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More info Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 11 Oct 2002 09:27:51
In Reply to: Messege to Ari., bruno, Thu, 10 Oct 2002 20:25:11 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The Check Engine light comes on when the ECU doesn't like what it sees from the sensors. An out-of-range AMM signal, a bad O2 sensors, engine temperature sensor, and much, much more can cause the CEL. But a big vacuum leak can cause the O2 sensor to read lean all the time, and give a 'bad O2 sensor' indication, even when it's not the sensor. So even engine codes need troubleshooting. All the CEL does it to tell you to bring it to a dealer, and that the problem is probably in the front half of the car.
First off, pull the spark plugs. They live in the engine and tell no lies. You want to see a nice uniform grey on all the plugs. I'll bet you won't. Of course, make sure the plugs are properly gapped to the specs in the manual/on the decal in the engine bay. If the plugs look worn or crudded up, replace them. If the engine has been running rich, you'll see lots of black, fluffy stuff on them. If it's running lean, they'll be white. Do any of them seem wet with fuel? Thats one possible sign of bad ignition. Do the tips look melted? That could be running way too hot, possibly from bad timing.
Next, make sure your timing is correct. Again, consult the decal, but from memory it's 16 degrees BTDC. When was the last time you replaced the spark plug wires? If they're over 3 years old, replace them. This is sounding like an ignition problem, no guarantee, just a hunch - so keep an eye out there.
The AMM doesn't test easily. You can do the 'glowing wire' test, but that doesn't mean the AMM is working right - just the burn off. But it's worth a try. Remove the input hose to the AMM. Start the car, and rev it to over 2000 rpm for a few seconds. Let it return to idle, and have someone turn the car off. somewhere between 5 and 20 seconds later, you should see the wire glow whitish for a second or two. This is the burn-off, which cleans crud off the AMM. This feature can work just fine and the AMM still be crap.
Try unplugging the connector on the AMM, and see how the car idles. If it gets better,it may be a bad AMM. That's because with no AMM connected, the ECU makes some assumptions. It will still drive lousy with no AMM.
If the plugs tell you that the engine has been running lean, look for vacuum leaks, but also look into the fuel system. When was the last time the fuel filter was replaced? Fuel system are not pretty to troubleshoot, because they take some special equipment and leaks are dangerous. But if you're running very rich or very lean, it could be a fuel issue - low fuel pressure (lean) could be clogged filter, bad Fuel Pressure Regulator, etc. Rich could be a bad FPR, too. The best thing you could do here is measure FPR pressure with a pressure gauge, and measure injector flow rate.
A Bentley manual will come in handy here.
posted by 192.249....
, Fri, 11 Oct 2002 09:27:51 <-- Viewing This Message
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