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-   -   2.4 Power issue, sluggish (http://www.wranglerforum.com/f210/2-4-power-issue-sluggish-253966.html)

bmpage84 07-06-2013 11:35 AM

2.4 Power issue, sluggish
 
Been chasing an issue with loss of power on my 2.4 for about a year now. (Yeah, yeah, I know, it’s a 2.4 and doesn't have any power to begin with! LOL)
That being said and out of the way………..

The Basics: 03’ TJ SE 2.4
Stock 5 speed NV1500 & NV231 Tcase w/an SYE (no drop)
4”lift, 33” tires, Stock D30/35’s 4:10/4:11 gears

Anyway, the engine has this intermittent “studder or hesitation” when starting out in first, and from first to second. I have to feather the gas and the clutch to get somewhat of a smooth takeoff from a dead stop. Many times during this “hesitation” I also get a sort of misfire/backfire/pop on the intake side. I really get the intake misfires if I work the throttle linkage by hand and race the engine.

I also have an issue when driving down the highway. Cruising at about 65 the engine will all of a sudden decide to start losing power, and start to run rough – as if only 3 cylinders are firing. Then the MIL will start to flash on and off, but it doesn't leave a code in memory. This can occur on a flat straightaway or going up a hill. If I dump it into 3rd and feather the gas the power will come back slowly, the MIL will go out, and it will run normal again.

Also it doesn't matter if the engine is hot, warm, or cold, it has occurred at all temperature ranges.

I have read a bunch of threads about this on here and on other forums and over the last 4 to 6 months or so have done the following:

Seafoamed the engine (twice) up the brake booster line, in the tank.
Removed and completely cleaned the Throttle body
Replaced: Coil pack, Wires, Battery, Spark Plugs, MAP sensor, TPS, IAC valve, Pre and Post O2 sensors, all 4 fuel injectors, and a new fuel pump assembly.

BTW, the engine idles fine, and all 4 cylinders check out OK on a compression test.

With the problem only being intermittent – Could it be the PCM itself? If the PCM was bad wouldn't it do it all the time?

Thanks,
B.

Slater451 07-06-2013 03:28 PM

I have that problem sometimes. I one of my plug wires starts to arc from the tip to the socket part.... I put diaelectric grease inside each wire plug ... That keeps it in check for a good long while till the grease dries out.... Also I run the stock NGK plugs and have had really good luck with them. Do you run a CAI or a cat back exhaust?

Jerry Bransford 07-06-2013 04:30 PM

I don't know why the engine is stumbling/losing power at 65/backfiring but 4.10 isn't enough gear for 33" tires with the four-banger. That's the main reason why your TJ is sluggish, regearing it to a lower ratio like 4.88 will restore the power loss caused by the larger diameter tires.

The MIL light flashing is likely indicating a misfire which could possibly be from a bad ignition coil. An external code reader might find a code or two that isn't showing up in your display when you display the DTCs via cycling the ignition key

If an aftermarket code reader shows a particular cylinder is misfiring, you can swap that cylinder's coil to a different cylinder & see if the misfire travels with the ignition coil or stays at the same cylinder. My Toyota was doing the same thing & I found one of the ignition coils was bad.

Dewstr1 07-06-2013 04:42 PM

Quote:

Originally Posted by Jerry Bransford (Post 3933309)
I don't know why the engine is stumbling/losing power at 65/backfiring but 4.10 isn't enough gear for 33" tires with the four-banger. That's the main reason why your TJ is sluggish, regearing it to a lower ratio like 4.88 will restore the power loss caused by the larger diameter tires.

The MIL light flashing is likely indicating a misfire which could possibly be from a bad ignition coil. An external code reader might find a code or two that isn't showing up in your display when you display the DTCs via cycling the ignition key

If an aftermarket code reader shows a particular cylinder is misfiring, you can swap that cylinder's coil to a different cylinder & see if the misfire travels with the ignition coil or stays at the same cylinder. My Toyota was doing the same thing & I found one of the ignition coils was bad.

I call BS on the gearing being inadequate. I have the 2.5 with 4.11s turnin 33s, and while its far from a Lambo, its plenty peppy. I can hit 80 and hold it there. I think there's another culprit.

Jerry Bransford 07-06-2013 04:47 PM

You're more than entitled to your opinion that 4.10 gearing is adequate for 33" tires with the four-banger engine but not many would agree with you. :)

Slater451 07-06-2013 05:29 PM

It doesn't have individual coils per plug it's got one coil pack for all 4. So If it were the coil pack I would think it would run like crap constantly my bet is still plugs or a bad wire

bmpage84 07-06-2013 08:04 PM

Thanks guys.

Jerry I agree with you about the gearing, they should be deeper but it's not that kind of sluggish.
The engine will still studder and misfire when parked and in neutral just by racing the engine.
I've checked for codes with my brothers $7500 Snap-on scanner and nothing. Even tried driving the Jeep around with the scanner in monitor mode but of course, since the problem is intermittent - it didn't pick anything up.

Slater:
The wires and coil pack are less than 3 months old, and I always use dielectric grease on my connections.
Running RE16MC (Champion) plugs, recommended by Chrysler TSB 08-008-04 regarding issues with carbon fouling on the 2.4 which can cause a sluggish behavior.
The jeep still has the welded factory exhaust - were you thinking a possible blocked CAT? Wouldn't that cause a constant loss of power?

Slater451 07-06-2013 08:39 PM

Yeah I would think that a clogged cat would cause constant power loss thru the rpm range... I can't think of anything else it could be other than a PCM issue. Wish I could offer more input

bmpage84 07-07-2013 07:53 AM

One of the members on the "other" forum offered this up:

"This is probably a long shot but when I changed my timing belt I put it back on 1 notch off and it ran okay but had a noticeable loss of power...took it back apart and redid the timing belt and valahh, back to normal power."

And ya know, I changed the timing belt last year!

Def. going to check into this further. Can you check a distributorless ignition system with an induction pick-up timing light? Believe it or not I still have one! If not, I would imagine that my brothers Snap-on scanner would be able to monitor timing, right?

Slater451 07-07-2013 09:12 AM

When my timing belt was a tooth off it would act as if I was hitting the rev limiter at around 2800 to 3200 rpm. As long as I didn't rev it any higher it would run great ....so you might be on to something there and I'm not sour if the old school timing light will work either ...good luck

prmc59 07-07-2013 09:09 PM

I had a similar issue with my 06 2.4 but it only happened at high speed with the AC on. The engine would lose power, the tach would drop to zero and the CEL would come on. I would turn off the AC and the engine would return to normal and the CEL would turn off. I took it to two dealers and neither could find anything "wrong", no error codes. The second dealer went ahead and reflashed the PCM and so far so good.


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