Starting to piss me off.....

[Ike83]

Okay....my car has ran GREAT throughout the entire time period I've owned it, which is about a year at this point. Recently I removed the smog pump and changed the spark plugs in my '87 Mustang, and everything has been fine for a couple of months.

The other day I was driving my car and I was coming off the highway, so I downshifted into 4th to allow the car to slow down on it's own. Well, the cars in front of me began to accelerate so I pressed the gas pedal down. POP! My car backfired then immediately began to accelerate normally. I tried to get it to do it again but I couldn't get it to happen.

Now it's happening once a day. It seems to happen ONLY in 3rd and 4th gear....and it ONLY happens when the rpms are below 2500. Everything ABOVE 3000 rpms the car runs strong. Or if I'm in 1st, 2nd, or 5th it doesn't matter where my rpms are. However, I have noticed a slight stutter when I'm in 2nd gear in low rpms. I can not figure out for the life of me what the problem is.

The first thing I figured was, I had a bad plug, I miss gapped it, or my spark plugs wires are going bad. I JUST re-changed my plugs over the weekend AND bought a new set of MSD 8.5mm wires and I'm STILL having this problem.

Remember, it's ONLY in 3rd or 4th gear BELOW 2500 rpms, my car will bog down, then POP, then accelerate normally.

I'm trying to figure out if this is a timing problem, if it's because I removed my smog pump and my car is running too rich, or if I'm having a valve train problem.

Can a car backfire if it's running too rich? Does this sound like I need to adjust my timing? I wouldn't understand how it could be my timing b/c the car has ran FINE for almost a year now. This problem came about a couple of months after I removed the smog pump and changed the spark plugs.

I know there's ONE plug that is hard to get the wire on it, but I'm almost POSITIVE the wire is connected properly so that CAN'T be the problem.

Has anybody else had this problem before or does anybody have ANY idea what it could be? I'm debating selling my 5.0 and looking for an '03-04 Cobra and this problem isn't helping me favor the 5.0.

Any help would be appreciative.

 

[Ike83]

SURELY somebody has either had or heard of this problem before.

 

[68keyblr]

Is it throwing any codes?

...and don't call me Shirley

 

[Ike83]

Is it throwing any codes?

...and don't call me Shirley

It's funny you should ask that. I've called Auto Zone and Advanced Auto Parts and asked if they could pull KOEO codes and they said they didn't have the machine to do that. Then I called Ford and they basically laughed at me due to the whole car being aftermarket at this point. At this point I'm not really sure what to do.

I've done some "searching" and have come with cleaning the MAF, buying new cap and rotor, new coil, or new TFI. I'm trying to figure out which one to try first.

 

[Ike83]

Is it throwing any codes?

I'm sorry.....no, the CEL isn't on but I hear there is a way to pull the codes using a wire and paper clips or something. I will be calling my mechanic to help me with that process, although last time we tried that it didn't work.

I'm more or less trying to find someone else who has had this problem and see if it matches mine.

 

[68keyblr]

Do a search, jrichker has an excellent set of instructions for pulling the codes with a paper clip or a test light. The code reader is only like $30 at an auto parts store.

 

[Ike83]

Do a search, jrichker has an excellent set of instructions for pulling the codes with a paper clip or a test light. The code reader is only like $30 at an auto parts store.

 

[ruudogs]

I would also go out and get a cheap code puller for the EEC IV. There is also a really good Ford repair manual for the EEC IV ignition sytems. I have had an 87 GT for 12 years and use the scanner and manuals quite often (more so then I like actually). See if the car is throwing any codes, then run the test stated in the manual for that code.

Your problem is probably related to the smog pump being removed. You might have some open vacuum lines now that are affecting the EGR valve for example. I have used the codes in the past to find problems with: EGR valve, IAC valve, O2 sensors, etc. It is really hard to isolated a throttle problem without the codes because there are a half dozen little sensors that could be causing it.

Does your 87 still have the speed density system? I had a lot of idle problems on my car with it and converted it over to Mass Air when I did a cam change.

Good Luck,

Paul S.

 

[Ike83]

Actually, it was already converted to MAF when I bought the vehicle.

Like I said, the car ran FINE for a month, now all of a sudden I'm having a slight backfire in the high gears when I'm running low rpms.

It is probably a minor problem, but I think I'm going to sell the vehicle for the same price I bought it last year.

I bought it at $5,500, and since then, I've added the BBK TB, BBK cold air intake, Pro-M MAF 75mm, and I've also added the Holley fuel pump.

If anybody wants to buy an '87 5.0 for $5,500 and fix the slight misfire issue, it's all yours. I've recently found a '95 GT I can't wait to get my hands on....so the sooner I sell it the better.

Believe me, I'm selling the car NOT b/c of the misfire issue (which I'm sure anybody could diagnose and fix), I'm REALLY trying to get my hands on this '95 GT with the Vortech supercharger. My car already has the Autometer Sport Comp tach with the shift light and Autometer pillar gauges, so she's already ready to go.

If anybody wants it, let me know.