Stalling & Revving problem
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New User
Joined: Aug 2010
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Stalling & Revving problem
Hi all I'm new to the Bronco ownership thing. I have a 91 Bronco, 5.0 engine. Lately it's been stalling when I first start it (after it sits for awhile) and once it's warmed up, the engine will rev at stops. It used to surge really bad but I had a mechanic friend come over and we replaced the IACV and disabled the EGR valve "for diagnostic purposes". It's not surging per se, but it does idle really high when I put it in park or come to a stop. Any suggestions on what else to check that might not be too expensive. I'm on a limited income and want to try anything that might help. THANKS for the input!
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
Welcome to FTE and the Big Bronco Forum. We will do our best to get you the most accurate information we can dig up.
As to your idle issues, I am going to assume you reconnected the EGR. (Idle will never come back to where it should be with the EGR disconnected). Have you pulled codes from the EEC-IV computer? Both a KOEO and KOER test would be in order before any further troubleshooting happens. This will save time and money. With the IAC being new, the next possible issue would likely be one of the thermal sensors in the truck. However, running the diagnostics tests will better pinpoint the real problem rather than arbitrarily replacing sensors that may or may not be causing your issues.
As to your idle issues, I am going to assume you reconnected the EGR. (Idle will never come back to where it should be with the EGR disconnected). Have you pulled codes from the EEC-IV computer? Both a KOEO and KOER test would be in order before any further troubleshooting happens. This will save time and money. With the IAC being new, the next possible issue would likely be one of the thermal sensors in the truck. However, running the diagnostics tests will better pinpoint the real problem rather than arbitrarily replacing sensors that may or may not be causing your issues.
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Well the EGR is still disconnected and we ran a bunch of diagnostics that set codes for the coolant temp sensor, which we replaced. Seemed (at the time) to cure the revving problem after it was warm but it was still fluctuating when idling. Now it's back to the same old problem a day later. Should reconnecting the EGR help? The guy that's been helping me says its really not needed, but I can reconnect it if needed. We also replaced three suspect vacuum hoses with new and cleaned the air temp sensor, and cleaned all the wiring connections (some had minor corrosion which is now gone). Frustrating!
The Southernmost Mod
Joined: Dec 2004
Posts: 6,902
Likes: 21
From: Caracas, Venezuela
I've been telling this a lot later, as it helped me: Clean the Throttle Body (the instructions will be in the TB cleaner can). And the Injectors (i've been told that when they're dirty, they could cause the stalling you described).
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