jim1940
Contributor
Posts: 139
Age: 73
Loc: Peoria, AZ
Reg: 09-17-09
|
06-16-12 02:29 PM - Post#2237913
I’m running a 1998 vortex 305 Chevy truck engine with 1989 Camaro heads, 1990 Camaro roller cam with a TPI setup in my 1940 Chevy. The TPI was converted to speed density and the only sensors are O2, Temp, IAC, Map, Oil and TPS. I have replaced the O2, Temp and Map. (not because they were bad the car came with the new ones.)
My problem is the engine rpm varies about 150 rpm. It will idle at 600 rpm then drop to 500 and jump up to 650 then goes back to 600. There is no set pattern and it happens in the close loop and open loop and at any RPM even when the wire is disconnect when you set the timing. I have the timing set at 0, checked the spark plugs and checked for vacuum leaks. Looking at the readings on the laptop I see nothing that seems out of the norm.
Anyone have suggestions in tracking down this problem?
take care
jim
|
|
 navygunner08
Silver Supporting Member
Posts: 611
Loc: New London, CT
Reg: 02-13-11
|
06-16-12 02:47 PM - Post#2237925
In response to jim1940
Have you cleaned your TB lately with carb cleaner or similar solvent? If so then you may have damaged your IAC.
|
jim1940
Contributor
Posts: 139
Age: 73
Loc: Peoria, AZ
Reg: 09-17-09
|
06-16-12 10:55 PM - Post#2238098
In response to navygunner08
Thanks for the reply, navygunner. No I have not cleaned the TB. But I will recheck the readings on the IAC using my computer.
jim
|
jim1940
Contributor
Posts: 139
Age: 73
Loc: Peoria, AZ
Reg: 09-17-09
|
06-17-12 07:54 PM - Post#2238486
In response to jim1940
From what I’ve read, the IAC motor should read 0 when the key is turned to on. If that’s true I have a problem with my IAC motor. It starts at 120 and when I start the car it goes to 160 and does not vary unless I run the RPM up to 2000 RPM and let off the gas it goes to 140 then back to 160. When I turn the car off it drops to 120. Should the IAC motor be replaced?
thanks,
jim
|
navygunner08
Silver Supporting Member
Posts: 611
Loc: New London, CT
Reg: 02-13-11
|
06-19-12 06:44 AM - Post#2239061
In response to jim1940
You may have to "re teach" the IAC the correct position. I am pretty sure the correct # is 10-15 steps at idle and then the ECM will control it from there. I do agree that your current # of steps is way to high. You many need to open up the throttle blades a little or drill a small hole into it. I dont know the relearn process for the TPI, but Im sure someone on here does. You can try the relearn process posted in the 88-98 trucks FAQ section.
|
65_Impala
Very Senior Member
Posts: 1593
Reg: 12-29-02
|
06-19-12 04:02 PM - Post#2239227
In response to jim1940
No, it doesn't read zero. The IAC is zeroed by being forced closed and then opened the correct amount to give the air necessary to start the engine. But the zero happens quickly and I've never noticed it showing on the laptop.
You can check the IAC by turning the screw to open the throttle blades. As you open the blades the IAC counts should go down. As you close the blades the IAC should go back up. The whole time the idle should remain stable.
You can also try unplugging the IAC to see if the idle stabilizes. If so, then I'd suspect a sticking IAC motor.
Edited by 65_Impala on 06-19-12 04:04 PM. Reason for edit: No reason given.
|
jim1940
Contributor
Posts: 139
Age: 73
Loc: Peoria, AZ
Reg: 09-17-09
|
06-21-12 10:59 PM - Post#2240041
In response to jim1940
Problem solved… bad coil in IAC. Installed new IAC, no more idle problems and now onto tracking down a slight erratic miss in the engine.
Thanks to all that replied with suggestions.
Thanks
jim
|
|
Gain extra benefits by becoming a Supporting Member 
drtyler (4)
