I have a 96 xj and it will crank but won’t start. If I throttle the gas while trying to start it will rev but as soon as I let off it dies. It has a brand new battery, spark plugs, spark plug wires, distributor, crankshaft position sensor, the idle air control sensor is clean, fuel pressure is good, and it has good spark. I’m stumped on what else it could be.

 

You should probably check the fuel pressure is ~49psi at rail valve

 

also it might be the idle air control sensor give it a clean but yes check your fuel pressure

 

Fuel pressure is good and I did clean the IAC

 

Create a vac leak by removing the crank case vent source at the intake manifold. With the intake hose removed you should be able to feel no vac at the throttle bypass inside TB. Slowly cover the manifold leak with a finger and vac should return to the bypass in the TB signifying that the valve is opening to maintain idle. I think I said that right?

 

Did you check the battery, spark plugs, spark plug wires, distributor, crankshaft position sensor, idle air control sensor, fuel pressure and spark?

Sorry, couldn't resist.

Next I'd pull the fuel injectors and give 'em a good clean. Can of carb cleaner and a 12V source.

How about some more history. When did it start? Sudden or gradual onset? Did it happen right after you got gas? Anybody in your neighborhood hate you?

 

cranking = turning over (they are the same thing). You mean cranking but not starting. Techs refer to this common condition as a crank-no-start.

Your symptoms match a failed IAC. If it revs and runs pretty well with a little gas pedal applied, this points to the IAC even more. If it runs very poorly, and giving it lots of pedal is the only thing that keeps it running and it dies the moment you let off, that is typically more associated with general system voltage problem.

A throttle position sensor (TPS) that is reading a high value can also mimic an IAC failure. Because if the computer thinks that you are applying some pedal - when you are not - it will not open the IAC as it should for idle RPM to be maintained with the foot -off- pedal. TPS value (at the computer) can be observed using an inexpensive OBD2 scanner. On your 96, the throttle position should be around 16-17% (specifically - mine is usually at 16.5 or 16.9).

If the part about it running poorly applies (read above), then you may want to do a general voltage test and clean up all of your ground connections and battery terminals.

 

Can you pull any engine codes with that?

 

On Jordans recomendation, I got the Basix ? OBD2 bluetooth reader, and used my android phone with free Torque software

It does read ENGINE codes, and show live data for many sensors

It did need a lot of fiddling with the firmware to make it recognise a '96 as NOT OBD1

but they guarentee it will work on all USA cars from '96 to (not sure when)..for about $30, its an indispensable tool

 

You said distributor is it a cap or a whole distributor if you put in a whole one it may be 180 degrees off or out of time

 

it would not run ....bang bang cough pop pop ...............................

 

pretty good chance its one tooth out, unless you were ultra careful, they (and other engines) typically will slot the dizzy back in 1 tooth out...I always mark the rotor to engine block position with a ruler and white marker

in this case it will try to start...180* out, it will never fire

 

The is just and old saying from my day doing mechanic work years ago some time a rebuilt engine time gears was set but the number 1 valves are opened so the distributor is off a 180
so you pull up and drop 180 and some engines the timing marks on the gears are not (dot to dot) (but top to top) I was just trying to help