Putt, putt, putt, bleh!

[ParadiseMJ]

The title is what my truck (88 MJ 4.0 AW4, 4x4) sounds like under the following conditions:

 

• Long drive (1/2 hour) at speed, stopping, then starting it up again within a few minutes.
• Short drive around town when the engine is all warmed up, then starting again within a few minutes
• Long drive (1 1/2 hours) at speed, then slow drive for another 20, then idling, Then turn off, and restart within a few minutes.

If it sits for an hour and it cools off a bit, it doesn't do it, it'll fire right up and purr like a kitten.

 

This ONLY happens every once in a while, like a couple times, every 3 months or so, then it clears up and runs like a friggin' champ.  When it's doing the putt, putt, putt thing...if I give it gas it dies.  If I put it in Neutral it tends to even out after a few putts. If I tromp on the gas pedal after the first incident of putting, and re-start it, starts right up and  it's smooth.

 

Any ideas?

[Fernando87mj]

Partially Stuck fuel injector/s flooding the engine ?

[HOrnbrod]

Sounds like it's sticks in open loop occasionally. Maybe it's time for a new O2 sensor? Or at least a wiring check..

[cruiser54]

Good idea to check the oxygen sensor although you can run without it. test the resistance on the O2 sensor pigtail between the black and red wires. Should be 6 to 8 ohms. 

 

What is your cPS output? 

[ParadiseMJ]

I thought of possible flooding, a stuck injector etc. which is why I tromped the pedal, which did help a little.

 

The O2 is only a couple years old.  The problem has been around for a year or so but it's so intermittent that I forget about it...until it happens again  :doh:

 

Good idea to check the oxygen sensor although you can run without it. test the resistance on the O2 sensor pigtail between the black and red wires. Should be 6 to 8 ohms. 

 

What is your cPS output? 

 

I dunno.  :dunno:  Don't have time to mess with it this week.  I get truck time this weekend.  Test the O2 ... key on or key off??

 

What's the O2 thread size if I wanted to plug it temporarily.  I DO have a cracked...kinda ruined knock sensor, too.

 

TIA guys.

[cruiser54]

I thought of possible flooding, a stuck injector etc. which is why I tromped the pedal, which did help a little.

 

The O2 is only a couple years old.  The problem has been around for a year or so but it's so intermittent that I forget about it...until it happens again  :doh:

 

Good idea to check the oxygen sensor although you can run without it. test the resistance on the O2 sensor pigtail between the black and red wires. Should be 6 to 8 ohms. 

 

What is your cPS output? 

 

I dunno.  :dunno:  Don't have time to mess with it this week.  I get truck time this weekend.  Test the O2 ... key on or key off??

 

What's the O2 thread size if I wanted to plug it temporarily.  I DO have a cracked...kinda ruined knock sensor, too.

 

TIA guys.

Key off and unplugged. You're testing the resistance of the heater element inside the O2 sensor. 

[HOrnbrod]

What's the O2 thread size if I wanted to plug it temporarily.  TIA guys.

M18 x 1.5. You can p/u an O2 sensor bung thread chaser tool at the Zone or any chain auto parts store and plug it up with that temporarily.

 

If the O2 sensor heater element is open, there's no O2 output to the ECU. On an HO that immediately kicks it into open loop. I don't know about the Renix junction box computer.