Hi, I just bought a 98 jeep laredo for $500 and it has a few problems and i am wondering if someone can help me figure out what to try next, 1st off the engine has a miss and the chk engine light is on. I Bought a Carmd and ran the codes to see what codes it was throwing and it was P0202 and P0302. which are #2 cylinder Injector and #2 cylinder non firing. So i changed the Fuel injector on #2 cylinder and also pulled the spark plug on that cylinder (It was totally Carboned up) So i replaced all the spark plugs,Wires,Cap and Rotor. But im still getting the Miss and also the same codes. Anyone have any ideas what else it could be? thanks

 

Check all vac lines and clean your throttle body

 

Ok, Ive done that and it did t make any difference. Also I might want to add it is a Inline 6 cylinder. Someone said it might be a coil Pack but it doesnt have the coil pac's on each cylinder it just has one single coil. I'm leaning to thinking it may be a stuck valve or something like that due to all the Build up that was on the #2 spark plug. all the others were clean as a whistle. the #2 was Black and had Grime build up between the little tit and the ceramic part.

 

Can you hear (stethoscope) or feel #2 injector clicking? If not check the wiring/connection.

 

Thanks for your rely, I've narrowed it down to the Number 2 Injector isnt getting a pulse. I hooked up a Noid light to it and i get nothing but i get a flash from all the other injectors. So what could cause just ONE injector to not get a pulse? could the ECM be bad? if so, wouldnt it be all the injectors not getting a pulse?

 

There are some really sharp electronics guys on this forum that might be able to help, but my thought would be to check the wires from the injector all the way back to the source, doing a visual and Noid check.

I just went out and checked my '97 injector connection. When I disconnected the connector (engine off/key off) I have a ground on the wire terminal closest to the front of the engine, no ground on the other terminal.

I would back probe the connector with a needle and run a lead to a good ground source and see if the injector starts operating. If it does then of course you'll be looking for a bad ground.

 

Ive been reading up alot on line about how the injector gets its pulse and things like that and from what ive found the Injectors get 12v positive anytime the key is turned to the on position and while the engine is turning over or running. The Negative is broken and engaged by the PCM or ECM on the fire wall from information it recieves from the Crank position sensor. So instead of the Injector getting 12v pulses to make the solenoid activate it has continuous voltage and the ground is "Grounded in Pulses"

The thing is, The number two injector isnt getting the grounding pulses for some reason. all the wiring is good...ive traced it all the way to the PCM. I guess im just going to replace that and see if it fixes it. Thanks for your help, I will post whether it fixes it or not.

 

If you're sure the wiring is good to the PCM, and it's just the one injector, then yes, it must be a bad driver in the PCM.