Constant speed draw back

[VdrumsRoland]

I had something odd happen today. I’m coming home driving on a highway (flat grade) going about 55 and I noticed something. It’s hard to explain but, it felt like my brakes were being lightly applied every 4-5 seconds. It also seems to happen with keeping a constant speed no matter the speed. So if I'm going 30 on a flat road it will do it. I have about 8k miles. Only thing I've done is change the oil this week, no other mods (yet).

Has anyone else experienced this? What could it be? Should I be concerned?

Thanks!

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[liquids]

Yes, I've noticed the same thing anytime I'm coasting in gear (3.6, M/T) and the grade keeps me at about the same speed.

I'll tell what I think it is then let someone else tell us why it's wrong ...
I believe that the engine control units used to turn off the fuel (set injector pulse width to 0) when coasting in gear with no throttle. From my experience with my JKU just from feel, I thought they did this after a few seconds of such coasting.
With the JL, rather than cut it off waiting for coasting conditions to change, I think it's turning the fuel to the injectors back on for a split second every 4-5 seconds. So rather than braking every few seconds, it's actually turning off engine braking every few seconds.

 

[bwright1818]

Everybody seems to describe it a different way and some people don't even realize it is happening. If your problem is what I think it is, welcome to the club and forget about FCA fixing it. There are at least three threads here that I think are related. Here is one:

https://www.jlwranglerforums.com/fo...ing-shuttering-doesnt-run-smooth.26370/page-6

I guess it is not so bad with automatics because they have played with the shift points to mask the fundamental engine problem. Mine is a manual and it is absolutely the worst-running vehicle that I have ever owned. It is pathetic.

 

[liquids]

Everybody seems to describe it a different way and some people don't even realize it is happening. If your problem is what I think it is, welcome to the club and forget about FCA fixing it.

I don't actually consider it a problem. I feel it, recognize what (I think) is going on, and agree with the thinking behind it.

 

[bwright1818]

I don't actually consider it a problem. I feel it, recognize what (I think) is going on, and agree with the thinking behind it.

You have more patience than me. I bet you can feel that the engine in your 1968 CJ5 runs more smoothly, though. In my JL, there are two stages to the draw-back feeling: The first, a kind of hum, which seems to be a smooth misfire, if you will, is semi-tolerable. If I keep it at that throttle setting for long, it will misfire erratically, sometimes to the point where the drive line will clank. THAT is NOT tolerable.

 

[liquids]

You have more patience than me. I bet you can feel that the engine in your 1968 CJ5 runs more smoothly, though. In my JL, there are two stages to the draw-back feeling: The first, a kind of hum, which seems to be a smooth misfire, if you will, is semi-tolerable. If I keep it at that throttle setting for long, it will misfire erratically, sometimes to the point where the drive line will clank. THAT is NOT tolerable.

Yeah, I'm not feeling either of those as you describe them. Do you have aftermarket exhaust? As far as throttle position, all of my "draw-back" is when I'm at no throttle, in gear (manual) and coasting, like when I'm approaching a red light some distance ahead and waiting for it to turn green before I have to brake. For your problem I'd probably take it in.

The '68 CJ isn't running at all as the carb is 10 feet away from me and the Jeep is 120 miles away. It's that way because the last time it was running it was herkin' and jerkin' like crazy. It was a stuck open power valve. (I'm guessing one out of a hundred people on here know what a power valve is and how it works. I was also ignerant about that until this summer.)

 

[bwright1818]

Lol I'm 63 so yeah, I know what a power valve is. I have taken my Jeep to two different dealers and had a test drive by a regional service tech. They know all about it. They are not going to fix it. It's insane.

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