4500 rev limit on 4.0 (glowing exhaust)

[miksior]

Hi guys, I am new to the forum

I have an issue with my rubicon 2005 AT.

It will not rev over 4500 while driving (on driveaway with reduction gearbox set to 'N' and A/T to 'D' it goes fine. And even after short full throttle open (5 secs), the exhaust manifold is glowing red.

I replaced timing chain, OPDA were poorly installed (180 degrees where it should be), replaced CPS, TPS, cleaned throttle body, replaced plugs, ignition coil, removed catalysts, measured fuel pressure under WOT (on a driveway), checked for all leaks or faulty air, logged all data during test with data logger. Everything looks smooth. The fuel trims are negative, the advance is going correctly with RPMS...

I am running out of ideas, I have some gut feelings that maybe valve springs are 'tired' and causing valve floating, but I did not really heard it is an issue in 4.0s?
I removed injectors and cleaned the manually, but maybe I should send them out for tests?

 

[speeding_infraction]

Is your exhaust flowing freely all the way to the back?

 

[miksior]

Last element there is, is a magnaflow muffler, all cats are gone. They were in good shape btw.

 

[macleanflood]

Did you use HP Tuners and remove the rev limiter in the PCM?

-Mac

 

[miksior]

Did you use HP Tuners and remove the rev limiter in the PCM?

-Mac

No, I did not. But I do not know the history of the car. I am fixing it after I imported it from USA.

But I thought, that original rev limit is somewhere around 5200? And the exhaust manifold definetly should not glow red, and AT should change gears under WOT ?

Also what I have noticed, during changing timing chain, that it fits the one from different 4.0, the one that has slightly more HP, so looks like camshaft were replaced. Possibly someone done some other mods.

PS: nice ride

 

[macleanflood]

Did you see any stamping on the front of the cam that would identify it?

Yeah the fun part of modifying a 20 plus year old vehicle is identifying what previous owners butchered or did right.

-Mac

 

[Woodrow]

Sounds like you've checked the usual things. Just spit balling here, but if the motor has been modified, maybe its running lean? To check that you'd need a wide band O2 sensor and to tune it, if necessary, HP tuners or maybe some help from @Wranglerfix.

 

[Wranglerfix]

To my knowledge, you cannot set a rev limiter in a pcm,

 

[BlueC]

the exhaust manifold is glowing red.... The fuel trims are negative,

Red hot mainfold usually = lean. Negative fuel = computer is trying to lean the mix further. I think you have either A - bad sensor(s) or B - a leak, probably in the exhaust.

 

[miksior]

Did you see any stamping on the front of the cam that would identify it?

Yeah the fun part of modifying a 20 plus year old vehicle is identifying what previous owners butchered or did right.

-Mac

The 2005 TJ rubicon should have cam with key and wheel with keyway.

mine is with dowel pin, that I saw were widely used in XJ, ZJ, TJs up to 2007. I did not notice any nubering, but I assume the camshaft must be narrowed down to the ones with OPDA. Looks like they have slightly more HP then rubicons, so maybe cams are a little bit more aggresive? or just someone replaced it because it was available in the neighbour hood

Red hot mainfold usually = lean. Negative fuel = computer is trying to lean the mix further. I think you have either A - bad sensor(s) or B - a leak, probably in the exhaust.

OK, my logic were -> blocked exhaust is the -> not enough timing advance.
Actually, what I can see in the logs, is that the higher the rpms, the trims go into negative:

Lack of cats justify S1 and S2 being the same.
Where cats were there, actually they went red, not manifold

To my knowledge, you cannot set a rev limiter in a pcm,

That is very helpful, thanks!

 

[SkylinesSuck]

Dzień dobry! I only briefly looked over the thread, but my first thought is very retarded timing. I see you said you replaced the timing set. Was that before or after this issue started? If it was off a tooth that would explain things. Is it the entire manifold glowing or just specific cylinders?

