5th Gen ('95-'99): High idle
Thread Starter
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Joined: Feb 2025
Posts: 7
High idle
My idle is reving at 2000rpm don't know what's causing it lm at a lose? Changed All air and throttle sensors. Sprayed brake fluid on intake and vacuum hoses, no change. Replaced plugs, wires and coils on the 3.1 and still it idles high? Can anyone guess where to go next, or has any one experienced this with the 5th gen monty? Also changed the eng coolant temp sensor and coolant level sensor, and cleaned throttle body and egr valve...whats left to change... the ecm computer and cam & crank sensors This is one tough cookie to break. Thanks kindly
Last edited by Rio976; Feb 18, 2025 at 02:12 PM.
Joined: Apr 2010
Posts: 12,606
From: Mentor, Ohio
I hope you really didn't spray brake fluid around the engine. That can be a pretty corrosive substance. I have used starting fluid and misted it around.
If the car is idling high, I wonder if the IAC is stuck open. Do you have access to a scan tool that let's you adjust the IAC to see if the engine performance changes?
If the car is idling high, I wonder if the IAC is stuck open. Do you have access to a scan tool that let's you adjust the IAC to see if the engine performance changes?
Joined: Feb 2008
Posts: 6,465
No offense intended, but the first step is to stop just randomly replacing parts. You're going to end up with a whole new engine one piece at a time by the time you get through this.
You've got to work through the diagnostics - figuring out what the data is telling you to isolate a cause and then verifying the part is actually bad before running out to buy a new one.
So looking at the data:
-what do the fuel trims look like?
-what about the front O2 reading?
-how about the IAC counts?
-any pending codes?
-upon startup is it going straight to 2k or is it trying to idle normal first and the engine is having to rev itself up due to an issue?
-TP%
In general you're trying to see:
A) how is the engine running overall? Is all of the added air being measured or is it trying to skew for it to keep stoich?
B) What is the pcm trying to do with the IAC?
That'll lead you to the next place to look.
In general though, the core problem is too much air is getting in and there are ultimately only 3 places it can come in:
-Through the TB
-Through the IAC (either intentionally or unintentionally)
-Through a leak post TB
The pcm data will make it pretty clear which it is.
You've got to work through the diagnostics - figuring out what the data is telling you to isolate a cause and then verifying the part is actually bad before running out to buy a new one.
So looking at the data:
-what do the fuel trims look like?
-what about the front O2 reading?
-how about the IAC counts?
-any pending codes?
-upon startup is it going straight to 2k or is it trying to idle normal first and the engine is having to rev itself up due to an issue?
-TP%
In general you're trying to see:
A) how is the engine running overall? Is all of the added air being measured or is it trying to skew for it to keep stoich?
B) What is the pcm trying to do with the IAC?
That'll lead you to the next place to look.
In general though, the core problem is too much air is getting in and there are ultimately only 3 places it can come in:
-Through the TB
-Through the IAC (either intentionally or unintentionally)
-Through a leak post TB
The pcm data will make it pretty clear which it is.
Last edited by bumpin96monte; Feb 19, 2025 at 07:27 AM.
Thread Starter
|
Joined: Feb 2025
Posts: 7
I hope you really didn't spray brake fluid around the engine. That can be a pretty corrosive substance. I have used starting fluid and misted it around.
If the car is idling high, I wonder if the IAC is stuck open. Do you have access to a scan tool that let's you adjust the IAC to see if the engine performance changes?
If the car is idling high, I wonder if the IAC is stuck open. Do you have access to a scan tool that let's you adjust the IAC to see if the engine performance changes?
Thread Starter
|
Joined: Feb 2025
Posts: 7
High idle rev
No offense intended, but the first step is to stop just randomly replacing parts. You're going to end up with a whole new engine one piece at a time by the time you get through this.
You've got to work through the diagnostics - figuring out what the data is telling you to isolate a cause and then verifying the part is actually bad before running out to buy a new one.
So looking at the data:
-what do the fuel trims look like?
-what about the front O2 reading?
-how about the IAC counts?
-any pending codes?
-upon startup is it going straight to 2k or is it trying to idle normal first and the engine is having to rev itself up due to an issue?
-TP%
In general you're trying to see:
A) how is the engine running overall? Is all of the added air being measured or is it trying to skew for it to keep stoich?
B) What is the pcm trying to do with the IAC?
That'll lead you to the next place to look.
In general though, the core problem is too much air is getting in and there are ultimately only 3 places it can come in:
-Through the TB
-Through the IAC (either intentionally or unintentionally)
-Through a leak post TB
You've got to work through the diagnostics - figuring out what the data is telling you to isolate a cause and then verifying the part is actually bad before running out to buy a new one.
So looking at the data:
-what do the fuel trims look like?
-what about the front O2 reading?
-how about the IAC counts?
-any pending codes?
-upon startup is it going straight to 2k or is it trying to idle normal first and the engine is having to rev itself up due to an issue?
-TP%
In general you're trying to see:
A) how is the engine running overall? Is all of the added air being measured or is it trying to skew for it to keep stoich?
B) What is the pcm trying to do with the IAC?
That'll lead you to the next place to look.
In general though, the core problem is too much air is getting in and there are ultimately only 3 places it can come in:
-Through the TB
-Through the IAC (either intentionally or unintentionally)
-Through a leak post TB
- The pcm data will make it pretty clear which it is.
Joined: Apr 2010
Posts: 12,606
From: Mentor, Ohio
no for some reason l got the car with the change over year to obdll and it doesn't scan with obdll or adaptor from obdl to obdll the scan tool l believe called obdl +? "DID NOT USE BREAK FLUID" sprayed break cleaner which dries or evaporates quick l read that the iac and tps have to be reset once changed? .thanks for reply
Even though this is a OBD-I car, there are tools to interface with them. I used to have access to a OTC tool and a SnapOn tools that interfaced and allowed sensor reads and ability to manipulate the IAC and EGR and a few others to see if they are responding accordingly. This is the OTC tool I used to have access to, but I don't recall the cartridges and such that were needed:
https://www.ebay.com/itm/36523288816...Bk9SR96fqoSkZQ
Thread Starter
|
Joined: Feb 2025
Posts: 7
OK, brake cleaner makes more sense.
Even though this is a OBD-I car, there are tools to interface with them. I used to have access to a OTC tool and a SnapOn tools that interfaced and allowed sensor reads and ability to manipulate the IAC and EGR and a few others to see if they are responding accordingly. This is the OTC tool I used to have access to, but I don't recall the cartridges and such that were needed:
https://www.ebay.com/itm/36523288816...Bk9SR96fqoSkZQ
Even though this is a OBD-I car, there are tools to interface with them. I used to have access to a OTC tool and a SnapOn tools that interfaced and allowed sensor reads and ability to manipulate the IAC and EGR and a few others to see if they are responding accordingly. This is the OTC tool I used to have access to, but I don't recall the cartridges and such that were needed:
https://www.ebay.com/itm/36523288816...Bk9SR96fqoSkZQ
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