85 Project - Update & more problems
Thread Starter
Burning Brakes
Joined: Feb 2007
Posts: 786
Likes: 6
From: Manassas VA/Flagler Beach FL
St. Jude Donor '13,'19
85 Project - Update & more problems
I know, I'm my own worst enemy. For every two things I fix, I probably break another.
I got lucky as my anti-freeze spillage was due to a heater hose and not the water pump. So everything is back together and it drives perfect, well almost. The only thing I notice isn't working now (besides the horn) is the fan doesn't come on. I replaced the thermastat with a 180 and bypassed the throttle body. I get home and the idle is about 6K in drive so I decide to do the idle adjustment. You know, the one with the volt meter. Well you know me and electric. I end up with the car idling at 8k in drive. So I disconnect the battery, hoping it will reset to factory preset or something.
Long story short, when restarted "Check engine light" is on. Idles too fast and light stays on. Help!
I’ll recheck all the wires I messed with but how do you reset the CEL after you fix the problem without a scanner?
Thanks in advance.
Glide
I got lucky as my anti-freeze spillage was due to a heater hose and not the water pump. So everything is back together and it drives perfect, well almost. The only thing I notice isn't working now (besides the horn) is the fan doesn't come on. I replaced the thermastat with a 180 and bypassed the throttle body. I get home and the idle is about 6K in drive so I decide to do the idle adjustment. You know, the one with the volt meter. Well you know me and electric. I end up with the car idling at 8k in drive. So I disconnect the battery, hoping it will reset to factory preset or something.
Long story short, when restarted "Check engine light" is on. Idles too fast and light stays on. Help!
I’ll recheck all the wires I messed with but how do you reset the CEL after you fix the problem without a scanner?
Thanks in advance.
Glide
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
I'm unfamiliar with the idle adjustment using a voltmeter.
Can you post that procedure?
There is a TPS setting using a voltmeter but it won't affect the idle speed. It provides a basepoint or reference for the ECM.
Set it at .54 +/- .05 volts and leave it there.
The idle adjustment is called the 'Minimum Air' control adjustment and it sets the operating point of the IAC which controls the idle speed.
Don't adjust the idle using the physical idle stop screw.
Are you sure you got the IAC plugged back in good after doing the TB bypass?
Can you post that procedure?
There is a TPS setting using a voltmeter but it won't affect the idle speed. It provides a basepoint or reference for the ECM.
Set it at .54 +/- .05 volts and leave it there.
The idle adjustment is called the 'Minimum Air' control adjustment and it sets the operating point of the IAC which controls the idle speed.
Don't adjust the idle using the physical idle stop screw.
Are you sure you got the IAC plugged back in good after doing the TB bypass?
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
I'm assuming he's talking about the TPS setting (as as noted by vetnut has nothing to do with the idle); considering he did the bypass and thermostat, the IAC is propably not plugged in correctly, and wondering if in all this, the attempt to set timing was done and the connector was unpluged on not repluged... or if he removed the TB he kinked the throttle linkage also.... just not enough to go on... so only guessing.
you should also post year and any mods to help diag problems.... pull codes and see if you have any errors listed...1st.. then post back...
you should also post year and any mods to help diag problems.... pull codes and see if you have any errors listed...1st.. then post back...
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
How to set idle and TPS:
1. Jumper ALDL pins A&B
2. Turn key on, wait 60 seconds.
3. Unplug IAC connector.
4. Remove jumper.
5. Start car.
6. Adjust idle set screw down until car idles at ~550 rpm.
7. Shut car off.
8. Reconnect IAC connector.
9. Turn car on.
10. Check TPS voltage, adjust so it reads between 0.56 and 0.65 volts.
Car may stumble a bit on first start after this, or not start right away, this is normal.
1. Jumper ALDL pins A&B
2. Turn key on, wait 60 seconds.
3. Unplug IAC connector.
4. Remove jumper.
5. Start car.
6. Adjust idle set screw down until car idles at ~550 rpm.
7. Shut car off.
8. Reconnect IAC connector.
9. Turn car on.
10. Check TPS voltage, adjust so it reads between 0.56 and 0.65 volts.
Car may stumble a bit on first start after this, or not start right away, this is normal.
Thread Starter
Burning Brakes
Joined: Feb 2007
Posts: 786
Likes: 6
From: Manassas VA/Flagler Beach FL
St. Jude Donor '13,'19
The year of the corvette was in the title of the post. The mods are the throttle body coolant bypass and AIR disconnect if you want to call them that.
The idle jumped way up when I disconnected the IAC. Never could get it to go back down. Vacuum leak? Timing?
I couldn't get a voltage reading at the TPS. All thumbs, couldn't get jumper wire in there or pierce the wires. Hope I didn't screw up the connector! I'm going to try pins this time. I had already loosened it and moved it trying to get the idle down, so that probably set off the CEL
I screwed up from the beginning by jumping the wrong pins in the ALDL.
I will try again and post an update tonight.
Thanks for the response!
The idle jumped way up when I disconnected the IAC. Never could get it to go back down. Vacuum leak? Timing?
I couldn't get a voltage reading at the TPS. All thumbs, couldn't get jumper wire in there or pierce the wires. Hope I didn't screw up the connector! I'm going to try pins this time. I had already loosened it and moved it trying to get the idle down, so that probably set off the CEL
I screwed up from the beginning by jumping the wrong pins in the ALDL.
I will try again and post an update tonight.
Thanks for the response!
Thread Starter
Burning Brakes
Joined: Feb 2007
Posts: 786
Likes: 6
From: Manassas VA/Flagler Beach FL
St. Jude Donor '13,'19
Update
Thanks guys. Set TPS today and that cleared the CEL. I haven't driven it yet but if the idle goes way back up when it gets hot, would that be a bad IAC?
