YACT: GM Quad 4 - rough idle

[JCobra14]

I recently (2 Months ago) purchased a 91' Oldsmobile Calais (Quad 4 engine) from an older couple. The car had 41k miles when I bought it and was in nearly perfect condition considering the age of the car.

I knew at the time of purchase the car would require some work, as it had been sitting unused for long periods of time.. In fact the car only had 1k miles put on it between '00 and '03. In the past few weeks i've noticed the car has gradually developed a rough idle. I've also observed a pretty noticable 'whirring' noise coming from the timing chain cover, on the left side of the engine. It is not noticeable from the interior of the car, but can be heard very clearly with the hood open. I'm wondering if this is normal for this vehicle, or would be indicative of a problem.

Up until this point i've done minor maintenance myself, oil change, front pads & rotors, fuel filter, plugs, just minor stuff, since i have no idea of the past maintenance done to the vehicle. Im curious if anyone here would have any advice for me before i find a tech to service it.

 

[Vette73]

Check the wire boots. Its does not have plug wires persay, but the boots under the coil cover can go bad, check those out.

Also clean the F/I's and throttle body.

Alos this motor was NOT known for being the most quiet of motors. It when forst made put out over 200Hp, so it was designed for power then shifted to a more netural setup, like what you have now.
Its not a bad motor, juts keep up with oil, every 3K, and the other stuff and you should be good.

 

[Excelsior]

I know exactly what is wrong..since I have a 93 Bonneville that had a rough idle too. All I did was get new spark plug wires. Bye bye rough idle.

 

[JCobra14]

Thanks for the reply marlin, when i changed the plugs i looked the boots over, and they looked to be in pretty good shape, clean no corrosion or discoloration or anything.

Forgot to mention in the original post, i ran some fuel injector cleaner through with my last tank of gas.

 

[JCobra14]

Originally posted by: Excelsior
I know exactly what is wrong..since I have a 93 Bonneville that had a rough idle too. All I did was get new spark plug wires. Bye bye rough idle.

Quad 4 engine uses IDI ignition, it doesnt really have spark plug wires in the traditional sense. How bad was the idle excelsior?

 

[Howard]

Originally posted by: JCobra14

Originally posted by: Excelsior
I know exactly what is wrong..since I have a 93 Bonneville that had a rough idle too. All I did was get new spark plug wires. Bye bye rough idle.

Quad 4 engine uses IDI ignition, it doesnt really have spark plug wires in the traditional sense. How bad was the idle excelsior?

IDI ignition?

 

[MikeMike]

u put in fuel treatment and that stuff???? complete tune up of the car, including wires might be necessary

MIKE

 

[JCobra14]

Originally posted by: Howard

Originally posted by: JCobra14

Originally posted by: Excelsior I know exactly what is wrong..since I have a 93 Bonneville that had a rough idle too. All I did was get new spark plug wires. Bye bye rough idle.

Quad 4 engine uses IDI ignition, it doesnt really have spark plug wires in the traditional sense. How bad was the idle excelsior?

IDI ignition?

Hard to describe... but all the ignition components are integrated into a module, that mounts on top of the plugs. So you have no spark plug wires per se... the distributor module sits directly on top of the plugs, with small "boots" connecting the plugs and the "distributor" module...

 

[JCobra14]

Bump --- Pulled the diagnostic codes out of the ECM tonight, only thing i got was 12 - which shows the diagnostic mode is working correctly. So no trouble codes were set