damageincracing

Ok, so I put gas in my 90 Cherokee just over a week ago (about 10 gallons), and the following day, it starts running like crap. When I start it up and let it idle, it runs rough, and when I "blip" the gas it stumbles then catches. If I "blip" the gas again, it's fine. When I put in gear to leave and I hit the gas, it runs "flat"- it goes, but there's no power. I'll drive a couple miles, then everything seems fine, it only stumbles occasionally. It'll only misfire once or twice if I force the issue and hit the gas a little harder. So I ran the gas down to about an 1/8th of a tank (thinking bad gas), put in some injector cleaner/fuel drier, and put another 10 gallons in. It runs a little better, but it still stumbles when I hit the gas after starting, and it still runs "flat" for the first couple miles. Once the engine warms up it's better, but not like it was. Any thoughts? I've ruled out the converter (since the engine would run worse when it's hot) and plugs/wires/cap/rotor. I will be checking fuel pressure as soon as I can get it into my work, but I put a fuel pump in it last year. With 207K on it, what are the odds the timing chain is wearing out? Never had one act like this all of the sudden before...

rangermonroe

Tag, as my 91 does something similar as operating temp is approached.

Lewark

Is it an automatic? I know mine did the same thing when my tps wasn't adjusted correctly.

damageincracing

Yeah, it's an auto. TPS was one of the things I was thinking. I had one go bad on my Daytona a long time ago, and it acted a little like this.

Lewark

http://autorepair.about.com/library/faqs/bl232i.htm
Here is a link on how to adjust it its simple and take all but 5 min to do. It's amazing how much better mine ran and shifted after I adjusted it.

damageincracing

Ok, way beyond irritated now. Went out on a limb and put a new TPS in today. Made sure it was adjusted to spec., and took it for a quick drive. No change- still runs like a turd. Double checked the TPS and made SURE it was adjusted right... Yup, still ran like a turd. So left work to go home, and now the blasted thing runs WORSE! Blasted thing stumbles/hesitates all he way up to about 35-40 mph, then starts missing and bucking. Didn't clear up after driving like it did before. Couldn't check the fuel pressure, since our gauge at work doesn't have the right fitting for the fuel rail. I have access to a DRB-II equivalent scan tool, anybody have an idea where the diag. plug ins are? Getting frustrated- never had this much trouble with any other car...

cruiser54

Check the fuel pressure next.

The DRB connectors are on the passenger side inner fender behind the bank of relays. But, you have to have the adapter for the DRB.

damageincracing

If I can find an adapter for our gauge at work, I planned on checking the fuel pressure tomorrow- one of our master techs has got to have that fitting! And I'm pretty sure that our scan tool has the drb plug, if not, we have an old Dodge mechanic that may have it. I was kind of hoping to have this cleared up... I have all my parts for the "neon" injector swap. Go figure something happens...

cruiser54

The fuel pressure gauge fitting is rather standard. Don't get your hopes up on the DRB adapter. It is unlike any Dodge product or any Jeep product after 1990,.

F1Addict

You are 100% certain that your spark plug wires are good? Tested for continuity and resistance? Checked clips for rust/degradation? Pulled boots and checked for fraying at the crimp? I ask only because I had a story identical to yours, even with the issue starting immediately after filling up... and the problem ended up being a bad plug wire. The focus seems to be on fuel delivery but here's one vote cast for spark issues... ignition module, coil, cap, rotor, plug wires, plugs.

Here's my story from a few days ago... https://www.cherokeeforum.com/f2/i-t...-found-131329/

damageincracing

Yeah- those were the first things I checked after the gas thing didn't work out. If it didn't have fuel injection and locked timing, I'd swear it acted like an old carbureted car with the distributor out of adjustment (I had an old Buick 350 that acted like this when I knocked the distributor loose)...

damageincracing

Ok, todays update. Cant check the fuel pressure (yet) since the adapter for our pressure gauge that EVERYONE is supposed to have- nobody has... Go figure... As for the DRB-II adapters we have, yeah, they would be good if the terminals were intact, so that's out (for now). Tomorrow I'm checking with my service manager to see if our sister dealerships (Dodge/Jeep) has an actual DRB-II that we can use for a day or two.

On to todays shot at the TPS... Got to work this morning and pulled the throttle body and did a complete and thorough cleaning (dang thing looks almost brand new.) and adjusted the throttle plate. Put it back on and tried adjusting it all 3 ways I've been told (even tried adjusting with voltages off BOTH connectors), no luck. So I just left it at the setting that made it run less like a rolling turd. Just so you guys know, I've been told 3 different settings for the TPS:

Input voltage (4.69v on mine) X .83 = 3.892v (I adjusted on the TPS until I got this voltage EXACTLY)

Set it at 4.15v (Alldata)

Set it at 4.2v (Allpar) This one actually made it run the best out of all 3

Idles like crap now, might have to tweak the stop screw...

Things that I KNOW:

Ground for TPS is good

Wires are good, plugs will be pulled if I can get time at work (might be saturday before I can do it)

No play in the distributor shaft at all. When I get some time (this weekend?), I'm going to check play in the timing chain.

It seems to be running rich. When I stomp on the gas (only way to get it to take off decent from a stop) it stumbles a little, clears out and pulls to just over 3 grand, shifts, stumbles, then pulls again. Once I'm up to speed and holding it steady, it starts to stumble/pop. And its gone through about 3/8ths of a tank of gas in 3 days (approx. 14 mile round trip to work and back for 3 days = approx 42 miles on 7.5 gallons of gas = about 5.6 mpg . Was getting 15 mpg 2 weeks ago before all this started...)

Catalytic Converter is NOT plugged (checked today)

EvstaG

Just from your last paragraph there, it sounds strikingly like a MAP sensor issue... Just with the sucking fuel and running terribly part... Ensure there are no leaks in the vacuum line running to this. Also you can test it, a procedure is here http://www.lunghd.com/Tech_Articles/...iagnostics.htm
Just a thought for ya.

damageincracing

Thanks, I'll put that first on my list for tomorrow.

cruiser54

I agree.