Lower power, more smoke, less MPG

[DP]

I've owned a '93 C2500 regular cab since Feb of 2000. This truck is a regular cab, 4L80E, 4.10, mechanical pump 6.5 turbo. Truck had about 120k when I bought it and was driven about 20k a year until early in '03 when I bought a Civic to drive back and forth to work. Since Jan of '03 it's only gone about 10k. I started doing a little more racing (cars, not the truck) this year and noticed that the truck doesn't seem to pull as well as I remember back in 2000 and 2001. From a stop when you roll into the throttle I get a significant amount of black smoke and a matching lack of power (this is while pulling a car trailer at about 5-6k). The truck feels a little worse pulling the open trailer at 5-6k than what I remember pulling 24' enclosed trailer at 8-10k that I used back in 2000-2001. The mpg has dropped as well. I used to get about 16.5 empty and about 12 pulling the 24' trailer. Now I'm getting between 14 and 15 empty, I haven't gone far enough with the little trailer to get a feel for the towing milage. EGT's are also up while towing the little trailer. It's pretty easy to get over 1100 (pre-turbo) while towing.
I've used an agressive mix of Stanadyne conditioner for the last 5 or 6 tanks and havn't really noticed a difference. I've also changed the air and fuel filters with little difference. I don't have a boost gauge installed. The truck has had a 3 inch downpipe and 3.5 inch exhaust since the second month I've owned it. I suspect the injectors are original, but the rtv around the timing cover led me to suspect that the timing chain could have been changed before I bought the truck, but that is just a guess.
Any input would be appreciated.

Dave Payne.

[MTTwister]

Speaking from a minimal knowledge perspective ( someone who knows will chime in) Initially sounds like low boost problem - (I'm a '96).
Vacuum to the turbo? Is the lever pulled in, and hard to open the wastegate when at idle? (assumption you have vacuum controlled wastgate.)
Vacuum from the pump to the wastgate solenoid on the driver's side valve cover? Vacuum from there to the wastegate vacuum pod? Check for old / broken vacuum lines. Pull the electrical contact on the solenoid and check for dirty contacts.

Then - with that many miles, probably 'could' use injector replacement. Stand by for realy knowledge, but something to look at in the interim. Good Luck.

[DP]

This truck has the spring loaded wastegate with no external inputs. I assume that it uses backpressure to control the opening. I don't know if lack of boost would explain the excess smoke right off idle?
I agree that the injectors and pump are probably getting tired, the truck is approaching 190k.
Thanks, Dave.

[moondoggie]

Good Day!

Smoke means:
</font> not enough air;</font> too much fuel.</font>Too much fuel doesn't happen unless someone turned up the pump. Black smoke + low power & high EGT's is almost ALWAYS inadequate boost. That is almost ALWAYS the Wastegate Actuator (mechanical on your truck) or a turbo problem (unlikely, but possible).

You need to get a boost gauge, even temporarily, on this truck. Then you will KNOW what's going on, instead of guessing. I have a temporary one laying on the dash of my 95 pickup (for 3 years now) that I made from an old vacuum/pressure gauge that mechanics used to use to troubleshoot gassers many moons ago. I drilled & tapped the intake post-turbo for 1/8" NPT & screwed in a brass fitting I got at NAPA. I then ran a small plastic tube from the fitting to the gauge, through the drivers side door hinge area.

Blessings!

Brian Johnson, #5044