MyE28.com

So the Jeep just hasn't been it's typically happily running self. It was showing some quirks, so I did my typical rotor, cap, plugs, and wire routine, which also resulted in installing a new distributor due to a stripped bolt. It was better, still not great. Recently, I also upped the oil viscosity (to 10W40) due to the running pressure being down from normal.

On the trip down to Va, it ran ok, but returned worse fuel economy than usual. While down there, I noticed a black puff on cold starts, and we figured maybe one of the injectors was leaking. I threw some GumOut Regane in it, and it seemed to perk up a bit with no more black puff on startup. Drove that tank out on the way home (getting still worse fuel economy) and tossed a bottle of Marvel Mystery Oil in the next tank. With that tank, it ran well, but it now idles like shit.

I'm starting to get really frustrated with it. My thoughts trend along these lines: coil and O2 sensor have 50k miles on them. Coil might be getting weak, but I don't think it explains the symptoms. O2 sensor is of the 4-wire heated Bosch variety, should still be good at 50k miles, right? After that, I started thinking of "maybes", like FPR (I think fuel economy would be even worse than it is), coolant temp sensor, or the infamous "something else".

Fuel economy is down by about 15-20% compared to my usual winter averages. I'd be willing to explain it away with the viscosity change if it were running well, but it just isn't. Timing was triple checked after the distributor change, and the shitty idle is a recent development, so I don't think that's it.

Thoughts from the peanut gallery?

Normal 'Rodney's not the expert' disclaimer applies, but it sounds like a possible fuel injector or FPR issue to me. If its running rich (which it sounds like from your symptoms) I'd consider seeing if one is leaking beyond the normal additive repair process.

Sounds like it's rich. What do the plugs look like? What do the injectors look like? ( I know the plugs are new, but after the drive how are they?)

Pull the injectors and get them cleaned/tested. Eliminate them as an issue first before replacing parts.

The original injectors only have about 230k miles on them. They CAN'T be the issue!

Injector replacement is something I've actually never done on any vehicle. Time to learn something new I suppose, too bad sets of new injectors are about $150 for this. I'd send the existing set to Cruzin', but at 230k miles of use they're likely not rebuildable to original spec. I should e-mail Rich and find out for sure though.

Jeremy

run them through an ultrasonic cleaner at home.... do you have one? might be a no-cost ('cept for time) repair.

coolant temp sensor/Intake air temperature sensor? Maybe maf/map sensor? with a voltmeter you could check em easy, also check the resistance in your coil. I'd also preform all these tests cold and hot. Do the free stuff first

spray some WD-40 in your Distributor and let it dry out for a few hours. You may have moisture in there. It's unlikely, but possible.

Fueled up today, put 93 in on a lark. Little less than half a tank's worth. It idles slightly better and runs a fair bit better. I think I might've picked up some lousy gas along the road trip somewhere. I'll run the current tank down to vapors and refill before I continue troubleshooting.

Jeremy

Always, always check the O2 sensor and see what it says and how it's acting. New injectors might make an overall improvement, but I doubt they are so bad to make it run like you're describing. Is it OBDII? Is it coding? If so check that. Even OBDI had some diagnostics built in, anything at all? If it's not throwing a code I'd pull the gas cap or something to make it go into a code so you can pull the fuel trim short term and long term.

OBD1 with MAP and O2 feedback. Very very basic stuff.

You need to use the SEARCH Function!! This has been discussed so many times folks are tired of answering it.

















Probably need the web sites to search. I just couldn't resist telling a beamter to use search. Sorry it wasn't one of the others. I do my searching on NAXJA, but I see you have a CJ, which has numerous forums. Maybe the TPS.

I did search.

Issue is, with the YJ, most running issues are the result of carbs, which were awful. The fuel injected YJs are pretty trouble-free in terms of running issues. Sorting through all the shackle, lift, "does this tire fit", engine swaps, and nutter bypass threads is a bit of a hassle. I think I'd find more information on putting a SBC GM motor into it than troubleshooting the one I have!

Well you see I don't know the smaller Jeeps codes. I would try NAXJA because they have an OEM forum that does not have all that lifted, twisted, worked, wheeled, tired and barred questions. Makes it easier to find info on a stock vehicle problem.

TPS is still my guess. My brother's XJ had a TPS that got wet and it caused driveability problems until the car would not start.

XJ did have the same motor installed, so that might not a bad place to fish for information. I'm only a member on one Jeep forum, jeepforum.com. I've never had much need for information that I couldn't figure out myself so I never poked around the different options, I know there's a bunch out there. The YJ is still a glorified farm cart, there really isn't much complicated about it.

Jeremy

Going down that road and searching for using the engine description instead of the model may be more fruitful, just like in BMWs, one could search for M30B34 when troubleshooting that engine and come up with results from multiple sources on the different chassis'.

I found this search for

Jeep 4.0 fuel injector troubleshooting on Google.

http://www.ehow.com/how_7564657_trouble ... ystem.html

While it seemed very basic, it's a starting point.

Here's some more basic info.

http://en.wikipedia.org/wiki/Renix

At 230 K miles , I would do a compression test or a leak down . Even for a 258, or 4.0 that is getting up there, so I would be cutting the engine some slack.

