Engine Breaking Up Over 3grand?

stangman11 · Sep 23, 2012

Ok this has been an on going problem thought I had it pinpointed but still nothing.

Ok ill try to give as much info as i can from the very beginning of the problem. When I first got the car it would randomly bog down while either cruising or under hard acceleration. Checked the fuel pressure and it was down to only 15psi. The car then got a new fuel pump and filter which corrected that issue, yet the problem was still their. I then began to look at the ignition. When I got the car the previous owner had installed an MSD cap and accel wires with new plugs so I had assumed it was the ignition module. New module went in with no success. With the help from you guys at a stang net I thought I had it pinpointed to a faulty pick up inside the distributor. Put a new distributor in and now its worse. At any time no matter if the engine is cold or hot anything over 3 grand under hard acceleration the engine breaks up while it climbs in rpm.

I am lost at this point I worked on it today and found a few burnt wires to the EGR and TPS only allowing 2 volts instead of the 5 needed. Repaired the wiring and I now have 5 volts but the problem still persists.

The only codes I have are running codes of 94 and 44.

Any help would really be appreciated i just want this thing running right.

jrichker · Sep 23, 2012

While you have your DVM out, check the red/green wire on the ignition coil for 12 volts or more while the engine is idling. No good 12 volts and you have an ignition switch problem. Do a wiggle test of the wires while you are doing the measurement to spot bad connections or broken wiring.

Your PIP sensor or TFI is very likely still the cause of your problem. A number of folks here at Stangnet have had similar problems, and found that reman distributors have a high failure rate.

If the coil hasn't been swapped, I would try that, it isn't expensive, less than $15. If the distributor has a warranty on it, take it back to where you got it and get another one. Or better still, get your money back and go to a different brand auto parts dealer and get one from them.

stangman11 · Sep 23, 2012

One step ahead of you just put a new coil in and still the same problem. Just made the checks and I have over 12v at the coil while at idle. The problem did seem to get more consistent when I put the reman distributor in. The only other thing I can think of is possible wires but I checked for any arcing and found none.

Noobz347 · Sep 24, 2012

Heat soak your motor by doing a regular drive until you reach op temp. Put your fuel pressure tester on and build pressure. Do you see any cavitation when you hit the relief valve?

stangman11 · Sep 29, 2012

Ok I know its been a while but I have been working a lot of hours all week and didnt have a chance to work on the car. I finally was able today to exchange the distributor for another one and get it installed. Without a doubt idles better and runs better but I still have it breaking up over 3 grand under hard load.

At this point I was going to put a new set of plugs in it because I dont know what the previous owner did any suggestions would be great.

stangman11 · Oct 2, 2012

Any suggestions?

twistedwankel · Oct 2, 2012

stangman11 said:
Ok I know its been a while but I have been working a lot of hours all week and didnt have a chance to work on the car. I finally was able today to exchange the distributor for another one and get it installed. Without a doubt idles better and runs better but I still have it breaking up over 3 grand under hard load.

At this point I was going to put a new set of plugs in it because I dont know what the previous owner did any suggestions would be great.

http://www.stangnet.com/mustang-forums/threads/breaking-up-86-aod-4200rpm-stock.862088/

I'm not getting any suggestions on my 4200-4500rpm WOT breakup either.

So I'm thinking of going with the Bosche (or other) Platinum Plugs simply because they have a lower resistance and fire 99.9% of the time. I have proven high quality factory properly gapped plugs and expensive wires with only 3k on them and installed a really good MSD coil good for 5500rpm using the stock distributor all to no avail (But they look really nice). Other than my WOT high rpm racing issues the car runs perfectly and I get 25mpg highway at 70mph. I really don't think I have a fuel issue. Other than replacing all the injectors? Nah waste of money. But I score a 90 on the cylinder test and the car runs great until the top of the HP rpm.

At least I can live with 4200-4500rpm by short shifting. If mine did that at 3000rpm I'd have to get rid of the car or seriously consider a carburetor again.

You have my sympathy. If I solve my problem I'll let you know.

Doug

ratio411 · Oct 2, 2012

stangman11 said:
At this point I was going to put a new set of plugs in it because I dont know what the previous owner did any suggestions would be great.

Wow, I would have changed the plugs the day I got the car if I "didn't know what the previous owner had done".
You could have gone through all that for mis-gapped plugs.

ratio411 · Oct 2, 2012

twistedwankel said:
http://www.stangnet.com/mustang-forums/threads/breaking-up-86-aod-4200rpm-stock.862088/

I'm not getting any suggestions on my 4200-4500rpm WOT breakup either.

So I'm thinking of going with the Bosche (or other) Platinum Plugs simply because they have a lower resistance and fire 99.9% of the time. I have proven high quality factory properly gapped plugs and expensive wires with only 3k on them and installed a really good MSD coil good for 5500rpm using the stock distributor all to no avail (But they look really nice). Other than my WOT high rpm racing issues the car runs perfectly and I get 25mpg highway at 70mph. I really don't think I have a fuel issue. Other than replacing all the injectors? Nah waste of money. But I score a 90 on the cylinder test and the car runs great until the top of the HP rpm.

At least I can live with 4200-4500rpm by short shifting. If mine did that at 3000rpm I'd have to get rid of the car or seriously consider a carburetor again.

You have my sympathy. If I solve my problem I'll let you know.

Doug

Did you check your valve springs?
They could be so tired that they float the valves at 4500.
Not a garauntee mind you, but something to think about.
You know better than I if the engine itself has ever been worked on, but if it hasn't, your valve springs are pushing 30 years old!
Sitting up for a while can even ruin valve springs... the ones under load anyway.

I love Bosch platinums myself. I haven't had much luck with them on TFI Fords though.
The last time at the parts store, the counter guy, that I know and like, said there was a "known" issue with using those plugs on a TFI.
He had no details, but just said there was an issue that was widely known in the auto business. I have yet to check into it myself, take it with a grain of salt.

stangman11 · Oct 2, 2012

The only reason I didnt do the plugs when I bought the car was because the previous owner had new accel plugs and wires. I decided to put a new set in anyway the car runs better but still breaks up.

I didnt think of the valvetrain thats a good point it does seem more noisey then it should. I guess Ill be pulling the valve covers next to check.

twistedwankel · Oct 2, 2012

stangman11 said:
The only reason I didnt do the plugs when I bought the car was because the previous owner had new accel plugs and wires. I decided to put a new set in anyway the car runs better but still breaks up.

I didnt think of the valvetrain thats a good point it does seem more noisey then it should. I guess Ill be pulling the valve covers next to check.

This just in. I just got back from having the year old fuel filter replaced. The car runs alot better on topend and I can pull all the way to 5k in second gear like I wanted to. 1st gear was crazy fast to 4.5k. So ratio411 gave me some good dope in my original post. I'm planning on waiting for a coupon and will be getting the injectors cleaned/rebuilt as needed next If I ever feel the need to mess with these heads I'll be getting some new better ones that actually flow on the top end AND maybe a cam?

I have a feeling that when my car sat for an unknown period prior to my purchase there might have been some garbage in the tank that washed off? I know it killed the first fuel pump I had to replace not long after getting the car.

Hope your issue turns out to be this simple!!

Doug

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