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2007 LP640 Balloon White
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Discussion Starter · #1 ·
I changed my plugs and air filters yesterday. Car has a low speed (low rpm) surging issue that I’m trying to resolve. Plugs were fine but replaced anyway. 2 coils looked like they had moisture at one point. I used some scotch brite to remove the corrosion. Zero improvement from the plug change, would like to Ohm test the coils and looking for instructions. Thanks all and Happy New Year!
291230
 

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There are endless tutorials on YouTube that show you how to test a coil with a multi-meter. Don't worry so much about what the numbers should be but rather look for which coil/s test different to the others. The chances of 12 bad coils is almost zero.
 

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If you have a low speed surging there are 2 things you should check for:

1. Make sure the throttle bodies are clean. For whatever reason these cars are super sensitive to dirty throttle bodies. Use a rag and spray throttle body cleaner to wipe the inside of the bodies and throttle plates as well as possible. It is not necessary to remove the bodies. I did this and my surging problem went away.

2. A broken or loose vacuum line in the head can cause surging. This can be more difficult to diagnose but the first thing is to check all connections and look for dried and cracked hoses.
 

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The loose hose or vacuum line is very likely. Do a smoke test on the system and see where any smoke leaks out of. I did this on one of my previous cars for similar reasons and i found a few small leaks. I was surprised because a visual inspection of the areas where I had the leaks looked all tight and secure.
good luck
 

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What is the procedure for smoke testing the system. Mine is having low speed problems as well. Visual looks ok but???
 

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2007 LP640 Balloon White
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Discussion Starter · #10 ·
Funny I was going to ask the same but have been away from the computer. I did do a quick cleaning of the TB's (remove hoses and wipe down the inside...no special cleaning fluid) and was surprised that it helped. I plan to buy some actual TB cleaning and slow down and do this more carefully in the event it helps further. Thinking vacuum leak could still be the culprit though.
 

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We used to use brake cleaner or propane to look for vacuum leaks. I dont know if that will screw up any sensors. You spray brake cleaner on the connections and watch for speed changes. Same with propane . Use a trigger torch and put near vac connections (Kill the ignitor). I just dont know enough about modern systems.
 

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I know on an HVAC system you put in a smoke bomb and look for leaks under pressure but dont know what to use on a car.
 
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