Question : '95 3100 Intermittent Rough Idle

[Century7667]

I've got a '95 Buick Century with the 3100 and about 93,000 on the odometer. I bought it 2 years ago, and it only had 60,000 on it then. So, it had some real light years for driving before I bought it.

The engine has a annoying rough idle when warmed up. Does not sound like a regular miss. I'm thinking a fuel mixture problem. Off idle tip ins can result in some hesitation, but power is great. Cold idle is fine.

As far as I know, the plugs are original, but I don't know if they are platinums or not in 1995.

I did get a CEL after I bought the vehicle, but it was for the knock sensor, which I did replace. I haven't checked for DTCs recently, but there's been no CEL either.

The kicker for me is the intermittent nature of the problem. It can go away and stay a way for a while. This would tend to make me want to discount plugs or a O2 sensor. It just went away recently when the weather turned more humid. Wires?

Anyone else experience something like this?

Thanks,
Ken

[robertisaar]

CHANGE THOSE PLUGS!

16 years is far longer than the plugs were ever meant to last. and i doubt you'll have platinums from the factory, i don't think that was common yet in 95.

assuming that doesn't fix your issues, you may be having an issue with your MAF, tap on it when the engine is running, see if it either fixes or makes the problem appear. if not, clean it anyway, it's probably due.

[Century7667]

I think I might have missed out on the platinums for that car. I also own a '96 Buick Century which I bought new, and it does have the platinums with 142,000 miles. It idles very smoothly. I also have a 2001 S10 with 136,000 on its original set of platinums. Understandably, I'm a real fan of AC platinums... They work!

The MAF sensor is very interesting. When I bought this car used, whoever it was that was doing the maintenance for the car forgot to replace the wingnut on the air filter, hence the screen on the MAF got dirty. What's the best way to clean one of these things? Take it off and spray it down and blow compressed air backwards through it? Do I have to be careful with how much air?

Thanks,
Ken

[robertisaar]

your suggested method of cleaning the MAF sounds like it would work, i'd just be careful with how much air is getting pushed by the sensor, i don't know how much force it takes to kill one of them...

[pocket-rocket]

There is also a can of MAF spray cleaner sold at parts stores. It's pricey, but it's made for cleaning MAFs and will not hurt it. I've read not to use brake clean, but know of people that have that haven't had any problems. MAFs aren't usually cheap, so I got the spray.

[robertisaar]

IIRC, that cleaner is specifically for the sensing element, not the screens... i'd clean the screen as much as possible with compressed air, then use the MAF cleaner on the element.

[Century7667]

IIRC, that cleaner is specifically for the sensing element, not the screens... i'd clean the screen as much as possible with compressed air, then use the MAF cleaner on the element.

Well, I guess I could always pull the sensor out (just 3 screws), then clean the screens.

I'm going to really start paying attention to the weather. I'm wondering if the plug wires have anything to do with what's going on. I've got a set, and I may as well do the plugs too.

Ken