From bad to worse

[Sully]

Recently I changed the spark plugs on my 99' TJ because it was hesitating and running rough. It ran great for about a week then it started running rough again and it was having a hard time starting. I'd have to crank it for a while. Well I didnt drive it for a few days and now it wont start. Any ideas?

[mud4feet]

How'd the plugs look when you took them out?? Look like they'd been fouling? Did you change out the wires, too? Maybe a bad coil pack??
Just throwing out some ideas.....thinking of things, other than plugs, that would've caused the hesitation/running rough. The dang computers make 'em a whole lot harder to diagnose. Dang O2 sensors cause fits, too, but I can't imagine them causing a "no-start".

Hope it's something simple........................someone's bound to be more helpful than me.

[Bounty__Hunter]

Is the check engine light on? I'd have it checked for a code.

My bet is the throttle position sensor (TPS) or crank position sensor (CPS).

	Crank position sensor A crank sensor is a component used in an internal combustion engine to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control ignition system timing and other engine parameters. Before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on the engine.

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[jps4jeep]

Originally Posted by Bounty__Hunter

Is the check engine light on? I'd have it checked for a code.

My bet is the throttle position sensor (TPS) or crank position sensor (CPS).

what I am thinking.

[Sully]

Took it to pep boys for the code, they said they didnt know what it was and wouldnt give me the code for some reason. Told me to take it to the dealer. To make things even better the saturn I have been driving sucked a valve on the way home tonight. Now I have to drive a jeep that only works when it wants to and I have two cars to fi.

[jfrabat]

Some time ago I found and bought a code reader that was compatible with the Jeep's OBDI (along with Ford, Chrysler, and GM, if I remember correctly, and all of the OBDII) and it has been very helpful. Price was not excessive, and it sure is a lot easier to read than counting the CEL with the strange timing it has... Maybe you can look one up on eBay or something.

[TerryMason]

I heard that advanced and pep boys won't give you the codes but I've alway had good luck with Auto Zone.

I did eventually get my own OBDII code reader though. It was only $60
While we find your parts, please enter your ZIP Code at PartsAmerica.com

[TerryMason]

oh yeah - you can find the computer codes in the reference section:
Reference - Jeepz.com

[Heydace]

Just judging by the symptoms I would look at fuel deliver or secondary ignition. You may have a few injectors leaking which could foul out the plugs or faulty secondary components, cap and wires.

[jeepin916]

any luck on this yet? iv heard of a few problems like this the codes were cam shaft or crank shaft sensor related and they were signal problems the one that i looked had a bad distributor. it would fire sometimes stall hesitate backfire etc.... well we pulled the distributor and the shaft gear was all banged up so intermitantly it would not get cam signals and also throw crank signal faults. might wanna check that if you havent figured it out yet if u did im interested in knowing what it was.... good luck