Very, Very slight stumble on the freeway

[BIGdaddy]

going 65, just crusing, not passing or anything.

engine missed a half-beat and kept chugging in the middle of my commute home...

I'm thinking the start of a fuel pump issue, clogged injector, TPS or CPS wires toasted...

I've run a bottle of injector cleaner through, I wonder if I should do another one, just to try and clean out a bit more varnish...

 

[ExpeditionJeep]

Big daddy,
how old are the plug wires on your jeep? It's very common for those 4.0's to stumble if the wires are breaking down. If they have more about 15K on them I would tune the motor (cap, rotor, wires, plugs) before I looked at sensors. Rarely does a sensor cause a misfire, it's almost always secondary ignition in my experience.
Marc

 

[BIGdaddy]

new cap,
rotor
plugs
wires
fuel filter
radiator
serp belt

in the last 500miles...

thanks for posting! any other thoughts?

 

[seanz0rz]

i had a similar problem on my truck.

replacing wires and plugs solved it. i also cleaned the MAF sensor, throttle body and idle air control valve, along with the rest of the intake tract.

possible timing issue? fuel pressure regulator? just some things id check before i went and threw money at it.

 

[BIGdaddy]

i had a similar problem on my truck.

replacing wires and plugs solved it. i also cleaned the MAF sensor, throttle body and idle air control valve, along with the rest of the intake tract.

possible timing issue? fuel pressure regulator? just some things id check before i went and threw money at it.

excellent...I'll check those out manana!

 

[BIGdaddy]

so weird. commuted just now. 24miles @ 65mph. nothing to report...

lol. I HATE intermittant problems. I'd rather have something just BLOW like my radiator a month ago. It just "started leaking".

 

[ExpoMike]

I agree, I hate intermittant problems!!! You might swing by an Autozone, Kragen, etc. and see if they can put a scan tool on and read if there are any codes thrown. A code won't always trip the check engine light so it might be worth checking.

Also, if the O2 sensor hasn't been replaced, that can cause some weird driveability issues.

First thing I would do would be checking the codes though. Good luck!

 

[BIGdaddy]

I agree, I hate intermittant problems!!! You might swing by an Autozone, Kragen, etc. and see if they can put a scan tool on and read if there are any codes thrown. A code won't always trip the check engine light so it might be worth checking.

Also, if the O2 sensor hasn't been replaced, that can cause some weird driveability issues.

First thing I would do would be checking the codes though. Good luck!

thats a good idea, I was thinking, too, that I should probably pull the trigger on a multimeter (long overdue), to test the CPS and TPS. I've got a test light, a timing light, I don't know why I don't have a multi-meter...lol.

 

[BigAl]

I agree, I hate intermittant problems!!! You might swing by an Autozone, Kragen, etc. and see if they can put a scan tool on and read if there are any codes thrown. A code won't always trip the check engine light so it might be worth checking.

Also, if the O2 sensor hasn't been replaced, that can cause some weird driveability issues.

First thing I would do would be checking the codes though. Good luck!

You can check for codes on your 92 by just cycling the key 3 times and counting the engine ligth blinks. You'll see 1 then 2 as the opening sequence, then you'll need to start counting the blinks, they come in 2 sets, so you end up wih a 2 digit code. Search jeep engine codes and you'll find better instructions and the codes.

If you don't know the age of your cps, I'd start there, barring codes, the 4.0 is noted for cps issues

 

[Haggis]

Well it's obviously a misalignment of your dilithium crystals in the trans warp star drive. What your feeling in the thrust cycle is not a stumble in the propulsion system but time dilation fluxes from over stressed tachyeon compensators. Push the intercom button on your captian's chair console and get one of them redshirts in Engineering to fix it pronto!

 

[Keaster]

Hey good news on the trigger pulling of a multimeter you can buy a cheap one at Harbor Freight for less than five bucks had mine for years works fine. Also some times if you run multi prong plugs (ie Bosch platinum 4s) they draw too much of a load and the wires and rotor tend to fail way prematurely like in 500 to a 1000 miles after install not that I know that this the situation in your case just food for thought best of luck also might be fuel filter?.

 

[BIGdaddy]

Hey good news on the trigger pulling of a multimeter you can buy a cheap one at Harbor Freight for less than five bucks had mine for years works fine. Also some times if you run multi prong plugs (ie Bosch platinum 4s) they draw too much of a load and the wires and rotor tend to fail way prematurely like in 500 to a 1000 miles after install not that I know that this the situation in your case just food for thought best of luck also might be fuel filter?.

well, the plugs I used were normal, one prong autolites, and the filter was just changed, but I certainly could change it again, in case there was some gunk that got stirred up and made it past the first change-out.

thanks!

 

[shogun]

I had a Very slight stumble years ago. Almost imperceptable, but I could feel it on the highway. I believe it turned out to be a slow deterioration of the fuel pump, that got worse until what appeared to be transmission issues occured. Trans guy said it looked OK and ultimately diagnosed fuel pump. Changed it and havent had problem since.

The not long ago had a very hard, momentary hiccup. Almost a complete reversal/shutdown of motor for just a second, might have spilled coffee if I drank it. Very rare, then occuring more often to almost every time I drove it, maybe twice a day. Checked like-new plug wirse and found one had broken the center conducter inside the D cap hole. Cut and replaced, no prob since.

Look at the easy stuff first, dont think "new" means correct.

 

[BIGdaddy]

its like the twilight zone. I drove it for a week, week and a half. No issues, no nothing. And then, BAM!, it does it on the freeway again. Same symptoms...

and then again this morning. One instance was in the heat of the day, one was in the cool dense air of this morning.

-Never cuts out under load.
-Never cuts out while coasting to a stop
-Always cuts out when my speed is around 62-65mph
-Always cuts out when I'm "cruising" with a mostly neutral throttle input...
-Always cuts out when I'm just barely removing or adding throttle to maintain speed.



I still love my jeep cuz it got me to work safely, though. :drool:

 

[JIMBO]

:sombrero: Well BD, just a thought, but

Usually when the engine "stumbles", it's not ONE intermittant plug/wire

A stumble usually means PRIMARY, coil/ignition/ignition keys hanging/battery positive fuses (at battery)distributer ECM plug

You didn't mention CRUISE CONTROL, that alone is another bag of worms

Good luck

:wings::bike_rider::safari-rig::safari-rig: JIMBO