No start/hard start, poor idle if at all, backfiring through TB

[shibbershabber]

Okay... part 165415451 in the saga I like to call "Why the hell did I buy a Chevy"

Anyhow... (1992 Suburban 1500 4x4 5.7TBI 150kmi)

After seemingly taking care of the issues that Ive recently had (see previous posts) the truck was running okay with only a few hiccups here and there, but totally driveable.

A few weeks ago I was driving and got a code 32 (EGR) but the truck still fired up and drove okay. The light didnt come on again until this week I was on a 200mi trip and while on the highway the CEL would come on and it was the 32 again.

But I got home without incident and a few days later I was heading out and it felt like it had very little power and as I pulled up to the light it started idling down and died. Starting it up again and feathering the throttle didnt keep it going either. I made it through the intersection by stomping repeatedly on the pedal. And that was it. Had it towed home. Tried it after it cooled off. but still it just cranked and cranked.

SO, in my previous adventures I have:

new fuel pump & filter
new injectors & harnesses
rebuilt the throttle body
EGR valve (1yr ago)
TPS, MAP, Knock Sensor
EST(ESC?) Module, Coolant Temp Sensor
Timing chain & gears
new dealer-installed Distributor assembly
plugs/wires/cap/rotor
Battery & Alternator
New computer

Anyhow, I replaced literally everything on this truck... hell I even rebuilt the tranny.

However i didnt do the EGR module... so I though that it would make sense that the one thing I didnt do is causing problems.
So I put one in and fired it up.

It was extremely rough. Had to really get on the throttle to keep it going, but it wouldnt hold idle. I could stomp it up over 3k but it wouldnt stay. and it also backfired out of the TBI... pretty impressive fireball too.

I can feel the diaphragm in the EGR valve moving. Im not sure if my EGR code is connected to this latest issue or not.


Do EGRs fail in other ways besides the diaphragm sticking? What else is in the EGR system?

Can an EGR issue even act like this?


Thanks!

 

[Johnbalderas90k1500]

One way to test the egr is to start your vehicle let it idle and remove the vacuum hose going to the valve. Get a vacuum pump or good old lungs and suck on that hose. If the truck sputters and stalls then its probably working.

 

[shibbershabber]

Replaced the EGR, the old one felt pretty good as its only a year old... but I swapped it for a new one since its under warranty.


Nothing. still not idling for . I can get the RPMs up to about 2k easy enough... but once I try to keep it steady it just falls flat on its face and dies.

 

[shibbershabber]

This truck is the biggest heap of I have ever owned... and I have owned a lot of crap.


Anyhow, went back to the dealer for diagnostics again. They said that the fuel pump is bad.


I refuse to believe it. I put a brand new pump assembly in less that 5000 miles ago.
I doubt that they checked much of the system beyod determining that the pump wasnt pumping.

I replaced the relay and nothing. Is there a fuse or anything that I can check?


ALSO, and I am sure that this is probably the issue because, well nevermind... but I know that the oil pressure sending unit is in the same circuit as the fuel pump & its relay. The wiring to and from my sending unit is a mess from God knows what the previous owner tried to do or fix, etc.

anyhow it is a mess of splices that I was going to clean up once the truck got its act together.

I noticed the wires tonight when I was putting the new relay in. at least two wires from back there went to the relay or were grounded by the relay mounting bolt.

Im assuming that I can just cut back to the best wire I can get to and reconnect things with good connections and see how that goes.

NOW, the question is... could this be the problem? The oil pressure gauge works just fine, could it be working and still not be making a good con with the relay?