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well, maybe not a catastrophe, but it certainly is irritating. i recently finished putting a new 4.0 in my '89 and am having some difficulty getting it to run right. when it first started, it idled fine and you could get the revs up smoothly. but when we first tried to drive it, it would stumble and hesitate on acceleration. i couldn't work on it for a few days, and when i started it up again, it worked fine and drove around town for a couple of miles before doing that stumbling/hesitation stuff again. i thought it was a timing issue so i've been playing with that, but it isn't getting any better. any ideas? i've got lots to do if i want to join you in moab, so i need this fixed!
thanks a lot,
dan f.
well, maybe not a catastrophe, but it certainly is irritating. i recently finished putting a new 4.0 in my '89 and am having some difficulty getting it to run right. when it first started, it idled fine and you could get the revs up smoothly. but when we first tried to drive it, it would stumble and hesitate on acceleration. i couldn't work on it for a few days, and when i started it up again, it worked fine and drove around town for a couple of miles before doing that stumbling/hesitation stuff again. i thought it was a timing issue so i've been playing with that, but it isn't getting any better. any ideas? i've got lots to do if i want to join you in moab, so i need this fixed!
thanks a lot,
dan f.
I had the same symptoms after i put my rebuilt 4.0 in it, turns out the distrributor was not aligned properly, got it rotated it to about 1/2 a turn(clockwise) and its been fine ever since, you will have to turn it around till it stops doing that. Its kind of hard to imagine such a trivial thing would do that, but trust me it fixed my problem, i wasted tons of money changing sensors and stuff.
thanks rav, but i'm not sure i understand what you're describing. do you mean changing how the rotor sits on the distributer shaft itself? or how the shaft is located in relation to the drive gear?
thanks again for the help, and keep the suggestions coming.
thanks rav, but i'm not sure i understand what you're describing. do you mean changing how the rotor sits on the distributer shaft itself? or how the shaft is located in relation to the drive gear?
thanks again for the help, and keep the suggestions coming.
what i meant is the distributor shaft(the one which goes into the block, you wont be able to rotate it much but it will definitely make it work, other things to check would be your EGR valve, fuel pressure, fuel pump, TPS sensor, CPS sensor, but definitely do the distributor thing first.
I have never done this on a 4.0, but I have on many other engines and here is what I always check. Make sure that the #1 cylinder is at TDC (visually inspect) and make sure it is not 180deg off. Then pull the cap and make sure that the rotor is at #1 cylinder.
I would check distributer and timeing before other sensors also. I my experience it usually is something silly like timing. Most engines do not run well if they are not at least timed close.
i put it so the harmonic balancer shows TDC and then try to put the distributer pointing at #1, but it seems like i can't get the distributer exactly where it should be. it gets close, but never seems dead-on. could it be that the balancer isn't correct? i tried loosening the distributer hold-down plate and moving it w/ the engine running, as was mentioned in another post, but this didn't really do anything. thanks
dan f.
Yes, the HB can be fawked......mine was like 30 degrees off on the motor I'm building into a stroker. The rubber deteriorates and allows the outer portion to spin on the inner.
You can not turn the distributor to adjust the timing like on older cars. You have to install it absolutely correctly. If even one tooth off you will get problems. Yes there have been reports of bad rebuilds w. the cam not indexed properly thus throwing off the dist timing even when dist installed correctly which requires the grinding off the locking nub on dist so it can be moved to make a compensating adjustment. (seach the archieves for info on indexing the dist in such situations). On install make sure the engine was on tdc on cylinder #1 on compression stroke (tumb over sparkplug hole feel for pressure) -- no pressure and you have it 180 off and on the exhaust stroke). Per FSM On dist install, if necessary using flat blade screw driver, turn oil pump gear shaft until slot is slightly past 11 oclock (slightly towards 12 oclock); install rotor; w/o engaging dist gear into cam gear postion dist into hole and line up hold down ear of dist w. hold down clamp hole; turn rotor to 4 oclock position; slide dist into block until it seats; the rotor should now be at 5 oclock; install holddown bolt. (note when removing dist from engine already properly set up you are to scribe a mark on dist housing below #1 terminal on dist cap to us and reference on install in which case the when rotor points at 5 oclock on install the trailing edge of rotor blade should be lined up with the scribed mark.) Also note to avoid be thrown off by bad HB reading check tdc visually through sparkplug hole on #1 cylinder -- look for piston at top of cylinder. Greg
The problem is that you say that it runs fine for awhile. This would eliminate the timing being that far off because if it's off a tooth then it will run like crap all the time.
I would think that it's your fuel system or even your TPS/CPS. Recheck all your electrical connections, I would replace the fuel filter $9, and then go from there. Also for some reason when I put my new motor in the TPS was way off so check that too. A bad vacuum line could cause fuel pressure regulator problems too.
PS -the best way to check for TDC is to pull the sparkplug!!!
thanks guys. i gotta go work on it again in a minute. i've been trying to get the dist just right and now when i start it, it usually idles fine (once the computer kicks in) and i slowly get the revs up and it starts to chug and go crazy. keep the ideas comin'
thanks,
dan f.
is there a way that while the jeep was sitting (month or 2), something in the fuel systtem could have gone bad? someone mentioned in another post that if you can hear the fuel pump, its bad. well, i think i hear mine, could this be the cause i have been searching for?
thanks again,
dan f.
