No codes - no idle?
Thread Starter
Instructor
Joined: Jan 2000
Posts: 234
Likes: 1
From: Wesley Chapel FL
No codes - no idle?
Still looking for cause of problem. 87 4+3 will not idle when cold, quits, backfires, etc. Gets better when warmed up. Checked for vacuum leaks, TB is clean. No codes set..............but it will not idle. Starts OK, then dies, which seems to indicate the start injector is working. As it gets warmer, from repeated starts, then it runs better and runs OK (?) when warmed up. Sounds like occasional backfire in exhaust, but idle problem goes away.
One suggestion was cold start valve, but not sure how it works or what to check. Any other ideas out there? Shop manual does not seem to help with causes for cold idle problem. Any help appreciated!
One suggestion was cold start valve, but not sure how it works or what to check. Any other ideas out there? Shop manual does not seem to help with causes for cold idle problem. Any help appreciated!
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: No codes - no idle? (Fla87)
Is the coolant temp sensor OK (check resistance when cold and when hot)?
What is base timing set at?
If it idles ok when warm but at the same speed when just started, inspect and clean the IAC motor and bore. The pintel may be carboned and stuck.
Here a scan tool would tell you what the ECM is seeing and doing.
The cold start injector is between #3 & #5 intake runners in the lower runner flange. It's driven by a temp sensative relay. It serves like a choke on a carb.
[Modified by 65Z01, 2:02 PM 11/4/2001]
What is base timing set at?
If it idles ok when warm but at the same speed when just started, inspect and clean the IAC motor and bore. The pintel may be carboned and stuck.
Here a scan tool would tell you what the ECM is seeing and doing.
The cold start injector is between #3 & #5 intake runners in the lower runner flange. It's driven by a temp sensative relay. It serves like a choke on a carb.
[Modified by 65Z01, 2:02 PM 11/4/2001]
Thread Starter
Instructor
Joined: Jan 2000
Posts: 234
Likes: 1
From: Wesley Chapel FL
Re: No codes - no idle? (65Z01)
Where is the temp sensitive relay (that controls the cold start injector) located? The motor idles fine when warmed up,.........but kind of acts like a stuck choke when cold. Don't think it is a fuel, since it backfires through exhaust and runs OK when warm. Is there a control for TB air that functions only when cold? :confused:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: No codes - no idle? (Fla87)
I believe it's called the Thremo Time Switch and located under the TB in the upper front of the block to the left of the Coolant Temp Sensor.
Pull the connector to the Cold Start injector and see if it makes any difference.
The IAC controls idle air to the TB and should cause the engine to fast idle when first started, especially when cold. That's why I suspected the coolant temp sensor as defective or maybe the IAC pintel as stuck.
Pull the connector to the Cold Start injector and see if it makes any difference.
The IAC controls idle air to the TB and should cause the engine to fast idle when first started, especially when cold. That's why I suspected the coolant temp sensor as defective or maybe the IAC pintel as stuck.
