Hello,

I have having trouble with my car starting up roughly since I've bought it. To this point I have replaced the battery, alternator, starter, EGR valve, PCV valve, Oil pressure switch, and more.. and this is just since June.

Anyway, sometimes the car will start up beautifully. Others, it will fire for 5-10 seconds and then finally turn over. Sometimes, it will fire for longer and not turn over. After the starter was replaced it worked great for about a week, then it went back to doing the same thing. When it'* firing and not starting, the RPM gauge reads ~500. Before the starter was replaced, it would fire but read 0 RPMs and wouldn't always start. If I get any RPMs to show then it would start up.

I should also mention that I am in the process of replacing my lower and upper intake manifold gaskets. The whole car was a big oily / coolant mess, so a lot of the parts may have been saturated and some connections may once again be as perfectly clean as when they installed them, but I'm going to clean it up really well after I get the new gaskets in.

Anyway, sometimes when the car starts up I get a SES light. If I drive it with the light on. It runs very rough. Hesitations when accelerating, sometimes even steam from under the engine. The light only comes on about 1/10 times I start the car. If I turn the car off and back on, it has gone away every single time. I had the codes read and here is what I got:

361 EST line not toggling
321 no 18X ignition pulse

I'm going to try cleaning the ignition module with a wire brush, other than that, would these be causing the above symptoms? What else should I be looking at? A donut exhaust gasket is also on order.

I found this forum that I found interesting and seemed to describe my problem incredibly well.. but I don't have all of the codes they mentioned. Thoughts are appreciated. Thanks.

check engine light on 95 bonneville - Automotive Message Forums

I should clarify.. I don't have any problems with it starting after long drives or anything like that. Seems to be random.

Read this thread and tell us if it applies:

https://www.gmforum.com/t258409/

Do you have a supercharger? Please add your year and trim of your vehicle to your signature line. That way when you start asking questions in other areas of the forum, we all have a better idea on how to assist you. Click on "Quick Links" above, go down to "User Control Panel" and then click on "Edit your Signature" It'* pretty straight forward from there.

From the codes, I would check the wiring from the ICM area to the crank sensor and the crank sensor itself. Do you know how frequently the crank sensor code will come back if it'* cleared?

I bought it used in June and assumed it wasn't supercharged, but how can I verify this for certain? All of the parts I have bought up until now for non SC have fit fine, but the upper intake gasket Autozone sold me for it doesn't fit.

I just had the codes read for the first time Friday since I originally bought it when there were a whole list of them. So no I don't know how frequently thy return. I would assume it'* everytime I see the SES light which is a couple times a week on an infrequently used car. So enough to be a problem.

Is the 8th digit of the vehicle'* VIN an "L" or a "1"? If it is a "1" your engine is supercharged.

It'* an L, so no SC. Does anyone know if Autozone will test the ICM? I do not hear any clanking as described in the other thread. But yes, hesitation occurs from stop or very low speeds.