Engine/Transmission (1994 - 1998) Low Boost, Low Power, High EGTs

[MMcCallie]

Problem has progressed over the last few weeks. After searching the forums i haven't found a likely cause. I used to be wastegated to 35 psi boost. Now i can hardly get into the mid 20s.



Used to see over 1,500 EGTs. Now i don't get to 1,400. During almost every acceleration EGTs climb above 900 degrees. Power is abrubptly cut off in the upper RPMs. Feels suddenly choked.



Smoke is about the same. Even under less throttle the engine feels less responsive, less powerful. Almost as if the cam plate has been changed to defuel on top, but it was most recently custom ground and slid all the way forward, as was the AFC. No engine tuning in over 2 months so i don't know what might have moved or changed.



I've sprayed starting fluid around the intercooler boots and the idle only raised when sprayed at the air filter. I previously noticed that when at low RPMs and boost while trying to accelerate hard, the throttle pedal was very stiff, hard to depress, heavy smoke. This problem is no longer present. Could the issue be with the AFC, wastegate, or GSK? Where should i begin?

 

[Smokin_Monster]

Sounds like your not getting the air you should be. Check your turbo for shaft play. Or your wastegate might be stuck open a little. Check the wastegate hose for any leaks. Double check your intercooler boots. Pull them off and check for any cracks or holes. This is where I would start.

 

[MMcCallie]

I didn't think of that until just a little while ago. I hope its not the turbo but i guess its not unlikely. I had it ported when the engine was last tuned. I'll check things out tomorrow if its not raining.
Thanks,
Matt

 

[MAllen1]

if you have a way of pressure testing the intercooler by itself, that would be my suggestion. I experienced the same problem as a mechanic when a customer came in with same problem. Come to find out, a rock got through the grille and missed the condenser, but, hit the intercooler. Does the turbo "sound" the same ( or louder) than usual?

 

[MMcCallie]

Turbo sounds the same, loud. Without the silencer ring it sings like a cricket even at idle. I've been running biodiesel, including over 100 gallons of B100 soybean oil, for the last few thousand miles. Could a clogged fuel filter be causing these problems? I've got an additional inline fuel filter, wouldn't be a bad idea to change them now anyway and see if my problem goes away.

 

[Smokin_Monster]

Yeah change your filters and see if that helps. The one tank of biodiesel I ran my truck would just die at random while I was driving down the road. It would start back up and be fine for a while. But it was the homemade stuff though.

 

[MMcCallie]

Changing the fuel filters brought back a lot of the missing power. No more hesitation in high RPMs. Under hard throttle testing, i was only able to pull off 60 mph for a few seconds in town. Boost is still only in the 20s. Perhaps i can find a stretch of road where i can open it up to near 100 mph so that i might see my boost get up to 35 psi. I used to see boost over 30 psi very frequently driving the same way in the same places. My smaller inline fuel filter was quite backed up and clogged when blowing through it. Had been approximately 8,000 miles since they were last changed.