HOMESLICERYRY

Whats going on guys? I just picked myself up a work van, its a 1999 Chevy Express 1500 cargo van with the 4.3 Vortec. Bought it for 700 knowing it needed work and have no problem putting the work into it but figured id turn to you guys for some help.
I am throwing p0300, u1041, and P0748.
The car is dumping fuel like no other, I can start it and run it but it bogs HARD under acceleration, if i manually shift through the gears once i get over 2500 rpms it seems to catch and drive ok. Once i come to a stop light though i have to give it gas to keep it running. The car is Also backfiring under load.
Now the P/O had told me he put 2500 into it but could not figure out what was going wrong. He stats the mechanic told him his computer was bad from being wet and had it replaced, which didnt help. Fuel spider was completely replaced, map sensor, and a few other little things. My stepfather who is my mechanic has been toying around with it when he has free time and noticed every single part on here has the dreaded Junkyard Chalk lettering on them. The computer when scanned is also stating the van is a 4.1. The P/O had told me everything was perfect up untill the mechanic claimed the computer had gotten wet. Since then it has been trouble doing the same things since.
I ask for help on here because my stepfather has his own shop, but due to him not wanting to bang me over the head he only works on it when he has some down time. So i figured Maybe somebody can have a clue as to what to look into
Van had aftermarket alarm that was tapped into the obd II power not allowing the scanner to read. Was removed now car can be scanned. Fuel pressure is reading a steady 60 psi, car has spark.
99 4.3 with 203k miles
Thanks guys

tsbrewers

My first question would be the computer saying that it is 4.1? Are you saying that the computer thinks it has a 4.1 engine? Sorry, just not sure what you mean here.

IF SO, I am guessing they have a wrong computer in there. I would look for a different one that is from your van, and then have it updated to the newest firmware from a good mechanic, or the dealer.

I would start there.

HOMESLICERYRY

Yes it is reading as my truck is a 4.1 which is wrong.My stepfather plans to get me one when the time allows, He told me it was the wrong one and had junkyard chalk on it.

tsbrewers

That would absolutely be my first try then. I am surprised it runs at all.

Brew

HOMESLICERYRY

Very odd but my computer number is ID 16263494, Which is what is in the van as we speak. My fear is the previous mechanic butchered up this truck

HOMESLICERYRY

Computer has been updated, van still having same issues, Compression is solid across the board. Fuel pressure is a steady 60. We put in a new distributor, plugs, wires and it seems to run a little better but no cigar. Could timing be off? CPS?

kevinkpk

First off, that ecm could have been flashed with incorrect for your van information. Second, cps will either not start or throw a reference code, is there any check engine light?

kevinkpk

Another thing, I am not totally sure if the knock sensor is part of the ecm, whats it's history?

HOMESLICERYRY

Yeah I am throwing p0300, u1041, and P0748.
The P/O stated the ECM was changed. It has the junkyard chalk writing on it like it was swapped in. The P/O's mechanic just threw parts at it

tsbrewers

Many factory parts will have the paint slash on it too. That is the workers at the factory doing checks.

I would look at the vehicle grounds. I *think* there are a couple under the drivers door on the frame. I would check these (and all of them) very well. Take them off, clean them all up, and make sure they are getting a good connection. The randomness of the codes is odd to me.

Brew