Weird Idle Issue (Stumble/Stall) SOLVED
Thread Starter
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
Weird Idle Issue (Stumble/Stall) SOLVED Thought I'd share.
So my car suddenly started stumbling at idle, then randomly dying from the stumbling. It was very frustrating to say the least. No codes, no nothing to point to a problem. IAC worked, TPS was good, fuel pressure, spark, etc. etc. etc.
My AC also had an intermittent issue. It would only work intermittently. I figured it was low refrigerant. But, I was out of town and didn't have my laptop or AC gauges. I couldn't take the heat (Black tinted glass T-Tops and Black Pleather equals not so cool in the car with anything over 75°F). So I decided to just charge it a bit. No bueno.
Alright, this is where it gets interesting. I decided to swap relay's to check that part of the AC system and when I grabbed the AC Relay the clutch kicked on. I let go and it turned off. So I swap relays with a known good one with the exact same symptoms.
Turns out my relay panel has some loose connection on the under side (it is 20 years old) and caused just enough connection for the ECM to "see" the AC was on, but not enough connection to actually engage the AC clutch. So the engine would expect an additional load and adjust IAC, fuel, spark etc for it but not get a load and the RPMs would be off for it's target. This caused the ECM to go berzerk and eventually lead to a rich idle/stumble/stall situation.
I fixed the relay connection issue and all is flawless again.
So for anyone with similar issues, this could be it.
So my car suddenly started stumbling at idle, then randomly dying from the stumbling. It was very frustrating to say the least. No codes, no nothing to point to a problem. IAC worked, TPS was good, fuel pressure, spark, etc. etc. etc.
My AC also had an intermittent issue. It would only work intermittently. I figured it was low refrigerant. But, I was out of town and didn't have my laptop or AC gauges. I couldn't take the heat (Black tinted glass T-Tops and Black Pleather equals not so cool in the car with anything over 75°F). So I decided to just charge it a bit. No bueno.
Alright, this is where it gets interesting. I decided to swap relay's to check that part of the AC system and when I grabbed the AC Relay the clutch kicked on. I let go and it turned off. So I swap relays with a known good one with the exact same symptoms.
Turns out my relay panel has some loose connection on the under side (it is 20 years old) and caused just enough connection for the ECM to "see" the AC was on, but not enough connection to actually engage the AC clutch. So the engine would expect an additional load and adjust IAC, fuel, spark etc for it but not get a load and the RPMs would be off for it's target. This caused the ECM to go berzerk and eventually lead to a rich idle/stumble/stall situation.
I fixed the relay connection issue and all is flawless again.
So for anyone with similar issues, this could be it.
TECH Fanatic
Joined: Aug 2008
Posts: 1,740
Likes: 2
From: Nebraska
If that doesn't work, check your low pressure switch near the shock tower. Take a piece of wire and jump the terminals on the plug and see if the compressor kicks on with A/C on. If it does, you probably have a bad switch.
Nice find! I hade a 01 bonneville in the shop once, Would run a while and shut off ect. I found that the underhood fuse/realy box had 3 bolts holding it togather and the bolts had backed way off. Tightened them up and away it went.
Thanks for the advice, I will try that and see what happens.
