95 blazer 4.3L fast idle

[deadsouls38]

Hello everyone...this is my first post..hopefully you can help...i have a 95 blazer 4.3l that when i start it it jumps to around 2000rpm then drops to about 1100rpm in idle. When i put it in gear it takes off by itself and will go 35 mph on its own. I pulled the egr valve and cleaned it out with no luck...still idles fast when i start it then drops. Is this blazer possesed or is there any hope? 116,000 miles on truck, new engine at 98,000

[cobra1]

make sure the throttle plate is closing all the way.

check the IAC. (idle air control valve) refer to a repair manual for cleaning and checking procedure.

[deadsouls38]

thanks for the reply...i cleaned the throttle plate and had the same problem...havent gotten to the iac valve yet..not enough hours in the day. One thing that i might add is that the gas millage is horrible and there is a really bad carbon smell coming from the exhaust. I will try to get to the iac valve tomarrow....thanks for the help

[DSSDOG]

Smells like a TPS to me.. (Throttle Position Sensor) btw Didnt the 95 Blazer have a Digital EGR Valve.. EGR valves usually cause the reverse affect dies runs like crap..

[cobra1]

Originally Posted by DSSDOG

Smells like a TPS to me.. (Throttle Position Sensor) btw Didnt the 95 Blazer have a Digital EGR Valve.. EGR valves usually cause the reverse affect dies runs like crap..

totally not EGR. as you said, EGR causes very rough idling and/or stalling, certainly not high idle speed.

the IAC on the other hand, controls how much air gets by the throttle plate when the trottle plate is closed. thus if the IAC is dirty or improperly set, too much air get by. the computer in turn, sets the fuel mixture to match the air the going in to keep the proper ratio.

[DSSDOG]

Also the other thing i would look at is a possiable vacuum leak at the "Infamous" plastic ass and bad idea if u ask me. Bakelite Intake Manifold it is also known to cause vechile to have Driveability problems


Bakelite = two unlikely substances combined together carbolic acid and formaldehyde to produce a versatile substance such as Chevys Intake manifold and Radiators. "Bakelite," a revolutionary, non-flammable, early plastic. "The material of a thousand uses," as it was called, made a splash in the 1920s, '30s and '40s.


Plastic parts under my TBI I think NOT lol...

[cobra1]

Originally Posted by DSSDOG

Also the other thing i would look at is a possiable vacuum leak at the "Infamous" plastic ass and bad idea if u ask me. Bakelite Intake Manifold it is also known to cause vechile to have Driveability problems


Bakelite = two unlikely substances combined together carbolic acid and formaldehyde to produce a versatile substance such as Chevys Intake manifold and Radiators. "Bakelite," a revolutionary, non-flammable, early plastic. "The material of a thousand uses," as it was called, made a splash in the 1920s, '30s and '40s.


Plastic parts under my TBI I think NOT lol...

ummmm..... he has a 95 w/CPI, the intake is all aluminum. the plastic upper wasnt used till '96

[deadsouls38]

Cobra1.....if your ever in New Mexico....i owe you a beer or two! Thanks for all the help...I took the iac and cleaned it as you instructed and it for the most part fixed the problem. It still revs to 2000rpm but drop right away to where it is supposed to be. The truck runs alot better. I think I might take it out and clean it one more time, if that doesnt work do you think i should just replace it? At least I now know the culprit.....Thanks

[cobra1]

yeah, id clean it again, and also clean the area where the manifold where the IAC mounts. then if its still not exactly as it should be, then replace it.

you can however check the IAC with an ohm meter. measure the resistance across terminals A & B and C & D ( top two and bottom two terminals). the resistance should be 40-80 ohms, if not, replace it.

if it checks ok, then you know a more thorough cleaning is needed.

also be sure when you re-install the IAC that the distance from the IAC mounting flange to the tip of the pintle is less than 1-1/8". if its greater than that, press the pintle in, till its less than 1-1/8"

[DSSDOG]

Originally Posted by cobra1

ummmm..... he has a 95 w/CPI, the intake is all aluminum. the plastic upper wasnt used till '96

Yeah i guess it all depends on the Birthdate 3/95 rather then 8/95 + I didnt see any mention of CPI but I have been known to miss shit before lol..