[burb_n_coach]

First of all i'd like to say hey to all... My son and I bought a project S15 jimmy with a bad motor 89 4.3 tbi. We got a donor motor and it started fine. the problem we are having is that the injectors are spraying more like a rain Forest and running very rich and sooty. Tho only code it has put out is the egr, that is new. The 02 sensor, injectors,o-rings, fuel filter have replaced with no change. Now I'm being told that the computer is fubar. Any ideas?

 

[Dexter]

Not necessarily, the computer could be seeing an excessive amount of carbon build up in the egr valve do to it running rich in general... Just a side effect of the tbi spraying out too much gas. It could be the injectors themselves with the problem, or the regulator. I haven't tore into too many TBI's but can only assume they would have a fuel regulator same as my CPI. And when that goes and can spray an over abundance of fuel. Wouldn't consider the computer to be bad due to it throwing that code alone.

 

[burb_n_coach]

That was my first thoughts too. The donor motor had a great spray when they test fired it for me. (had to change intake to fit the 89) I installed the injectors and regulator from the donor and had the same problem.

 

[pyros46290]

check the fuel pressure regulator and try a fuel injector cleaning. maybe the injectors got an itty bitty sumthin stuck in there and they wont close all the way

 

[burb_n_coach]

Sorry for the confusion. I see that my postings weren't very clear.
We installed the motor with the 89 intake. Looking at the spray of the injectors (because of rich exhaust smoke) notice that one screw from the regulator housing was missing. The screw had taken out a valve on the 180k motor i pulled. This is when I found out from previous owner that he had change the injectors and regulator. My first thoughts was that he had put in the wrong parts in causing the bad spray. I installed the injectors and regulator that was on the donor motor ( these had a great pattern in the other truck) but got the same result. I now realized that it wasn't an injector or regulator problem, and reinstalled the new parts. A friend of mine has a scanner and it shows low voltage for the egr and tps system, and the resistant checks shows them to be good. That is the reason for believing that it could be the computer. ? Could a low voltage in the computer cause the spray to look like a pressure problem while dumping huge amounts of fuel?
Thanks to all that have taken the time to respond

 

[91sdime]

Kinda difficult to diagnose over the net...but it could be the computerhas gone screwy..or somewhere along the lines the wire that feeds the 5volt reference to the sensors has gotten pinched or something and is causing the problem also..

 

[tom3]

Are the injectors spraying a nice cone fine mist or streaming fuel? Might have a pressure problem. First thing with a screwy compter scan is to unplug and reconnect the computer plugs a couple times. Cleans off the terminals and can actually fix many problems.

 

[tek88]

what i would try is the coolant temp sensor. I had that problem and went crazy over it but after 3 hrs of checking everything out i realized it was my coolant temp sensor. try it and let me know.

 

[burb_n_coach]

hey Tom... thanks for the reply... The spray is not a nice cone that i would like to see, but more like a huge drizzle.... I replaced the fuel pump and pressure regulator and got the same result. We also replaced the computer with a donor and changed the prom to the new puter. I'm wondering if there is anyway i can check to see if the right prom is in this truck. ( The computer was changed before I got it, and I'm not sure that they knew to change the prom ) I can't find any sites to help me out with that. There has got to be a way to find this info out without paying a garage $60 an hour. At that rate my son could only afford about 10 mins.

tek.. The coolant sensor make sense because of the thing seems to run in closed loop. The gauge is showing 195 - 200 so if the puter is recognizing this I think it should be ok. If anyone knows where I can find the values for the inputs of the puter ( ladder diagrams or flow charts with voltages ) maybe I could make some sense of this. thanks for the reply

This truck has got all my chevy friends befuddled, but iI have not lost hope. It will live again....

 

[meeh350]

i take it that you checked the fuel pressure when you replaced the regulator and all that crap? and not just when the truck is off... but when its running, then running WOT.... should hold around 9-14 psi the whole time......

The computer reads temperature from a seperate sending unit, my 89 has a sending unit on the passender side head and on the intake.... not sure which is for what

warm up mode (more fuel feed) is open loop.....not a big deal.. just making a correction

know anyone with a scanner, if so throw it on and read the values... and see if its going closed loop.... read the 02 cross counts and all that good crap.... make sure its going from lean to rich alot (thats a good thing)
the scanner readout will help tell you if any sensors are bad and point you towards which one it is

ok just read about what you did with the scanner...... tps and egr........
check some grounds.... do you have them all hooked up.... especially the one on the back of the driverside head..... poor ground will cause the computer to see different voltages than it should. wierd things happen when injectors start to see voltage on the ground side because of a bad ground. The computer starts to back feed and seek a ground in odd places. if they are hooked up maybe run a test wire from the ground on the back of the head to the neg terminal... sometimes you will find a bad connection and the test wire fixes the problem leading you to that ground


got any exhaust leaks befor the 02 sensor.... if so fix them.... they will lean the exhaust out and make the computer think the engine is running lean thus the computer feeds more fuel.

