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Re: Advise needed Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 17 Sep 2002 13:29:27
In Reply to: Advise needed, Vlad, Mon, 16 Sep 2002 19:36:58 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'm going to assume the car drives fine, it's just a poor idle condition.
Idle is a tough time for an engine - it has very little torque, but can see some big loads (A/C compressor, etc).
First, address Daren's idea. Yes, if you have an electrical power or ground problem, it could affect the engine. With the car idling, hit the brake pedal. Any change? Turn the headlights on, hit the brake pedal, turn the blower to high. This puts on a big electrical load. If you get no or minimal change in the idle, then it's probably not an electrical problem. If you get a big idle jump, make sure that the ground strap to the engine is good, grounds to the ECU, sensors, etc, are all in place, and clean up any of the engine ground points.
I'm going to assume it isn't electrical. First, check for vacuum leaks. Yes, you did, but do it again. Pull the right front turn signal assembly off and make sure the hoses to the charcoal canister are in place. Wiggle hoses - if the idle changes when you wiggle a hose, find out why. I've had hoses split on the bottom where you can't see, but wiggling it opens the crack up bigger.
I think vacuum leak, because at idle there is a lot of manifold vacuum, so there's the biggest 'draw' to pull air in through a little leak. And at idle a little bit of air can make a big difference.
There are four short, fat hoses from the intake plenum to the intake manifold. Make sure they fit well, and that the clamps are tight. There is a lot of surface area where the hoses fit onto the metal tubes, and a little gap will let in a lot of air.
Pull the spark plugs. How do they look? They should be a light grey. If they're stark white, then you're running lean. This could be due to a vacuum leak or low fuel pressure. Yes, it could be the O2 sensor, too. But the plugs don't lie. Determine if the engine is running lean, rich, or just right from the plugs. Check ALL four. Then stick a digital voltmeter on the output of the O2 sensor. See what it says, and compare to the 'truth' of the plugs. If the plugs are white (lean), but the O2 sensor is stuck at 0.9 volts (rich), you know the O2 sensor is lying.
You should expect to see the O2 sensor output swinging between 0.2 and 0.9 volts. Yes, it's fancier than that, but if you see it swinging, a lot of things are going right.
How does the car respond when pulling away from a light? Does the car accelerate nicely when you hit the gas gently, or do you have to mash the throttle to get the engine to respond from an idle? It's a non-turbo, so it's not going to spin the tires, but it should have a nice throttle response. If it hesitates, almost as if it's ignoring your foot on the throttle, think AMM. The AMM measure the airflow and schedules fuel. If it doesn't see airflow due to a vacuum leak, it won't add fuel, and the engine will bog. If the AMM is faulty, it won't recognize more air when you hit the gas, or the engine load increases (A/C compressor kicks on), and won't add fuel.
Lastly, check your FPR. If you've got low fuel pressure, it won't help the idle. THis will show up as a lean running engine, and the O2 sensor will also indicate lean (0.2 volts).
It's a start...
posted by 192.249....
, Tue, 17 Sep 2002 13:29:27 <-- Viewing This Message
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