Jeremy wrote:XJ did have the same motor installed, so that might not a bad place to fish for information. I'm only a member on one Jeep forum, jeepforum.com. I've never had much need for information that I couldn't figure out myself so I never poked around the different options, I know there's a bunch out there. The YJ is still a glorified farm cart, there really isn't much complicated about it.

Jeremy

They all used that damn motor. My Grand Cherokee had it. [Until it devoured the #3 piston @ 100K miles. Now it has a 4.6 stroker version of the same engine.] Should be lots of knowledge out there - although I haven't looked for much.

Bit of an update. Everything I checked was fine so I decided to pull the codes even though the CEL wasn't lit or flashing. Got at least one code I knew was from an issue I had over a year ago. On a lark, I decided to reset everything by disconnecting the battery for a while and then reconnecting.

It's running much better since then. I'm not sure exactly what happened, but it seems the ECU adapted to some temporarily bad data. Hopefully it keeps running well.

Jeremy

Jeremy wrote:Bit of an update. Everything I checked was fine so I decided to pull the codes even though the CEL wasn't lit or flashing. Got at least one code I knew was from an issue I had over a year ago. On a lark, I decided to reset everything by disconnecting the battery for a while and then reconnecting.

It's running much better since then. I'm not sure exactly what happened, but it seems the ECU adapted to some temporarily bad data. Hopefully it keeps running well.

Jeremy

That's some good news. I hope it was as simple as that.

Vance

My new draggin' wagon, since selling my Dodge diesel, is this '93 example, 4.0 auto with the all-time 4WD.

You see the only cosmetic warts.
We had a the '95 V8 version several years ago, boy did it suck down the gas.

I say all that, to say, "I'll be watchin' you're threads Jeremy", just in case...

1st 5er wrote:My new draggin' wagon, since selling my Dodge diesel, is this '93 example, 4.0 auto with the all-time 4WD.

You see the only cosmetic warts.
We had a the '95 V8 version several years ago, boy did it suck down the gas.

This won't be much better. I think yours has the 3-speed Torqueflite, so 60 mph will be ~3k rpm. With the 5-speed in mine, I'm lucky to break 20 mpg on the highway. Typical city mileage is ~15 mpg. Still, it's a stone simple machine that's pretty durable, IME. Well, except for blowing the engine.

The recent trip to Dallas to pick up the wife's new-to-us Touring returned 17.4 mpg round trip in the Jeep.
Where as the Touring on the return trip got 27.7 mpg.
In the Jeep's defense, it was carrying my large toolbox, extra spare tire, a bunch of other crap, and dragging the tow dolly, just in case...

I knew about the mpg of the 4.0 because at the same time she had the 318 a friend had a '91 4.0
that he was trading in and offered it to me for the trade in offer,
so I drove it for a short time and removed the warts before passing it on to a friend's son as his first car.
IIRC that 318 ran somewhere close to 15 mpg highway.

They are really, IME as well, very durable vehicles.
But that all-time AWD feel takes some getting used to.

I picked this up too to have a beach runner for surf fishing expeditions.

All is good...

1st 5er wrote:But that all-time AWD feel takes some getting used to.

Huh? More neutral handling and better stability in rain and crosswinds takes getting used to? This AWD system would be transparent if the 2WD were any damn good at all. As it is, though, you can break a wheel free almost any time and the thing slides like nobody's business on ice or snow. My wife hated it. I'd say, "Did you have it in AWD?" "No. The snow wasn't that deep." I have found no measurable difference in fuel economy with AWD engaged, so mine is always in. I might put it into 2WD once or twice a year just to see if it will still go. I use 4WD on completely covered ice or snow surfaces for a number of reasons we don't need to explore now.

Shouldn't this be in the "tech" section?

C.R. Krieger wrote:

1st 5er wrote:But that all-time AWD feel takes some getting used to.

Huh? More neutral handling and better stability in rain and crosswinds takes getting used to? This AWD system would be transparent if the 2WD were any damn good at all. As it is, though, you can break a wheel free almost any time and the thing slides like nobody's business on ice or snow. My wife hated it. I'd say, "Did you have it in AWD?" "No. The snow wasn't that deep." I have found no measurable difference in fuel economy with AWD engaged, so mine is always in. I might put it into 2WD once or twice a year just to see if it will still go. I use 4WD on completely covered ice or snow surfaces for a number of reasons we don't need to explore now.

There's no 2WD option on our model.

L_N_Love wrote:Shouldn't this be in the "tech" section?

Not e28 or BMW related, so no.

There were (I think) 3 different drive systems available on the first generation Grand Cherokee. Part time 4wd (probably the same system I have in my Wrangler), full time AWD, and the "QuadraTrac AWD" system. QuadraTrac systems had a locking center differential, the regular AWD system did not.

Mine has three options;
4WD
Neutral (disengages all drive gear for towing)
4WD Low

1st 5er wrote:Mine has three options;
4WD
Neutral (disengages all drive gear for towing)
4WD Low

That's either the Command Trac or Select Trac, depending on vintage, which is their 1st or 2nd generation shift-on-the-fly system.

Command trac is the manual locking hubs . Selectrac is the shift on the fly. My wags only lock the center diff in low range. A wag in AWD is awesome in wet weather or snow. Deep sand too.