Hi Everyone,

Im not new to the forum world as I own plenty of Fords but am certainly new to this one and hope you all can help because I am STUMPED!!!

I am the proud owner of a 1987 F150 302, 4x4 short bed (father son project) and after sitting for 3 years its had a number of issues, all have been resolved but one!

My current problem is the truck is breaking down under load (approx 1/2 throttle or more). When the pedal is on the floor the truck falls on its face, backfires and hesitates...i think you get the picture. The truck starts up like a charm and will idle for hours, even revving the engine causes no problem. Idle is as smooth as the truck has ever been. IMO it seems as though this is a fuel issue, since their isn't a "mis" with the engine or a breakdown in timing. Prior to this issue it did run rough, the engine would cut off, and the timing was off so below you will see the replacements that have taken place in the past 6 months:

New Distributor, Plugs (gapped correctly) and Wires
New Ignition Coil and Connector
New Idle Air Bypass and Connector
New Fuel Pump (on Rail and In Tank)
New Fuel Filters
New EGR Connector
New TPS (roughly 8 mo old)
New MAP Sensor
New Water Pump, Power Steering, Alternator, Battery
New Seperntine Belt
New Gas Tank and Fuel Lines
New ECU
New 19# Injectors

Recently this weekend I broke down and decided to change the injectors since that was the last thing that had not been touched. So off with the plenum, in with the new 19# injectors and still no fix!

Any help you can offer is certainly appreciated!

Thanks

 

Mine is doing the exact same thing. Random ignition misfire under load. Ignition Control Module is more than likely the culprit and I don't see that on the list of things you have replaced. I would try that next and I'll be not to replace anything you have on your list.

 

This is assuming that when you replaced your distributor, you re-used the old ICM.

Let me know how this goes!

 

One more thing - could also be the pick up coil. This would also cause random ignition misfire. I don't really know which is more likely to cause this though.

 

coffmajt...thanks for the reply and certainly appreciate it. To be honest I don't know about the ICM and will certainly replace it regardless (good insight). Of all the things listed the distributor was the only item I had a shop install because I ended up on the side of the road, lol, and had it towed. How do I find the ICM? Is it connected on the front of the distirbutor?

 

Yes. It is attached to the front of the distributor. You can't miss it. If you decide to replace the the ignition coil pick-up, it is located inside the distributor.

 

Quite a list of parts replaced. Have you checked for codes? I would check for stored codes and then If you run the KOER test, it may be able to pinpoint your problem. I'd suspect the ICM if it wouldn't start when it was already up to operating temp. Normally its a start or no start condition with the ICM, bad or not bad. Also as was mentioned the PIP/Stator could be bad.

I would check the TPS for good voltage from bottom out to WOT. There should be no major swings in voltage. If there is, that to can cause your problem. New parts can be bad and at this point, if it isn't a Motorcraft product, I would be inclined to check it carefully.

Only other thought is a clogged exhaust, particularly the catalytic converter. Sure nothing made a nest up in the tailpipe.

 

All that work and you haven't checked fuel pressure yet?

 

His problem sounds exactly like mine. I don't suspect fuel delivery problems. My symptoms lead me to believe it's a spark issue (random ignition misfire), but anything is possible. For about $75 I am replacing my PIP, ICM and coil from Rock Auto. And that price includes overnight shipping. I'll be sure to respond to this post on whether or not my issue gets resolved. I do hope this isn't a fuel delivery problem.

 

Thanks for all the replies everyone, should finally have a chance to start checking somethings tonight or tomorrow to see what all should work. Due to work most of them time I get to work on it is on the weekends and i will certainly keep you updated. As for the Self Test is sounds like a great idea to see if any codes are there. I have seen that in my Haynes manual just have never doen it before.

When i changed the injectors i also changed the fuel pressure regulator and considering all of the other parts replaced i just by passed checking the fuel pressure but will prob. I did check the exhaust and no issues there....i have a glasspack dumped underthe cab with shorties and doesnt appear to be an issue.

Like coffmajt said anything is possible, and Im sure its a simple fix its just trying to find it.

 

GTS9MPG - Just wondering if you've made any progress on this issue. I'm having the exact same problem on my '89 F-250, it loses power under load as if a couple cylinders are cutting out. When I let off or downshift it cuts back in. Normally I would think plug wires or coil, but I see you've replaced all that and still having problems. Have you figured it out yet?

 

CircleRat I appreciate the follow up. Ive been fairly busy with work and am certainly moving forward but not sure if its considered progress yet.

So i picked up a scanner and ran the KOER test (the KOEO gave me a system pass). Below is what the test read on the scanner:

21 - ECT out of self test range
44- Thermactor Air Injection System Inoperative (right side)
33- EGR valve opening not detected

To be fairly honest Im not sure where to go from here. I will be doing a little research to figure out what the heck 44 is and I am actually borrowing a fuel pressure gauge to determine if the fuel pressure is what it needs to be.

 

Well correct me if I'm wrong but I believe ECT is Engine Coolant Temp and EGR is Exhaust Gas Recirculator, both these codes may come up on a cold engine. The Thermactor Air Injection System is the air pump injecting air into the exhaust manifolds to help burn unburned hydrocarbons. I don't see how that would cause intermittent power loss but what do I know...

Normally I would think a plug wire is shorting to ground, the distributor has a carbon track inside arcing between two cylinders, a bad coil wire or weak coil. But you've replaced all these and still no fix, correct?

 

I had similar symptoms in my 95 F-250. The catalytic converter was all clogged up. Huge difference in performance. Will the truck run good again if you let your foot off the gas (after it loses power)?

 

Mine does, but it accelerates with good power and shifts through the gears strongly. The power loss usually occurs when torque demand goes up at low rpms, such as in overdrive and starting up a hill. Then when I either let off a little it cuts back in, and if it downshifts it goes back to full power.

Come to think of it I do smell that 'rotten egg' odor at times...