Mechanics

CHEVY S10 BLAZER 4.3 TBI.....DUMPING TOO MUC

1988 Chevrolet S-10

Electrical problem
1988 Chevy S-10 6 cyl Two Wheel Drive Automatic 230k miles

Here is my issue. I bought a 88 s10 blazer 2wd with the 4.3L v6. I got the blazer fairly cheap because the guy wasnt mechanically inclined and didnt want to fool with it.

Anyhow, it starts only when you hold the pedal down. Once it does start it has a strong fuel odor and the ground is black from all of the carbon coming out of the tail pipe.

I replaced the coolant temp sensor and rebuilt the fuel pressure regulator. Still the same issue. Today I took it to a shop I deal with from time to time and my buddy put a computer on it. Only code it came back with was MAP SENSOR or high voltage. I replaced the map sensor and it still has the same issue. I have checked the EGR valve by pushing in on the diaphram and best I can tell it is fine. The truck will not run worth a crap with both injectors plugged because they are spraying so much fuel. With 1 injector, you can get it to putt down the street.

My next step is to just replace the computer, but I wanted to see if someone could shed some light on this issue or perhaps someone that has been through the same thing.


Latest progress:

Ok, I'm back on this project now that the holidays are over. After testing voltages and hooking a computer up to the blazer, I was left with the computer being bad. I put a new computer in today and the car started up and ran like crap for a couple mins and then cleared up. I turned it off for a couple minutes and tried to restart and nothing. I replaced all of the plugs using A/C delco. Once again, started up and ran fine. It would even sit there and purr like a kitten. This didnt last long and it would try and stall out, and then clear up and run fine and then repeat the cycle. I was able to drive it home from the shop about 10 mins away and it ran good with the exception of the pinging and valve clatter. Not sure if it might have some water in the tank or not. I got home, turned it off and let it sit for about a hour. Went back outside to start it up, and would not start unless I held the pedal down. I'm really not sure what direction to go at this point. Would the IAC cause this and OR the EGR valve?

Right after I put the new computer in, the truck started up and ran fine. It sat there and idled for about 10 mins with no issues. Today, I pulled all the plugs out and cleaned them, fired the truck back up and the injectors were once again dumping fuel. Just cranking the motor the injectors were dumping fuel like crazy. Keep in mind it did not do this after I put the new computer in at first, but it did the exact same thing with the old computer in. I had them order me another one and will pick it up in the morning. I am really confused at this point and I hope it was just a faulty computer.

Today's progress:

I put the new computer in and still the same. It will idle somewhat decent on 1 injector but is still dumping fuel. I ran the truck about 5 mins or so and could smell something funny and then seen smoke coming from underneath the truck. I looked underneath and it was REAL hot from the converter back. First time it's done this. I hope the converter is not bad now because the whole exhaust system was replaced last year.

Tonight I checked the map sensor using a voltmeter and a vacuum pump and it seems to be fine pressure and voltage wise. I have pulled the EGR off yet but I did apply pressure to it with the vacuum pump and I could see the diaphragm open and close and it seemed like it was moving pretty smooth.

Far as IAC, I could visually see the pintle moving in and out when I would bump the throttle. I havent checked the TPS yet, I will do that tomorrow.

Sorry for the long post, but I figured the more I could explain what I have done, the more it would help someone to be able to help me.

UPDATE today 1/21/2010

I spent nearly all day rechecking, back probing sensors, checking vacuum on the MAP, EGR solenoid, EGR valve seems to be working fine. All of the sensors are within specs far as voltages are concerned. The service engine soon light was out on the dash so I replaced that today. Put the new computer in and I still get the same result, dumping too much fuel out of the injectors. I am not getting a check engine light kicked on and it has been hooked back up on the computer at the shop and no codes are being kicked back.

I am really at a loss at this point. I am getting this computer replaced today just in case it's a computer issue seeing how the blazer started up and ran as soon as I put the first new computer in. I have heard a couple say the proms (chips) were known to go bad. I'm not sure if this is my issue or not.

I just cant figure out what is going on since I am not getting any codes what so ever.
Avatar
Mrdonnie
January 21, 2010.




This is a good one. First, chances are the catylatic converter is toast. It sounds like it melted down. Remove it with the new computer to see if that makes a difference. Also, are you sure the injectors are good and they are not the problem? As far as the proms, they have been known to go bad.

If you are replacing the computer again, remove the converter to see if that changes anything. Also, recheck the temp sensor to make sure it's not sending a reading to the computer telling it it's -40 degrees outside or something crazy.

Let me know what you find.

Joe

First off, thanks for taking the time to read through my problem.

Ok, buddy of mine came over after work with his computer. The MAP, TPS, IAC, are all showing fine. The 02 sensor goes rich to lean back to rich but that is because of the amount of fuel. We pulled the injector assembly out and checked the o-rings on the injectors and they are fine. I also pulled the regulator assembly apart and rechecked all of that, it was fine. We got it to run a little better by adjusting the distributor with the (ECT) wire I believe thats what it is called, unplugged. No codes are being kicked out. My buddy is thinking maybe at one point someone might have changed the injectors out with V8 injectors. He said he has seen it happen in the past. I am going to see if I can find a couple injectors tomorrow and see what happens then. I have not picked up the new computer, but I dont think at this point it is a computer issue. Unless the proms are bad which I am going to see if I can find some of those tomorrow also.

Tiny
Mrdonnie
Jan 21, 2010.
That would do it. I have seen it done before too. Infact it was on a corvette. The car ran really bad, and that is exactly what was wrong. Wrong injectors. Pick one up and compare it to what you have. If you can see a part number, compare it and if they are a different brand, ask the parts store if they can cross reference them.

Let me know what you find.

Joe

Today was another day wasted. I picked up 2 sets of injectors from the salvage yard. I tried both sets and got the same results. Too much fuel. I also replaced the computer, nothing changed.

So, at this point myself as well as my buddies have ran out of ideas. No codes are being kicked back, the converter is fine, the injectors are fine. Only thing I have not done is check fuel pressure but I dont know how to place a tester on a TBI set up. I know on newer cars they have a port on the fuel rail. It has been suggested to me that it's possible the wrong pump could have been put in the tank and I am getting around 60 psi instead of 13 psi. I dont know if this is even possible because wouldnt the pressure regulator not allow that much pressure, or would it bust the diaphram?

Tiny
Mrdonnie
Jan 22, 2010.
The pressure regulator could be bad. To check it you just tap into the fuel line where it goes into the TBI. Yes a bad regulator could cause this. For some reason I thought you checked it.

I said in the previous post I took the regulator back out and everything was fine.

Tiny
Mrdonnie
Jan 22, 2010.
Okay, I looked back through a couple but don't see it. Regardless, you removed the regulator and it's ok?
AD

Yeah, it's fine

Tiny
Mrdonnie
Jan 22, 2010.
Only 2 things I can think of myself, would be the proms or a wrong fuel pump. I am going to pick up a tester next week and see what kind of pressure I am getting.

Tiny
Mrdonnie
Jan 22, 2010.
You may want to check out a nationally recognized parts store to see if they will lend or rent one to you. Usually they lend them hoping to sell a fuel pump.


AD