GenVibe - Community for Pontiac Vibe Enthusiasts

I have been having a very annoying issue for the past month or two where the car will shake from a rough idle when the car is in gear at a stoplight or stop sign and the fan kicks on. It idles rougher than I think it should anyway, but when the fan kicks on it is like a back massage. The only thing I could compare it to is my old saturn with a 6 puck clutch and solid motor mounts. Since it gets worse when the fan kicks on, I want to believe the problem is electrical in nature. Any ideas?

were your climate control setting is in defrost mode?

1st---I believe your ECU is a "drive by wire" type...even at idle. NOW the 2003-2004 and AWD thru 2006 are "throttle body" design. Meaning there is a seperate IDLE speed air control unit(ISAC) under the throttle body. FYI- these early engines do have the exact issues you describe. As I have also been dealing with. But yet to totally cure. As this is very noticable when it's winter here and temps are below freeezing. ...I really am not totally sure later engines have eliminated this ISAC valve. Reason I am not sure...they are still running coolant lines to the same spot on the drive by wire engines to speed warm up. You need to look at the "throttle body" and see if there is a 3 wire cionnector to the bottom of the body area. There may be some posts w/pics confirm whether or not it's there. A service manual will point this out. Lastly the MAF has a temperature sensor which could be misinterperating the incoming air temperture...thinking it's warmer than reality. AND do you have an OILED filter like a K&N...these can foul the air temp sensor. And defrost on or off should not hurt the way the engine runs. I do know the 1.8L ECU is programmed to boost the idle speed if the front defrost is on along with other possible electrical loads. AND Do you have a 1.8L or 2.4L engine? A long shot is...maybe your alternator is failing not enough voltage ?

I drive a 2.4L.The engine run in high idle when ECU sense an increase of current draw particulary from:1. Defrost2. PTC heater** if equip with cold weather package. This is also called heater amplifier. This engages when you call for heating when your coolent temp not yet been reach at WOT. It kicks in the electric heat automaticly when you turn on the blower when the cabin air temperature set at the heating range.How PTC heater works is when the ambient is cold, the resistant at the PTC core is low, more current draw and heat up rapidly. Then when the temperature gradually increase till it reach to a preset temperature that the resistance is in maximum while the current inrush is diminished and the heater would shut off.

I know a lot about the 1.8L. Now the 2.4L not as much. But here is what I do know. The 2.4L is the old Camry Rav4 engine. Now been updated to 2.5L. It's been drive by wire for a long time. If your fan was drawing too much power...you'd blow a fuse. So check the simplest thing. Idle voltage with a good digital Voltmeter. You should see 14.2v at normal idle speed. The 1.8L have idle up for the A/C , defrost and rear window defrost because these put a significant load on the "small" 1.8L. In fact all 4 cyl. cars do have idle up for all these...except maybe the rear window. So you should see the idle jump when choosing the A/C or front Def. As I said before, if it's not in the owners' manual the "cleaning of the intake" which the dealer stated....I think should be under warranty...I think. Lastly how loing has it been like this?...since day one? if yes...they can adjust it. Via scanner tool or mechanically at the throttle sensor...somewhere. The ECM tells the fan to kick based on the temp. And on and in the 1.8L calls for "idle up". So lastly could you have an ECM problem? These issues are usually mechanical as descibed above. Where to look? This is what I do not like about "drive by wire". I tnink this should be warranty if under 36k. The "car don't run correctly".

Do you think you should plug in the scanner to see if the car is engine is running too lean/too rich? Or some ground wire came loose? Vaccum hose got unplug?