1988 Jeep Wrangler engine/carb issues

[trekker1701]

Hello,

I have a 1988 Jeep Wrangler that I am having some issues with. It has the 258CI engine (129,000 miles) with an automatic transmission. I have gotten rid of the 2bbl Carter and had it replaced with a Weber 32/36 manual choke carb (K551-M). The engine does burn oil and often have 1-2 plugs that oil fowl (one very bad) and have to be cleaned/replaced regularly. I think the one that fowls badly is due to the gap on the plug regularly closing. I have been told that the piston might be hitting the plug, but it does not do it all the time.

The main issue I am having is fuel economy and the exhaust smells very rich. The carb is at its max lean adjustment and it has to be set here for it to run well. It idle around 650-675 rpm. Any other adjustment causes lots of smoke from the tailpipe and very ruff idle. I have also installed a fuel pressure reg and it is set at 3 psi. The carb max setting is 3.5 psi. It will not run right at 2.5 (idles fine but stalls when driving), so I have set it at 3 and all seems well. I am getting around 12-13mpg in the city right now.

I have taken the Jeep to a mech that was recommended to me but every time it goes to him he generally makes it worse (Not going back to him anymore). It always fails emissions and has to be tweaked to pass and then reset to drive right.

Any suggestions would be greatly appreciated. Also does anyone know a mechanic in the Tucson area that is good with Jeeps and/or Weber carbs?

-Eric

[OlneyJeeps]

It was the last thing I would ever have thought of (put in NEW engine, carb, remanufactured distributor... still failed): ignition control module. Your Jeep uses the motocraft multi stage module. Engine will idle, but runs crappy untill 2nd stage (little over 1300rpm).

module is on drivers side fenderwell, 3 bolts (5/16head?) accessed from inside of fenderwell. Take module to Autozone/pepboys and have it tested ( you have to read book and use pin2pin leads, as there is not a plug in tester adapter for your module).

[Curly]

On the fouling plugs, have you tried a hotter heat range? Look at the part number on your existing plug, and ask for a higher number. Example: RBL13YC, ask for a RBL15YC.
Increasing the heat range means the operating temperature of the tip will be hot enough to burn off any oil that trys to collect on it. I have gone as much as 2 heat ranges hotter to solve a problem with oil fouling on plugs. The trade off is the exhaust will smoke a lot more from the burning oil.
My experience is that the folks working at Auto Zone, Checker and so on are just trained to use a computer, and will give you a blank stare when you ask for the higher heat range. Best to go to Napa if you are unsure of the exact number you need.

Timing: what is it set at? Try advancing as much as 4 degrees over Base setting.

Curly

[trekker1701]

ONLEYJEEPS - I will have the ignition control module checked out this weekend. Thanks for the info.

CURLY - I believe I have the hottest plugs in the Jeep already (according to Checker Auto parts anyways) but I will check at Napa and see what they say. I am currently running Champion plugs in it now and I think they are 14's or 16's (probably 14's). I have no idea what the timing is set at. I assume it is "where it is suppose to be" since I had the vehicle worked on at a local mech shop who works on alot of Jeeps when I had them install the new Weber carb...but this is the same mech who normally makes it run worse. I will check on the timing and adjust as you recommend and see how it goes from there. Thanks for the info.