Dylan Byfield

So I have an 89 xj with the 4.0.
​​​it has a backfire, and hardly any acceleration.To the point of avoiding busy streets because it's so slow. If it's in park or neutral the rpms move as should, when in gear they climb very slow. I'm talking fat guy riding a scooter in Wal-Mart slow. It has a fluctuating idle, almost always lower than avrage. Alot of the roughness has been fixed with new parts. Also it doesnt sound right. Its hard to explain but sounds like something is stopped up, or maybe just contantly flooded. I removed the muffler and still the same. Nothing stuck in the "converter" either. Here's a list of all I've done.
Tps
Map
Knoc​​​​​​k sensor
Checked and cleaned cps​​​​​​
Cleaned aic
Cleaned throttle bod​​​​​​y
Plugs,wires,cap,rotor bug
Fue​​​​​​l filter
All injectors less than 6 months old
Fuel pump around a year old
All vaccume leaks fixed
Refreshed grounds
Pulled valve cover, no broken springs or stuck valves that I could see
Catalytic converter has been hollowed out, cherry bomb glass pack
Fuel pressure checked with guage, steady 31psi but when shut off it builds pressure. Not sure what that means
Pulled distributor, gear isn't worn and in time
I'm running out of money and running out of patience. Does anyone have another idea of what to try? I'm new to the page, thank you in advance for the help
​

Jeepwalker

You've done a lot. Pretty much most things I would recommend. I commend you on your persistence! Couple questions and a few suggestions:
1) Have you done a compression test? Probably not it, but just wondering if there was a leaky valve.
2) Have you measured the vacuum at idle/drive? (what do you see?)
3) Verified spark plugs are good? I've bought new ones which had internally grounding ..hard to debug b/c you expect new plugs to be good (??).
4) Spark plug wires? Coil? I had a vehicle do this once to do wires grounding ...and I've had bad coils before. Bad coil wire can play tricks too. Aren't there some coil wires which are directional (??). Not sure.
5) Temp sensors? Is there an ambient temp sensor? Have you metered out and cleaned the intake temp sensor? They get gummed up. (I had a tk that would balk due to bad temp sensor.)

6) I once had a car that acted like you are describing. It would idle ok all day long but drove like something serious was wrong with it. It turned out to be a lot of water in the gas!! I also replaced a crapload of items and eventually, by luck, happened to notice a lot of moisture around the carburetor plates. Well I had gotten a bunch of water in the fuel from a previous fuel stop. It took probably 4 tanks of gas and lots of HEET to work it out. You could also have something clinging to the fuel pick-up sock (??). I mean, it might be worth a look inside your tank. They're not that hard to remove.

7) You didn't say anything about the O2 sensor.
8) Did you check the EGR? and EGR piping. Probably not it, but worth a look.
9) Brake booster vacuum issue? (when you hit the brakes).
10) The TPS has an adjustment proceedure, maybe you've done it. Again, just thinking outloud of things which may or may not be possibly contributing...
11) Battery up to charge ...or possible low/no charging issue?
12) Cleaned out behind the IAC really well, right?
13) Got the right TPS? There have been reports of bad (cheap) ones. Can you see the readings?
14) I recently had a similar issue I debugged with a GM 80's truck. Pretty much acted like you're describing. I replace a lot of sensors too, but it turned out that the magnetic pulse assembly beneath the rotor inside the distributor was cracked. There could be a pick-up coil in there that's shot or broken wires (??).
15) Do anything with the crank pos sensor? Wait, I see you did. Cross that off.
16) Faulty fuel filter? (sure your pressure could be good, but what about FLOW?)

....Just thinking outloud here on some ideas......

You might consider one of those Renix monitoring devices (google: Cherokee fan controller), or maybe a Snap-on 'brick' scanner with old cartridges that work for your system so you can see "Real Time" sensor readings, and on-road readings ...or do you have access to one? Would be a good investment ....if you plan to be a serious Cherokee owner. The 'Troubleshooter' cartridge has some good stuff on it too. Of course, once you get this working, you'll probably never have a problem again!! (hopefully)
.

Dylan Byfield

I have not checked compression or vaccume, (don't know how to check vaccume.) Plugs champion,pulled wires one by one there all good. Also know the coil is hitting, sadly I know this because I accidently pulled it and it lit my a** up like a dang Christmas tree. Haven't noticed any moisture. It just happened out of the blue on my way to work. Luckally I was passing my dad's house and took it to his shop before it left me stranded. It's fixed enough I can drive it when I need to since it's my only transportation. It just turned me into the guy the rest of us are usually cussing for driving so slow

Dylan Byfield

[QUOTE=Dylan Byfield;3524391]I have not checked compression or vaccume, (don't know how to check vaccume.) Plugs champion,pulled wires one by one there all good. Also know the coil is hitting, sadly I know this because I accidently pulled it and it lit my a** up like a dang Christmas tree. Haven't noticed any moisture. It just happened out of the blue on my way to work. Luckally I was passing my dad's house and took it to his shop before it left me stranded. It's fixed enough I can drive it when I need to since it's my only transportation. It just turned me into the guy the rest of us are usually cussing for driving so slow
Also know the plug wires are good

Jeepwalker

I edited my previous post and added more items. Please go back and re-read.
If it happened 10 minutes after a fuel fill-up, well, that would be suspiscious. Check inside the distributor like I say, just went through this with a truck of similar era.

Youtube how to check vacuum. It's really important. Tells you a lot. I'm at around 14 inches at idle on mine, but at around 1,100 it jumps up to around 19". If you can't pull good vacuum then you learned something. Could be a bad intake gasket ... Reread all the things I wrote.

I'm sure it's frustrating. Hopefully we can get enough ideas out there to help you find the problem.

Dylan Byfield

Right now that's definitely out of my budget. My plan is to get it running good enough to not be a worry. Save up and get a better Dailey and start turning it into a toy. That way I can work on it when I have the time and money instead of rushing. I think I'd like it and working on it a lot better that way. Right now I'm about ready to drop a match in it and buy a bicycle.

Jeepwalker

I think the Cherokee fan controller that does real-time on-road readings is like $40 ..or something, isn't it? You've got 10 times more than that in *your* diagnostic time tracking stuff down! Not to mention the unnecessary parts you've thrown at it. Go take a look at it and the video.

cruiser54

Acted up shortly after a fillup?

That's what happened on my wife's 88 a few times. this is the fuel pump ground wire inside the tank.

cruiser54

what does the fuel pressure do when you pull the vacuum line off the fuel pressure regulator? should jump to 39 PSI.