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Discussion Starter · #1 ·
I've posted about this before but could never track down the problem so I've been ignoring it, but I noticed a new "symptom" last night.


A little recap, the car has this surging issue that usually happens when the AC compressor kicks on. The RPM's don't just adjust for the load, the engine actually starts to surge and go Vroom -- Vroom -- Vroom for a few seconds and then it'll level out until the AC comp kicks in again.

Well every once in a while it'll do it without the AC on, and last night it was dark out and I noticed the headlights dimmed whenever the RPM's kicked down in the surge. Was that just a symptom of the RPM's dropping in the surge or could it be an alternator issue?

99 Vulcan
 

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Alt.

:unsure:...I believe your on the right track. It's not a real task to remove it and carry to local parts store to check, but before going to a lot of trouble, go to your local WalMart auto center and they will check it FREE on the car. Have them check your Battery as well. Good luck,
david......:unsure:
 

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test the alt out put. my lights dim for a split sec when the a/c kicks on. but i dont get surging after. i would agree with shelia i would look at the iac with the surging issue.
i am wondering, with this happening when the a/c cycles, what sensors are used to compensate the new load. hmmmm
 

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Discussion Starter · #5 ·
In my efforts to track down the problem I have already replaced the IAC and thoroughly cleaned the upper intake manifold. I wish it was those, as they are cheap repairs lol
 

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The reason your lights dim and follow the surge is that your alternator is not putting out a full charge when the RPMs dip that low. It is not a Symptom to your real problem, when is the last time you replaced your Fuel filter? I had an issue very close to this one and my fuel filter was clogged causing the fuel pressure to fluctuate to the engine. It's obviously not an issue with air the only thing left is fuel and spark, a fuel filter may fix the issue but it could also be your Cam position sensor getting ready to give up the ghost it just hasn't thrown a code yet.


Troy.
 

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Discussion Starter · #7 ·
Fuel filter was replaced around 97,000 miles. I'm at 108,100 miles now. The cam position censor is original though there's no chirping or codes.
 

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I've had both the surging and the lights dimming problem. I fixed the surging with a new IAC and throttle body cleaning. The alternator drove me absolutely crazy. It got to the point where I even called Identifix for a tech support call. They suggested tensioner replacement. That didn't solve the problem. Turns out (after an alternator replacement and a lengthy discussion with my buddy who works at a junk yard) that Ford alternators of this vintage are know for weak brush springs. High RPMs throw the brushes off the slip rings and they don't settle back down on the rings quickly. That's where you get the lights dimming.

Put in a new alternator and problem went away. Disassembled old alternator and found the springs were bluish and distorted. Very little springiness left in them. No wonder they were flying off the slip rings.

Just posted that FYIW.
 

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Discussion Starter · #10 ·
I really wish the problem was my throttle body, intake, or IAC but I've taken the intake and TB off at least five times now to thoroughly clean them and verify all the passages were clean.

I replaced the IAC and the car runs noticeably worse when I disconnect it. The RPM's fall to nearly 500 at idle with it disconnected.

So on the table is Cam position sensor and fuel filter? I'd like to add fuel pump to that list.. I've got no evidence to support a failing pump but the pressure might beginning to fluctuate. Anything else you guys can add?
 

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Before I'd change out the fuel pump, I would check the fuel pressure with the old filter installed and then replace it. Then check your fuel pressure again to see if the new filter cured the problem. I'm just guessing here, but odds are your fuel pump is in the fuel tank. Not a fun job dropping a fuel tank. Btdt twice.
 
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