mongold88

Ok so I've got a 98 4.0L auto 4x4 recently and I've got a weird issue that I'm trying to hunt down. What happens is when I first start driving, after a minute or two, the throttle acts like there is no response, then picks up, then no response. This goes back and forth for 30-60 seconds. When it happens the jeep starts to slow down speed wise. Now if I let it sit to warm up it will go through a rough idle( kinda like a misfire) for the same amount of time, then it's good to go. This only happens when the motor is cold or after a medium time of sitting, like going in for something to eat or shop. Also it will not set a light either!!

I've installed new plugs, wires, cap and rotor, cam pulse sensor, and throttle position sensor.

mongold88

Any ideas??

SeriousOffroad

CEL?
List of Error Codes?

XJwonders

Frank. He mentioned that it doesn't set off CELs

Did u replace TPS with mopar brand one?

Those from parts houses don't really work.

mongold88

No I didn't get a mopar one. The TPS is from carquest.

SeriousOffroad

Put a scanner on it.......

mongold88

I have it shows to stored codes or pending codes.

SeriousOffroad

Start with the basics...
Clean all grounds, perform a thorough throttlebody cleaning.

mongold88

Just out of curiosity if it was a ground issue wouldn't it happen all the time with a crappy connection? Not just on start up for 30-60 seconds? And same curiosity about the carbon build up?

CCKen

I have experienced a similar problem with my '99 Heep. Replaced the Upstream Oxygen Sensor and it fixed it. However, I suspect the oxygen sensor heater(s). So check the O2S Heaters fuse in the PDC first.

mongold88

I've heard that as well about the oxygen sensor

SeriousOffroad

Might want to see if your injectors are closing 100%.

A loose ground can cause intermittant problems.

Roler

The mentioning of backfiring always makes me think of CPS....

Parsnip

X2 on Cps. When I go mudding if some gets up on the bell housing or even just muddy water gets up there, it will run like crap, rough idle, sputter, then return to normal after a couple thousand revs (usually about 30-45 secs)

mongold88

Do you ever get a check engine light with the crank position sensor? And how hard are they to change?