I have a '95 Chevy Tahoe, 6.5L, that has been acting up.
A couple of weeks ago, there was a loud clunk, the check engine light came on, and since then it has trouble starting, will lurch when driving at slow speeds, and occasionally gives off black smoke when driving up mt. passes. The problem originally seemed to be with hot starts, not cold starts. Now, its often all starts. The local diesel experts checked all the codes, originally thought it was the crank sensor, then diagnosed it as a bad PCM computer. $450 later, with a new computer, and lots of diagnostic fees, the truck still has all the same issues with no answers from the dealership or the diesel shop. the only codes they get now are for the EKG, which they say is in fine shape. They are suggesting replacing the fuel injector pump for 2 grand... based on a hunch.

Around 9 months ago, I converted the truck to veg-oil with the Frybrid system. Wondering if this could be effecting it? I clean my oil with a centrifuge, heated to at least 150',so it's usually pretty clean. And I have not been using veg oil much since the problem began. I read some of the other threads about the optical sensor and put a double dose of Diesel Kleen in, drove around 100 miles, and it does not seem to be getting any better. Possibly worse.

Any thoughts?

First off, lesson learned never take it to the stealer or crooks.

Check the codes yourself and post what numbers it gives you. there is no EKG, do you mean Crankshaft Position Sensor (CPS)? DTC 19?

Checking codes is simple and free with a paperclip across A&B OBD contacts, turn IGN to on and watching flashes from SES light, look in the stickys for more info. never crank with jumper in.

After you check the codes clear them, with jumper in and IGN on depress both pedals for at least 15 seconds and watch to see that you only have DTC12. Then turn off IGN and remove jumper.

Fire it back up and see what codes come back.

Then unplug the CPS and see how it reacts, does it start. Plug CPS back in. Unplug OS, how does it react, does it start?

Do LP tests. check LP pressure with vac/fuel pressure gauge.

They probably guessed an IP because its expensive, and they know the PMDs commonly fail.

Sorry... freudian typo. Not EKG, but EGR. The only codes showing are for the EGR. Thanks for the response.

did you check the codes yourself, dont trust what they tell you.

EGR codes are of no consequence, will impact nothing, just stop EGR from working.

check the codes and post what you find, get real acquainted with your truck.