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kalamykid, Shop Owner/ Tech
Category: Chevy
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My Silverado is surging and aborting on a smog test...complete tune

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My Silverado is surging and aborting on a smog test. I tried a complete tune-up--new everything. I am out of ideas of possible causes.
When you had the smog test done what part of the test failed? Is the check engine light on when the engine is running? DOes the check engine light come on when you turn the key to the run position with the engine not running?
Customer: replied 7 years ago.
It is aborting when the tester runs the engine at higher speed "under load." "Check Gages," Battery symbol and "Service Engine Soon" lights all come on when I turn the key as far as I can without actually starting the car.
Does the check engine light go out after you start the engine?
Customer: replied 7 years ago.
Yes--there are no warning lights on when the truck is running.

Can you tell me more about the aborting issue? how do they do the test?

Customer: replied 7 years ago.
The truck does fine through the rest of the test, but when he brings the speed up to 50 mph (the rear wheels on a treadmill) the engine surges, or has the powedrops and raises, so he can't keep the speed steady and the CA state software causes the test to abort. I have had the truck in three times and he has tried repeatedly each time. After the first time I replaced the spark plug wires (the truck only has 95,000 miles and had a tuneup a couple of years ago), but it failed again. After the second aborted attempt I took the truck to a mechanic and had the plugs, cap, rotor, air filter, fuel filter, pcv valve and ignition coil. It still had the same problem and aborted again today.

Your problem is going to be one of the following,\

1. A vacuum leak at the intake.

2. Low fuel pressure.

3. Bad iac.

4. A bad egr or stopped up ports in intake.

The first thing I would do would be to clean the iac and egr valve and ports. Do a vacuum leak check on the egr while you have it out to make sure it hold vacuum and the prental opens with vacuum on it.

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