karen7

Updated with as much info as I can remember so you only have to read this 1 post instead of going thru the entire thread...

Hi, I am new to the forums but I am at a loss and need some serious help. Almost 2 weeks ago my fiance and brother replaced a motor in an 88 cherokee with an 89 motor. Reason replaced high miles, getting hard to start, leaking oil, possibly head gasket needed replaced. Found a used motor with 80,000 on it guaranteed to run as it ran great before removed from vehicle.

It sounds like a really bad mower. It idles erratically, backfires into the throttle body, timing retards and advances itself.
I have had about 13 ppl out to check including a certified mechanic with no luck. At this stage I just want to know what the problem is and fix it. Enough was spent.

So far we have replaced/changed/tried:

From old working motor to new motor-
exhaust manifold
intake
head (rocker arms & push rods) yes it was torqued properly and not warped
distributor
TPS- from new motor to old motor -tested and adjusted 5.4v input, 4.42v output
stepper motor-from new motor to old motor

new parts:
plugs
wires
cap
rotor
distributor
MAP sensor
CPS
timing cover gasket
head gasket
fuel filter
ignition module
ECU-won't even start it


things we checked:
Gas is fresh
cat not clogged
compression good on all cylinders
all vac lines attached properly
timing chain in time by marks and 15 pins counted
correct firing order
flywheel not damaged
getting spark from all cylinders
fuel pressure test results-getting 31 psi with vac line and 39 without
fuel pump working properly and attached hose not rotted or damaged
leak down test on cylinders was good
fuel volume test done-good volume


Questionable:
new plugs are black and sooty
injectors spraying a stream not a mist
after changing fuel filter sounds and runs better, but still backfiring when u give it throttle, runs bout 3 mins shuts off, starts back up immediately, bout 3 mins shuts off. Have to play with throttle before it takes it, still seems as if advancing and retarding itself.
paper spacer on CPS? didn't have 1 with the new 1
Harmonic balancer wobbling really bad

Next on my to do list...
*Bought new HB, waiting for more light to try it on for size.- got it on-working without wobble
*Picked up O-rings to stop leaking injectors- done and no leaks
*check timing with timing light- wow, this is a task!!!

What am I not checking? Forgetting? What should I try now? Please help. Thank you to anyone who can help or give ideas.

vistacruiser

I'm not an expert on that year BUT ... I'd be especially anxious to see the results of the comp check. If it were me, that is what I'd want to check first.

Next, I would want to pull each plug and see if the problem could be isolated to one or more particular cylinders. Might get clues from the plugs as to what's firing, what's not, what's rich or lean, oil fouled or sooty ... Kapish, so far?

Next I would roll the motor over with a wrench til number one is top dead on the compression stroke (a finger in the plug hole will confirm compression stroke) and the timing mark is at 0 on the scale ... then I would check to be certain that the rotor is pointing to the number one plug wire position on the cap. Then there can be no doubt that the timing is correct. If not , R&Reinstall distributor correctly. The timing chain was never removed, right? There's a few more places to recheck ... stay cool. You'll get it.

karen7

All checked individually and firing.

This is how we timed it. Then I was told to try moving it 1 tooth counter clockwise, and did this. I also moved each wire on the cap 1 position counter clockwise, a jeep shop told me to try that as sometimes that helps. Still didn't work.

No it was not, although it was checked for proper timing.

Any other suggestions? I would also like to have a comp read, but I can't move the jeep, there is not enough power. When you try to accelerate it won't rev.

Abovetimberline

I would do a compression check first and make sure they are all at 120-150,if they are all ok then I would make sure the timing is good,and that the rockers are at 19ftlbs torgue when engine is at tdc, I know you said this was all ok,but the only things that will cause backfire,is timing,bad valves,or valves not reseating if tightened to far,plugged cat,or a bad vacuum leak,you said it was advancing and retarding timing on its own,a vacuum leak will do the same.
I help a friend with his truck today because it would not run,and all it was is a vacuum hose that fell off,but it was the first one of the intake.

vistacruiser

All that is needed to make the motor run is; spark, fuel air mixture, timing and compression. So, let's eliminate timing, OK? Is each injector spritzing? No air blockage? If so, eliminate fuel.

Sorry about asking this again in a different way ... but with all the backfiring and such, ..is there not even ONE plug that looks any different from any other?

But frankly it sounds like it's boiling down to the comp check. Just get it as warm as you can ... pull all the plugs, hold the accelerator down and run the check on each cyl and record the results ... then let us know. Sounds like that's gonna' tell the tale.

captainwoot

Still really sounds like it is outof time......or poor compression, but the motorworked before right? I'm not a renix man but could the igition module have something going on?

