2002 Century misfires on 2 and 5

[Silver Cloud]

Hi,

While getting my water pump replaced, I had the mechanic do a diagnostic. He found occasional misfires on Cylinders 2 and 5 only. I figured that's why there's a rough idle, though it seems to be smooth at higher RPM. The cat is already signalling low efficiency, so I don't want to dump any more unburned fuel into it. The mechanic's estimate was $125 for three new coils, $225 for a module, and $150 for labor. He says the wires and plugs are okay. Since the car will eventually require a lot of expensive repairs that I can't do, I wanted to save some money on this job, especially since replacing the coils and module is one of the easiest jobs on this car. The coil for 2 and 5 was some blue thing, not standard GM. I replaced it with a standard GM part. No change in the rough idle. I ordered a Carquest module on Ebay, but when I installed it the car wouldn't even start. To make sure I hadn't messed something else up, I put the old module back in. It ran like usual. Got all my money back.

So now my decision is where to get a good module for a reasonable price (or I'm open to suggestions from wiser heads). A local Buick dealer wants $455, the MSRP. Summit Racing had one made by Standard Motor Parts for $80 but their site blocked the order because apparently it is not CARB (California) compliant. I emailed Standard and am waiting to hear back. There's quite a selection of them online, priced from under 50 to the 200s. But how do I know if they're any good, or if they're CARB compliant? Is the car able to detect a non-CARB module and refuse to run with it? I'm thinking of asking the mechanic if I can just buy one from him, since he must have a reliable source (he can't afford to install DOA parts), and I 'd rather have him get any markup than anybody else. Any thoughts?

 

[chem_man]

The vehicle itself cannot tell a CARB compliant module from a non-CARB compliant module. California leaves that to the repair facility and emissions inspectors. The only part I know of where there is a difference is the catalytic converter. CARB compliant cat converters have more catalyst metals in them than non-Carb compliant catalytic converters.

If you changed an ignition coil and there was no change in the occasional misfires on cylinders 2 and 5, then there is something else going on - perhaps bad spark plug wires, or as the mechanic suggested, a bad ignition control module (ICM). Or, a defective coil was installed.

Yes, the ignition coils and the ignition control module are quite easy to replace on a Buick Century. I replaced them on our 1999 Century about 6 years ago.

I am finding the best place to purchase quality top of the line auto parts is rockauto.com. However, I do know that they cannot send some parts to California if they are not label compliant relative to California Proposition 65 if I recall correctly. If the part does not have the proper label identifying with respect to Prop 65, they will not send it and cancel the entire order. If you are in Arizona, they have something quite similar.

About the only way around it is to have the parts shipped to a friend or relative that lives outside of California and then have them ship it to you. A hassle I know, but you can still save significant money that way.

As far as the parts go, In your shoes, I would purchase three new ignition coils manufactured by Standard Motor Products that are labeled either as Standard Brand or Blue Streak, and have the part number DR39. You do not want to purchase their value line ignition coil part number DR39T. I would also purchase their Standard Brand ignition coil module, part number LX346. Rockauto sells the ignition coils for ~$21.00 each and the ignition coil module for $~$79.00. Of course you have to pay shipping and sales tax, but that should not be that much. So, for right around $145.00 you can purchase premium quality parts from a reliable source. By the way, Standard Motor Products has been around for over 100 years and they have a very good reputation for manufacturing and selling quality parts.

As an aside, Standard Motor Products does sell a line of "value oriented parts" which is their T series parts. They are of a lesser quality than their non T-series parts and come with a much shorter warranty. Standard's premium line typically comes with a 3 year 36,000 mile warranty, and their Blue Streak line of ignition coils come with a lifetime warranty.

Good Luck!

 

[Silver Cloud]

Thanks. I was wondering what he difference was with the "T" series parts.

 

[02LTD2.0]

I totally agree with @chem_man on the choice of Standard Motor Parts products. I once had misfires and changed all 3 of my coils to Blue Streaks and haven't had any issues since. At the same time that I had changed the coils I had put in a new ICM from Delphi. The Delphi ICM was fine until about a week after the 2 year warranty at which time it gave me a no start situation. Fortunately I had the original ICM in my trunk and was back on the road in a few minutes. I have never had an issue with an SMP product. Can't say the same for Delphi.

 

[chem_man]

I have to agree with @02LTD2.0 about Delphi. On another automotive related forum I frequent, the professional folk have been saying for the last few years that Delphi products overall have gone down in quality, and are no longer a trusted brand to count on.

I put a Delphi fuel pump in our 1999 Buick Century in 2018 when the factory pump started to die. Then two years later (and less than 5000 miles), I had to warrant that Delphi fuel pump because it was dying. If this one starts to die, I'll likely eat the cost and purchase a GM Genuine OEM one if I can find one.

 

[02LTD2.0]

Bosch is another brand that I stay away from on these GM cars. I had a Bosch fuel pump fail in 6 months on a 1997 Olds 88. I replaced it with a Carter and it never gave a problem after that. I don't use Bosch O2 sensors either. I use either GM genuine or Denso.
Just my 2 cents.

 

[CorvairGeek]

I know so much is just the same rebranded junk anymore. I was NEVER a Bosch fan, so the hub falling falling off this pump was quite impressive to me. It was held on with some sort of adhesive when installed on the shaft. Just glad my daughter wasn't in accident when the piece of junk fell apart, and we didn't lose the hub pulley. Surprised it lasted as long as it did from the way it was assembled.