1990 gw performance problems

[jerry_handrahan]

Last week my 1990 gw (360 v8) started acting up. When it is cold it runs fine, but when it gets to operating temp. it starts to falter. When you give it gas it may go or it may miss or stall or backfire through the carb. Then it runs fine for a couple minutes. I replaced the coil/plug wires/ and dist.cap with no change. I suspect the carb. because of its occurence only after it reaches operating temp.
Any suggestions????
jerryh

[Bob Barry]

My first inclination is to check if the choke is sticking or staying closed. Even a partially closed choke can cause what you describe.

[ August 06, 2001: Message edited by: Bob Barry ]

[Lindel]

There are a couple of other possibilities, too. The ignition module is the criminal of choice for FSJ's (it lives on the drivers side fenderwell, next to the hinge), and if you look at the front of the carb, where the fuel line comes in, you may have a small brass cylinder, about an inch in diameter. That's a secondary fuel filter, and will solidify with today's pump gas. Never seems to hinder fuel flow when cool, but I had the same problem with my now dead 87 on 2 different occasions, and this was the cause both times, after the Jeep had warmed up, and was on the highway. It would idle, but the minute I applied throttle, it would buck and sputter, and if it died, would be almost impossible to start.

[Lindel]

BTW, the cure for the filter is to punch a hole in the filter medium, or just get adapters, and get rid of it!!

[SpruceMoose]

and if that stuff doesnt work, remember that a backfire thru the carb is usually a sign of a lean mixture. check the accelerator pump. its possible that when on choke the symptoms are being masked by the extra-richness of the choke, and when the choke comes off you are left with a lean condition when trying to accelerate. btw, a backfire thru the exhaust system (technically called an after-fire)is usually a sign of a too-rich mixture.

sm.

[Stauter]

Went thru this with mine, 84 GW, 360, did TFI upgrade, rebuilt carb twice, replaced module, was better but still acted up when warm, I finally found the culprit!! the power brake booster check valve was bad causing a vac leak. was ok when cold because choke was giving it the extra gas to compensate, when warm it was lean and running poorly. Idles much smoother now, doesn't stall and much better power. Only $3.99 worth changing to see if it makes a difference.

[coolram]

Mine would do this black smoke and rough idle from time to time.Found the brick was broken in my cat and would clog it up.It would rattle around making it sound like i had something loose or scraping.I "serviced" the cat and replaced the muffler.too.She idles very good now but I'll take a look at the booster check valve.