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Trying to figure it out...

BIG1RED9

NAXJA Forum User
Location
Coarsegold CA
I have done a fair amount of work on my 87 Wagoneer with a 4.0. I have been bringing it back to life after sitting on jackstands for 7 years. I want to make sure that whatever this, first it won't leave me stranded and to isolate it so I can fix it.

I will be driving along and every 10 to 15 minutes I feel a sensation that is a lot like a trans overdrive upshift. Prior to the soft jolt, RPM shows it in OD. By the time my eyeballs focus on the tach the event is over and I miss it. I was hoping to see if there was a RPM change caused by the engine or trans.

Recently the engine died while on a 2 lane road at highway speeds (very stressful) feeding my concerns. Turned out to be a poorly installed ignition switch which I replaced. I also cleaned and lubed all the ground points, relays and sockets.

In case it is relevant
I have replaced 98% of the brakes (everything but the power booster). New hubs and cv axles. Replaced rear bearings, replaced all u-joints and rebuilt the transfer case.

I have factory dana axles The rear end has always made more noise under throttle than coasting(on next years repair list). The interior is pulled except the driver seat and therefore louder than typical.

Appreciate the help to solve my mystery.
 
If it happens around 2000-2400 RPM it is likely an O2 sensor. Either the sensor itself or the wiring. Pay special attention where the wires run up the front of the motor. If they are routed wrong they can cook on the exhaust.

A poorly functioning O2 sensor can run the motor lean near peak torque and it will buck. May run fine below or above this RPM.
 
Thanks Cruiser

Refreshing connectors seems to have solved the issue. Not sure which one as I pulled cleaned quite a few including the C101.
 
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