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Join Date: Feb 2009
Location: Japan
Posts: 498
whole car vibrates - solved

for info copied from BF, car 1994 BMW 740i: this issue just started to occur, when I first start my car it will vibrate the entire car, similar to a miss-fire yet it is not miss-firing and is firing on all 8, when I put it in drive and start driving it will vibrate like then it is perfectly fine. It will do it on a cold start with 4 hours of sitting but subsequent starts after the issue has gone away does not bring it back.
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It could be a few things, but I will ask about the O2 sensors. When were they last changed? I had a sillier rough start issue, turned out it was my sensors. They were very new. I swapped to BOSCH and the problem was gone.
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It has newer Bosch, they are a little less than a year old with about 7k miles on them.
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maybe either not enough fuel or too much. Try the following when the engine is cold and you have waited some hours> Switch ignition on, wait 2-3 seconds, switch off, switch on, this will start the pre-priming process for the fuel line/pump.
If that works, then your check valve on top of the fuel pump is defective and the fuel runs back into the tank till the pressure is gone in the lines between tank and fuel rail. BMW E34 Website: 535i hot start
Flooded: BMW E31 E38 E32 Starting A Flooded M60 840i 840ci 730i Or 740i
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Unfortunately that did not temporarily solve my issue If I very lightly rev the engine at idle the vibration is the worst, but not nearly as bad as when driving through it, at about 1K then is eliminated above that then reoccurs as it revs down
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Do you have a diagnostic tool? Or do a stomp test to see if there are fault codes
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Just checked with Carsoft and the car has no faults. Stomp test didn't bring up any either. My buddy mentioned about it possibly being engine mounts, how would I know for sure?
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I doubt if it would be mounts, it would always be an issue.
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That's what my thought here was too. I tested my intake temp sensor a few weeks ago and it would vary resistance with temp changes.
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grab a used 404 DME that probably has much fewer heat cycles on it.
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I was thinking the same thing, watch a new DME solve all my issues that have been occurring.
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I started the engine with my hood open and after reinstalling covers was constantly blasted with air, did quick little rev and found my fan clutch decided to go out. cratch that, I took a look again and I somehow lost a fan fin and did not damage anything thankfully. I don't know where or when that happened being I have not heard any noises of one breaking.
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Then you can be lucky, I have seen pics of fan fins making damage to the hood, the radiator and other parts. Replace the fan blade and the fan clutch.
Fan clutch test and operation is explained here http://www.mwrench.com/Whitepapers/FanClutchtest.pdf
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Well the fan imbalance form the missing blade can certainly cause vibrations. Also may explain why its more an issue when really cold as the fan is fully engaged for a short while. You can operate without the fan blades and rely on the electrics until it gets warm out. Just avoid standing still in one spot for too long, electric fans can only do so much.
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Old 02-05-2018, 06:56 PM
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