Engine loses ALL power when in WOT.

[BlackFox5.0]

It ran fine before it happened, then out of no where it starts acting like this.

I changed the fuel filter, changed a plug wire that got too close to a header (thought that was the problem), changed that plug, check maf voltage and it's there, same goes for tps. Cleaned the IAB, looked over the entire engine for anything wrong, nothing.

It idles perfectly, it drives ok until you get into the upper rpm band, and most noticeable at WOT, where the engine seems to lose all power, like it bogs down, and revs slowly, it's not cats.

I can't think of anything else that would cause it. Any suggestions?

 

[blk9450]

mine was doin the same thing, saturday i changed the 02 sensors, it runs great now

 

[BlackFox5.0]

O2's would change the a/f ratio I think. Im'm not running lean or rich. My father thinks it's a timing issue and how the computer changes timing while driving. We think the TFI module could be the problem. Anyone know what happens when they fail? It's still the stock module from 1987, and I know Ford had a big recall on them....

 

[astronut1885]

I'm still confused as hell on this one. We checked every damned thing on the car, and nothing helped. I think your dad might be onto something. I'll talk to Norm in the morning, see what I can do.

 

[ninety15.0]

I am having the axact same problem....its like the car runs fine until it gets up to about 3k or until you floor it. I did a complete tune up plugs wires cap rotor pcv fuel filter cleaned TB and MAF and K&N...i have checked a million things also and i am now in the process of checking the fuel pressure. I have been trying to fix this problem for like three weeks now and i have changed a ton of things....i cant think of any more. Any help or others suggestions would be awesome. I am not familiar with the TFI module and im not pulling any codes for the O2's so im stumped.

 

[blk9450]

tfi's usually break when they get hot only, when they cool, they usually work again...

 

[astronut1885]

My old GT did this, bogged like a MOFO at WOT, all I did was clean the IAC, the TB, and lubed that stuff up, and it went back to normal. Don't know why, but it worked. It's a real bitch when you slam the pedal, and the power you're counting on just isn't there. The car feels like a 4cyl Honda or something.

 

[astronut1885]

Uh, when something breaks, doesn't it mean it's broken. I've never heard of a busted car part fixing it's self when it cools...I wish my tranny would do that

 

[BlackFox5.0]

So far this is what I have done.

Changed fuel filter, Checked plugs, replaced one and a bad wire, did not fix the problem. Checked timing still at 10* where it was before. removed upper intake, saw a lot of oil in the runners, changed intake gasket, and disconnected PCV, looked over entire engine, tested TPS and MAF volatages and compared them to another mustang with a good tune, and they were very close if not the same in comparison.. plugged stock ignition back in, did nothing so I went back to my MSD. Cleaned MAF with electrical contact cleaner (might have helped a little?)

I e-mailed Pro-M tech and they told me to call thier long distance tech line

If I'm not in WOT then it seems to run pretty strong, but as soon as that pedal hits the floor, it just falls on it's face, BUT....the car SOUNDS like I'm hauling ass, almost as if it's pulling too much timing in WOT....which is what my father is suggesting is happening.

i know some boosted guys run with the SPOUT out, Can I do this to see if it fixes the problem? thing is I don't know what to set the timing at since the base and total timing will be the same because the computer does not retard or advance timing withthe SPOUT out....

And yes, my car feels like a 4cyl when in WOT, and I'm only making like 3-4psi of boost instead of the 6psi I usually make

 

[BarnStang]

astronut1885, the TFI module (Thick Film Ignition) is an electronic component. Like a computer chip. Heat causes expansion, cold contraction. The TFI can get a small fracture in a tiny foil run that seperates when it heats up due to expansion, and make contact when it cools off-contraction...in this regard, it can break and then work again. Eventually it will fail completly, but not until it drives you crazy for a couple weeks or months. Most auto parts stores can test a TFI module for you.

 

[BarnStang]

Also, no one has mentioned the TPS. What are the TPS voltage reading/settings? It could have a dead spot at the top of the range....

 

[Hydrocarbon]

I second checking the TPS for a dead spot. I believe it should have 5.v at WOT.

If you think its advancing too much at WOT. You could try leaving the SPOUT connector unplugged, which would cancel all ignition advance. Then take it for a quick test drive.

.

 

[ninety15.0]

If u take the spout out the car is going to rev real quick and the comp is not going to make any adjustments in regards to the timing, like it should. It may work but its going to rev like a mo-fo if u nail it in first or second....I have a question though, how would u know if the TPS has a dead spot at WOT or any position for that matter? how would u test for that? key on engine off? or both on? thanks and good luck with your problem...because its the same as mine!! haha

 

[Hydrocarbon]

If u take the spout out the car is going to rev real quick and the comp is not going to make any adjustments in regards to the timing, like it should. It may work but its going to rev like a mo-fo if u nail it in first or second....I have a question though, how would u know if the TPS has a dead spot at WOT or any position for that matter? how would u test for that? key on engine off? or both on? thanks and good luck with your problem...because its the same as mine!! haha

You might be right since I've never tried it. I assumed it would be like disconnecting the vac advance on the old dizzies.

When the car is KOEO. I would think you could use a analog VM and probe the two wires on the TB while someone slowly opened the throttle from inside the car. While you monitor the swing of the needle on the VM.

 

[BlackFox5.0]

We tested the TPS, throughout the entire opening of the TB there was no drop off, and at WOT the voltage was 4.9v, with it closed it was at .996v

 

[astronut1885]

Yeah, his TPS read just like mine. I don't know what could be causing this... The only thing we didn't mess with was the TFI

 

[BlackFox5.0]

Yeah, his TPS read just like mine. I don't know what could be causing this... The only thing we didn't mess with was the TFI

And coil....I'll try changing it today. It's the MSD TFI coil, but it could fail just like any other.... I'll put the stock one back and test it out.

If that doesn't work, I'm going to try to manipulate my stock MAF meter with my tweecer that just came in today

 

[astronut1885]

He got the Tweecer... AWWRIGHT....hopefully you can get it goin again!

 

[BlackFox5.0]

Ok it seems like it likes the stock sensor with the tweecer a little better. I cleaned the MAF probes again, and it didn't do anything. Does it sound like it would be the TFI module?

 

[BlackFox5.0]

I took the TFI module out, tested it, and it was ok, cleaned it up put new dielectric grease on it, and put it back in, and it's just as bad if not worse. I moved the timing up to maybe 11*, I had it at 10* before. The skipping is worse and comes on sooner than it did before.

I changed back to the stock coil, and nothing....

What the hell could be causing this!!!!!!!!!!!!!!!! I've tried everything!!!