jimmycollins214

Good evening everyone,

I was hoping that someone would be able to help me out. I have exhausted all methods of research and hands-on approaches.

1989 Jeep Cherokee
4.0 2wd automatic

It idles perfectly fine. The problem is that when I press the throttle, it immediately hesitates and bogs out. No matter how far the throttle is pushed it does the same thing. The shop that I was at couldn't even figure it out.

Here is a list of the new things...
-fuel pump
-spark plugs
-wires
-cps
-tps
-idle air control
-starter

Now, here is the story behind the whole situation. I went to a shop because I had been hearing knocking underneath my floorboard. I assumed that it was my u-joints. The shop pulled my drive shaft, but actually found out the u-joints were fine. It turns out the rattling was coming from a lose transfer case cover. The PO had apparently not put all of the bolts back in it at some point. Anyways, the shop put some more bolts into it for me. When I went to leave afterwards, the bog problem was suddenly present. I literally turned around, and went back to the shop. I spent hours there. They went over everything. The checked my MAF, vacuum, fuel, and ignition. Now, here is where something interesting happened. While running, the tried to turn the distributor. While they were turning it, absolutely nothing happened. There was no change in timing or anything while they were turning it.

Is this a sign that the distributor is shot?

Does it have something to do with the transfer case plate?

Just anything that anyone could do to help me would be.....well.....a great help. Please take my appreciation in advance.

tjwalker

Base timing for the 4.0 is controlled by the computer; turning your distributor isn't the way to adjust timing.

I know you replaced your fuel pump, but you should still verify fuel pressure to be sure.

For your 89, you should have 31 psi of pressure at idle. Then disconnect the vacuum line to the fuel pressure regulator (be sure the line doesn't have any raw fuel in it which is a sign of a ruptured fuel pressure regulator) and the pressure should jump to approximately 39 psi.

Lots of possibilities here. Stay on it. This is an interesting problem. I do not however, see any relationship to your current symptoms and the transfer case plate. That doesn't control anything related to engine management, fuel, spark, etc.

jimmycollins214

Firstly, thank you for your prompt response!

The shop checked the fuel pressure at the fuel filter. It was right at 30psi.

The only reason I even related the transfer case plate to anything was just because it was completely fine before.

This whole situation is literally just blowing my mind. It's also really getting to the mechanics as well.

I've even tried to ask some of my friends, just to bounce ideas off of them. Have you heard anything about it possibly jumping timing? I was thinking that if timing was off, that it wouldn't idle as smooth as it does.

jimmycollins214

I also read something about a catalytic converter...any thoughts?

djgrayxj

Note from DJ
If you don’t have this information bookmarked in your computer do so.
Thanks cruiser54 for all of your time spent putting this information together.
New cruiser54 Tips Index as of 03-13-2014
Renix Bible link is below:
https://www.cherokeeforum.com/f51/cr...x-tips-153657/

I see that the shop replaced the TPS if it was not adjusted after replacement here is how to adjust it.
See #8 in cruiser54 Renix Bible above-TPS testing and adjusting.
Catalytic converter testing is covered in #16 Vacuum test for exhaust restriction.
In your new parts list I don’t see a new fuel filter mentioned was it replaced?
Also you stated that the fuel pressured was measured at the fuel filter. The correct procedure is to measure it at the fuel injector rail as described by tjwalker.
Is the Jeep home or still at the shop?

jimmycollins214

I had actually replaced everything, except for the fuel pump.

The thing that was driving me crazy is that it was running just fine before I took it to the shop. That's why I was thinking that perhaps it wasn't the sensors. However, I will get them tested and reset according to that guide.

The fuel filter is only a couple months old. It was literally one of the first things I did after I bought the truck.

Unfortunately, the jeep is still at the shop. On top of that, it would be labor day weekend lol.

I happened across another posting that mentioned something about the spark plugs... It said that he tried to replace with Autolites and the problem developed. It then went on to say that he fixed it by putting Champions back in it. I really don't feel like that's the problem with mine, because as I mentioned before, it was running just fine before it got to the shop.

I'm really leaning to the catalytic converter issue. I'm thinking that perhaps while they were underneath it they may have knocked something loose that finally finished plugging the cat up. I had heard some rattling before, but had only credited to some old bushings in the suspension. Another write up that I found had said that the cat can actually start making a rattling sound once it has bit the bullet so to say.

I very much appreciate the information that you have given me. I am going to relay it to the shop as soon as they give me a call today. I will also definitely follow up to let cherokeeforum know what the fix is!!!

cruiser54

Get over the "coincidence" part of this situation and start doing proactive things as DJ suggests.

Tobey

When the cat on my car (2005 GTO) broke, it rattled like crazy. Sounded like it was a heat shield or some other relatively light piece of metal. It's possible that the transfer case cover was never the issue, and the shop finished off the cat while knocking on things to find the noise. And, my car ran fine with the crazy rattling noise.

jimmycollins214

Well guys...

Apparently the shop was not open today like they said...
I ordered a walker direct fit catalytic converter, as well as a New o2 sensor. Keeping my fingers crossed for tomorrow.
I've also been doing more research and someone said something about jumped timing. Anyone have any experience with this?

Tobey

I've only been driving for 28 years, probably 450,000 miles at least. I can count on zero fingers the number of times I've seen an engine timing chain jump a tooth. It seems like everyone's heard about it. Some people know somebody that knows somebody to whom it happened. But it's exceedingly rare. Even cars that use belts usually break the belts before they jump a tooth. Not saying it's impossible. Not saying it's never happened. I'm just saying it's not very likely.

If it's an ignition problem, it's more likely to be in the distributor or in the electronics.

jimmycollins214

Alright guys, she runs again!!!

Turns out the wires from the New cps had found their way to the manifold...burned right through them

I hadn't looked before, but apparently the PO cut off the cat and straight piped it. I had never noticed.

On top of all of that, the distributor also got replaced. I honestly should have known better when I got the truck and found motorcraft spark plugs in it...can you guys guess what kind of distributor the PO modified to fit? Yep....motorcraft

She's purring like a kitten again.

I just want to thank everyone for all of their input. Cherokee forum is one of the biggest wealths of knowledge. Especially the members that are posting and helping out.

cruiser54

I'll post this up just cuz:

xavethebassist

Is the distributor actually modified?? Jeep used motorcraft distributors out of the factory for a few years, along with a few gm components!

cruiser54

Motorcraft and Lucas were suppliers. Yep. Nothing unusual about that.

jimmycollins214

The bottom portion of the distributor had actually been grinded off to fit in the port. I couldn't believe it when the mechanic showed it to me. Also, the PO had put it in 180 degrees off.