Topic: New engine won't idle

[e-town]

Hey guys,

So I recently had to replace the engine in the YJ with a reman unit. At the same time I decided to get rid of the coolant lines through the IM and run a newer style T-stat housing with the coolant temp sensor in it. So everything went together fine but after starting it would only idle for a couple of minutes before the idle would drop and then it stumbled and shut down. Same deal when I restart it. I can keep it running with the throttle but it just wont idle.

Everything on the engine was working before the swap so I don't think it's a sensor issue. I'm guessing either the new setup has issues or I screwed up the vacuum lines somewhere. The only other thing I can think of is the distributor is off a tooth. Anyone have any thoughts? I need to get the heep back on the road.

Oh yeah... it's an 89 w/ TBI.

[sharpxmen]

my guess is the vac lines given that the t/b was installed correctly, i'm not familiar with TBI but there's a guy here who's quite proficient with the vac lines on those but you should post some pics though.

[Torch_Ind]

Hey guys,

So I recently had to replace the engine in the YJ with a reman unit. At the same time I decided to get rid of the coolant lines through the IM and run a newer style T-stat housing with the coolant temp sensor in it. So everything went together fine but after starting it would only idle for a couple of minutes before the idle would drop and then it stumbled and shut down. Same deal when I restart it. I can keep it running with the throttle but it just wont idle.

Everything on the engine was working before the swap so I don't think it's a sensor issue. I'm guessing either the new setup has issues or I screwed up the vacuum lines somewhere. The only other thing I can think of is the distributor is off a tooth. Anyone have any thoughts? I need to get the heep back on the road.

Oh yeah... it's an 89 w/ TBI.

if the distributor was off it wouldn't run worth beans even with fuel !!

I would check vacuum lines.. and check if there is a way of resting the computer in those? if it's used to a worn out engine that could be why.. it may take some time to get the computer to relearn

[chardrc]

my bet is the computer is not happy with the coolant bypass.. your symptoms sound almost identical to this guy who did the same

hi guys new here.
 in my search for more power on my 86 2.5 XJ TBI 5spd. i figured i could bypass the coolant flowing thru the manifold and free up some hp with a colder manifold.
 so i went to lowes got a 1/2" T fitting with a 3/8 port in the middle. 2x3/4"barbed 1/2" pipe thread adapters.
 removed coolant temp sensor from manifold and instaled it in T. cut and moved hoses from the manifold to a straight shot from t stat housing to heater thing with the coolant temp T pluged in the middle.
 ok did not turn it into a power house but it cruises way better on the highway! going up hills, i travel everyday to work, without downshifting from 5th -4th now!  :shock:
 great right...wrong
 for some reason now it sometimes stumbles at low RPM, always lacks power at low RPM and ocasionaly dies when droping to idle.
 but it runs so great above low RPM!!!  :evil: (how low i don't know, no tach! but maybe under 1500rpm,a good blip of the throtle will get it going)
 any ideas how to get it running better all the time?
 does coolant run around the EGR on this? an maybe the EGR is causing the problem? tried unpluging the vacuum but no dif.
 gonna try resetting the ECU today while at work.

 also should i try increasing plug gap as i have a hotter coil but stock gap.
any other sugestions?
 thanks guys. :D

http://4bangerjp.com/forums/index.php/topic,2016.0.html

i would try rerouting the coolant through the manifold and see if it idles again.

[e-town]

Well I had a look at it yesterday and found a vacuum leak but fixing it didn't help. I then put the coolant lines back to the factory setup and I can now idle and drive but going up hill I have no power at all. I can't tell if this is due to the extra load on the engine or just the hill. I don't want to stomp on the loud pedal to find out since I haven't broken the engine in yet. I think there might still be some air in the cooling system since the heater doesn't blow very hot, but I'm not sure if this could effect my power output.

[e-town]

Well I thought I should update even though it's a bit embarrassing. It seems the problem was an obvious one. I just needed to seat the rings in. Seems the 4 banger wont run so good when all your combustion power is blowing into your crankcase. A couple of nice drives and she's running like new now.

[Dylan]

Good to hear you got it figured out.  Wouldn't it be nice if everything would be fixed by simply driving a bit?