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Dave Nova
Dave Nova, Buick Technician
Category: Buick
Satisfied Customers: 1808
Experience:  ASE Master Certification. GM World Class Certification
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Getting P0301 code. Changed plug, ignition wire, coil pack,

Customer Question

Getting P0301 code. Changed plug, ignition wire, coil pack, and ignition module under the coil pack - still getting P301. If I accelerate RPM, get a constant speed variation.
JA: How old is the transmission? Have you checked the fuel filters?
Customer: This is at an idle in park. Have not checked filter, but will put a pressure gauge on fuel rail.
JA: What is the model/year of your Buick?
Customer: 1999 Century
JA: Are you fixing your Century yourself? What have you tried so far?
Customer: Yes, as I said, I changed plug, wire, coil pack and ignition module.
JA: Anything else you want the mechanic to know before I connect you?
Customer: That is all I can tell you at present
Submitted: 7 months ago.
Category: Buick
Expert:  david craig replied 7 months ago.

Hi Im David, thanks for visiting the site. do you have a noid test light?

Customer: replied 7 months ago.
No, what is that? I do have a timing light I use just to see if there is a spark being fired. I could see missing flashes from the timing light when clamped around the #1 wire. That was making me think it has to be electrical. This coil fires for both #1 and #4 (waste spark) but I only ever see the P0301 code for #1.
Customer: replied 7 months ago.
BTW - a year ago I had the same code - changed plugs and wires. A month later it popped up again. Changed the coil pack, Then I did not have it for a year until recently. Swapped coil pack again, but no change. Then changed plug and wire again. Still not change. That is when I changed the ignition module under the coil packs. Still will not clear, sets code again after a few minutes of idle. If I give it gas (in park) it surges.
Customer: replied 7 months ago.
No hurry on this - can now sitting for a month - it is an extra vehicle. I am leaving home now for a bit. Talk later.
Expert:  david craig replied 7 months ago.

a noid light checks the fuel injector getting a pulse command from the computer. i imagine you can use a test light. but you need to hook it up to the #1 fuel injector connector to both contacts. if the computer is telling it to pulse, the light will rapid flash

Customer: replied 7 months ago.
I can probably check that with my Fluke meter or an oscilloscope? I happen to be an electrical technician.
Expert:  david craig replied 7 months ago.

not a fluke meter you cant. maybe a scope.

Customer: replied 7 months ago.
Back again. So I am to look for an injector pulse? Just voltage at the injector, or do I need to measure current? I do have a hall-effect device that can measure DC current as well as AC on the scope. But will that prove the injector is opening on the pulse? I probably will not be able to get to check this for maybe a week. How long do you keep these cases open?
Expert:  david craig replied 7 months ago.

these only stay open for 6 days. its best you you run to harbor freight and buy a cheap noid light set.

Expert:  david craig replied 7 months ago.

just checking in to see how its going

Customer: replied 7 months ago.
Just got the noid light this weekend. Hope to be able to test it soon. I do not have a garage, so all work is outside in the weather, which has been very cold lately. Was sunny today, but had to go out of town. Hope to find time soon.
Expert:  david craig replied 7 months ago.

ok, well keep me in the loop