The_Dude

This is my first post here but I have looked on this forum many times and have solved all my problems. I was going to take a wheeling trip in the mountains this weekend. I stopped to fill up before hitting the hill. As I twisted off the gas cap there was a hissing sound (gas vapor) escaping. I filled up the tank and didn't think much about it. I got nearly all the way to the top of the mountain (9000ft) and 30 min of driving and it stalled.

I pulled off to the side on an uphill incline. I twisted off the gas cap and very loud hissing sound as 20lbs of gas vapor comes out. 15 min later there is still visible gas vapor coming from the tank and I am unable to re-start. I turned the jeep around so that now it is facing downhill and I am able to re-start to a rough idle. check engine light comes on and now I start back down the mountain with gas cap removed. 30 min back down the mountain (mostly coasting with engine idle) I stopped in a pullout one time during decent and the engine shuddered and then re-gained idle.

Back in town now, car driving fine, I stopped at autozone and bought a new gas cap and had the guy read the check engine code. He said #1 misfire was all it had. I put on the new gas cap and drove to red robin for lunch with no problems. Came back out from lunch and it took 3 tries to start. I made it to the edge of the parking lot and stall. Then I re-started immediately without pressing gas pedal the rpm would go to 1800 or so then come back to 1000 and idle normal. I put it in drive and made it to the first stop light, as soon as I took my foot off the gas, it died. It continued to start and stall about every half mile or until I hit a light. But sometimes when there was no stop light it would just start to die even as I was above 1700rpm and accelerating.

I thought it could be a bad CPS but the symptoms were slightly different with that because I just replaced the CPS one month ago and if I had my foot on the gas the engine would not die. But with this problem, there were a few times when I was accelerating and holding steady at about 2000rpm and I could feel the engine start to shudder and then it would slowly die. If I pressed the gas when it was starting to die, it would not respond, like it was getting starved of gas. As soon as it would die I could start it right back up with one or two cranks, and it would do like I said start to around 800rpm and shuddering and then without pressing the gas VROOOM up to 1800 rpm then back down to steady normal idle 1000rpm running smooth and I would slam it into drive and make it would run perfect for about half a mile before it would die again. I did that all the way home, about 15 times. At one point when the engine died I removed the new gas cap and was surprised that the same gas vapors released, but leaving it off didn't seem to help the problem.

Any help on this is greatly appreciated. I really hate to think bad CPS, that thing was not so easy to remove/install. I was reading about TPS and heat soak as possibilities. It was over 100 degrees today but engine temps were normal and on the mountain it was maybe 88 degrees and it's over 100 here on a regular basis and we've never had this problem before.

Thanks in advance!

Radi

Doubt it's the CPS. Check your fuel pressure, and check the vapor canister/vent line for blockage.

bighouts5591

I had very similar issues to you and it was my TPS, they don't always throw the code when they go out. It takes about 5 mins to change out. Could also be an o2 sensor. I would try the TPS first and return it to the parts store if it doesn't fix it

The_Dude

Would a TPS cause vapor to build up in the tank though? I'm going to check the vapor canister and line first I think. Any other ideas would be cool

Radi

TPS tells the ECU (and TCU) what you are doing with the accelerator. It could cause your drivablility symptoms. I'm a bit suspicious your fuel pressure is dropping, perhaps intermittently, but checking the TPS operation is quick and free....do that first.
Neither will affect fuel tank pressure, that is supposed to vent into the charcoal canister.