non-Caddy info needed

[Rhino 21150]

This is a great club and a great forum. Is there one this good for my cheapo Cavalier? I am on several and the answers are ALL related to increasing the power and handling. I want to fix the rough idle.
Please, lets not restart the reason for selling a car THAT PROVIDES HALF MY INCOME.

[Bill Gauch]

I would think you would do well in a general automotive forum. Alternately, you could always try asking here:
http://www.jalopyjournal.com/forum/index.php? TARGET=_blank>http://www.jalopyjournal.com/forum/index.php?

These guys seem have a combined knowledge of anything mechanical-automotive. Just make sure you post an intro (dedicated forum for that) about yourself first before you ask a question. I might also include "somewhat OT" in the subject line, as that site is a rodding site focused more on "traditional" rods, but they have over a million posts and tons of users.

Alternately, what is this rough idle problem you have? Also, what are the specs on it (year, FI or carb, etc.)?

[Rhino 21150]

1994 Cavalier, 2.2l, 136K, tbi, few if any repairs to engine, new plugs about 5K back. New filters and oil change. It has always idled roughly, makes the coffee spill out of the cup holder. Engine runs very smooth (for cheapo) at all other speeds. Plenty of power (for cheapo), good (30+ mpg) on gas. The only thing I can think of is the temp gauge reading 160. It has a new t-stat, 195, not leaking anything yet.

[Bill Gauch]

So, no matter what, the temp gague never reads higher than 160, even with the higher temp tstat in there? Sounds like you have a bad tstat or temp sensor. If it is sending bad data to the computer, though, I would expect you would also get bad gas milage. Have you tried pulling the air cleaner/housing off the intake side of the TB and spraying the heck out of it with electrical cleaner (carb cleaner may work also). There should be a sensor in there which can build up a little residue. When you say it has always idled rough, do you mean since new or new-to-you? I would also suspect the plugs/wires even though you just replaced them. You can try pulling one plug wire at a time with the engine running to make sure evey cylinder is firing.

Finally, if the only reason the rough idle bothers you is that it makes the coffee spill out of the cup holder, you could try putting it in an actual cup. It has to be easier to drink that way. Ehh... To each his own.

[Bill Gauch]

Oh yeah, one other suggestion/question... Have you tried pulling the engine codes? Some box-store autoparts places like Autozone will pull the codes for you for free, but I wanna say that you probably have an ODB-I, so, with an analog multi-meter, you should be able to pull the codes yourself. If its ODB-II, though, just find someone to plug a scanner into it.

[Porter 21919]

Use a vacuum gauge and get some readings:

http://autorepair.about.com/cs/troubleshooting/a/aa112401a_2.htm TARGET=_blank>http://autorepair.about.com/cs/troubleshooting/a/aa112401a_2.htm

http://marinemechanic.com/site/page26.html TARGET=_blank>http://marinemechanic.com/site/page26.html

http://www.secondchancegarage.com/public/186.cfm TARGET=_blank>http://www.secondchancegarage.com/public/186.cfm

Start with some compression readings first.

HTH,

Porter

[Mike #19861]

 The 160 reading is somewhat telling. It should be in the region of what the thermostat setting is. But it could be a defective sensor or gauge. There are as many as 3 temp sensors on an engine, but many use 2. One is for the gauge, and the other for the ECM. If there is a third, it will be for the cooling fans. But most often, the ECM controls the cooling fans.

 If you have access to a scanner, you can read the engine temps through that. It will be the temperature the ECM sees and you can verify the actual temperature of the engine. If it is too low, fuel consumption will be high, and it could be part of the reason for a rough idle.

 And clean out the throttle body. Prop open the throttle blade, and spray in some choke cleaner. Use an old toothbrush to clean the back side of the throttle plate and the bore, flush it clean with more choke cleaner.

 Remove the IAC motor, and clean the pintle and spreay in more choke cleaner into the passage.

 Check for vacuum leaks, particularly in the PCV and MAP sensor systems. That can cause an elevated and rough idle.

 If that does not help, check the condition of the plugs. Focus on any cylinder that exhibits abnormal plug wear or fouling. Do a compression test as well. 4 cylinder engines will not tolerate as much differential as a V-8 will. It should be in the 140 psi range for all cylinders.

 Mike