Low Exhaust Back Pressure

[JKP]

Yeah, he's shifting before peak HP. Need pull to 5K or so.

4.0L I-6 242 cu in - 2000-2006
* 190 hp @ 4,600 RPM
* 235 ft/lbs @ 3,200 RPM

And no, the Jeep shouldn't be shaking. The shifter in my 06 doesn't even move at idle.

 

[staplesofficewar]

Yeah, he's shifting before peak HP. Need pull to 5K or so.

4.0L I-6 242 cu in - 2000-2006
* 190 hp @ 4,600 RPM
* 235 ft/lbs @ 3,200 RPM

And no, the Jeep shouldn't be shaking. The shifter in my 06 doesn't even move at idle.

I’ll give it a shot after it learns new o2 sensors.

The shifter doesn’t shake, the body kinda lopes around. Almost like it’s cam’ed up. Best way to describe it.

 

[MikeE024]

The shifter doesn’t shake, the body kinda lopes around. Almost like it’s cam’ed up. Best way to describe it.

Motor mounts, transmission mount, and body mounts all in good shape?

No interference with the drivetrain and body?

 

[staplesofficewar]

Motor mounts, transmission mount, and body mounts all in good shape?

No interference with the drivetrain and body?

No lift if that’s what you mean. Replaced Engine mounts last weekend. I have the tranny mount but haven’t installed it yet.

 

[MikeE024]

No lift if that’s what you mean. Replaced Engine mounts last weekend. I have the tranny mount but haven’t installed it yet.

You said the body was shaking so I was wondering how the isolators looks on your body mounts

 

[GoldenGorilla]

There are a few possibilities re the lope. The stock cam doesn't lope even though it has a 108 LSA but idle is set pretty low. You said the cam was replaced. If you have it's card it would be helpful. It's very possible it an aftermarket cam was used like one from Comp.

The OE motor mounts feel very smooth but are made of pretty soft rubber. I switched to MORE Bombproof mounts with rubber Clevite bushings and get enough vibration that I programmed a higher idle.

 

[D's Jeep Wrld]

12.64 seconds in a stock Jeep? That sounds reasonable to me. I’ve got a Banks turbo (nearly an extra 100 hp at the wheels) and I don’t think I can do much better than 9 or 10 seconds. Stock Civics outrun me.

Not trying to hijack the thread here
But I will say,This makes me a bit more proud of my 0-60 On my Lj on 33s,baby cam,ported head/intake ARH header tuned by me and it has netted me this:
11.32 in the eight with a horrible reaction time (1st time at a strip,2nd run)
Id usually net close 11.2 on the street but thats me driving it like a honda and banging limiter on 1st&2second letting it spin lol
The best I ever got was closer to 10.1 I believe? Haven't really tried since tbh,I'm just having fun

but yeah these newer civics are peppy !..... I got gapped by a new ford suv off the line......With that said the want/need of a stroker is there

 

[staplesofficewar]

With that said the want/need of a stroker is there

I was just thinking that tonight at dinner! Start saving my dollars I guess

 

[staplesofficewar]

There are a few possibilities re the lope. The stock cam doesn't lope even though it has a 108 LSA but idle is set pretty low. You said the cam was replaced. If you have it's card it would be helpful. It's very possible it an aftermarket cam was used like one from Comp.

The OE motor mounts feel very smooth but are made of pretty soft rubber. I switched to MORE Bombproof mounts with rubber Clevite bushings and get enough vibration that I programmed a higher idle.

I didn't consider that. The cam on the work order (PO kept all paperwork, so I have a full folder) indicates Melling M-Select CLMC1377 Cam with lifter kit.

Online says it has the same LSA as stock.

I thought the lope might be from bad mounts, so I got a set from Rock auto - nothing special - just the WESTAR ETK100

 

[GoldenGorilla]

The link I have for a site with all the stock and aftermarket cam grinds is down, but the LSA and lifts match so I assume duration does as well.

Changing the drivers side motor mount isn't the easiest thing to do.

I'd see how it runs with the correct O2 sensor installed. You need to unplug the battery for 10+ min to discharge the PCM and force learning mode, and then drive 15 min or so to bring the O2 sensor state back to emissions ready before you can pass judgement.

As others have indicated, I don't think your jeep is majorly down on power as you're not throwing codes, bucking, stalling etc. But it sounds slightly off. I have 2 more ideas relating to work done by the prior owner if these don't solve it, but don't want to send you on a wild goose chase.

 

[NashvilleTJ]

... You need to unplug the battery for 10+ min to discharge the PCM and force learning mode, and then drive 15 min or so to bring the O2 sensor state back to emissions ready before you can pass judgement.

...

Or disconnect the positive terminal and touch it to the negative terminal. That resets the PCM immediately with no waiting.

 

[staplesofficewar]

Or disconnect the positive terminal and touch it to the negative terminal. That resets the PCM immediately with no waiting.

This is what I did. But it let it sit there for about 5 min.

 

[staplesofficewar]

Changing the drivers side motor mount isn't the easiest thing to do.

That’s why I waited until I had the intake and exhaust off! I can’t image attempting that side with everything in place

Here is the service order from the cam. I don’t think anything else could be a red flag, but who knows.

 

[SkylinesSuck]

Check out this page from Summit Racing https://www.summitracing.com/parts/...wlzej_faxgxu71zijbxfv9klup9pa2d_c1y8kzvh3bnp4

Description makes it sound like a mild upgrade, but I think it's probably just general marketing gobledeegook. I am not familiar with stock cam specs off the top of my head though.

 

[MikeE024]

Or disconnect the positive terminal and touch it to the negative terminal. That resets the PCM immediately with no waiting.

This is the way folks talked about in the cam-crank difference thread. I do that or remove the negative from the battery and turn the ignition and lights on for near instant drain. Many ways to skin the cat.

 

[staplesofficewar]

Check out this page from Summit Racing https://www.summitracing.com/parts/...wlzej_faxgxu71zijbxfv9klup9pa2d_c1y8kzvh3bnp4

Description makes it sound like a mild upgrade, but I think it's probably just general marketing gobledeegook. I am not familiar with stock cam specs off the top of my head though.

I mean, that would be sweet if that was the case !

 

[staplesofficewar]

Quick Update
My last MPG check was 11/24/25. Since then lots of fixes, including the last O2 sensor changes. Ill upload a recent LTFT in a while.
I drove about half a tank before the O2 sensor replacement, and half after.
MPG now calculated at 17.4.
Note - I put slightly larger tires on it since the last MPG check (and last 0-60 check). So the 0-60 check will be slightly slower when I do it again because of the tires, and in theory also MPG vs stock tires.

Stock tires: 30x9.5R15
New tires 245/75R17 (31.5x9.65R17)

 

[staplesofficewar]

View attachment 665231

Before chart above - average LTFT around 5-6 when on throttle.
Below is new - average LTFT does appear more controlled. This is after about 120 miles driving after PCM reset. Will continue to watch

still have lope at idle. Starting to wonder if the shop properly broke in the cam and lifters with proper run cycle and oil with additive...or if that would even cause an issue for real.

 

[JKP]

If they didn't properly break it in, it will wear the lobes and lifters in no time.

 

[staplesofficewar]

If they didn't properly break it in, it will wear the lobes and lifters in no time.

Was just reading up on it. Internet can be a great thing sometimes. 25 years ago it was off to the shop, phone a friend or get some sort or repair manuals.
Being it was 18 months ago AND multiple thousands of miles, if the break-in wasn't done correctly, it would have much worse problems.