1993 Full Size Blazer Idle problems....HELP!

[Luckymal]

I have a 1993 4WD Blazer w/ 5.7 and 119,000K miles. It was running great. It all started with a rough idle, very slight. It soon progressed into a rough idle and would continue until the engine warmed up. Any speed below 40 MPH felt as though the timing was off. Now it is throughout the operating range except when in passing gear. The engine wants to die when shifted into reverse and even worse when shifted into drive.

I started by checking for vacuum leaks with carb cleaner (no leak was noted), changed the plugs, wires, dist cap, rotor, and fuel filter. Oh and I did clean the TBI in the process.

The problem was still there... I changed the idle control valve and again the problem was still there. I checked the MAP voltage when static and while running it checked good. I measured the resistance through the full range of the throttle for the throttle position sensor it checked good. There were no jumps it was a smooth transition within the ranged called out in the Haynes manual.

I changed the EGR valve and solenoid and guess what... the problem was still there.

I gave up I drove to the dealer for a more in-depth diagnosis and they said that one injector was dribbling gas but that they thought it was the PCM (ECM). I bought a new PCM and the problem is still there. I checked the resistance of my injectors the Haynes manual I have said it should read between 1.16 to 1.36 Ohms, I read 1.7 ohms on both. Do I have bad injectors? I don't know I am an amateur when it comes to cars, by trade I work on aircraft electronics (avionics).

Any suggestions would be greatly welcome...tips, hints, leads, and/or web sites.

I did not check the fuel pressure due to the fact that I do not have a tee fitting to put in line to check the pressure, and the 93 does not have a factory fitting installed. I did assume however that the dealer would have checked that when it was there for diagnostics.

[JohnO356]

Might not help, but can't hurt. Buy a couple of cans of Seafoam at the parts store. Pour one in a tank of gas and follow directions on the second can for use in your intake. Might clean up that dribbling injector if nothing else.

I'd sure ask the dealer if they checked the pressure, but they'd naturally tell you "certainly"

[ChevyTech]

Don’t assume that the dealer tested the fuel pressure. The diagnostic they did was most likely only what can be looked at with a scan tool and nothing more.

Look at the injectors immediately after you shut off the engine and see if they drip at all.


TBI injector resistance:
At an ambient temperature of 20c the resistance of a TBI injector should be 1-2ohms.
A typically reading would be 1.2 to 1.3 Ohms
Injector resistance specs are published at room temperature or 68 degrees Fahrenheit unless otherwise noted.


I see it’s your first post. Welcome to the message board.

[Luckymal]

Thanks for all of the help. The problem was resolved by replacing one of the injectors. I held a cut sheet of cardboard under the injector and the idle did not change, so I repeated the step on the other injector and the engine died. I replaced the drivers side injector and it started right up and idled better then when I bought it.

Thanks again for all of the help.

[ChevyTech]

Glad you got it repaired

Thanks for the update on what fixed it.