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Don't assume the symptoms are linked Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 21 Jul 2009 04:17:40
In Reply to: intermittent lurching and burning engine smell, emma, Mon, 20 Jul 2009 15:20:05 Members do not see ads below this line. - Help Keep This Site Online - Signup |
It might be different symptoms of the same problem, or it can be multiple problems. The best troubleshooting technique is to try to solve them one at a time; otherwise you can waste a lot of time trying to come up with a screwy scenario that fits all symptoms, including low tire pressure.
How old is the battery? If it is more than 3 years old, it could be just tired. And if the battery has gone flat a few times, it's pretty much toast. Every time a battery goes flat, it loses the capacity to hold charge. Do it a few times, and it's the same as adding a few years of use.
Step 1 - get a voltmeter, and measure the voltage on the battery when the car is running. Ideally, start the car, bring the engine revs up over 2K for a few seconds, then let it idle with the AC and fans off. You should see above 13 volts on the battery posts (13.2, 13.5). If you see a voltage less than 13 (12.8) , then I'd suspect the voltage regulator, which lives in the back of the alternator, needs replacement. I'd also replace the battery. You just don't want to replace the battery because a bad VR killed it, and then left the bad VR in.
Step 2 - lurching. Pull the spark plugs and look. Is the gap right? Do they look like the engine is running lean (very white) or rich (black and sooty?) How old are the cap, rotor, and wires? My first thought on lurching would be ignition, so I'd replace the cap, rotor, and wires if they're getting old. Check the timing. If that doesn't do it, consider replacing the ignition coil. I've seen cases where the coil develops an open circuit, and causes the engine to miss at certain RPM.
Step 3 - burning smell. This could be a whole host of things. Look for the obvious, like scorched belts, missing exhaust heat shield cooking the battery or cables, etc. After a long drive, pop the hood and look for smoke. One place I would suspect is a leaky valve cover. The engine is tilted, and if the valve cover leaks (and they all leak eventually), the oil oozes out and makes its way onto the exhaust manifold, and you smell it burn. With a cold engine, look above the exhaust manifold. If the area from there to the valve cover is black and oily, or just black and gummy, clean it off. If after a few days you see a film of oil developing, replace the valve cover. It's not a big task at all, and can solve a lot of burning smells.
Yes, your alternator could be cooking, which is causing a burning smell, flat battery, and intermittent electrical loss. But I doubt it. Instead, hit the problems separately. If it is one problem, you'll find out eventually anyway.
posted by 75.11.49...
, Tue, 21 Jul 2009 04:17:40 <-- Viewing This Message
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