Weird long crank time/TPS issue, help!

So I've had an intermittent long crank for roughly 6 months now and it's really starting to get old so I'm trying to diagnose it. It's on a 2000 XJ 4.0. About 35k on the motor and about 150ish on the sensors and auxiliary components (what didn't come with the long block). New fuel pump, now a new TPS, and new MAP. At first I thought that I somehow screwed up the check valve on the new fuel pump but after thinking about it I realized that if priming the pump doesn't affect how long it cranks before it starts then it's prolly not the check valve. Haven't confirmed w/a fuel pressure gauge though. Sometimes the first start of the day is ridiculously fast and other times it has to crank for about 3-5 seconds. However, it seems to be more consistently bad when the motor's hot. Also, occasionally when I'm in the gas from I'd say about 3/4 throttle on up, I feel some stumbling around 3800rpm that reminded me a lot of how it felt when my fuel pump was poopin out on me. One more thing, I have a scanguage and it's showing that the throttle position is jumping around about 16 percent but mainly at idle. In other words, it will flash from 1 to 17 very briefly every couple seconds. A new TPS didn't change anything. However, when I disconnected the TPS connector it quit jumping around. Maybe I'm focusing on the wrong component but a bad TPS sensor/wiring could lead to intermittent longer crank times correct? My other guess was CPS. Any ideas smart peeps?

Milford Cubicle II said:

Sometimes the first start of the day is ridiculously fast and other times it has to crank for about 3-5 seconds. However, it seems to be more consistently bad when the motor's hot.

Click to expand...

Search Heat Soak on .

Milford Cubicle II said:

Also, occasionally when I'm in the gas from I'd say about 3/4 throttle on up, I feel some stumbling around 3800rpm that reminded me a lot of how it felt when my fuel pump was poopin out on me.

Click to expand...

Clean the Idle Air Controller (IAC), and put a can of Techron or SeaFoam injector cleaner in the next 2 gas tank fill-ups.

If this is not the TPS at fault, consider replacing the Coolant Temperature Sensor.

It does it when the jeep's cold too so I'm gunna eliminate heat soak. Plus I HAD heat soak issues but my new header/exhaust seemed to take care of that. Also once it fires and runs it's smooth. When I had vapor locking from heat soak it would idle rough for several seconds.

And because of the "hiccups" while in the throttle I'm eliminating the IAC too. Both were good thoughts though, I appreciate it.

Check all of your main grounds. If the ground connexion gets dirty or contaminated, it causes the "zero reference" for the sensors to go stupid on you...

That makes sense, I've already upgraded all of my main battery cables with 2/o welding cables but I forgot the one from the back of the valve cover to the firewall! :doh:

Could that be it??