Novak Conversions Jeep Wrangler YJ radiators

1993 YJ 2.5 slow start and very bad idle at startup

Kunze4u2

New Member
Joined
Nov 23, 2024
Messages
6
Location
St. Augustine, Florida
Hello.
New to the forum, but have searched here a lot in the past.

I have searched a bunch of common threads on here but still can’t find the answer to the issue that I’m having.

I have a 1993 Jeep YJ with a 2.5L engine and the AX5 five transmission. 188,000 miles. When Jeep has been sitting for a while and I started up, it often takes a very long time to start and when it does start it idles incredibly low sputters a lot and sounds like it’s not fully running. If I give it gas, it will stall. Once left running for about 3 to 5 minutes, The RPM will stay right at 1000 and the jeep runs perfectly fine every time.
This does not depend on temperature as it did it all summer.
Once the engine is warmed up it has no trouble starting.

I have replaced the following:
New fuel pump
new fuel filter
New fuel hoses
new idle air control valve
new throttle position sensor
new crank position sensor
new map sensor
new fuel pressure regulator
new intake, air temperature sensor
new coolant temperature sensor
New Distributor, cap, rotor, wires, Plugs

No known exhaust leaks or vacuum leaks.. at least from what I can tell.

Battery starter, and alternator check out fine when tested.

CEL comes on with Key
Only codes are 12 and 55 because I use a battery disconnect sometimes.

I am stuck.
I drive it every day and I’ve never been left stranded but I would like to get this fixed. Any help would be greatly appreciated. Thank you!
IMG_6975.jpeg
 
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Reactions: dihismason5
Hello.
New to the forum, but have searched here a lot in the past.

I have searched a bunch of common threads on here but still can’t find the answer to the issue that I’m having.

I have a 1993 Jeep YJ with a 2.5L engine and the AX5 five transmission. 188,000 miles. When Jeep has been sitting for a while and I started up, it often takes a very long time to start and when it does start it idles incredibly low sputters a lot and sounds like it’s not fully running. If I give it gas, it will stall. Once left running for about 3 to 5 minutes, The RPM will stay right at 1000 and the jeep runs perfectly fine every time.
This does not depend on temperature as it did it all summer.
Once the engine is warmed up it has no trouble starting.

I have replaced the following:
New fuel pump
new fuel filter
New fuel hoses
new idle air control valve
new throttle position sensor
new crank position sensor
new map sensor
new fuel pressure regulator
new intake, air temperature sensor
new coolant temperature sensor
New Distributor, cap, rotor, wires, Plugs

No known exhaust leaks or vacuum leaks.. at least from what I can tell.

Battery starter, and alternator check out fine when tested.

CEL comes on with Key
Only codes are 12 and 55 because I use a battery disconnect sometimes.

I am stuck.
I drive it every day and I’ve never been left stranded but I would like to get this fixed. Any help would be greatly appreciated. Thank you!
View attachment 123532

Update, I just replaced the fuel pressure regulator and saw no change in the behavior. When I started up it almost seems like one of the cylinders isn’t firing incorrectly. Looking for solutions to this issue.
 
Update, I just replaced the fuel pressure regulator and saw no change in the behavior. When I started up it almost seems like one of the cylinders isn’t firing incorrectly. Looking for solutions to this issue.

Okay, you've replaced this part twice now. I have to ask, how did you test for it? Did you rent/borrow a fuel pressure gauge?
 
Double check your wires are in the correct order. Check condition of the spark plugs. Perform compression test - easy to do. Perform leak down test to see if you have issues with head gasket, stuck valve, worn rings. If your engine comes back with semi unhealthy numbers you could seafoam the fuel, crank case and head. Next oil change you could also start using Lucas high mileage oil stabilizer. I did all of the above and my engine now runs reliably. If the tests show terrible numbers your engine is past its prime.
 
Novak Conversions Jeep Wrangler YJ radiators