• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

ENgine swap done, now have high idle

ROBZ95Xj

ROBZ95Xj

NAXJA Forum User
Location
Keene NH
vechicle is a 1998 Cherokee 4.0 AW4 242

motor is from a 93 Cherokee, i swapped all sensors from the 98 motor to the 93, also installed a 99 intake, it wil idle around 1200 and gradually go to 1500, if you rev it it will stay around 2k, any ideas? everything apperes to be hooked up
 
TPS? ive had intermitten problems with idle and after a couple YEARS of living with it the CEL through a TPS malfunction code. now it runs like factory. thats probably no help, but hell... its a $30 part. couldnt hurt.

any CEL codes? have you run a compression test? where did you get the motor from and what/how did you check it before dropping it in?
 
Last edited:
VAhasnoWAVES said:
TPS? ive had intermitten problems with idle and after a couple YEARS of living with it the CEL through a TPS malfunction code. now it runs like factory. thats probably no help, but hell... its a $30 part. couldnt hurt.

any CEL codes? have you run a compression test? where did you get the motor from and what/how did you check it before dropping it in?
Click to expand...
motor was from my 93 wich had 203k on it, never had any issues with it , when the motor blew up in the 98 the #6 pistion blew into a bazilion pieces, pieces were found in the intake and the tb, we swapped the sensors to another tb

last night i disconected the batt to let the comp reset, went out today after work and started it up, idled fine for a couple mins till it started to warm up the the the rpms climed to 1800 and stayted, if you rev it it will hang for a lil bit then drop to 1800, i thied usin a unlit map gas torch to fund a vac leak with no luck, i may try tightming the intake bolts a lil more even though they were touqed to spec
 
ehall said:
idle air controller could be having problems, disconnect and see if blocking the port with your finger kills the engine. if it keeps running you have another air leak somewhere
Click to expand...
its not the iac, im pretty sure its the intake gasket, i can out my hand over the whole throttle body and it wont kill the motor, i think i can hear multiple leaks, sounds like the intake gasket
 
Maybe in AZ and other smog states, but not here in Mass/NH as far as I know.

Also, sounds like intake/exhaust gaskets to me too. Probably intake due to your "choking the engine" test.

EDIT: federal guidelines appear to be that you keep the engine management and emissions gear from the later portion of the vehicle, which is satisfied since Rob moved all the sensors and manifolds and junk from the newer vehicle onto the older motor.
 
Last edited:
when i did the exhaust manifold swap on mine i forgot to reconnect the brake booster vacuum line. it idled at 2k. for you to be idling at 1800ish rpms, that would have to be one huge intake gasket leak.
 
asp said:
when i did the exhaust manifold swap on mine i forgot to reconnect the brake booster vacuum line. it idled at 2k. for you to be idling at 1800ish rpms, that would have to be one huge intake gasket leak.
Click to expand...
ive unplugged every vacum line, rpms jump up, ill plug the hole and the drop to 1800 again so it aint a vacup leak, im gonna mock up the header and intake on the 98 motor to make sure there not inter fering with each other
 
kastein said:
Maybe in AZ and other smog states, but not here in Mass/NH as far as I know.

Also, sounds like intake/exhaust gaskets to me too. Probably intake due to your "choking the engine" test.

EDIT: federal guidelines appear to be that you keep the engine management and emissions gear from the later portion of the vehicle, which is satisfied since Rob moved all the sensors and manifolds and junk from the newer vehicle onto the older motor.
Click to expand...


AS you may have found out, it's got nothing to do with State Law, it's FEDERAL law and, no just keeping the engine management and emissions (exterior) gear from the other engine does NOT comply with the law. A short block would, however using the old heads, valves does NOT comply.
Now, I, myself, don't give a rats a$$, however there is a lot of mis-information, often, on these forums and, for this particular law, the fine is a big 'n ;)



Fred
 
Before you tighten down the header end nuts and middle bolt, make sure the intake manifold seats correctly in the dowels and that the header has equal clearance to the left and right of the IM(there can be up to 1/8" of play). I've used copper rtv in the past. Good job on the swap. Fred, welcome to NAXJA. This forum is here to provide help.
 
Last edited:
appears the leak was at the bottom of the #5/6 runners now maybee the intake binded up on the dowel pin oth sompthing, anyone have and sugestions in wich order to tighten the bolts down? or any other tips so this time things go better, thanks
 
StealthXJ said:
AS you may have found out, it's got nothing to do with State Law, it's FEDERAL law and, no just keeping the engine management and emissions (exterior) gear from the other engine does NOT comply with the law. A short block would, however using the old heads, valves does NOT comply.
Now, I, myself, don't give a rats a$$, however there is a lot of mis-information, often, on these forums and, for this particular law, the fine is a big 'n ;)Fred
Click to expand...

Smog referree in the great state of Kaliforniastan, didn't give 3 shits about the long block, only that all emissions equipment was in place. Dunno about AZ though....
 
upon futher inspection of the mopar gasket today it dosnt fit properly, lft nice holes under the 5 and 6 runners
 
StealthXJ said:
As an aside, that is not an answer to your question, just a note here.
That swap is illegal.



:)
Fred
Click to expand...

1. 91-98 H.O. 4.0 engine--same freaking engine.

2. Go buy a reman 4.0 engine--tell the builder it absolutely has to be certified to be the exact same year as the engine it is replacing--cover your ears to you don't loose your hearing from the uproarious laughter, just like everyone else is laughing at you right now. :roflmao:
 
im guessin this is suposed to be a renix gasket, or is just from a bad batch, but dosnt line up with the intake

98_007.JPG


now gots a feel pro gasket and just took it for a spin around the block, first time its left the yard since early feb:party:
 
You must log in or register to reply here.

Similar threads

P
2K IDLE - Odd Shifting - TPS? (I know.. I know)
Replies
3
Views
2K
Unclewolverine
U
N
2000 XJ, high miles, lots of new parts, still have vibration
Replies
10
Views
1K
N8N_99xj
N
T
1999 XJ crank, no start after engine swap
Replies
0
Views
300
Turbo_Ted
T
R
1994 Cherokee Country 4.0 poor engine performance
Replies
12
Views
731
RCP Phx
R
A
Very odd idling issues
2
Replies
38
Views
4K
Rob Mayercik
R
Back
Top