SnakeyesTx
10-22-2007, 08:36 AM
Well, its getting cool outside finally down here in Houston; been waiting for this for about 3 months now but an ugly monster started poking around again and is making my car run pretty close to god aweful. Last year I had enquired about this and the cause and solutions were sparse. Hopefully by now someone else may have been through this issue and can say "Oh yeah, its this!"
Under normal conditions where temperatures are over 80 degrees F outside this almost never happens. Usually in cooler weather or when it rains outside (so the temperature dips a bit) does this occur.
I'll try to explain this in story form a little bit using a trip to work as an example (much like this morning).
Start the car, release the parking brake, head on my merry little way to the quik-e-mart about a mile away. Leave the car running to let it continue warming up (the neighborhood is still moderately safe to do that suprisingly enough), grab my 1-liter tea, pay, walk outside, and the car does one of two things when I get there :
* Idle is bucking god awefully between 850 down to maybe 200 rpm then the ECU recovers banging it back up to 850, and repeat. The fluctuation is rapid, not a slow change in rpm.
-or-
* Engine stalls because the ECU couldn't recover
Okay, no biggie, get in the car, restart the engine, see the check engine light on (this code always comes up o2 sensor, I guess its a generic code for what ails my engine - I had replaced the o2 sensor and the relay last year when this all started as a precaution) I start driving along with the CEL on, and once the slushbox is in 3rd or 4th I basically pump the pedal a few times (sometimes a dozen times) while I'm rolling along around 40-50mph and the light will shut off and I continue on my way.
Pass a few green lights, weave through a little traffic... all is well.
Slowing down to a red light. Stop. Sometimes engine is bucking when I get to a stop pretty bad where the back end of the car dips with every pulse making me look a little foolish at lights. Sometimes the idle is smooth at the stop. Either way, if I'm stuck at the light for more than 60 seconds or so, the CEL comes back on, the idle goes bonkers again, sometimes stalling the engine. If it doesn't stall, I pop into neutral give the engine a rev or four and the light usually goes away and the idle is trying to normalize again. If the light turns green before I can clear the light, I continue in Drive but now the car feels really sluggish until I do the 40-50 pedal pulse thing to clear the light.
This could happen at every red light, which is pretty annoying.
Now, this never happened past last year. The engine was replaced last August because of a bad head-gasket and head crack. The old engine ran fine, no lights, no issues for 15x,000 miles or so and averaged 22mpg with the a/c on. This new engine at best gets 14.9mpg in more city-style driving (rarely do I get to drive on the highway for very long to effect overall milage). I wanted to suspect the throttle position sensor (as it effects idle speeds on some vehicles, and even shift points on some chryslers), but it doesn't explain why it only happens in cooler temperatures outside. So... what gives?
-Almost non related note : Acceleration and power seems to be a LOT better when the air is cooler outside and I don't have the CEL on or being stuck at lights for the idle issue-
Under normal conditions where temperatures are over 80 degrees F outside this almost never happens. Usually in cooler weather or when it rains outside (so the temperature dips a bit) does this occur.
I'll try to explain this in story form a little bit using a trip to work as an example (much like this morning).
Start the car, release the parking brake, head on my merry little way to the quik-e-mart about a mile away. Leave the car running to let it continue warming up (the neighborhood is still moderately safe to do that suprisingly enough), grab my 1-liter tea, pay, walk outside, and the car does one of two things when I get there :
* Idle is bucking god awefully between 850 down to maybe 200 rpm then the ECU recovers banging it back up to 850, and repeat. The fluctuation is rapid, not a slow change in rpm.
-or-
* Engine stalls because the ECU couldn't recover
Okay, no biggie, get in the car, restart the engine, see the check engine light on (this code always comes up o2 sensor, I guess its a generic code for what ails my engine - I had replaced the o2 sensor and the relay last year when this all started as a precaution) I start driving along with the CEL on, and once the slushbox is in 3rd or 4th I basically pump the pedal a few times (sometimes a dozen times) while I'm rolling along around 40-50mph and the light will shut off and I continue on my way.
Pass a few green lights, weave through a little traffic... all is well.
Slowing down to a red light. Stop. Sometimes engine is bucking when I get to a stop pretty bad where the back end of the car dips with every pulse making me look a little foolish at lights. Sometimes the idle is smooth at the stop. Either way, if I'm stuck at the light for more than 60 seconds or so, the CEL comes back on, the idle goes bonkers again, sometimes stalling the engine. If it doesn't stall, I pop into neutral give the engine a rev or four and the light usually goes away and the idle is trying to normalize again. If the light turns green before I can clear the light, I continue in Drive but now the car feels really sluggish until I do the 40-50 pedal pulse thing to clear the light.
This could happen at every red light, which is pretty annoying.
Now, this never happened past last year. The engine was replaced last August because of a bad head-gasket and head crack. The old engine ran fine, no lights, no issues for 15x,000 miles or so and averaged 22mpg with the a/c on. This new engine at best gets 14.9mpg in more city-style driving (rarely do I get to drive on the highway for very long to effect overall milage). I wanted to suspect the throttle position sensor (as it effects idle speeds on some vehicles, and even shift points on some chryslers), but it doesn't explain why it only happens in cooler temperatures outside. So... what gives?
-Almost non related note : Acceleration and power seems to be a LOT better when the air is cooler outside and I don't have the CEL on or being stuck at lights for the idle issue-