First off, I am so glad I found this forum!!

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.

Thanks in advance for your time.

 

try checking the voltage on the TPS sensor, it could be high when the throttle plates are closed, and the computer thinks that its at WOT so it shoots out more gas.

 

Any idea what the voltage should be?

 

whenn the throttle is closed it should read around .5v at WOT it should read about 4.5v

 

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?

 

What is your fuel pressure? That black stuff coming out of your tailpipe isn't carbon. It's from a bunch more fuel than you need. I believe you probably have a TBI fuel injection from the way you describe your EGR valve. Fuel pressure should be 9 - 13 psi. Sounds loke someone may have put a Vortec pump on it which will put out 60 psi with no problem. And yes they'll fit. Look the same. Had the opposite thing happen to me on my Vortec thanks to my friendly auto parts guy not paying attention. Check it out. I would be real curious to know what the reading is.

 

It's not a pump issue. 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, 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.

 

Ok, here os today's latest news.

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.

Hopefully someone can chime in and help me out here.

 

I would check the fuel pressure. For a TBI engine you need about 11 psi. If someone put in the wrong fuel pump you could be at 60 PSI.

 

What kind of pressure should you have when you turn the key on? When I turn the key on, it jumps to 35psi. With the injectors unplugged, it's jumping up to 50-55psi when cranking the motor. I cant get it started because the cylinders were so full of fuel.

Should the pressure be that high just on crank?