So I've been having issues with my fuel injectors sending to much fuel. At idle I can smell unburnt fuel, had someone tell me there was black clouds coming from my tail pipe (which I know its unburnt fuel), and have been having an issue with starting up my 99 xj sport 4.0L. Someone i know told me its my temp sensor for the computer but id like advice from fellow jeepers. anyone have suggestions on what to do to solve the issue of fuel injectors sending to much fuel? thanks!

 

Which injectors do you have in it?

 

I have the stock injectors. if its any help, i have a 3" intake tube with a pod filter and upgraded (8mm) spark plug wires.

 

and how old are the plugs? and is the check engine light on?

 

the plug wires are 25-26k miles old, just replaced the spark plugs. and no check engine light

 

I doubt that the injectors are at fault, there are so many things that can cause this....cap, rotor, wires, plugs, a vacuum leak, faulty O2 sensors etc.etc. etc. the check engine may be off, but there is still valuable information stored in the pcm that can only be seen with a scanner, not a code reader...fuel trims can be watched with the scanner to determine in which direction to look for the cause of your running rich at idle, and yes a faulty coolant temp sensor( the one in the thermostat housing) can cause the ECM/PCM to receive false information which will effect fuel injector pulse width(the amount of time the injector is open)

 

ok, now i did replace the exhaust manifold recently so i had the injectors disconnected and intake manifold out, cleaned the throttle body and iac sensor. i never reset the pcm when i was done because i didn't think i would have to. should i start with resetting the pcm, and how do i go about resetting it?

 

the easy way is with a scanner, but you can also just disconnect both terminals from the battery, and hold the two battery cable ends together for about 30 seconds, as this will drain the stored energy in the PCM resulting in clearing learned values, reset as it were

 

Any check engine light? Have you checked for any stored codes? If not, I would start there before throwing parts at it.

Edit: I see ***** got you going. Disregard.

 

no check engine light, haven't checked for stored codes. only times engine light came on was for misfires in cylinder 1 and once for bank system 1 to lean but im pretty sure ive solved those issues since i have seen the engine light on in almost 3 months now!

 

^^^^ B4 disconnecting battery...

 

ok so i reset the pcm, didnt see any stored codes before hand. still have a long crank till start up and not 100% sure if it fixed the fuel injectors sending to much fuel, ill know more once i get some deliveries at work and have a chance to drive it to tell if the injectors solved themselves with resetting the pcm.

 

ok, so resetting the pcm did not solve the issue with injectors. gonna try to find a temp sensor for the computer at one of the local auto part stores and start there.

 

Resetting it requires (iirc) ~50 cycles of start-up and driving in your usual style. It may take a week or two before it is fully reset. I suggest waiting until then before you start throwing parts at or you're probably going to become frustrated when the results you're expecting don't obtain.

Patience.

 

have you done a fuel pressure test and leak down. could be a stuck wide open injector