engine stumbling

The idle speed is controlled by an Idle Speed Control (IAC). This is located on the lower part of the throttle body. The most likely thing that is happening is that it is sticking. The first thing I would do is clean your throttle body with carburetor cleaner. Some of the cleaner will pass through the IAC. If that doesn't help you can clean the IAC by removing it, but you will probably need to remove the throttle body. It is possible that the IAC has an intermittent open circuit. If that is the case you will need to replace it.

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Ron- I forgot to mention that the stumbling, low rpm problem stops if I disconnect the vacumn line leading to the intake manifold, (the vacumn is in the mid twenties and stable), and attach, in line, a fish tank bleeder value set to about 10 pounds of vacumn. When I do this, the milage hits around 34.5 miles per gallon, and the rpms do not drop when coming to a stop. Advise and counsel please. Steve

Do you have a 1.5 or a 1.8 engine? Can you follow the vacuum hose in question and tell me where it leads past the solenoid or vacuum chamber?

One thing you can check fuel pressure regulator on the fuel rail. Pull the vacuum hose and see if there is gas in it.

Edited by ronrutgers on 18 August 2006 at 3:11pm

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Hi-

It is a 1.8, and the 8-10 inch vacumn line comes from the left side (looking from radiator side of engine)of engine and on the back of the intake manifold into a solenoid with two wires and a rubber piece on the front of it. From there, it goes into a 16 inch rectangular metal tube that seems to feed the injectors. No gas in vaccumn line.

That's your fuel pressure regulator. The next step would be to check the fuel pressure. The pressure should be 39-46 PSI. without vacuum. Since restricting the line would increase pressure, it may have low pressure. When you are checking pressure momentarily pinch the return line. It should go up to 70+ PSI. That will determine if the fuel pump is capable of creating enough pressure. As I remember these have all banjo fittings on the pressure lines, so you need adapters to hook up a gauge.

Edited by ronrutgers on 18 August 2006 at 5:33pm

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I followed your first advise. The carb. plate and barrel looked like the inside of a tar barrel. I cleaned it all, and guess what? It runs like new. Many thanks,

Steve

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