Engine/Transmission (1994 - 1998) Loss of Power

[Jfam]

Disclaimer: I did search the site under "loss of power" and WOT and found some helpful, though not conclusive information.



Problem: Sudden loss of power in the entire throttle range. By sudden I mean that she was running fine one day, and then without warning a significant loss of power. Guessing it is down by 20-25%. Particularly noticeable after lockup.



Symptoms: Besides obvious slow moving tach and slow to gain speed (most noticable in the 60-70 mph range), there is no black smoke! Used to leave a black cloud and sometimes spin the wheels from a stop. Also, after lockup when floored, black smoke appeared... . not now however.



Clues: I am fairly sure these symptoms appeared right after I had the radiator replaced and the transmission cooler lines fitted with new seals (Did the shop have to take the high pressure turbo lines off and not get them back on properly?)



Also, I noticfed a slight "bucking" only at WOT and lockup a few weeks before that. It disappeared and was attributed to a poor batch of fuel. (If so, did it clog filter?)



Previous repairs: About 18 months ago the IP was repaced (Piers Diesel) with a slightly hotter pump. While trying to run down the problem that turned out to be the IP, I replaced the overflow valve and the lift pump. The fuel filter has 10K on it



I cannot detect any loose clamps on the turbo lines or cuts. Will do fuel filter next. I thought maybe she was not opening to WOT, but a check of that seems to indicate that it is OK. Could the throttle lever on the IP have "slipped" and is not permitting WOT? (I doubt it)



Thanks for the help

 

[SSkinner]

If you think power loss happened after service repair. Check all turbo clamps by tightening them with socket. Check them all with socket a visiual will not show a loose clamp. , Check the afc tube out the back of the IP to the intake manifold to see if it is melted. It maybe possible the turbo wastegate actuator diaphram is torn leaking boost pressure by. (Have seen this but rare). Start here first it is the easiest thing to do. If all seems fine then the problem is probably fuel related.

 

[Jfam]

Will check

Will check with a socket when I get home. Here at the beach house I do not have many tools or the manual. What is the afc tube and how do I identify it? Part of the Banks Git Kit was a new wastegate, so I would not suspect it (would you?).

 

[Joe G.]

You can test the AFC by taking it off and going for a test ride. If the AFC was the problem it should smoke like crazy on acceleration and have plenty of power.

 

[Matthug]

The AFC housing might have blown the diaphram. Do you have a boost gauge? Look closely for torn/ripped intercooler boots along with loose clamps.

 

[DJWyckoff]

AFC AIR FUEL ratio CONTROL

the AFC is on the back top of your pump it is identifed by the air line going in to it. it controls the Air Fuel ratio when un hooked air pressure from the turbo will not be factored in to fuel delivry and excessive smoke will appear at low or no boost. MACK calls this a "PUFF limiter".



your problem lies in the fuel system do your filter and carry a spaire check th lift pump mine stopped or reduesed smoking 3 days before my lift pump went.

 

[Jfam]

Big Clue and Probable Solution

I was checking the line from the wastegate to the AFC and noticed that about 5/8" of untarnished line was exposed at the rubber hose line that connects to the AFC. I took off the hose, but no problem there. I then traced the line back toward the wastegate and saw that it was sung up against the exhaust manifold. When I pushed it away I noticed clearly a worn spot and what appeared to be a hole. Hard to see with my old eyes, but I had the kid next door come look and he said there was a hole.



I am having the line "repaired" by my local mechanic as I do not have the time or inclination to get under the truck and do all the dirty work. He says he feels it can be fixed without a total replacement. Will post results...

 

[Matthug]

That should be your problem, AFC isn't getting a proper boost signal.

 

[biggy238]

Aneroid Fuel Control=AFC





Sounds like you had yourself an un-intentional Valet switch.





Do the 94-95 model years use the same plastic Tubing that the 96 uses for the air source?

 

[Matthug]

My 94' has a metal line to the AFC.

 

[Jfam]

Problem SOLVED!

The hole in the line from the wastegate was the problem. Cost almost nothing to fix.



Thanks to all respondents. I have put Joe G's motto on my shop wall: DON'T FIX IT UNLESS YOU KNOW WHAT THE PROBLEM IS!!!!!