 

[SkylinesSuck]

I just read through more carefully now and I strongly suspect your issue is camshaft and/or timing related. Was it ever running correctly or has it been like that since you've owned it?

 

[HDRider]

The International Brotherhood of TJ

 

[miksior]

The International Brotherhood of TJ

i love it. And I am really glad i got the one with tons of the mods, as they are not available in EU. All JKs, and JLs

I just read through more carefully now and I strongly suspect your issue is camshaft and/or timing related. Was it ever running correctly or has it been like that since you've owned it?

It has never been running correctly. Some minor things like idle were fixed, but this one is constantly from the purchase. When i found out that CPS were 180 degrees misinstalled, i were sure it was it. But it was not. Right now i have a small feeling it works slightly better after the fixes, but it might be just illusion. Nevertherless 4500 rpms and not going further on WOT are from the start and nothing fixed yet. Without WOT actually works pretty smooth, and accelerates in nice pace up to 120 km/h(i think 75mph). The temp under the hood altough is hot, despite engine beeing cooled properlly. I even got some freshly installed black protective pipes over the cable melted, on the driver side, and reaar arb hose melted. It was routed on driver side. Definetly something off with the temperature on exhaust.

 

[miksior]

Dzień dobry! I only briefly looked over the thread, but my first thought is very retarded timing. I see you said you replaced the timing set. Was that before or after this issue started? If it was off a tooth that would explain things. Is it the entire manifold glowing or just specific cylinders?

The timing advance, according to manual is not adjustable. In theory. In practice i could rotate opda body? I were carefull with replacing timing, but be honest. It is not some fuckdd up german idea with thousands of tensioners, and chains. The 2 tooth facing each other, close fit of the chain,
And small rubber tensioner in cover. and that is it. Altough, is there anything tricky about it, I am not aware?

Also here are the timings. At least computer looks like corrctly baheving with timing:

 

[Steel City 06]

To my knowledge, you cannot set a rev limiter in a pcm,

With a tuner, you actually can adjust the factory rev limiter. At least for 05-06, stock is set at 5,300 RPM and uses the fuel cut-off strategy. There is also the option to limit by spark (I'm guessing similar to idle spark torque/RPM control), but this is not enabled in the default tune.

 

[BlueC]

4500 rpms and not going further on WOT

Clarify this for me (us), is that sitting still in neutral/park, or is that accelerating down a road?

 

[ColoJeep]

Dzień dobry! I only briefly looked over the thread, but my first thought is very retarded timing. I see you said you replaced the timing set. Was that before or after this issue started? If it was off a tooth that would explain things. Is it the entire manifold glowing or just specific cylinders?

This is my thought also. Timing that is very late results in afterburning .

 

[BlueC]

This is my thought also. Timing that is very late results in afterburning .

Interesting. I've never run into that situation. I've dealt with 180 out, but not excessively retarded timing. What other signs would point to that?

 

[miksior]

Clarify this for me (us), is that sitting still in neutral/park, or is that accelerating down a road?

On Neutral/Park I have the cut out on 4000 I think, do not remember, but I think there is some jeep restriction from revving to the limiter.
When I put AT to D, and Reduction gear to N, it is actually revving to over 5000. Didnt revv for too long, cause I do not want my neighours to hate me. Altough did not see red manifold. At this point also the fuel presessure looked good.

When accelerating on the road, and not pushing pedal down, but letting jeep accelerate it goes well, to around 120kmh (altough it has long arm, 35s treppador) so I rather stick to 100kmh. But when I go with pedal fully down (WOT) it reduces the gear, and try to accelerate, it goes to 4500, does not change gear, does not go any further. When I tried the same on locked 1st gear, it also went to 4500 and not further. I did not checked the fuel pressure under load on the road, cause my pressure gauge hose is too short.

Once, before some changes, on the LowGear, locked 1 in AT, and holding WOT for longer time (20 secs/30 secs) I were able to have some spikes of 5200 rpm. Didnt try it again though.

But I would say it pretty much exclude RPM limiter set in PCM.