Wild One

Especially with it popping out of the intake. Make sure that the distributor was/is installed on the compression stroke TDC, the popping out the intake could be the distributor firing 180 degrees out (this happens if the distributor is installed and timed with the engine in its exhaust stroke TDC).

The other improper timing possibility is the camshaft, it too can be installed 180 degrees out - this will also cause popping out of the intake and the poor running state that you have described.

In either instance, I have seen engines run (Very poorly!) on only a few cylinders while popping out the intake at idle - the instant that any attempt is made to rev the engine it chokes and refuses to accelerate all the while the popping out of the intake increases.

As far as the renix stuff goes good luck, it either works well (or as well as any renix system can) or very poorly to not at all. Good luck with the project.

nw-xj-scott

i wish i could simply say "Change your XXXX" but you have done everything i would advise!

When you do fix it. Please do post!

karen7

Yes, I was told is was and ran smooth sounded good, no knocks.
All were firing, but I will check again today. I made sure they were all gapped properly, I even checked a couple from different cylinders to make sure the plugs were actually getting fire.
I have gone over the vac hoses again and again. I am using the Haynes manual as a guide. I will go over all of them again.

vistacruiser

This really sucks, Karen. I feel your pain. Was this, by chance, a motor from a junkyard?

vistacruiser

Check ALL of the cyls for spark at the plug. Don't assume anything you do not verify with your eyes. While all of the plug wires are disconnected, crank the motor then pull all of the plugs and check that they are each one wet with gas. Lay them all out in order and observe the color and condition of the tips ... sooty or oily ... wet from gas ... what? If you have a camera, take a pic of all the plugs lined up like little tin soldiers and post it ... then finally run your compression check ... you have or can lay your hands on a compression gauge, right? ..... remember only those four things that I mentioned earlier are needed to make it run with no backfiring and reasonable power ... the remainder is tuning.

Hope this is not a bad valve or two ...

karen7

Yes originally the motor was purchased from junkyard. Here's how it went...

The guy I bought it from was looking for a motor for his jeep. The junkyard near him got in a jeep from rearend collision. They called him, he came and listened to it and told them yes, they pulled motor the following day. He had it sitting for a year and sold jeep and motor. I got the motor. He guaranteed the motor to run or my money back. But fiance will not pull the motor after putting almost 2 weeks of blood sweat and tears. He's already taken 2 days off work and an entire weekend just dedicated to it.

Compression test done
#1-140
#2-145
#3-135
#4-150
#5-140
#6-130

Checked for spark again on all cylinders-sparking just fine. The plugs are kinda sooty (they were just bought new last weekend). I don't have a pic because the jeep is 10-15mins from my house (at my moms) and I got this msg after I left there. Also cleaned the trottle body with cleaner. Seems like everything we do makes it run a little better but still not right.

OK, so what now? I am trying and rechecking everything you tell me.

captainwoot

compression doesn't seem that bad, not to repeat everyone else, make sure the distributer is installed correctly TDC on #1 cyl compression stroke. Beyond that I am at a loss. Anyone else????

karen7

Yup distributor is set correct TDC compression stroke. (which is the louder of the 2 compression strokes)

vistacruiser

Good girl .... gotta' follow instructions EXACTLY .. otherwise ya' might miss the problem ... go in circles forever

the comp numbers sound OK, so far ... you did it with all the plugs out and throttle pedal depressed and motor warmed up, right? If you didn't do it exactly that way, better redo it. We're gonna' recheck the other three necessary things ... gettin' tired of this yet?

Next we're gonna' tackle 'fuel' and 'air' mix

Did you use the injectors and fuel rail from the original motor or the J yard one? How old is the gas in the tank? Could that gas be contaminated with water? Was new gas mixed by chance with old gas that could have been contaminated... say older than a year?

Air box is installed and a filter in it, right? If not put the box on hook up the hoses and remove the a. filter for now. I'll give you more once you've gotten this done ...exactly this way.

That'll do for now ... check out that stuff and answer all the questions I asked you, no shortcutting .... but a word on Junkyards ... they ALL offer this bogus replacement guarantee on motors ... frankly only the MOST reputable yards can be trusted .... most of them will say anything that comes to mind to make a sale, make up a phoney story or whatever. Afterall, they're not the ones doin' the labor, are they? ... all that work you have done is NO SWEAT off of their back whatsoever... and I'm sure they'll be happy to give you another one too, soon as you bring that one back .. but what'll the NEXT motor be like? ... nice, eh?



What part of the country is this?