the problem to get worse over time but be so easly fixed but turning the ignition switch off then right back on?

 

Go back and read my post.....my recommendation is from experience, I've dealt with more unique problems caused by those ignition switches than I can remember and some of them were very similar to yours. The switch is less than $10 and easy to replace.