 

[tek88]

the temp sensor is different than the one that reads on your guage. there is one on the side of the block passenger side and one right by the thermostat. the one by the thermostat on ur intake is the one that controls the computer not ur guage. that is what i would try i had the same problem before and its a $10 part.

 

[football2003]

i had the same problem on my 94 4.3 TBI and it was the MAP sensor it would run real rich black smoke etc i would look into that

 

[burb_n_coach]

ok.... meeh, The gas pressure is ok running. Now that you mention the grounds, they are all three hooked up but that may not guarantee that they are making a great connection. I'll make that my next check. as for the exhaust leaks... lol.... I ended up replacing it all by time it was all said and done.

tek, thanks for letting me know the difference on the temp sensors. My buddy Jim says that his scanner reads what the computer sees and that was 196 so that should be ok.

football, sorry i didn't mention that map sensor has been replaced.

Thanks to all who are trying to help me past this. My sons birthday was last tuesday and he is wanting to drive this thing.

 

[91sdime]

Do you think you could have kinked the fuel return line when you installed everything..that would cause a severe increase in fuel pressure and cause the problem you are having..but I guess a god visual inspection and a pressure gauge would have to be used to verify/eliminate that.

 

[burb_n_coach]

91sdime, That is a very good point. I have inspected the fuel lines for kinks, but if the return line was to be plugged it would not only cause a possible higher pressure but excessive amount of fuel being forced to the injectors. YEAH!!! I have yet another avenue to go down. Wish I didn't have commitments tonight or I'd try it now. Thanks

Meeh, I unhooked all the grounds and scuffed them up with a med. scotchbrite pad. no differance. Thanks for the idea though.

 

[burb_n_coach]

ok.... I not only reinspected the fuel lines but also rechecked pressure and flow. I even had the return line running into a gas can, no restrictions on either line. (made sure the short line into the tank was clear also). While working on the lines i noticed some electrical tape on one of the wires that go from the alt. to the cab. I pulled back the loom and found that someone had twisted and taped a wire in place of a fuseable link. I got a new link and crimped, soldered, heatshrinked and taped the connection and cleaned the connections at the alt. I really thought at one point I was onto something with the bad connection and all. No changed. (while working on the wire I had the battery unhooked for both saftey and resetting the puter)
I inspected the rest of the wires in the wireloom and found no other problems.

Is there anyone that might know how to find out what PROM chip this 8062 puter is suppose to have in it ? I beleive the puter has been changed because one of the plug retainers is missing.

The chevy shops around here want me to bring it in. (they won't tell me) I think that would be a $70 an hour nightmare.

Still open for suggestions, Thanks

 

[meeh350]

dont take it to a dealer.. they will replace parts until its fixed... charge you 60-80 bucks an hr and give you a bill for hundreds of parts that are unneeded....

i have about a million ideas to fix it I just am not going to type for hours
Get another computer for around the same years... it will at least run... ive swapped computers alot with out checking numbers .. even had one out of a fullsize with a 4.3 4 years newer than mine... check the harness, see if there is any more splices... find a good tps.. try it... i could go on for years here... ide almost need to see this thing........

i wish you leaved in pa.... ide have it fixed in 20 mins
its just too dang hard to diagnos online

 

[burb_n_coach]

meeh, I refuse to deal with dealers.... not only do they change parts untill it its fix, but they charge book for each part they replace. Meaning that if they replace a part in 5 mins, they charge standard half hour diagnostics for each part. I'm on my way to a friends again to run the scanner to see if anything changed since i found out that the MAP sensor was the wrong one. (even though it was new by previous owners mechanic).
The injector spray hasn't changed but want to see if the cross counts are more in range.
The 8062 puter was used on the 2.5, 2.8, 4.3 and chevy only knows how many more engines through the years. I'm thinking that the puter might be from something other than a 4.3 which may be throwing the base perimeters of if it has the wrong PROM.
Just thinking.... if it takes me 12 hours round trip to PA, I'd be time ahead to drive your way. lol.... thanks for the reply
I love this site.... used to hang with GMtrucks.com but got no replies at all.
Thanks to all, will keep informed.
NOT BEATEN YET!

 

[burb_n_coach]

update and thanks to all who have given input.... come to find out, the person who had this jimmy before me had an ace mechanic, or should I say acehole mechanic... this thing had the wrong Map sensor, wrong Egr solenoid, wrong temp sensor, and seems that the mechanic is the one that replaced the fuseable link. ( the one that was replaced with a piece of wire, twisted and taped). after replaceing the MAP,temp sensor, and solenoid... we hooked up the scanner and everything was well in range. Been three days now, running much better. scanner had been showing (Flood Clear mode) untill then.

Thanks again

 

[meeh350]

how did you come about that, just replace everything with new?