What's causing rpm to raise? - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > What's causing rpm to raise?

FS: 2007-2013 Jeep Wrangler "HALO" Angel Eye KitFS: Wranger BRIGHT License Plate LED! Just $3! Great valueOfficial Chassis Saver Rust Preventive Truck & Auto Un

Reply
Unread 08-07-2011, 03:09 PM   #1
provinT13
Registered User
1999 TJ Wrangler 
 
Join Date: Oct 2007
Location: Colorado Springs, Colorado
Posts: 4,632
Cruise control redline!!!!

*EDIT* (I had made this thread originally on the symptoms he was describing, but now I got to see what was really happening so I am editing it)

My friend was describing a few problems he was having with his 1991 Sahara YJ, 4.0L, manual trans. I got a chance to drive it and this is what is happening. When cruise control is on, and he puts it in reverse, with the clutch still depressed, the cruise control takes over and opens the throttle all the way to red line. The only way to kill it is to take it out of reverse. With cruise control off this does not happen and it is only in reverse. He had a friend put on some tail light guards on a day before this started happening. I looked at his work and he had cut the wires to the lights, didn't re-crimp them, and just taped the wires back together. I figured something was getting crossed at the reverse lights so we re-wired everything correctly but it is still happening when he puts it in reverse. For now I have unhooked the cruise control linkage, but I need to know how to chase down this electrical problem. They must have fried something when they taped the wires back together because they were touching, maybe something with the reverse lights since it only happens in reverse? Something is telling the cruise control to give it more gas when it shouldn't be. Is there a relay or something that may be stuck? I don't know much about the YJ cruise control system.

__________________
2 Hands Working Do More Than 1000 Hands Praying

94 YJ Build

99 TJ Build
provinT13 is offline   Reply With Quote
Unread 08-07-2011, 03:26 PM   #2
Noltz
Registered User
YJ Wrangler 
 
Join Date: Oct 2010
Location: Hamilton, Ontario
Posts: 746
Easy thing to check on is the IAC being sticky. Use some throttle body cleaner in park and see if it cleans up at all.
__________________
-Noltz
'91 Frankenheep YJ. 4.0, 4" BDS, Richmond 8.8, Titan 12k, 35" KM2's, rust.
'88 YJ, 4.2/4.0 head, +4" & shackles, BFG 33's (sold)
Noltz is offline   Reply With Quote
Unread 08-07-2011, 07:40 PM   #3
roklok
Registered User
1995 YJ Wrangler 
 
Join Date: Aug 2006
Location: Central Pa
Posts: 141
Quote:
Originally Posted by noltz View Post
easy thing to check on is the iac being sticky. Use some throttle body cleaner in park and see if it cleans up at all.
iac?
__________________
1995 YJ, 4.0, 5 speed, hardtop, bone stock.
roklok is offline   Reply With Quote
Unread 08-07-2011, 09:37 PM   #4
R3V413
Registered User
2000 TJ Wrangler 
 
Join Date: Aug 2011
Location: Blissfield, MI
Posts: 180
Quote:
Originally Posted by roklok View Post
iac?
Idle air Control Valve. They are normally mounted right before the throttle body, but I dont think the 91's have an IAC. The only thing that comes to mind is a vacuum leak, or sticky EGR valve. Make sure you check ALL the vacuum lines for hole, cracks or even dry rot. With the EGR valve, you can check it by letting the vehicle warm up, and when it is place 2 fingers on each side of the valve and have another person hit the accelerator and hold it at 1500 RPM. While they are doing this, you need to feel to see if the diaphram of the valve is moving up due to vacuum. If it isnt then push up on it with all 4 of ur fingers and it should start to run rough or even stall. If not then you need to replace the valve. If you dont feel it move then its not getting vacuum, but if it dont make the engine run rough or stall then its not holding vacuum. Make sure you check the lines before you check the valve.

