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Are you familiar with the 2.5L engine missing at about 2100

Customer Question
rpms?...
are you familiar with the 2.5L engine missing at about 2100 rpms?
Submitted: 2 years ago.Category: Jeep
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Customer reply replied 2 years ago
I have replaced numerous electronic parts and the engine has been rebuilt to specs
Answered in 8 hours by:
10/4/2015
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago
sprinkles08
sprinkles08, ASE Certified Technician
Category: Jeep
Satisfied Customers: 23,236
Experience: Chrysler/Dodge/Jeep Master Certified, ASE Master and Advanced Certified, Trans and Hybrid Specialist
Verified

Hello and welcome to Justanswer!

What is the year and model of the vehicle?

What parts specifically have been replaced?
When did the problem start opposed to when the engine was rebuilt?

Can you describe the symptoms?

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Customer reply replied 2 years ago
This is a 1999 Jeep Wrangler. I purchased the vehicle with a blown engine so i do not know if there was a miss prior to the engine failing. of course no one will give you information like this when they are selling, the just want to sell.I have replaced the MAP sensor, IAC, CPS, Distributor, Cam Shaft Positioning sensor, Temp sensor, spark plugs and wires, coil, TPS and i believe this is all. if you mention something I can tell you if it has been done.The engine has a slight rough idle and seems to miss pretty bad around 2000 to 2100 RPM's.
Gas mileage is bad
Customer reply replied 2 years ago
Also the transmission has been rebuilt because I thought it was a shifting issue. there is one vacuum line on the intake that is plugged and i do not know where it goes. i cannot seem to find any place for it
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Are any fault codes setting?

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Customer reply replied 2 years ago
No
Customer reply replied 2 years ago
the fuel tank was removed and cleaned also
Customer reply replied 2 years ago
i have seen a lot of posts on this issue and no real answer to the issue has been revealed
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

How was cam timing and distributor sync set?

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Customer reply replied 2 years ago
Are you referring to the timing chain installation?
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Cam timing is the timing chain, yes. Cam/crank sync is the cam sensor drive installation.

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Customer reply replied 2 years ago
Cam/Crank sync I believe I just installed the sensors. they can only go one way as I can recall. the flywheel only went on in one position. the timing chain was installed as per the required alignment. the distributor was installed 180 out and then corrected. there is no adjustment for advancing the timing due to a tab so when it is in it is set. i checked number one on compression and it is aligned with the number one plug wire on the distributor and the timing mark is on "0" on the harmonic balancer.
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Have you measured manifold vacuum at idle?

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Customer reply replied 2 years ago
No. I have never done this before
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Do you have a vacuum gauge?

Do you have a scan tool to monitor data?

Has a static and running compression test been done?

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Customer reply replied 2 years ago
No Vacuum gauge but I can get one.
I only have a code reader no scan tool but i may be able to get with someone who does
and static and running compression has not been done. The engine was just rebuilt by myself and another mechanic.
Customer reply replied 2 years ago
what should the vacuum be ans what should the fuel rail pressure be?
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

If you can get a vacuum gauge and let me know what you find that would be great. See what vacuum is at idle and whether or not the needle is steady. A scan tool may be necessary to monitor data.

Fuel pressure 49 +/- 5 PSI, usually close to 50 PSI with a healthy fuel system.

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Customer reply replied 2 years ago
Will do. how can i get back to you?
Customer reply replied 2 years ago
also is there some where i can get a vacuum diagram to see where the mysterious line that is not connected should go?
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

You can just come back to this question and reply as you have been this morning and I will get notification that you replied.

There is vacuum diagram on the label under the hood. If you're unsure about what you're seeing I can take a look if you can upload a picture of the lines or nipple in question.

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Customer reply replied 2 years ago
that would be helpful. there is no diagram on the hood anymore
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

The nipple is most likely supposed to be plugged if you don't have any stray lines or other issues but I'll take a look if you can upload a picture.

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Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

It looks like some lines may be moved around to different nipples but the one that's plugged off most likely should be. It's obviously not plugged in a factory way but most likely just had a cap on it. I think I see a line on a nipple on the top side of the intake that should have been hooked up on the side, and it looks like the crankcase vent/PCV makeup air hose is down on the side instead. The PCV makeup hose from the valve cover should have gone to the nipple on the top of the intake toward the rear, I believe I see a smaller diameter 90 degree nipple on top that most likely went to the side of the intake. You should have one line from the intake to the purge solenoid, one for the brake booster, one going to the valve cover, and one other for cruise control and the heater box.

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Customer reply replied 2 years ago
Ok let me trace these and I will get back with you. Thank you so much
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

You're welcome!

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Customer reply replied 2 years ago
Ok I haven't traced the vacuum lines down but the vaccum is 21 to 22 and the fuel pressure is 46 when you turn the key on bu drops to 40 after a couple of seconds. When running, it is fluctuating between 46 to 50
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

If you rev the engine to where the problem happens what is your vacuum then?

Is the needle steady or moving?

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Customer reply replied 2 years ago
My mistake. Idle is 18 to 19 and when you Rev the engine to 2100 it goes to 20.5 and pretty steady. The engine does not seem to have the miss while sitting still and reving to 2100. It is very noticeable when driving though
Customer reply replied 2 years ago
I traced the vacuum lines down and they seem to be correct. I did move the ccv line to another port where I swapped it with the vacuum line for the evap canister. The vacuum line on the top of the intake goes to the passenger side of the vehicle in the fender. I do not know where it goes from there. I believe it is the climate control
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Is it automatic or manual?

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Customer reply replied 2 years ago
Automatic
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Will it miss if you brake torque it to the same RPM? If so then you can see what vacuum is doing at that time.

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Customer reply replied 2 years ago
Let me check this this evening
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Ok.

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Customer reply replied 2 years ago
I brake checked it and it held a vacuum at 8
Customer reply replied 2 years ago
Did not seem to missfire
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

The miss does happen while driving, correct?

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Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Can you try unplugging the upstream oxygen sensor and see if it runs any differently?

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Customer reply replied 2 years ago
Need a little help. Is it the one right below the Exhaust manafold
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Yes, upstream means before the catalytic converter.

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Customer reply replied 2 years ago
Great. Now you want me to disconnect it and drive it
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Correct.

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Customer reply replied 2 years ago
Same result. I have been 110 miles and used a little over 1/2 tank of gas
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Do you have a scan tool to monitor data and misfire monitor?

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Customer reply replied 2 years ago
I will check
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Ok.

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Customer reply replied 2 years ago
U can get one but it will be the latter part of next week. My job is taking me out of town. I will touch basis with you then
Jeep Mechanic: sprinkles08, ASE Certified Technician replied 2 years ago

Not a problem.

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Satisfied Customers: 23,236
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