4.0 timing issues

S

Scorpa

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Apr 6, 2020
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Florida
I bought a 2006 Jeep X with 92K for $4,800 that had one cam lobe worn, he said that a rocker arm got twisted and held down on the cam. He noticed it was running rough and thought it was a bad coil pack so he replace it and it didn't fix the problem so he pulled the valve cover and saw the issue. He pulled the engine and trans (6 speed manual). He said he was just going to rebuild the entire engine but just didn't have the time and lost interest.
When I picked the Jeep up the engine and trans were out and he had removed the cylinder head. At my shop I inspected the rotating assembly closely and it spun easily with no sighs of any problem, cylinders had little to no wear and no lip at the top of the cylinders. The head look good and I also filled the chambers with gas and watched to see if it would lead through the valve seats... it did not, so I figured instead of rebuilding the entire engine I would just replace the cam, lifters and push rods.

Once all the parts arrived I installed the new parts as I have done many time before on all sorts of engines. After the build and the engine, trans, were back in the Jeep and I hit the key switch it sounded like it was 180 degrees out (which i know it was not) I rechecked the TDC by bringing #1 cylinder up on compression stroke using my finger to feel pressure, once at TDC I checked the OPDA and it was correctly lined up with the corresponding holes.. it still sound like it is 180 degrees out. I than replaced the OPDA with a new Crown unit using the old and the new cam sensor plug... It still sounds 180 degrees out.

Now here is the weird part I purposely set the OPDA out 180 degrees out to see what would happen and it still sounds 180 degrees out. One other thing... my oil pressure gauge does not move when cranking with plugs out but, with a manual oil pressure test gauge it reads 20 psi after about 15 sec of cranking.

I am at a total loss, I have pulled the timing cover to re-check the timing marks are lined up... Perfect, I checked the new cam, lifter and push rod part numbers to see if they were correct for this 2006 vin S.... they are correct parts (Melling)... What gives here? Has anyone else ever seen or heard of something this weird. How can this engine not crank differently when I purposely put it out of time 180 degrees? I since timed it all correctly and guess what.... I still sounds like it it way out or time. HELP.... Please. I'm sending some pictures, one is of the old cam which shows the worn lobe.

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Scorpa said:
I bought a 2006 Jeep X with 92K for $4,800 that had one cam lobe worn, he said that a rocker arm got twisted and held down on the cam. He noticed it was running rough and thought it was a bad coil pack so he replace it and it didn't fix the problem so he pulled the valve cover and saw the issue. He pulled the engine and trans (6 speed manual). He said he was just going to rebuild the entire engine but just didn't have the time and lost interest.
When I picked the Jeep up the engine and trans were out and he had removed the cylinder head. At my shop I inspected the rotating assembly closely and it spun easily with no sighs of any problem, cylinders had little to no wear and no lip at the top of the cylinders. The head look good and I also filled the chambers with gas and watched to see if it would lead through the valve seats... it did not, so I figured instead of rebuilding the entire engine I would just replace the cam, lifters and push rods.

Once all the parts arrived I installed the new parts as I have done many time before on all sorts of engines. After the build and the engine, trans, were back in the Jeep and I hit the key switch it sounded like it was 180 degrees out (which i know it was not) I rechecked the TDC by bringing #1 cylinder up on compression stroke using my finger to feel pressure, once at TDC I checked the OPDA and it was correctly lined up with the corresponding holes.. it still sound like it is 180 degrees out. I than replaced the OPDA with a new Crown unit using the old and the new cam sensor plug... It still sounds 180 degrees out.

Now here is the weird part I purposely set the OPDA out 180 degrees out to see what would happen and it still sounds 180 degrees out. One other thing... my oil pressure gauge does not move when cranking with plugs out but, with a manual oil pressure test gauge it reads 20 psi after about 15 sec of cranking.

I am at a total loss, I have pulled the timing cover to re-check the timing marks are lined up... Perfect, I checked the new cam, lifter and push rod part numbers to see if they were correct for this 2006 vin S.... they are correct parts (Melling)... What gives here? Has anyone else ever seen or heard of something this weird. How can this engine not crank differently when I purposely put it out of time 180 degrees? I since timed it all correctly and guess what.... I still sounds like it it way out or time. HELP.... Please. I'm sending some pictures, one is of the old cam which shows the worn lobe.

