warm idle surge in gear

[Quick4door]

Trying to track this down. 95 e420. new plugs, caps, rotors and dust caps. updated wiring harness has been on for 2 years. smoke tested last night, no leaks. no difference with a replacement EZL. unplugging the maf does make it idle smoother. if i give it a slight amount of throttle in gear, at a stop light for instance (with the brake on) and bring the idle speed up to say 800, it evens out and goes away. cruise works fine, no loss of accelleration or driveability other than idle surge in gear when warm. I'll pull codes later this week but no check engine light on.

What else should I be checking?

 

[gsxr]

How bad is the surge? ±50rpm or ±250rpm? Etc. If there are codes (LH, EZL, E-GAS) that will help but you may not find any.

Could be tough to pin this down without live data. Not sure what else to check, vacuum leak was my top guess. For grins, disconnect and plug the 8mm tube at the MOT / purge valve and see if there is any change.

 

[Quick4door]

It starts as 50 and then gets worse, where it's almost died in less than 10 seconds from when I stop, unless I just feather the throttle a little. I'll check the line and report back.

 

[Quick4door]

Checked it last night. Unplugged the vac line to the EZL, immediately started chugging so that seems good. pulled the vac line where it attaches to the MOT valve and found it wasn't making a good seal. I didn't see this in the vac test because that's where I introduced the smoke for the test. Seems to have fixed the issue! Thanks GSXR!

 

[gsxr]

The other end of that 8mm tube goes through a small orifice at the intake... this isn't a good location to introduce smoke into the intake.

I'd use the metal pipe for the brake booster vacuum. Unscrew the plastic pipe at the front/center of the intake manifold and feed smoke into the metal pipe that goes directly into the intake.

 

[Quick4door]

I'll give that a try tonight.

 

[Quick4door]

I've been driving it now for over a week, and there are no concerns at this point. It has healed itself! Adjusted the throttle cable, trans cable, and all is driving and shifting like buttah.