help

[roger Biddlecombe]

01 Trak, 90k, Problem engine miss under load, I have just driven my fully loaded including 10ft cargo trailer with motorcycle ,from Arizona to Canada,it had a miss on hills then getting to Ontario ,Oregan,no power at all,took to shop had scanned,no codes, on testing found fuel presure reg valve reading to high,replaced no diff,will not rev, the mechanic in the end unbolted the exhaust at manifold,instant power,took to muffler shop,found the right precat had collapsed & blocked the main cat, had these replaced,we have power,but all the rest of the way home on hills the engine starts to miss at approx 2200rpm this gets gradually worse with incline,but if I boot it so it changes down & the revs pick to say 3000rpm it goes fine, I am now home & I scanned it no codes, it has no load or trailer, but there is still a miss, New parts put in fuel filter,HT leads, Plugs autolite APP103, Have any of the experts out there got any sugestions on where I go from here,any advice would be appreciated,I am a retired mechanic but find the new technology a litte baffeling, surely ther should be codes showing ???

 

[roger Biddlecombe]

To add to previous info I have excal & have tried it in all 3 tune modes = no differance

 

[Nelson Atwell]

I'd guess the IAC needs cleaning or you have the cracked vacuum elbow issue. Do a search here on "IAC cleaning" or "cracked elbow" for troubleshooting information.

 

[Rodger Tellefson]

Look under Projects\Maintenance for IAC Cleaning by Todd Z.

 

[Bill Cooksley]

I would suggest looking at the plug wires it sounds like you have a wire brakeing down good luck. Bill

 

[Mike Wilson]

Several vehicles I have owned that showed similair symptoms under load

all turned out to be bad plug wires. Open up the hood in a dark place, or

at night and prod the wires with a non-conductive stick or piece os plastic.

I use a shop vac extension wand for this. Look for arcing and sparks to ground

while doing this with the engine running.

 

[Kevin Palmer]

I would have felt you fouled a plug for sure. However, since you changed them, I would go for a defective plug wire.



The IAC should not be an issue at a loaded speed as it simply exists to handle the idle. Since your at 2000 plus RPM's. the IAC is not the culprit...

 

[EddieS'04]

Plug wires.....