87 Rough Idle
Thread Starter
Instructor
Joined: May 2006
Posts: 182
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From: Metairie Louisiana
87 Rough Idle
I had the intake gaskets changed on my 87, now Im having a rough idle. It seems as though the ignition is breaking down as you hit certain RPM's (like flat spots). I also noticed that my voltage is lower than usual. Any ideas?
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
If you notice the voltage is lower than usual, check the connection/voltage (VOM) at the battery and alternator. Also check for vacuum leaks at they are very usual when taking apart the intake. It would be good to connect a fuel pressure guage to the windshield to see is the "flat spot" is due to fuel or spark. Is the SES light on the DIC on? If so start there first. Make sure the injectors are getting signal.
What voltage numbers are you seeing when the car is running?
Your not very far from me. hehe
What voltage numbers are you seeing when the car is running?
Your not very far from me. hehe
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Voltage is o.k., should be about 14.0v at idle. Have you checked the TPS to make sure it is .54v closed throttle plates and increases with no pause or jump, too at least 4.0v WOT. Besides using a fuel pressure guage while driving, if you want to check the ignition module...Autozone will do it for free. How are the condition of the plugs? So, this didn't start until the intake gasket was changed?? If so I would be checking vacuums and connections around it too.
Thread Starter
Instructor
Joined: May 2006
Posts: 182
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From: Metairie Louisiana
Originally Posted by RRT vette
Voltage is o.k., should be about 14.0v at idle. Have you checked the TPS to make sure it is .54v closed throttle plates and increases with no pause or jump, too at least 4.0v WOT. Besides using a fuel pressure guage while driving, if you want to check the ignition module...Autozone will do it for free. How are the condition of the plugs? So, this didn't start until the intake gasket was changed?? If so I would be checking vacuums and connections around it too.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by my87vet
Before changing the gaskets I had a very small miss at idle, hardly noticeable. We did check for vacuum leaks and there were no leaks. The plugs, wires, and cap were changed within the last month. I will pull the module and have that checked today. I had the transmission rebuilt this week and really want to drive the car, but the rough idle spoils that new transmission feeling. Hope the module does the trick.
Thread Starter
Instructor
Joined: May 2006
Posts: 182
Likes: 1
From: Metairie Louisiana
Transmission had a whining in gear, had it rebuilt. We just put it on a fog machine to check for vacuum leaks, none found. Took distributor apart and checked all ignition parts, nothing found. Ran 1/3 can of Sea Foam through intake, did not solve problem. The car will idle smooth, than a rough idle for 2 seconds, and keep on repeating. Fuel pressure is strong and steady. Mechanic said it feels like ignition is shutting down and then coming back.
