HELP '98 Cav RS 2.2 SOHC, bad gas mileage, rough idle

[BlackJack]

**already used "search" with no results, or used wrong keywords**

ok, normally I wouldn't bother, but a nice young lady in my car club is having trouble with her '98 Cav RS 2.2 (SOHC) automatic.

I can fix 3400's all day long but never messed with a GM 4-banger.

Symptoms - rough idle (shaking) but smooths out when just a little gas is applied, and gets unusually crappy gas mileage.

My suspicions are:

1) bad/dirty MAF (inside the TB?)
2) dirty injectors
3) old/fouled plugs.

Gave her a can of Sea Foam to run through with half a tank of gas, then if it doesn't iron itself out, I'm going to pull the plugs. If those are clean/normal, then I'm going to pull down the TB (MAF) and work it over. That fails, I guess it's the injectors, and that's gonna suck for her.

Anyone else have experience with this problem, or have suggestions of other things to check?

[sburke]

Could be the MAP sensor or the EGR system too. I had a very similar problem on my 2.4 The engine recirculates a little bit of exhaust gas to save on emissions it does this by a sensor and a very small tube. I'm sure you know all of that, but to the point.....my tube had a small tear in it. I just replaced it and zip tied both ends so that it would not come off or flex and tear. On my engine it is located in the middle of the throttle body. Come by some time and I will show you or we can address it at the meet on sunday.

-sburke

[sburke]

Also, I was getting a diag code (check engine). If she is not getting that then I would go with new plugs.

[maxximuss1]

in my experiance with j bodies they always have rough idles. i tried changing out my plugs to fix that problem to. i thought i was habing a misfire in my engine. the car ran beter but it still idles rough. a friend of mine got his 2.4 96 sunfire gt up to 300hp for racing but the injectors were to much for the car and the engin was running way to ritch and his exaust cloged with soot. the car wouldnt start at all cause there was no where to send exhaust. his engin still runs rough now, when he gets it to run. besides checking your engine mounts the only thing that would correct that problem would be to ballance the engine lol. as for the bad gas milage i get about 10km/l city and he got about 100 miles to the tank lol.the factory specs are about 15-16 hwy, the more you do to those things the more they eat up.
and as for what sburke said i have no codes come up and never have. and the only reliable problem my friend has is the intake sensor. but i dont know much about computers. and my friend other friend had that tube for recirculating the exhaust taken off and his ran fine. i think he fixed it now.
any ways hope some one finds this usefull. i know that black jack prob wont see this cause im a bit late

[DaFlyinSkwirl]

Originally Posted by BlackJack

**already used "search" with no results, or used wrong keywords**

ok, normally I wouldn't bother, but a nice young lady in my car club is having trouble with her '98 Cav RS 2.2 (SOHC) automatic.

I can fix 3400's all day long but never messed with a GM 4-banger.

Symptoms - rough idle (shaking) but smooths out when just a little gas is applied, and gets unusually crappy gas mileage.

My suspicions are:

1) bad/dirty MAF (inside the TB?)
2) dirty injectors
3) old/fouled plugs.

Gave her a can of Sea Foam to run through with half a tank of gas, then if it doesn't iron itself out, I'm going to pull the plugs. If those are clean/normal, then I'm going to pull down the TB (MAF) and work it over. That fails, I guess it's the injectors, and that's gonna suck for her.

Anyone else have experience with this problem, or have suggestions of other things to check?

firstly, the 2.2 is a pushrod OHV, not ohc. Its cam is in the block, just like a V8, V6, or any other pushrod engine.

shaking could be associated with transmission trouble or a motor mount being loose, I'd say check those out and make sure they're nice and tight.

There is no MAF sensor on the OHV, but there is a MAP sensor. Unfortunately, the MAP sensor has nothing to do with the fueling of J-bodies since they're alpha-n (similar to Speed Density tuning, but more primitive) the only thing that would be effected by the MAP sensor being bad would be spark advance

..which could still lead to the crappy gas mileage. I'd say start with mechanical basics (like you said) check the plugs and wires out. Don't forget to think about the fuel filter as that may also be needing replacement.

How bad is crappy gas mileage? I noticed sometimes people think they're getting bad mileage when really they're just driving a LOT. Have her trip odo her next tank of gas and see how long it truly lasts. Have her try to avoid excessive periods of time letting the car idle so the reults are true to form.

[10pracing]

Give the thing a tune up and have the injectors professionally cleaned. Simple.