kstopp

After a recent 500km highway trip, my XJ has been taking a few extra seconds to start up.

I have done the following:

1) Tried the poor-mans fuel pump prime with no change. The pump is a 6 month old Carter along with fuel filter and tank.

2) Checked TPS with a digital and analog meter for dead spots. Idle and WOT readings are within spec.

3) Checked coolant temp sensor and intake air temp sensor. Both are within spec for a few different temperatures I checked.

4) Cleaned the IACV

5) Checked spark plugs and spark plug gap (0.035"). Rotor, cap, plug wires and plugs were replaced in the last 6 months.

I'm going to get my hands on a vacuum pump so I can test the MAP sensor and see if I can find an oscilloscope to check the CAS output.

Anything I could be overlooking?

Firestorm500

Looks pretty thorough to me.

Alpha 1-4

Battery amp output low?

1arunem

Not that you have the same issue but I noticed my crank time becoming longer and longer. After replacing the injectors it is back to normal. Figure I had one or more bleeding through/down.

kstopp

I got a hold of a fuel pressure gauge. 33PSI key on, engine off. ~31PSI engine running at idle, 41psi vacuum line removed from fuel press regulator.

Those numbers all look good according to FSM. I then did a leakdown test:

Over 30mins the pressure dropped from 33 to 25psi. The FSM allows for 20psi in 30mins, so it passes this test also.

I forgot to mention that I also checked for vacuum leaks by spraying a can of throttle body cleaner around the vacuum lines and connections.

Battery is good.

Occasionally on a hot restart, it starts up with no delay. Not too sure what to think of that.

KnightKrawler

Mine also cranks awhile when cold and hot start up is quick, I'll be curious what resolves your issue.

kstopp

Still haven't gotten to the bottom of this yet. Occasionally while taking a long time to crank it will sputter a bit, like a vehicle that the timing is incorrect.

I came across this thread: https://www.cherokeeforum.com/f2/col...rm-fine-83014/

Seems like a new IACV solved the similar problem for him. I have this symptom:

kstopp

Just wanted to post back here, a new IACV solved this problem.

I tested it out before ordering the valve by tapping the throttle to open up the throttle plates a little bit while cranking. This made up for the lack of air coming from the IACV.

The factory IACV pintle was much further out than the replacement valve. The document with the valve stated that the pintle should not exceed 28mm past the body. The old one was much further out, and I believe broken internally. I should mention that it's a good idea to reset the PCM before starting the Jeep back up. I forgot and it reved up to 2500RPM before settling down to normal idle speed after the computer realized the % it needed to adjust the new IACV.