Spitting, sputtering, and backfiring. Oh noes

Okay so Fist things first, '89 cherokee 4.0L 4x4 Auto.

Now to the crappy part. So for the last year MY jeep has just sat i would fire it up every 2-3 weeks, drive it around the block and park it.

About 3 weeks ago i wrecked my BMW and the jeep became my daily driver.

Every once in a while it will sputter really hard and i will loose all power. The jeep stays running but it wont rev over 6-750 RPM. If i hold the throttle down or bounce the throttle it back fires So loud it sets off alarms and the local police show up.

The last 2 times it has happened i cycled the gear selector from park thru 1st and back to park and for some reason it seemed to stop sputtering. I really dont think this had any effect.

Also earlier today it had an episode and i got it to stop sputtering and shut it off. about 20 minutes later i went out and fired it up and it was sputtering again.

Any ideas guys.

Could be tons of things. TPS comes to mind. They can be checked with an analog VOM. Got one available?

I agree that testing the TPS would be a good idea. And also know that the TPS on an 89 IS adjustable and adjustment is important.

Next thing is to verify fuel delivery. Backfiring can be indicative of a lean condition.

Verification must be done WITH a fuel pressure gauge on the schrader valve of the fuel rail. With an 89, you should have 31 psi at idle, and when you disconnect the vacuum line for the fuel pressure regulator (be sure that vacuum line is pulling good vacuum), the fuel pressure should jump to approx. 39 psi.

Could be other things (verify all exhaust components such as manifold, etc.) but the above should be ruled in or out early in the process.

Everyone has given you good advice.

I would, however, start with the battery--get a full charge on it. Renew your grounds--dipstick tube, main ground cable, and the POS braided strap from the head to the firewall. Sitting like that things tend to go to hell.

But would that cause massive mis-fire issues?

If the available voltage to the engine management system drops below 9 volts, all kinds of weird crap can and will happen. Reference voltage to most of the sensors is supposed to be a nominal 5.0 volts. When the available voltage is too low all kinds of freaky weird data is getting sent back to the PCM.

Note: starting the engine every couple weeks and driving it around the block and parking it again really wasn't keeping the system charged up. If you had driven for 20 minutes or so it would have been better.