1982 c3 high idle
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
1982 c3 high idle
I have a good condition 1982 c3 CFI with a high idle problem, and I want to diagnose the broad system that is causing it. Cold run notes are as follows:
Time 0m 0s (0:00) Starts immediately at 700 rpm, 40 psi oil, coolant cold
1:30 climbs to 1600rpm
3:30 drop to 800rpm
5:50 750rpm coolant ~120
7:00 800rpm coolant ~130
10:00 850rpm coolant ~130
12:00 900rpm coolant ~130
15:00 tach 900rpm coolant ~130
stabilizes at this level
Heres some stuff I've already done.
1) set timing back down to 6 degrees, was at 13 before
2) blocked off all headlight vacuum lines and the vac line going to the air throttle thing next to the air filter
3) I tried blocking the air passage to the IAC at 18:30, rpm drops to 850rpm but not more. Uncovered IAC and it goes back to 900
4) I've searched for vacuum leaks like hell. I can't seem to find anymore
Can someone tell me some diagnostic procedures to figure out what system is causing the problem?
Time 0m 0s (0:00) Starts immediately at 700 rpm, 40 psi oil, coolant cold
1:30 climbs to 1600rpm
3:30 drop to 800rpm
5:50 750rpm coolant ~120
7:00 800rpm coolant ~130
10:00 850rpm coolant ~130
12:00 900rpm coolant ~130
15:00 tach 900rpm coolant ~130
stabilizes at this level
Heres some stuff I've already done.
1) set timing back down to 6 degrees, was at 13 before
2) blocked off all headlight vacuum lines and the vac line going to the air throttle thing next to the air filter
3) I tried blocking the air passage to the IAC at 18:30, rpm drops to 850rpm but not more. Uncovered IAC and it goes back to 900
4) I've searched for vacuum leaks like hell. I can't seem to find anymore
Can someone tell me some diagnostic procedures to figure out what system is causing the problem?
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
That isn't that high really, but what is the TPS set to? You have a small vacuum leak either at TB base gaskets or top plate lid.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
If you have the GM manual, it's in there for sure. Look on page 6E-60 under TPS Adjustment and it continues on the next page 6E-61 with pic.You need to set it to that value, .525v.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Melting Slicks
Joined: May 2021
Posts: 2,265
Likes: 1,310
From: Fleming Island, FL
How are you checking the coolant temperature. 15 minutes later and the coolant temperature is still only 130? Like I said in the other post IAC position is based on coolant temperature.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Melting Slicks
Joined: May 2021
Posts: 2,265
Likes: 1,310
From: Fleming Island, FL
The engine temp is coolant temperature. Are you sure that your thermostat is good? A simple thing like a thermostat could be your whole problem. These cars don't throw a code for low coolant temperature like OBD 2 does.
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Melting Slicks
Joined: May 2021
Posts: 2,265
Likes: 1,310
From: Fleming Island, FL
Even 160 is way too low. The Crossfire system will never function properly if the car never comes up to temperature. You can check it a number of ways. Just put a new one in. They're cheap enough.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Melting Slicks
Joined: May 2021
Posts: 2,265
Likes: 1,310
From: Fleming Island, FL
Remove the ECM fuse (located in the battery box) and leave out for a few minutes, reinstalled the fuse and drive the car and get it up to at least 40 MPH for a few miles. This will reset the ECM. The ECM has to learn the idle.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Oil pressure light? Also, Im not really worried about it blowing up. The reason why I wanna fix high idle in the first place is bc when I shift into drive, the car jerks alot, which I think is causing damage to the transmission/flywheel, not to mention the mounts. Otherwise to be honest I wouldnt really care much. Thats the only major thing I have to fix before Im comfortable driving it regularly.
Melting Slicks
Joined: May 2021
Posts: 2,265
Likes: 1,310
From: Fleming Island, FL
Oil pressure light? Also, Im not really worried about it blowing up. The reason why I wanna fix high idle in the first place is bc when I shift into drive, the car jerks alot, which I think is causing damage to the transmission/flywheel, not to mention the mounts. Otherwise to be honest I wouldnt really care much. Thats the only major thing I have to fix before Im comfortable driving it regularly.