Idle revs drop on high beam - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

rev · 05-20-2004, 02:07

Weird problem been around for a while and I had given up trying to solve it. From time to time the idle revs, when stopped at the lights, would drop (car shuddered) for a brief period then went back to normal then drop and return etc. Been doing it for ages and wasnt a big deal. My mechanic can fine no codes or faults. But tonight I wanted to make sure my high beams were working so at home before switching of the engine flicked on high beam. In Drive, the revs dropped and the car shuddered. Low beam rev back up and shudder much less but still there a bit. Replicated over and over. In Park with the revs raised no noticable difference. Any clues why switching to high beam in Drive would change the idle revs/smoothness?

Cheers

damo03 · 05-20-2004, 02:39

There are a few possibilities for this. When you have lights on, or heaters, loud stereo with full sik subbies, or other current draining devices, there will be a load put on the alternator. Most car's revs will drop when a load is put on, however it shouldn't cause the engine to knock or shudder. If it does then
1: the battery could not be holding much of a charge and the engine is relying too much on the alternator
2: the alternator is shot and not efficient
3: there could be some other electronic ignition/fuel injection related issue where the engine isn't sensing the load and raising the revs accordingly like when u turn the airconditioning on.

When it is in park it isn't affected as much because there is no transmission load on the engine.

Hope this helps

Damo

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87' Xf Fairmont Ghia on Gas. Gas Cam, bored out 40thous, high compression, steering lock that doubles as a weapon!

ebxr8240 · 05-20-2004, 05:59

Try turning idle up alittle???But it is normal for this to happen but idle speed control should step in and correct it..Check or clean it if raising idle speed doesn't work..Keep in mind how far you turn idle so you can return it...

mongrelEB · 05-20-2004, 08:35

Yeah, what they said

rev · 05-21-2004, 03:09

Thanks for the suggestions. Getting the idle speed controller changed on Tuesday after talking to the mechanic, and also the fuel injectors done to fix a running super rich when cold problem.

Cheers