idle problems on a 92 Sonoma

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clmoran

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I have a 92 Sonoma with the 4.3L TBI. The truck runs really rough when you atart it. Some times you rev it up and it starts idleing fine, other times, the check engine light comes on and it acts like it is flooding out and will not idle at all. Other times it starts fine and runs great. I changed the Idle Air Controler, Rotor and Cap, and that did not fix it. Has anyone had this same problem and know what fixed it? When the check engine light comes on it is codes 33 and 45. I changed the O2 sensor, but know that the 45 is not being caused by a bad O2 sensor. The 33 is either the MAF or MAP or can also be caused by a rough idle which is what it is doing at the time the codes pop. Any help would be greatly appreciated
 
clmoran said:
I have a 92 Sonoma with the 4.3L TBI. The truck runs really rough when you atart it. Some times you rev it up and it starts idleing fine, other times, the check engine light comes on and it acts like it is flooding out and will not idle at all. Other times it starts fine and runs great. I changed the Idle Air Controler, Rotor and Cap, and that did not fix it. Has anyone had this same problem and know what fixed it? When the check engine light comes on it is codes 33 and 45. I changed the O2 sensor, but know that the 45 is not being caused by a bad O2 sensor. The 33 is either the MAF or MAP or can also be caused by a rough idle which is what it is doing at the time the codes pop. Any help would be greatly appreciated
Click to expand...

Clean your EGR valve or replace it. You may also want to run 2 cans of http://www.seafoamsales.com/. Here is a link that my help you use the Seafoam properly. http://gmcowners.com/gmc-forum/showthread.php?t=13770

Good luck and keep us posted. ;)
 
Pulled and cleaned the EGR valve. It was not very dirty and is operating properly. That was not the problem. Could it possibly be the EGR control valve?
 
clmoran said:
Pulled and cleaned the EGR valve. It was not very dirty and is operating properly. That was not the problem. Could it possibly be the EGR control valve?
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Check all your vacuum lines and replace any that may be damaged. A code 33 from the Map sensor is common for low vacuum. Keep me posted and good luck. ;)
 
A little more update on the idle problem. The truck seems to be flooding itself out and missing real bad when cold. I am leaning toward changing the TPS. I am also thinking about just rebuilding the entire throttle body with all new parts and replacing the distributer, coil, plugs and wires. Not sure if the truck has a thermostat in it or not. Seems like an easy fix, but kicking my ass.
 
clmoran said:
A little more update on the idle problem. The truck seems to be flooding itself out and missing real bad when cold. I am leaning toward changing the TPS. I am also thinking about just rebuilding the entire throttle body with all new parts and replacing the distributer, coil, plugs and wires. Not sure if the truck has a thermostat in it or not. Seems like an easy fix, but kicking my ass.
Click to expand...

Keep us posted. :D
 
I took the vacuum line off the EGR valve this morning and then started the truck. Low and behold it ran like a champ. I felt the line and the EGR solenoid was applying vacuum trying to open the EGR valve. I caped off the line and it seam to run fine. I will post again in a few days to let everyone know if this actually fixed the problem.
 
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