I have a 93 4.0 auto and recently it has been acting up. the jeep idles fine but when i put it in drive and start going and get past about 1300 to 1500 rpms the motor starts cutting out, almost like its missing on a few cylinders, even though its not, at i have about 1/2 power. once i get past about 3000 rpms it will kick in a little, the motor sounds good but only gives me about 3/4 power, then finally at about 3500 to 3700 it kicks in again and gives me full power, but i dont like keeping it at that rpm. i have replaced the tps and o2 sensor thinking they would fix it and it has new plugs but it didnt work. i have tried searching the site for the same problem but came up with nothing. any input would be awesome, thanks.

 

Did you replace the wires, cap and rotor also when you did the plugs? I'd start with that if you haven't. Also refresh all your grounds and battery terminals until shiny. Maybe even replace the fuel filter and run some injector cleaner for good measure.

This is all routine maintenance that you should be doing anyway.

 

Try Running a bottle of injector cleaner through it. Not saying it will work but dirty injectors come to mind. Does your exhaust smell rich at all? Is there any smoke in the exhaust?

 

i did the plugs about a week ago, i havent done anything with the wires or cap, i dont think it is a spark issue though, but i will look into it. i have been running injector cleaner through it every couple of full tanks cause i have had a few other problems with it in the past (bad fuel pump and filter) i have had a new pump and two new filters in the past couple months, and i took the fuel filter off this morning and blew it out and put it back in, same problem. and no it doesnt smell rich, and no smoke. it just sounds like it isnt getting enough fuel.

 

o2 sensor. They can effect lower RPM's, but are bypassed at WOT. It's ultimately a fuel delivery issue, I'd guess. But I still say blame lies in the o2!

 

even though i have a brand new one?

 

Ahh.. Sorry, missed that in original post.. But yes. It may be a bad sensor still.. Sometimes they are faulty, not likely though.. If I may ask, what kind/how much did you pay for o2?

Dunno man.. You've done all the likely stuff.. Computer reset at all?

Have you inspected the tank itself to see if there's any crap in there.. I suppose if you've done the filter, you'd have seen if there was any material in there.. Hmm... Umm.. The cap and rotor are cheap.. Might be worth a replacement. I know you said you don't think it's spark. Can you get it on a code reader to check sensor function, etc. while its acting up?

 

its a bosch, and it was like 50 bucks. when i took the pump off i looked in the tank and it was clean. and my filter is an inline filter outside the tank so it is easy to get to and replace, will probably get a new one today when i get the cap and rotor then take it to my hs autoshop and try and read some codes.

 

I am pretty sure it's a fuel delivery issue. I had an issue with my injectors when I replaced them. Injector one had this plastic tip on it and it had shifted when I installed it causing a bad spray pattern. This resulted in similar issues to yours. There us a chance you have done crud in your fuel rail, or in an injector. You might even have a bad injector. It's a PITA but you might want to clean out your fuel rail and test your injectors with a 12v power source. You can send them out to be cleaned for between $15-$20 a piece depending on where u send them.

 

ok i will look into it. i wouldnt be surprised if there is crap in my system, i think i have been getting some bad fuel lately so i could have gummed it up. i will try to pull some codes first and then go from there. what injectors would be best if thats the issue?

 

i took my jeep into my high school auto shop and couldnt get any codes out of it. i drove it to work and barely made it. after work i had my buddy drive me to get a new cap, rotor, and plug wires. i got it all in and it fired right up, then went to drive it. at first it did ok, then i got going and once i hit 2000 rpms it started cutting out again.

the new parts did help a little bit but it still has no power and sounds like poo. any other ideas of what could be wrong before i start dumping more money into it?