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#1
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86 300E CIS problem
Hi everyone. As a recent first time MB owner this site has been a lifesaver. I have a problem with my 86 300E that seems to have come out of the blue. It starts and idles ok, but has no power and throttle response is terrible. When I floor it and hit the WOT switch it immediately runs normally, let off even slightly and its back to no power. Does anyone have any ideas or suggestions? The help is much appreciated.
Things replaced in the last 3,000 miles: air filter, fuel filter, plugs, wires, cap, rotor, (all bosch). 195,000 miles, good vacuum at 650 rpm idle. Thanks again everyone. |
#2
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Does the car upshift too fast? [in top gear by 20 mph?]
If it does, than that's similar to [one of] the problems I have with my 300E. I tried the brute force EHA adjustment [lots of threads on this forum] and found that a quarter turn worked wonders [but not all there yet] I also replaced the temp sensor [the more expensive, two connector version] My next steps are to check the crank position sensor and the oxygen sensor. If these check out as good, then replacing the injectors is the probable next step. |
#3
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Let me say this... recheck some of your parts.
Bosch wires are not the best quality-check them with an ohm meter versus the manual specs. Make absolutely sure you have the correct H9DCO plugs and not the subsitute HR9DCO plugs. The correct ones are about $2.5/each at the dealership. I'd guess it's something simple- check pressure and volume on the fuel pump. Make sure the fuel filter flows good- yes I know it's new. I'd guess it's either 2 or 3. But like mentioned before- you can check your 02 sensor-but failure should cause it to run rich. Measure your temp sensor on the head and make sure it is in range. Check the airflow meter to make sure it moves freely. Sometimes they have to be adjusted. Michael |
#4
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86 300E problems
two strong items to check. The EHA valve itself - it's design is to act as a accelerator pump for this car. When you need more fuel quickly, then it gives you that strong shot of fuel and maintains it. Also, not sure if you have a throttle advance solenoid that controls vacuum used for aceleration, if so, on pass side behind/beside the washer bottle. Has vacuum lines going to it with a check valve somewhere along the line. Check valves could be cracked also, cheap fix.
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#5
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Thanks for the advice guys.I have not had a chance to look at it yet but yesterday afternoon I took it out for a drive and it ran absolutely perfect. So last Saturday it had a hell of a time getting anywhere unless the throttle was pinned to the floor. Then Wednesday without having touched a thing it ran perfectly. Is there anything in this fuel system that might fail intermittently
and cause this? Thanks for the help. |
#6
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It sounds like you are lean at anything other than idle or WOT. There is a potentiometer ("pot") in the mixture control unit that tells the brain how much enrichment to provide. There is also a three position mechanical throttle switch (idle, WOT, all other). I think your pot may have gone south and you are OK at WOT because when the brain gets the signal from the switch, it overrides the pot's signal.
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Chuck Taylor Falls Church VA '66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe |
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