rough idle

Have you checked closely for a vacuum leak?

I checked all hoses and used a gauge that showed good vaccum with no deveation.

When you replaced the plugs, were the plug boots replaced? Some coils come with new ones, some dont. Sometimes they will arc through the side of a bad plug boot causing a rough idle.
See the guide below on misfires

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

I can feel the vehicle pulsating when stopped. Also when I am driving and let off the accelerator it slows down tremendously almost to a complete stop, this just recently started. It happens every time, does not matter about morning, evening, or temperature. I have never replaced the fuel filter, could this be causing my problem, or what are my options? Please help.

Has the check engine light come on?

Thanks for replying. No check engine light on. It has been tuned up also. It feels like it is restricted when I accelerate.

There are a couple things this could be caused by. First, I would like you to check the catalytic converter to make sure it is not plugged. That will cause a loss of power. Also, the fuel pump pressure should be checked. The fact that the light has not come on tells me that it is not sensor related or electrically related.

Here is a how to for checking fuel pump pressure:


https://www.2carpros.com/how_to/how_to_check_fuel_pressure.htm

You will need a fuel pressure gauge. Most parts stores will lend or rent them to you. Also, as far as the converter, with the engine running, see if it feels like there is enough pressure coming from the exhaust. Also, listen for any hissing or rattling sounds near the converter.

Let me know what you find.

Joe

I have a 2002 Jeep Liberty 3.7L, 6 cyl, 4wd Auto. With 170,000 miles my Jeep is idling very rough at start up. If I let it run for 15-20 minutes, turn it off, then start it up again after waiting 30 secs, it usually runs smoothly and can last up to 30 miles. If I turn it off and let it sit for more than 30 minutes, it will start idling rough again and stall when I slow to a stop. I have a had a vacuum leak repaired, fuel injector replaced and all of them cleaned, one coil replaced, spark plug wire for 6th cylinder replaced, internal computer module replaced, right side oxygen sensors replaced, complete carbon flush and compression is good. Diagnostics tell me that the 6th cylinder is not firing as it should be. I am trying to find out what else could possibly cause the 6th cylinder to not be firing as it should.

If you don't have a code for the temp sensor...change it anyway!

Vehicle looses power going up hills. Rough start from complete stop until gas pedal is pushed half way down. Check engine light continuously flashes while idling or driving. Codes in computer are multiple misfires cylinders 1-6 all. Plus both downstream o2 sensors heated. I was told two answers. And the 3.7 is coil over plug on all 6 cylinders. Thank you. Bill.

how long since plugs/coils???

i would also do a compression test.

from all these failures, i would look closely at wiring harness for damage

Roy

Working on a 2002 Jeep Liberty. Doesn't have any codes coming up. I have already replaced the CPS, CKS, 2 coils, all 6 plugs and cleaned the TB and IAC. Issue has improved but not by much. It is smoking and smells of gas when running.

first scan for codes and check fuel pressure including fuel pressure after shut down.then check for a vacuum leak or hoses disconnected or holes in them

I have already scanned and don't have any codes, also checked fuel pressure and vacuum hoses. One weird thing was while trying to figure this out had fuel injector on #2 disconnected from harness and coil and plug out on #1 and the engine smoothed out a lot.

you cancelled the companion cylinder by doing that and it will run smoother.

did you do a compression test??

Roy

Haven't yet, does this one recommend operating temp for compression check or not(I don't have a book that covers the 3.7 V6)

Also just talked to the customer and was told a compression check was done about 4 or 5 months ago and was fine then.

Trying to figure out why i am getting such poor mileage and rough idle, have replaced all plugs and done fuel treatment and injector cleaning, and then had computer codes checked as well as compression, took out new plugs and still no gunk, any suggestions would be great help

What I have found is many times a bad O2 sensor will cause the problem described. Has it been replaced?

Also, does the vehicle seem to have a normal amount of power?

because of the miles also check cam or followeres for wear, maybe a lobe is rounded off and you get compression but valves aren't workin g right. that wold not show up on a compression check or fuel pressure regulator may be screwed up as well

Did compression check today and #1 cyl was 0, all others were between 155 and 175 psi after 6 strokes(first stroke was above 130 on all but #1). looks like either a valve is stuck open or a valve spring broke. Customer deciding what he wants to do now

it may be more thatn that. that may not be a free spin motor so look for engine damage inside cylinder. Or pump oil in cylinder and seeif compression comes up at all.

I used a small LED snake light to look in through the plug opening and all I could see was the piston, of course don't get to see much that way. Plus with the research I have been doing this model Jeep with the 3.7 has a sludge problem and valves like to stick open. Also some cases of broken valve springs.

Engine Performance problem
2006 Jeep Liberty 6 cyl Four Wheel Drive Automatic 50000k miles

po300 code engine misfires rough idle at times new plugs didn,t help what next?

Did you replace the ignition wires? Also, have you checked for vacuum leaks?

you'll see when or if you get teh valve cover off