Good Luck with it!
R3V413 is offline   Reply With Quote
Unread 08-11-2011, 04:15 PM   #5
provinT13
Registered User
1999 TJ Wrangler 
 
Join Date: Oct 2007
Location: Colorado Springs, Colorado
Posts: 4,632
He told me a friend said it was the tps sensor, it will be over here Saturday so I will get a good look then thanks guys
__________________
2 Hands Working Do More Than 1000 Hands Praying

94 YJ Build

99 TJ Build
provinT13 is offline   Reply With Quote
Unread 08-11-2011, 05:26 PM   #6
oldtime_ironman
Web Wheeler
1991 YJ Wrangler 
 
Join Date: Dec 2010
Location: 14304 Niagara Falls, NY
Posts: 2,540
Quote:
Originally Posted by R3V413 View Post
Idle air Control Valve. They are normally mounted right before the throttle body, but I dont think the 91's have an IAC. The only thing that comes to mind is a vacuum leak, or sticky EGR valve. Make sure you check ALL the vacuum lines for hole, cracks or even dry rot. With the EGR valve, you can check it by letting the vehicle warm up, and when it is place 2 fingers on each side of the valve and have another person hit the accelerator and hold it at 1500 RPM. While they are doing this, you need to feel to see if the diaphram of the valve is moving up due to vacuum. If it isnt then push up on it with all 4 of ur fingers and it should start to run rough or even stall. If not then you need to replace the valve. If you dont feel it move then its not getting vacuum, but if it dont make the engine run rough or stall then its not holding vacuum. Make sure you check the lines before you check the valve.

Good Luck with it!
Just FYI the 1991's *do* have an IAC in the throttle body. But other than that, your post is spot-on.
oldtime_ironman is offline   Reply With Quote
Unread 08-11-2011, 06:34 PM   #7
provinT13
Registered User
1999 TJ Wrangler 
 
Join Date: Oct 2007
Location: Colorado Springs, Colorado
Posts: 4,632
I didn't think there was an EGR valve on the fuel injected 4.0L
__________________
2 Hands Working Do More Than 1000 Hands Praying

94 YJ Build

99 TJ Build
provinT13 is offline   Reply With Quote
Unread 08-11-2011, 11:58 PM   #8
R3V413
Registered User
2000 TJ Wrangler 
 
Join Date: Aug 2011
Location: Blissfield, MI
Posts: 180
Quote:
Originally Posted by provinT13 View Post
Is there anything that sticks out of it only acting up in in 1st and reverse gears? I didn't think there was an EGR valve on the fuel injected 4.0L
Yes there an EGR valve, it is mounted on the intake manifold. And if it is a TPS problem, it would constantly be reving up when at an idle state, no matter what gear your in. One thing that I forgot to mention before, is a real easy way to check your vacuum lines (besides a visual inspection) is you can spray brake cleaner, carb cleaner, starting fluid, or anything of that sort on the line and if you hear it rev up, then you know where your leak is.
R3V413 is offline   Reply With Quote
Unread 08-12-2011, 07:38 AM   #9
pasinbuy
Registered User
1994 YJ Wrangler 
 
Join Date: Feb 2007
Location: florida
Posts: 3,834
Quote:
Originally Posted by R3V413 View Post
Yes there an EGR valve, it is mounted on the intake manifold. And if it is a TPS problem, it would constantly be reving up when at an idle state, no matter what gear your in. One thing that I forgot to mention before, is a real easy way to check your vacuum lines (besides a visual inspection) is you can spray brake cleaner, carb cleaner, starting fluid, or anything of that sort on the line and if you hear it rev up, then you know where your leak is.
Brake cleaner and carb cleaner, are ok to use.

I would never use starting fluid, way too dangerous.
pasinbuy is offline   Reply With Quote
Unread 08-12-2011, 01:06 PM   #10
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 13,702
No egr on the Multi port fuel injections, only on our Throttle body injections. See if its really spiking or if the rpm indicator is pegging. I would check the crank sensor. It gives the output for the RPM. I bet its loose or going bad.
Que89YJ is offline   Reply With Quote
Unread 08-13-2011, 10:04 AM   #11
provinT13
Registered User
1999 TJ Wrangler 
 
Join Date: Oct 2007
Location: Colorado Springs, Colorado
Posts: 4,632
Turns out it's the cruise control, I have edited the OP
__________________
2 Hands Working Do More Than 1000 Hands Praying

94 YJ Build

99 TJ Build
provinT13 is offline   Reply With Quote
Unread 08-13-2011, 05:11 PM   #12
provinT13
Registered User
1999 TJ Wrangler 
 
Join Date: Oct 2007
Location: Colorado Springs, Colorado
Posts: 4,632
bump
__________________
2 Hands Working Do More Than 1000 Hands Praying

94 YJ Build

99 TJ Build
provinT13 is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.