jretzky

Hello!~Everyone, just this morning I start up the Jeep and back up and start down the road and it popping in the exhaust and has no power.
The Jeep is an 1989 Cherokee Laredo and has an fuel injected 4.0 liter engine.
The first thing that comes to mind is the timing chain is going.
Then I think it might be something as simple has a bad distributor cap.
The last time I drove the car was 2 days ago and it was fine.
By the way the engine has about 160,000 miles on it.
I looked under the hood and the motor was running, but not good.


I got back into the car and stepped on the gas and it had no response.
Any one ever have this happen?


jretzky

austinjoe13

Check the MAP sensor tube, it goes from the throttle body to the sensor on the firewall.

cruiser54

Like this:

CompleteCherokee

You said you looked under the hood and it was running rough as well? So bad running both at idle and at throttle. As mentioned above, check MAP first as its easiest. Next I'd check timing and then for a clogged cat.

cruiser54

Timing is not adjustable.

A vacuum test would be good. Tip 16.

The old MAP to throttle body hose would be the FIRST place I'd look.

jretzky

Good morning!~all, and thanks for the reply. Haven't had a chance to look at the Jeep yet...today after work.


It is parked at the bottom of our hill.


The 4.0L engine starts and when I open the hood the engine was running, but had a little bit of a miss to it. Usually it ran smooth. It didn't seem to respond to stepping on the gas peddle.


I will check the MAP sensor and the tube you were talking about.
I have several cats and kittens running around my place and I wonder if one of them got into the engine compartment.


I have a parts Jeep and maybe that one has what I need.
It was popping loud in the exhaust.


Thanks!~jretzky


I replaced the fuel pump about 3 months ago.

CompleteCherokee

I was suggesting to check timing to see if the timing jumped

cruiser54

They don't generally. Unless of course someone fails to secure the distributor down.

jretzky

Well I checked the tube from the MAP sensor to the throttle body and it appears to be good. I didn't take it off to see if it was clogged.
I was thinking about it last night and I remembered it popping once in a while the previous week, but it still had power.


Tonight I will pull it back up to the house.
I was going to pull the #1 spark plug and put it on the compression stroke, line up the timing mark and see if the rotor is pointing to #1 on the distributor cap.


That's what we'd do in the olden days before they had all these sensors.
Other than that I'm lost.


Thanks!~John

CompleteCherokee

I was referring to the chain stretching and jumping a tooth. My old man had that happen on his 1990 4.0 back in the mid-90's (it had over 200k on the ticker though).

cruiser54

Even more rare.

jretzky

Good morning!~I got the Jeep back up to the house last night after work.


Funny thing, I drove it with no trouble at all and it was about 85* outside.


Then I pulled the distributor cap and appeared to never had been changed.


It was really bad and warn out, especially the center and the contact places for each cylinder.


I looked at the rotor and it was really warn out.


I only started having the problem when it had rained over the weekend (all day Saturday and most of Sunday). It was Monday that the car started to backfire and have no response to the gas pedal.


This morning it was damp outside and the windows were wet, but the car started right up and seemed to run good, that is until I started down the road and it back fired a little. I thought...no way and drove it back home.


Could it be just the cap?


Could any thing be affected by the moisture outside?


Thanks!~John

cruiser54

Cap, rotor, and wires. Do them all.

DFlintstone

Probably the plugs also...

CompleteCherokee

spray some WD40 inside the distributor, as it will displace any water / moisture. Use a good lint-free rag to wipe it all down with. Then do this: