05 Liberty Renegade Misfire

[teeje]

Possibly injectors. But the 3.7s were known for bad valve seats. Had that issue with my last engine. Before the last engine blew and had that misfire i issued marvel mystery oil and it cleared the misfire right up. Try that. You can put it in the oil and in the tank. Just make sure to read the directions


2002 Jeep Liberty 3.7L with brand new engine
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[LibertyTC]

Ya right now I've got 6 new coil packs and no engine light, yet still a low count, random misfire just slightly above idle.
I am currently using 4oz MMO to each 10 gallons of Chevron 94 octane, ethanol free gas, hoping to clean injectors & valves.
I'm doing an oil change & filter On Monday using Penzoil Platinum full syn with half a quart of MMO in oil.
Then it's going back onto highway for a solid 200 + mile boogie again.
Will monitor oil color & if it turns dark soon, will do a change again.

 

[uss2defiant]

timing slightly off?

 

[mk_v]

I've never heard of the marvel mystery, is it pretty good? I have only ran ethanol free gas since I got it, with 44k miles. The marvel mystery is it supposed to clean and lubricate the injectors? I'm probably not going to get a chance to work on it until next weekend. My plan was to check the resistance on the injectors, pull check spark plugs again ( they are relatively new if I remember correctly replaced in the last 15k miles I have it written down in my records just going from my memory), check fuel pressure if I haven't found the problem with the injectors. I'm going to try and find that marvel mystery, don't you guys think I should figure the problem out before driving?


Mk

 

[mk_v]

timing slightly off?

Wouldn't that cause a rough idle? If not how do you check that? I've heard the camshaft sensor could be the problem.


Mk

 

[uss2defiant]

You can buy MMO at walmart.

I think you'll need one of those expensive those or a multichannel oscilloscope to debug a possible timing issue. Sorry not a pro here.

I've had to replace the CPS and CKS on mine but my CEL code was specific to that and not a misfiring issue.

 

[mk_v]

You can buy MMO at walmart.

I think you'll need one of those expensive those or a multichannel oscilloscope to debug a possible timing issue. Sorry not a pro here.

I've had to replace the CPS and CKS on mine but my CEL code was specific to that and not a misfiring issue.

So if it were timing Id probably have to take it to a mechanic it sounds like. Have you used the mmo before? Is there anything that may be better? Thanks


Mk

 

[adamkrz]

When I purchased mine back in 2003- about a year later I started getting random misfire codes along with #6 misfire, under warranty they replaced the valves and maybe valve seats, it ran well with the codes.

No codes in the last twelve years.

 

[uss2defiant]

Yes. I use MMO on a regular basis in both gas and crankcase.
Other alternatives you could try would be chevron techron concentrate or gum out regane.

I use them as preventative maintenance so I can't say from experience whether they would work in your case.

 

[teeje]

I've never heard of the marvel mystery, is it pretty good? I have only ran ethanol free gas since I got it, with 44k miles. The marvel mystery is it supposed to clean and lubricate the injectors? I'm probably not going to get a chance to work on it until next weekend. My plan was to check the resistance on the injectors, pull check spark plugs again ( they are relatively new if I remember correctly replaced in the last 15k miles I have it written down in my records just going from my memory), check fuel pressure if I haven't found the problem with the injectors. I'm going to try and find that marvel mystery, don't you guys think I should figure the problem out before driving?


Mk

Yes it's good. I'd give it a shot


2002 Jeep Liberty 3.7L with brand new engine
Sent from my iPhone using Tapatalk

 

[mk_v]

If it did turn out to be the valve and valve seats any idea what that would cost to fix? Thanks for the help everyone


Mk

 

[teeje]

If it did turn out to be the valve and valve seats any idea what that would cost to fix? Thanks for the help everyone


Mk

Local machine shop would be able to tell you


2002 Jeep Liberty 3.7L with brand new engine
Sent from my iPhone using Tapatalk

 

[mk_v]

Anyone know what the injector resistance should be ?


Mk

 

[teeje]

Anyone know what the injector resistance should be ?


Mk

Test a known good one. There ya go


2002 Jeep Liberty 3.7L with brand new engine
Sent from my iPhone using Tapatalk

 

[Hockeygoon]

If it did turn out to be the valve and valve seats any idea what that would cost to fix? Thanks for the help everyone


Mk

How did you come to that conclusion?

The actual machine shop work shouldn't be that expensive, around a few hundred per head. The problem is getting to the point and are you going to replace the timing chains, tensioners and sprockets? Even at a decent "cheap" shop you are looking at $1500 - $1900.

Doing it yourself will save a lot of money but its not an easy project.

 

[mk_v]

How did you come to that conclusion?



The actual machine shop work shouldn't be that expensive, around a few hundred per head. The problem is getting to the point and are you going to replace the timing chains, tensioners and sprockets? Even at a decent "cheap" shop you are looking at $1500 - $1900.



Doing it yourself will save a lot of money but its not an easy project.

I haven't come to that conclusion. That was just a what if. I checked the resistance on the injectors and there wasn't a outlier in resistance. I ran it for a while yesterday and ended up getting the mult misfires after about 2 hours.


Mk

 

[Hockeygoon]

I haven't come to that conclusion. That was just a what if. I checked the resistance on the injectors and there wasn't a outlier in resistance. I ran it for a while yesterday and ended up getting the mult misfires after about 2 hours.


Mk

I missed the "If" at the beginning of your post. I doubt its a valve seat, they don't come and go.

 

[mk_v]

One thing I just noted I've lost some oil. On the x patterned side it has lost maybe 10% so ~1/10 a qt. I've never burned oil or lost oil it's always been right on the full line. Nothing milky in the oil either. Could it be the head gasket?


Mk

 

[adamkrz]

I would do a compression test just to make sure.

 

[mk_v]

Yeah I will do that this weekend I'm thinking


Mk