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Old 07-06-2016, 06:56 PM
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Join Date: Apr 2004
Posts: 68
Two new nagging issues

1992 300E with 44,000. I bought the car about a year ago with 35,000 miles. On cold start idle stumbles but does not die but very low idle about 500rpm or less. Becomes normal very quickly. Then the tranny does not upshift like it did before. I have to drive 4 or 5 blocks before it upshifts and then all OK.
After purchase, replaced injectors, seals, ignition wires, rotor/cap, temperature sensor and the OPR. Engine ran perfect until now. I have to drive 4 or 5 blocks before it upshifts and then all OK. All thoughts and knowledge appreciated.


Last edited by handyjay; 07-06-2016 at 06:58 PM. Reason: Corrected spelling
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Old 07-06-2016, 07:37 PM
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Join Date: Sep 2004
Location: Seattle
Posts: 1,971
Scrape the crust/crud off of the dist cap electrodes and see if that helps.
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra
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Old 07-06-2016, 08:19 PM
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Join Date: Oct 2004
Posts: 4,194
These cars have an upshift delay when the engine is cold. It forces the engine to rev higher which in turn gets the catalyst active quicker. Totally normal behavior.

Engine stumble when started that clears quickly is a hallmark of CIS injection. With newer injector nozzles, running some injector cleaner through it may yield some improvement but I wouldn't hold my breath.

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
Milled & ported head, 10.3:1 compression
197 intake cam w/20 advancer
4 ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff
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Old 07-08-2016, 12:48 PM
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Join Date: Apr 2004
Posts: 68
I know the delayed upshift is normal for this 300E, but none of my previous MB's have had such a long delay. When I disconnect the vacuum valve electric supply the tranny shifts as normal. I assume the engine coolant temperature sensor sends the signal to the ECU and the vacuum is vented to allow normal operation. The sensor is only a year old. Could I have a sensor failure?

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