P1294 high idle problem

Jeepster78

Jeepster78

TJ Enthusiast
Joined
Aug 8, 2021
Messages
109
Location
Albuquerque, NM
Need some help with this issue on my daughters Jeep. She had a CEL come on about a week ago and when I checked the codes had a p1294 code so I did some research and changed the IAC with a Napa part and pulled the throttle body and cleaned it well as well as the IAC port. I cleared the code and it ran great for a week. My daughter said yesterday the CLE went on and now the engine idles at 2-3k rpm’s. I checked the code and same p1294. I read a few threads and some suggest checking all the vacuum which I already did briefly but will go through them tomorrow thoroughly. Other suggestions say to replace with oem parts and possbly change the TPS. I also ran a can of carb cleaner through there TB while it was running with no change. Does any one have any other suggestions to what may be the cause. Should I take the Napa IAC back and get an OEM? Any help much appreciated.
 
Ok so I checked all the vacuum lines and no leaks. I also switched out the TPS with a Napa part and still has a high idle. Cleaned all the connectors real good but no luck. I then unplugged all the connectors that are on the throttle body and started it up and had a low idle about 500rpm. When I plugged in the map sensor still had a low idle but when I plug in the tps it has a high idle and if I just plug in the iac the idle is also high. It seems to me that it’s either the tps or iac is not working correctly. I think these jeeps are picky with the Napa or cheap parts so I ordered a ntk tps from rock auto and a walker iac and will switch them out when they come in a few days.
Does anyone have any other possible suggestions to what’s causing the high idle?
 
You can test the TPS voltage with the ignition ON, but not running by back probing the wiring for to the TPS to determine IF there is a problem.
Be careful when back probing to ensure the 5V reference probe does not touch ground or the other wires probe; insulated probes are recommended.

 
Ok so I checked the tps sensor and it’s working fine switched out the Iac and the jeep when I start it will rev up to about 3k rpm’s and stay there. I have looked for a cracked intake manifold but didn’t see anything obvious and read where is may be a bad intake manifold gasket or cracked intake manifold. I also read that you can spray break cleaner on the intake gasket and see if it is sucking air which may. E a cause of the high rpm’s. I didn’t do that due to the engine reving so high yet. Any thoughts or suggestions on what may be causing this or should I just pull the intake manifold and see if it’s cracked and replace the gasket and go from there? If I do need a new manifold where is the best place to get one. It is the 4 cylinder 2.5L.
Thanks
 
Ok I think I found the issue. Last night I started the engine and immediately it went to about 2.5k rpm’s and stayed there. I then Sprayed carb cleaner on the intake manifold where it meets the head and on the port that is closer to the firewall It would decrease the rpm’s. I also inspected the intake manifold as good as I could and didn’t see any cracks in it so hopefully I won’t need a new one.
I have a few questions.

If I would need a new intake manifold what brand and where do you get one at?

Is there a recommended gasket brand to use.

Is there anything else I should replace when I replace the gasket?
 
I know this is an old thread but I’m dealing with a similar issue..what did you end up finding out was it the intake gasket.. I’m pulling my hair out here
 
Tbiz said:
I know this is an old thread but I’m dealing with a similar issue..what did you end up finding out was it the intake gasket.. I’m pulling my hair out here
Click to expand...

Yes I had a tiny leak at the gasket. I know it is common for the intake and/or exhaust manifold to crack too but mine just had a tiny air leak causing the rpm’s to skyrocket. Get some carb cleaner and shoot a bead around the manifold and if you get the engine to sputter you know you have an air leak. Good luck.
 
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