Poor running 700 need some help diagnosing

[ndmtnsledder]

Sorry I know this is the wrong forum but figured the engine is the same. Anyway I have a friend with a 04F7 ext completely stock it had always ran good tell he took it out of storage last fall. It runs good unless you try and accelerate quickly and almost acts like its bouncing off a rev limiter at around 6700rpms. If you accelerate more slowly it will go all the way to peak rpm. It acts like a electrical problem but not positive.

So far we have rebuilt the clutches and swapped with a different one, replaced coil and plug wires along with plugs, checked the APV servo motor operation valve movement and cable lengths, and did the test on the stator per the AC service manual. We are running out of ideas and he doesn't want to spend money shooting in the dark replacing expensive parts. The local AC dealer only has a sled mechanic in the winter and we'd like to get it fixed before its time to go west.

 

[76FOMOCO]

6800 is when the valves open have you pull the valves out and check to see if they are dirty and sticking? when they are out check the cable to be free of movement and not hanging up as well.

 

[fasta76]

Is it EFI?? I would check the TPS sensor also.

 

[diggerdown]

It does sound like a servo problem, but you said you checked out the servo, valves and cables. I have seen servo motors that cycle correctly, but fail to work properly. Have you put the sled on a good stand and reved it up and held the R's above 6800 for a short period of time to make sure it keeps the valves open?
Also check your wire harness. The servo works by the ecu sending voltage to the servo when you reach a certain rpm, the servo turns and the cables stop the turn in the proper place, there is a contact in the motor that feeds power back to the ecu telling it that all is good. If the indexing is wrong or the contact has shorted the ecu does not get the feed back and the power feed is cut.
It is possible for the tps to out of wack too, you need a tester for this one. You can buy one for $100 or make one for $6.00 or run it to a dealer and it takes about 5 minutes to check it out.

 

[Proven]

What length did you set the powervalve cables to?

 

[diggerdown]

35.5mm or 1.35" exposed cable.

 

[ndmtnsledder]

I think we can borrow the dealers TPS tester and try that. I don't remember the exact length its been awhile since we looked at it but I know it was the updated specs for the cables. We'll have to try the stand out and make sure the apvs keep operating and not just the initial cycle. Thanks for the ideas we'll try them out and see were they lead us.