"C" engine EGR; fix it or lose it

[farmerpatrick]

OK,
I'm at the point where it's either continue to spend time and money fixing and troubleshooting the EGR or spend time and money deleting the EGR. My situation right now is I have a new EGR solenoid, new EPR solenoid, new vacuum control valve, all new vacuum lines, and new MAP sensor. The EGR valve works, because if I remove the vacuum line it closes. BUT, the EGR valve never closes on it's own. What sends the signal to the EGR valve? TPS??
With EGR set up, I get black smoke like crazy, due to the MAP sensor reading high manifold pressure all the time, and telling the computer to send more fuel (I think). But, with the EGR valve undone, I never get any black smoke.. and almost 20mpg.
Now, I recently bought a non-EGR intake manifold to build an intake setup on. Something like the one on Dr. Lee's. BUT, won't I need to get a "J" engine PROM to get the computer to send the correct amount of fuel with no EGR.. no input from the MAP sensor, etc. So, how much will a PROM cost me, and where can I get one besides the dealer?
What's the best course of action for me to do this properly and economically. I have no idea how much a PROM will run me.
Some advice please. The wife is going to be upset if I keep spending money on this thing and throwing it down the drain. Like the EGR, has already cost me 165 bucks.. and if I just ditch it all, she'll see it as money thrown away. Even though I look at it as a learning experience and a chance to improve through misfortune.
Please give advice.
Thanks,
Patrick

[britannic]

You have a mechanical pump in the 1991, so no computer is required to control the fuel delivery. Get rid of the EGR and enjoy!

[G. Gearloose]

ya, what britannic sez! Yank that crap out

[arveetek]

As the others have stated, the computer does nothing to affect fuel delivery in your truck. Not until 1994 did a computer start affecting fuel delivery on GM diesel trucks, and that's when the electronic DS4 injection pump came out. On your truck, the only thing that affects how much fuel is being squirted into the cylinders is your right foot!

The reason for black smoke is probably the fact that the EGR is opening up all the way when it shouldn't, allowing an excessive amount of dirty exhaust gases to be introduced back into the intake, causing the available oxygen to be displaced with the same amount of fuel being injected, making a less effecient burn which means more smoke.

Swapping computers will gain you nothing. You need to remove the EGR and block it off, or replace the intake manifold with a J model. Then, remove the bulb from the SES light. It doesn't monitor anything important on the engine at all. Just emissions junk.

Casey

[Dieselboy]

Story time: :D

Back in the day, when my suburban was a 1/2 ton, I plugged the EGR system and disabled the vacuum to it. That rendered the intake-gumming emissions system non-funtional. I kept the C intake with J code intake gaskets and all the associated parts in place to make everything look factory for state inspection purposes. I never had a problem except low power. smile.gif

When I built the new engine, I completely ditched the whole emissions setup in favor of a dual plane J intake. I still haven't had a problem.

If you're residing in an area (CA for example) where you're fighting emissions standards and keeping up appearances around inspection time is important, then I would plug and chug until that dreaded day when PPM and sniffer tests are implemented. If not, then swap in a J intake, deposit the EGR system in the nearest trash can, and enjoy a small power improvement.

:cool: