I think my jeep has an injector problem, I have a bad miss that I can't get rid of. I've change the plugs, wires, cap, rotor, fuel filter and O2 sensor. I can't find a vacuum leak either. It's not a slight miss, it's a hard miss if that makes sense. The only thing left is the fuel system, I think maybe an injector is not firing or flowing. I'm going to get my meter an check them tomorrow, if they ohm out okay is it possible they still aren't flowing or maybe sticking? How do I tell if they aren't flowing? How do I clean them if I pull them?
Not sure how to tell you if they aren't flowing. But to clean: I took a cardboard box, and made 6 small holes in it. Marked each hole for the corresponding injector, and set them in. Then I put a little fuel injector cleaner in the top of each one (the same kind available at any parts store that you add to the tank), and let it sit for about 48 hrs. Then I flipped them over, and repeated the procedure, again for 48 hrs. Then I took each one and LIGHTLY scrubbed them with a soft bristle brush (I used a soft tooth brush). Once clean, I replaced them. Might want to change out your o-rings when you do this. They are cheap to replace anyway.
I was doing a motor rebuild so I had the time to let them sit for that long. You could probably get away with 12 hrs on each side, just to let gravity pull a little cleaner through it. Oh, and I poured a lot of injector cleaner into my fuel rail as well. I got a lot of black stuff out of when I did. I just poured a little in, shook it up, dumped it, and repeat.
1991 YJ, rebuilt 4.0L in spring 2009 at 234,000 miles, no lift yet, slightly offset wheels, 235/75/15 tires for now, rag top, sold the hard top. Over 35,000 miles on the rebuild and counting.
When one of my injectors stopped working I got engine code 27. I chose not to clean them, but instead upgraded them from a vendor on ebay. Not sure if the 4.0 can use injectors from a different vehicle but the 2.5 can use 19# bosch ones.
You can also get them from a junkyard from any of the dodge or chrysler cars listed there. I just pulled 4 from a sebring this past friday, $5 each. But that was the only one they had, most of the other cars and vans were V6's. I still need to find 2 more. These are the newer EV6 injectors with the old style plug for the wires. They are the 4 hole design and better atomize the fuel for a better running engine. Be carefull if pulling from a neon. Apparently there are 2 diffrent 2.0 engine, one is SOHC, the other is DOHC. Only the DOHC has the correct injectors. The SOHC one has ones that look the same, but are slightly shorter and wont work.
'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, WJ knuckle/brake conversion, hydroboost. Warn M10000 winch. Hope to some day build a stroker for it.
'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
Future mods: NV4500, NP205, high pinion D60 front and smooth bottom D60 rear, e-lockers front & rear. SOA with 35X12.50's
Timing is set by the computer and is not user adjustable.
Several yrs ago I had an intermittant miss on my '92. Finally I replaced all the "other" sensors: coolant temp, manifold air temp, crank pos, cam pos, and manifold absolute pressure. It fixed the problem.