When my '94 E320 is lukewarm and it's in Drive or Revers (or any other gear), it idles funny. You can see the rev-counter going up and down, and you can feel the engine revving a bit up and down. If I put the car in Neutral, the problem goes away.
If the engine is fully warm or cold, there's not a problem.

The previous owner told be about this problem, but he had never come around to fixing it. He had replaced the engine wiring loom, so I know that's not the problem.

What could be causing this funny issue?

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Dag Boesterud
Norway Europe
1994 Mercedes-Benz E320 Wagon
1990 Audi 100 Turbo Quattro Sport Exklusiv

I was having a similar problem with my '94 E320 Tourenwagen, along with a nasty stumble under acceleration. The previous time this happened it was mostly resolved by replacing the spark plugs, but it never quite went away and then got steadily worse over 15k miles until I could no longer stand it.

After again replacing the plugs but to no effect, I decided to replace the coil packs and spark plug wires, et voila, problem solved: it purrs like a kitten when at idle, no matter how hot/cold, and pulls like a freight train all the way to redline with nary a stumble or shudder.

I love this car.

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Robert Fini

'12 ML350 BlueTec, 87k
'06 E320CDI, 270k
'05 T1N Sprinter 2500/Pleasure-Way Plateau TS, 69k
'97 C36AMG, 313k (son's)
'94 E320T, 249k
'93 190E Sportline LE, 168k (daughter's)
'84 190E-2.3/5spd (Stage Rally Racer)
'66 230 W110 Sedan (Barn Find, Vintage Racer build in progress)

Both My gassers need new plugs...the wagen...and the intruder.

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77' 300D, "Cartman" SOLD @ 150K (didn't know what I had)
83' 300SD, "The Superdon" 325k+ @ 28mpg
95 E320 wagon, "Millennium Falcon" 231k+ @ 24 Mpg
95 E300D, "Sherley" 308k @ 33.69 Mpg, currently anticipating a head
99 Suzuki Intruder "Trudy" @ 45 mpg

There is a grey vacuum hose under the intake, in the back, near by the oil filter. If it gets pulled off, the idle will lope up and down. Check that before digging in further.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff