1990 bronco idle problem
Thread Starter
|
New User
Joined: Feb 2007
Posts: 20
Likes: 0
From: minnesota
1990 bronco idle problem
I have a problem with my bronco! It doesn't Idle up when I start it or when I turn the a/c on. there no codes. I put in a new idle circuit, a new pvc and a new tps. Every ounce in a while she revs to 2000 rpms I shut it off and restart it it runs fine, if I unplug the IAC it revs to 2000 rpms I plug it back in and the idle goes back down I disconnected the battery for ten minutes and it still does it what gives?? I am confused Please help
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
No codes? I find that impossible to believe especially if you have disconnected the IAC. That alone will generate a code for an open circuit to the IAC. And even if there are no faults the code 11 or 111 will be returned which indicates the system passed the self test.
Exactly what did you replace? Not sure what you mean by "idle circuit".
Exactly what did you replace? Not sure what you mean by "idle circuit".
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
As I mentioned earlier the IAC being disconnected should generate a fault code and furthermore with the engine at full op. temp. disconnecting the IAC should cause the truck to fall on its face and die at idle. If it doesn't, you have a vacuum leak or worse, someone has messed with the throttle plate stop screw in the throttle body. Either is something that must be rectified before your idle problems will go away. Cleaning the IAC won't do anything if the idle takes off with it disconnected.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Disconnecting the IAC with the engine running or starting with it disconnected WILL generate code 81 or 543 depending upon the age/model ECM in the vehicle. You can have idle issues related to the IAC without getting codes but disconnecting the IAC WILL generated "IAC circuit failure" codes.
Trending Topics
Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
No big deal really... you are correct in that you can have idle issues caused by a dirty IAC and never get a code from it. But the OP stated he had disconnected it and still gotten no codes which is impossible unless it was reconnected BEFORE he started the truck again.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
There is no idle control sensor... the IAC is the actual valve and solenoid air flow control for the engine at idle. The engine functions at idle are controlled by a series of thermostatic and pressure sensors that monitor the "ignition trilogy" (air, fuel, spark/heat). The MAP, ECT, O2, and TP all contribute to the information the PCM uses to maintain idle.
Any condition that allows the engine to idle HIGHER with the IAC disconnected is more likely a vacuum issue or an idle stop screw that has been adjusted... BTW it should NEVER be adjusted.
Any condition that allows the engine to idle HIGHER with the IAC disconnected is more likely a vacuum issue or an idle stop screw that has been adjusted... BTW it should NEVER be adjusted.
Elder User
Joined: Apr 2010
Posts: 645
Likes: 1
From: Richlands, NC
Maybe I replaced the Idle control valve?
No, no.. It was an electrical part that I replaced to fix that problem.
Gah, I wish I could remember..
I have a 1990 Ford Bronco with a 5.0L 302 V8.
It had a Idle Control Sensor or a.. something like that..
Can't believe I can't remember..
No, no.. It was an electrical part that I replaced to fix that problem.
Gah, I wish I could remember..
I have a 1990 Ford Bronco with a 5.0L 302 V8.
It had a Idle Control Sensor or a.. something like that..
Can't believe I can't remember..
Elder User
Joined: Apr 2010
Posts: 645
Likes: 1
From: Richlands, NC
I know what it is!
(I had to look through old receipts)
You've got to replace the Idle Air Valve AND Throttle Position Sensor.
You've got to replace BOTH of them.
Make sure you disconnect the battery before you put them in.
Then reconnect the battery AFTER they are both in.
They work together, and they program themselves.
(I had to look through old receipts)
You've got to replace the Idle Air Valve AND Throttle Position Sensor.
You've got to replace BOTH of them.
Make sure you disconnect the battery before you put them in.
Then reconnect the battery AFTER they are both in.
They work together, and they program themselves.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
If there are no codes being thrown to indicate there is something wrong with the TPS, it is unlikely that replacement is necessary. TPS can develop "dead spots" like any potentiometer but with the problem being at idle, if there was a problem with the TPS you would get a fault code.
Thread
Thread Starter
Forum
Replies
Last Post
justin richter
Excursion - King of SUVs
12
Apr 11, 2017 08:56 PM
Blake12
1997 - 2006 Expedition & Navigator
6
Jan 25, 2016 08:08 PM