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Codes?
 
As 1 more sanity check, have you run it with the valve cover off to observe whether or not the valve train appears to be operating correctly?

Might want to post a video so people can hear the 180-out sound you're talking about.
 
The Jeep oil pressure gauge is fake, you can't rely on it. It probably sounds 180 out just because it's not firing. Have you checked for fuel at the injectors, smell gas at all? If you get pressure at the spark plug with your finger you found TDC and at least those valves are working.
 
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*Yes the valve train moves and looks correct. I checked each cylinder at TDC observing the push rods when torquing the rockers @20lbs

* Yes it is getting fuel, if I don't pull the fuel fuse it will flood the cylinders while cranking without plugs in.
* Yes, I felt pressure while #1 was coming up and I ran a compression test on all cylinders... It goes like this from #1 through 6: 140, 135, 135, 128, 138, 132.
As I am spinning it over there is blow back at the intake, you can see some of the hoses move when air rushes out.
 
Yes, the crank sensor is located above the starter on the bell, it's a new part as well. The original was broken when he pulled the engine.
 
Well, sounds like you have fuel and compression. So maybe no spark?

Not sure how you check the ignition system in a case where it won't run. Might be some test/troubleshooting steps in the FSM.

One more random thought. Is it possible the exhaust is totally clogged?
 
I have spark on all six cylinders... however it is erratic, meaning all six plugs are continuously sparking and not just when each cylinder comes to it's TDC. I have never seen anything like this before. And yes it does this on two separate coil pack units. I'm probably going to have to take it to the dealership where they can run a diagnostic on it.
 
Scorpa said:
I have spark on all six cylinders... however it is erratic, meaning all six plugs are continuously sparking and not just when each cylinder comes to it's TDC. I have never seen anything like this before. And yes it does this on two separate coil pack units. I'm probably going to have to take it to the dealership where they can run a diagnostic on it.
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That’s normal 4.0 fires not only on compression stroke It’s just the way it’s set up with one coil per two cylinders
 
Put the old OPDA back in the engine and see if that fires it up. If no, spray some starting fluid. If it still won't pop then there is some big timing issue. Cam sensor, crank sensor, check for a bent pin in the ignition circuit wiring harness? It is something simple and fairly obvious. The big stuff always is it seems.
If you have fuel compression then spark has to be it.
 
I'm going to check all the pins and connections. Does anyone have a link to an 06 trouble shooting jobber manual?
 
only one is the 02 sensor and that's because I have it unhooked so I could remove the breather. No other codes.
 
Goatman said:
Put the old OPDA back in the engine and see if that fires it up. If no, spray some starting fluid. If it still won't pop then there is some big timing issue. Cam sensor, crank sensor, check for a bent pin in the ignition circuit wiring harness? It is something simple and fairly obvious. The big stuff always is it seems.
If you have fuel compression then spark has to be it.
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I did that already several times... everything I do now is redundant.
 
After taking it to a shop that has a big diagnostics machine I found out that If you are doing a rebuild, changing the cam i.e. rotate the engine with the OPDM oil pump/cam sensor out you will never get it timed correctly without using a machine to do it. Yes you can just change out an old one for a new one AS LONG AS YOU DON'T TOUCH THE ROTATION AT THE CRANK BEFORE YOU SET THE NEW ONE IN. This is 2005/2006 4,0's only.
 
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So I assume you got it going now that’s great I don’t understand why you can’t remove opdm rotate engine and put in same location it’s a mechanical connection

Maybe someone can explain that in case it ever happens to me
 
Al
Davidtj said:
So I assume you got it going now that’s great I don’t understand why you can’t remove opdm rotate engine and put in same location it’s a mechanical connection

Maybe someone can explain that in case it ever happens to me
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All I know is, that he confirmed I had the engine on TDC #1 cylinder and the OPDM was correct but yet it was out 120 degrees. He used his machine to calibrate the OPDM to match TDC. I personally have never see anything like this in all my years of do this stuff. It seem like the usual straight forward mechanical alignment, but it's not.... somehow.
 
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I can imagine the PCM doing something funky like that. Like maybe every ODPA tone wheel reads a little differently and the engine can match the position of the wheel to the position of the engine as long as it knows the last position the engine was at. The previous owner may have had #1 120 deg off of TDC when he stopped it the last time.
 
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