G320 M104 ideas on troubleshooting rare hesitation, low idle, vibration only after highway driving

[JamesC]

Hello all,

Any suggestions on the following symptoms: 94 G320 ~92,000mi. A vibration, low idle and then hesitation starts only after +30mins of Highway driving in any temps (+100f or 40f) and every 15th-20th highway drive. Never around the city. We are not sure if this is speed, speed + distance or possibly just distance related. Condition starts as soon as you slow from highway speeds to a crawl/stop like exiting the highway to a light.

-Replaced plugs, wires, coils 2,000mi before this started happening.
- Any gas level (replaced filter and some hoses 1k before this started happening)
-Either driving or at Idle in Drive or Neutral
-Truck vibrates like it's almost stalling
- Can not accelerate no matter pedal position to above ~25-30mph
- Have not tested extensively but has gone away in as little as 15 mins after a restart

Any ideas of where to start? Thanks!

 

[gerryvz]

As a first step, I would pull all of the codes, and reset them. Then drive the truck 25-50 miles and see what codes come back.

For mechanical systems, as a starter I would do the following:

I would get the MAF (mass airflow sensor) tested by a shop with the appropriate equipment to do this.

I would also test the ETA, which on this model is known for having bad wiring internally and externally.

Also -- has the upper wiring harness been replaced? These too suffer from faulty wiring.

There is the highest chance that one (or all of) these two wiring-related problems is the cause of your issues.

 

[JamesC]

Thanks Gerry! Will get started on these

 

[kiato4]

Sorry to point to another forum, see my issue here: 1995 G320 (M104 engine) running problems - Club G-Wagen Forum

Sounds somewhat similar and ended up being the oxygen sensor. Also check coolant temp sensor and look for vacuum/air leaks.

 

[JamesC]

Thanks for the reply!

 

[AMGTesTDriverNJ]

Thanks for the reply!

Where are you located?

 

[JamesC]

Where are you located?

DFW, Texas