'98 TJ Bucking Bronco

Does that mean it is stalling or partially stalling repeatedly?

Jerry

Jerry...

It's not stalling out. It sounds like a misfire and at this point, I just don't know whether or not its a fuel/fuel delivery problem or a spark problem. It misses, jerks, bucks. I may drive 5 miles down the road and everything is fine. Then I'll get a miss... or a flurry of misses... and everything is fine for another few miles down the road. Funny thing is that at idle there seems to be absolutely no problem. At slower speeds (like around town) it may do it... but rarely.

Mark

Sounds like maybe the crankshaft position sensor or camshaft position sensor. Any stored codes?

Jerry

A co-worker has a code reader that I think he'll loan me. Just out of curiousity, where are these two sensors located, how costly is the fix, and is it a DIY job?

Thanks!

Mark

The camshaft position sensor is located under the distributor cap, and the crankshaft position sensor is located on the outside of the flywheel housing, on the driver's side up near the top. The camshaft sensor is easy, the crankshaft sensor is easy too but access to it is not, it takes long arms and long socket extensions. Neither part is expensive to buy... $80 or so for the crankshaft sensor, unsure for the camshaft sensor but probably less than the crankshaft position sensor.

Jerry

Jerry,

My buddy hooked up his code reader and no codes displayed. He does have a couple of questions tho... What is fuel pressure supposed to be and what is the "bleed down" rate? He also noted (by looking at the tailpipe) that it appears I'm running a bit rich, but also wondered if that had something to do with all the chemicals (the HEET and injector cleaner) that I'd had in the last couple tanks of gas.

Really appreciate any help.

Mark '98 TJ '98 XJ

Thanks LW! Really appreciate the pictures showing where all this stuff is located! I'm saving this one!

Mark '98 TJ '98 XJ

That's why I made the site. :)

If you see something that doesn't look right or come across more data please let me know.

I had exactly the same problema with my 91 4.0 yj about a month ago. It turned out a serious vacuum leak was the couse -- Don't know why but the tube that goes in the pcv valve (actually called ccv here) was completely disconnected from the valve...!!! I fixed the leak with a new ccv valve & problema went away as if knife-cut!

hth, me

You might be very right. I replaced the plugs too, and all ignition components (on different ocassion) The plugs looked like they were never replaced (gap was more than double!)

*am not 1st owner :(* but it does run great! :)

49 psi is the fuel rail pressure. It bleeds off pretty quickly when you depress the Shraeder valve near the injectors. If it's truly running too rich, it's likely that the upstream 02 sensor is going bad, that is the sensor that sets the air-fuel mixture. Have you checked all your plugs for wear and unusual appearance?

Jerry

Yup. Changed the plugs the other day as part of my own effort to find a diagnosis and cure. The old ones looked good. Brown-greyish deposit on them. I changed 'em anyway, just to make sure.

i will, thanks

Well, by cracky, it's fixed. It didn't come about without a story, though. I took off from work at noon yesterday (Friday) and set out to my local AutoZone store to drop about $150 on new oxygen sensors. En route, something happened that hadn't before. Specifically my "CHECK ENGINE" light came on. Now I KNEW that I had to have some sort of codes that would display (none did the previous day when my buddy plugged in his code reader). So, when I got to AutoZone, I asked the counter guy if he had a code reader, which he did. He checked it and got a code "TPS/Pedal Travel Sensor". Well, neither one of us knew what a Pedal Travel Sensor was, but both knew what a TPS was. However, the counter guy still suggests strongly that I've got a fuel filter problem and that should be my priority fix. I thanked him and decided that it was now time to go see the Jeep repair guy at a dealership. Drove crosstown and talked with the Jeep technician who really felt it was the throttle position sensor, so I went to their parts counter and asked if they had one. Nope, but they could order it. I had 'em check with a dealership 35 miles down the road. They had 3 of 'em. I got on the cellphone and asked them to hold one, I'd be right there. An hour later, I've got the new one on and everything is back to normal! Now I can get back to spending $$$ on my Jeep for fun things.

Thanks to everyone who provided assistance with this.

Mark '98 TJ '98 XJ

Took a long ccruise with it yesterday. Ran just fine. Got home and it started bucking severely as I was slowing to a stop. Kind of like you didn't let the clutch out coming to a stop. It died, but I was able to start it again. A few miles down the road, it bucked again when taking off from a stop (this time, like letting the clutch out too quickly when taking off). I got home with it ok, tho. Today, it turns over but won't fire at all. What now?

Mark

M. E. Bye wrote: | On Sat, 04 Sep 2004 07:20:47 -0500, M. E. Bye | wrote: | || On Wed, 01 Sep 2004 17:39:45 -0500, M. E. Bye || wrote: || ||| About a week ago, my '98 TJ (2.5L, 5-speed, 71K miles) began ||| missing at highway speed, bucking like a bronco. I chalked it ||| up to a bad tank of gas, so I dumped in a bottle of HEET and a ||| bottle of fuel injector cleaner. The problem continued, so I ||| did the same thing with my next fill-up at a different station. ||| No improvement. Since then, I've changed the plugs, installed ||| new wires, distributor cap and rotor, have cleaned the throttle ||| body, and have disconnected all electrical connections to the ||| throttle body and fuel injectors and have sprayed electrical ||| contact cleaner on them. I still have an intermittent miss at ||| speed. Not as severe as before, but I still have the problem. ||| What's next? ||| ||| Thanks in advance for any assistance! ||| ||| Mark ||| '98 TJ ||| '98 XJ || || Well, by cracky, it's fixed. It didn't come about without a || story, though. I took off from work at noon yesterday (Friday) || and set out to my local AutoZone store to drop about $150 on new || oxygen sensors. En route, something happened that hadn't before. || Specifically my "CHECK ENGINE" light came on. Now I KNEW that I || had to have some sort of codes that would display (none did the || previous day when my buddy plugged in his code reader). So, || when I got to AutoZone, I asked the counter guy if he had a code || reader, which he did. He checked it and got a code "TPS/Pedal || Travel Sensor". Well, neither one of us knew what a Pedal || Travel Sensor was, but both knew what a TPS was. However, the || counter guy still suggests strongly that I've got a fuel filter || problem and that should be my priority fix. I thanked him and || decided that it was now time to go see the Jeep repair guy at a || dealership. Drove crosstown and talked with the Jeep technician || who really felt it was the throttle position sensor, so I went || to their parts counter and asked if they had one. Nope, but || they could order it. I had 'em check with a dealership 35 miles || down the road. They had 3 of 'em. I got on the cellphone and || asked them to hold one, I'd be right there. An hour later, I've || got the new one on and everything is back to normal! Now I can || get back to spending $$$ on my Jeep for fun things. || || Thanks to everyone who provided assistance with this. || || Mark || '98 TJ || '98 XJ | | Took a long ccruise with it yesterday. Ran just fine. Got home | and it started bucking severely as I was slowing to a stop. Kind | of like you didn't let the clutch out coming to a stop. It died, | but I was able to start it again. A few miles down the road, it | bucked again when taking off from a stop (this time, like letting | the clutch out too quickly when taking off). I got home with it | ok, tho. Today, it turns over but won't fire at all. What now? | | Mark

I may have missed it, but how many miles are on it?