'99 Grand Prix - Check Engine & Shaking On Start-up

[josiahpr83]

Hello all,

I have a '99 Grand Prix SE and am currently having an issue. So far, on only cold start-ups the check engine light will start blinking and the car will shake. If I apply gas the shaking will stop. However, as soon as it gets back to idling, the shaking starts back up. The car will stop shaking after it has been driven for awhile, the time that it takes appears random, however, it could be stopping after the car has warmed up. This problem just started occuring and does not occur on every start-up.

My only thought so far is maybe an oxygen sensor?

I would love to hear anyones thoughts and or suggestions, regarding this issue.

On a second note, is there a way for this model of GP to display the error/computer code without a third party reading device? If there was, I would love to know what code the computer is displaying from the check engine light.

Thanks for any assistance!

-Josiah

[GTP Dad]

Check the Idle Air Control Motor. It could be dirty and not allowing enough air for the fuel mixture on start-up. To clean it simply remove it from the throttle body, spray it with carb cleaner, allow to dry and reinstall. You may find a code for the O2 sensor due to the mixture being too rich, that will throw it off and cause a code. If it is too rich for too long it can damage the sensor and it will need to be replaced. Also, you cannot read the codes in an OBDII system without a scanner.

[deb0704us]

This happened to me in my '98 GP GT the other day. Hubby had changed the oil one night, and then the car sat in garage for a day or two. I go out to start it up two days later. The car was really shaking, on start up and pulling out of the garage, and the Service Engine Soon was flashing. Went to Plan B, took my daughter's car instead. Then hubby came home to try my car and said "it's fine". So I took it to autozone to read the code. The code meant Misfire in Cylinder 5. They said it probably needs a tune up and it could be plugs or plug wires. The light has gone off and it hasn't happened since. Hubby looked at the plugs and said everything looks fine. Now I drive on pins and needles because I'm afraid it's going to happen again.

[99ggp]

I have a 99 GP SE that had the same problems. It was the fuel injectors. I had a mechanic replace one that was bad but it only fixed it for a while, then another went bad so I replaced the rest myself. After replacing them it runs great. There pretty simple to change yourself but it takes a lot of time if youve never done it before but you can save a lot of $. I borrowed a scanner from a big autoparts store for free. Misfire codes are P 300's. P301 for cylinder 1 misfire etc.