lose throttle when engine is cold

[jeepers_creepers]

Hey guys,
Need a little help. My 98 sahara is having some trouble accelerating before the engine warms up. When I first start driving in the morning. I’ll step on the gas and the engine cuts out, sputters and stops accelerating. It leaves me coasting for a while. If I leave the peddle to the floor it will eventually, after a few seconds kick back in, but will cut out when I shift into the next gear. It seems that if I rev it up I can reduce the amount it happens but it still persists.
Once the engine warms up its fine and drives as good as it ever has. Anyone out there know what might be wrong? I’ve had it to two of my best mechanics and they have no idea. I’d like to get some feedback before I take it to the dealer and risk getting the run-around again.

[gtmud]

Are you getting any codes( engine light on). I think in your Jeep there is a sensor (cold start) that tells the computer when the engine is cold, allowing a richer mix of fuel till it warms up. This could be the problem. If you have the 6 cylinder, I think its the sensor that is screwed into your manifold just in front of the throttle body.

[gtmud]

Are you getting any codes( engine light on). I think in your Jeep there is a sensor (cold start) that tells the computer when the engine is cold, allowing a richer mix of fuel till it warms up. This could be the problem. If you have the 6 cylinder, I think its the sensor that is screwed into your manifold just in front of the throttle body.

[jeepers_creepers]

Nope, not getting any ck. engine light and nothing showed up on the dygnostic either. I tend to agree that it may be a sensor due to the fact that it only happens when the engine is cold leading me to believe it's not of the mecanical nature. I do have the 4.0L. Is this a common problem? Have you ever heard of it happening before? I puzzled why a faulty sensor wouldn't show up on the dygnostic check.

[fredjacksonsan]

How long since you've done a tune up?

It'd also be helpful to know what the mileage is....

[jeepers_creepers]

Was just tuned up in the spring (May). had a new clutch put in, in May, new water pump last month and new breaks and tires this month. Got 61K miles on it. I've been driving it the past two days and it is getting progresively worse. I didn't drive it today. It was starting to make poping noises when it would kick back in. i'm about to call the dealer to make an apt. to bring it in.

[fredjacksonsan]

I'm thinking it could be the throttle position sensor or the crankshaft position sensor.

[jeepers_creepers]

I've gone back through the history of postings on this forum. A few others have had simalor problems and the suggestions were also related to the cold start sensor and crankshaft pos. sensor. I'm hoping to find out soon for sure as I have caved in and droped it off at the dealer. I'll post what they tell me as soon as I hear back from them.....


Just heard back form the service department. They have no idea. So, I suggested to take a better look at the sensors you wrote about. They are going to look into that. thanks for the help guys! We'll see........ I'll keep you posted.

[jeepers_creepers]

It was a lazy O2 sensor.
After a week and a half of searching. and $680 later. put new wires, pugs,cap, rotor, and throtlebody cleaning.Basically a tune up.

[JEEPTJZ]

Originally Posted by jeepers_creepers

It was a lazy O2 sensor.
After a week and a half of searching. and $680 later. put new wires, pugs,cap, rotor, and throtlebody cleaning.Basically a tune up.

HI
I have a 99 auto-6, that is doing the same thing as yours but mine does it hot as well. At freeway speed there is no problem only when leaving a stop light (under 2 grand)does the bucking and snorting start.
Has the o2 sensor completly fixed your jeep?
thank you for your time!
joe