Here are my symptoms:
-bad gas milage (went from 16mpg time I filled to around 10-12mpg)
-ticking noise from spark plugs once engine warms up and is reved slightly
-have noticeably less power when accelerating up to about 35mph, fine above that speed.
-stumbles every once in awhile when starting up like a cylinder isn’t firing
-No check engine light

Here is what I have done to try and remedy the problem:
-Checked plugs they look fine and I just changed them about 9k miles ago
-replaced exhaust/intake manifold gasket
-checked for cracked exhaust manifold but it was fine
-replaced all 4 O2 sensors
-fixed fuel evap system leak (didn't help with symptoms)
-Welded up exhaust leaks (except small 1mm diameter hole they missed which hisses pretty loudly)

Can you guys help me troubleshoot this problem?

 

this sounds like exactly what just happened to mine. check the fuel pressure and see if all injectors are spitting. also check the grounds for a good connection(might as well clean them up too)

 

Have u done a leak down/compression test?

 

Check your injectors, mine ran like crap down low had 2 melted injectors... And the other day it started missing real bad turned out my grounds were extremely dirty.Sanded them and all is good now. Pull the injectors clean them up some with carb cleaner and check the tips, when u put them back in just out vasoline on the o rings and it will slid back together easy.

 

I'll be watching this thread, I've got nearly the exact same problem. Compression test showed fine though, fuel pressure is fine too. If I ever get some extra friggin time I've got a different set of injectors to pop in just to see what happens.

 

CEL?

 

I have no CEL- only light on is airbag light due to broken clock spring.

-I plan to swap out the injectors with the extras I have to see if that helps.
-I can probably do a leak down/compresson test at the on base auto shop here
-I guess I can start testing sensors- CPS, CTS, MAP, MAT, etc because I really don't want to just throw parts at this

 

Double Post Deleted

 

When was the last time you replaced the spark plug wires? They could be "leaking" and letting the spark jump to something other than the spark plugs.

Just reread the post, you don't have plug wires. But the boots can still be bad.

 

He doesn't have plug wires........

 

Well here is what my plan of action WAS to do about this during the next couple days:

-Remove the spark plug ignition rail (as you all mentioned, no wires unfortunately), and check out the connectors, ensure good contact, add some dialectic grease and pull/recheck the spark plugs.
-Test the fuel pressure (supposed to be 49psi +/- 5psi) in order to see if the fuel pump is possibly bad
-Replace the fuel injectors with the stock ones I have
-Remove the serpentine belt primarily to see if the power steering pump might be going bad/make sure the pully spins freely. My engine trouble started around the same time I installed a used power steering pump/box tapped for hydro assist, and the pump has started shaking sometimes.
-Compression and/or leak down test to check cylinders/pressure/head gasket/cracked head
-Check/replace sensors


I say I WAS planning on doing this over the next couple days because I think I just may have solved my problem.


Other than power steering pump install, and only other thing I did around the time the engine started acting up was run some seafoam through the master cylinder vacuum line. So with that in mind I figured maybe the vacuum line didn't reseal fully when I put it back on the master cylinder, causing a slight vacuum leak (which I couldn't hear). So, I added some hose clamps on both ends of the master cylinder vacuum line and put some teflon tape along the edge of the master cylinder inlet plug. To my surprise it started idling smoother/quieter after this. I took it on a long test drive and it felt noticeably more responsive right away when accelerating. On the highway it felt like the engine didn't have to work as hard to maintain speed. I also replaced two worn out boots on some vacuum lines that connect to the intake manifold to ensure those were not leaking.

While these actions made a pretty noticeable overall difference when driving, I honestly can't really tell if the jeep is driving as good as it used to, since it has been 2-3 months since the last time it was running perfect. Plus since replacing my motor mounts, adding hydro assist, and sealing up my exhaust leaks it just feels much different than it used to. Therefore, I still plan to do all the things I listed above just to make sure there aren't multiple problems here. However, before I do anything else I need to see if I fixed the gas mileage issue, so everything is on hold until I go through a tank or two of gas. I definitely have my fingers crossed, but I will report back with my findings.

 

GREAT investigative work sir! God bless for serving and our protection!


yeah those vacuum leaks are pesky and drive ya up the wall at times.

I think the seafoam treatment you did may have changed the way the jeep "feels" from what you have gotten used to.....

I have never used it, and don't plan to ( I have a long block sittin at my dads garage, just itchin' to be unleashed!)

I will take the original and tear it down and redo everything on it......so's I have a spare ya know! ( i like having spare stuff!)

meanwhile back to your saga, I hope you keep us posted, its always great to hear some folks how to fix-its and final solutions, as it always helps those in need!

again, many thanks, and best of luck to you sir!

cheers!

cpnwrench

 

I appreciate the support.

It is true that the seafoam could have had ill effects on the engine/lowered the compression, but I have used it in on my xj about 2 other times and it helped..who knows I also just recently noticed that the previous owner left a half inch diameter hole (meant for plugging a sensor into) wide open on the aftermarket cold air intake they installed. Maybe I should start researching that stroker or ls swap I want to do eventually.

Anyways I will update this thread soon once I see the gas mileage.

 

I am not a pro but do read alot on this forum. Have you reset your system after doing all this? remove your positive and negative connections from the battery. Touch the 2 leads together for about 30 seconds and reconnect them. From what I have heard this will reset your system and make it "relearn". secondly another great thing I have learned recently is this:
If you haven't already here is an awesome fix that helps with shifting and other problems some people run into. Takes about 5 seconds to do:
https://www.cherokeeforum.com/f2/free-quick-fix-41821/