JeepingDan

Did you do a leak down on each cylinder to make sure you don't have a bad valve? A bad intake valve would cause it to backfire out of the throttle body. Recently I had a vehicle in my shop that was doing that and turned out the hydraulic lifters were stuck. Wouldint hurt to check.

vistacruiser

What the heck is this?

Put your finger in the hole and plug it tight .. and turn or have someone the motor with a wrench on the crankshaft or PS pump til you feel the 'POP' or distinct strong puff of air on your finger. THAT is the compression stroke.

vistacruiser

Good point Itz ..
Certainly a possibility with a Jyard motor ... but all the "sharpshooting" hasn't produced much so far though ... IMHO, she needs to stick to the basics for now .... go through the time tested trouble shooting process and she WILL get it.

karen7

He did it with all loosened but not out. Will redo test as soon as we can.

Yes, I don't know what that means but he said yes. LOL I must say I am learning alot here.

From my original motor

No it does NOT have water, it actually ran out of gas just before it got the motor swapped. I bought fresh gas over the weekend, ran it out last nite and bought more fresh today (always from the same station).

No, filter not in it and not all hoses are hooked to it. Will take care of that ASAP also.

Yes thats how they did it. Sorry, I was told it was the louder of the 2 compression strokes.

I'm in Pennsylvania

Abovetimberline

with those numbers on comp,you have a good motor,the timing has to be spot on,beside making sure you are at tdc,it is just as important to make sure that you are on the o degree mark on the balancer just putting your finger over #1 or placing a rag in #1 to find tdc,is not enough,if it is not at 0 degrees,or the dist is not pointing at #1,it will not start,or it will miss. I just went through this with my 89,and a 1/4" either way it would not run right or run at all,I even broke off the dog ears to assist in getting timed.

karen7

The ears are broke off mine too

Yup at 0, made sure myself.

I have read the entire Haynes manual front to back several times. By the time this is fixed, I'll be able to fix an I6 4.0 myself.

nickjc13

mine was a vacuum leak. but i also have a stroker. and that thing SUCKS. air like crazy. also are you sure its on the compression stroke?

Abovetimberline

this is the dumb question after all you have been through,are the wires correct? and on the back of your intake is the vacuum port for the vacuum bottle,unplug it and cap it,it will isolate any leaks you may have there. Also is your map sensor in the bottom hole of the throttle body and not the top one,is the rubber gromet still in there? Have you been able to check the vacuum? I know you said it runs but not well. Plu a vacuum guage into the back port and see what it is.

karen7

Yes, I checked that myself also with the book.

Yes and yes

Positive. and I have gone over all vac lines, so has my mom. Oh yeah she good with diagnosing car problems but even shes stumped on this one.

vistacruiser

Plugging the hole with a finger is only meant to discern the compression stroke from the exhaust stroke, Above ... not time the vehicle ... geez ... don't think anyone suggested that it could be timed by feeling the pop, did they?

You are right about the timing being spot on though, Above ... just has to be.

Actually, Above, those comp numbers don't necessarily signify a good motor either ... although it may be good. If the plugs are not removed it may not crank fast enough and the if throttle is not held open it can inflate the figures on cylinders with bad intake valves by as much as twenty percent ... look at the two lowest numbers again and then tell me that you think that if they were 105 or 110 instead, that you would still consider the motor good ?? Don't think so.

Ran dead outa' gas, Karen? Hmmmm .... might have sucked in some junk up into the sock too. What happened to your original motor, may I ask, please?

I bet you will. You sound like a very smart girl. That's 'L'6 though not I6.

My mother is in Wmspt, ... Howler lives in Allentown and I'm comming to Philly in a couple of weeks for parts for one of my motorcycles and up to my Mom's place too. If it's still on the fritz then and you're nearby ... be happy to stick my schoz in there and have a peek ...

karen7

It ran out of gas enough that it would crank but not start for more than a second. I still have the other motor, covered sitting in front of the jeep.

Philly is about an hour north of me. I am very close to the MD/DE line. The jeep is actually in the town of Oxford (19363).

vistacruiser

I meant what happened to it that you had to change it out? Sorry.

I could have checked google ... but ... how far from 81?

captainwoot

What??? there is only one compression stroke. 4 stroke theory suck, squeeze, bang, blow. compression being "squeeze"!!!!!! This should blow your finger out of the spark plug hole, or when the compression guage needle moves up.

Gearhead41987

Changed out a motor in a cherokee this past weekend. Ran into the exact same problem. Stumped me, and all my mechanic buddies... Turns out the old motor had a flywheel that was slightly different. The ring around it with the magnents for the Crankshaft sensor were just a wee bit different. Try putting the flywheel from the other motor in there. I'll bet you that will do it.

karen7

I'm guessing the person that told me there are 2 compression strokes told me wrong.
Changed motor out because high milage, getting hard to start, and leaking oil was told may need head gasket.

The flywheel is the exact same part # for both years tho. I left the flywheel from my motor but bought a new CPS. Should I get an 89 CPS then since thats what the motor is. And like I said the flywheel is the same according the the auto parts store.

Well over an hour i believe. Not too sure, don't travel that way much.