Weird idle and strange bogging
#1
07-10-2006, 11:01 PM
Weird idle and strange bogging
A 2000 coupe.
Strange idle issues.
When cold, it seems like the car starts and runs fine.
It's only when the car is driven, then parked, then started again until the problem emerges.
I took apart the throttle body area, blew air through the IACV and the EVAP lines...not clogged.
After doing this, I started the car up and it idled a little low...almost died, caught itself and continued.
No engine codes.
02 sensor trims (short term are 5% or lower)
Any ideas? Maybe a bad IACM?
Strange idle issues.
When cold, it seems like the car starts and runs fine.
It's only when the car is driven, then parked, then started again until the problem emerges.
I took apart the throttle body area, blew air through the IACV and the EVAP lines...not clogged.
After doing this, I started the car up and it idled a little low...almost died, caught itself and continued.
No engine codes.
02 sensor trims (short term are 5% or lower)
Any ideas? Maybe a bad IACM?
#2
07-11-2006, 03:11 AM
RE: Weird idle and strange bogging
mine does the same thing, runs great cold when it warms the idle is everywhere and car wants to die. whats an iacm?
#3
07-11-2006, 03:30 AM
RE: Weird idle and strange bogging
If you have a scan tool that can check live sensor data then when the car warms up check the reading for the coolant temperature sensor. I'm thinking that your coolant temp sensor is telling the computer that the engine is cold all the time. WHen the engine is warm, the computer is still giving the engine the fuel requirements for a cold engine which is too much fuel. Really what is an IACM? Is it the same thing as an IACV?
#4
07-11-2006, 09:52 AM
RE: Weird idle and strange bogging
ORIGINAL: AgentofDarkness
If you have a scan tool that can check live sensor data then when the car warms up check the reading for the coolant temperature sensor. I'm thinking that your coolant temp sensor is telling the computer that the engine is cold all the time. WHen the engine is warm, the computer is still giving the engine the fuel requirements for a cold engine which is too much fuel. Really what is an IACM? Is it the same thing as an IACV?
If you have a scan tool that can check live sensor data then when the car warms up check the reading for the coolant temperature sensor. I'm thinking that your coolant temp sensor is telling the computer that the engine is cold all the time. WHen the engine is warm, the computer is still giving the engine the fuel requirements for a cold engine which is too much fuel. Really what is an IACM? Is it the same thing as an IACV?
Immediately after starting the car the idle dropped and stumbled.
My understand of the IAC system is that you have an IAC valve which is the actual nipples and a motor or switch that allows air to pass through.
It may all be considered the IACV though. Not sure. Not too familiar with these cars.
#5
07-11-2006, 10:34 AM
RE: Weird idle and strange bogging
Can you detail exactly what happens? When will the car stall out? What happens before? Everything you can tell me would help to figure out whats going on. How does the O2 sensor readings look right before it stalls out? Normal would be oscillating b/w 0 and 1v but the car has to be hot for the O2 sensors to give readings.
#6
07-11-2006, 10:41 AM
RE: Weird idle and strange bogging
ORIGINAL: AgentofDarkness
Can you detail exactly what happens? When will the car stall out? What happens before? Everything you can tell me would help to figure out whats going on. How does the O2 sensor readings look right before it stalls out? Normal would be oscillating b/w 0 and 1v but the car has to be hot for the O2 sensors to give readings.
Can you detail exactly what happens? When will the car stall out? What happens before? Everything you can tell me would help to figure out whats going on. How does the O2 sensor readings look right before it stalls out? Normal would be oscillating b/w 0 and 1v but the car has to be hot for the O2 sensors to give readings.
I have a somewhat limited view of it.
At idle, it appears that the primary 02 sensor likes to wiggle around 800mV or so. Certainly below 1V.
I don't know the mV converstion to AF but I'm assuming it's near stoic. The 02 sensor is not throwing any heater codes or anything to indicate that it is going bad. My co-worker had an 02 sensor replaced a few months ago...but does not know which one it was. So there is a 50/50 chance that the primary sensor is new.
When I was in the car, we started it half-warm. Coolant temp was probably around 140 at the time. It idled a little under 1k. Probably around 800. Seemed normal...then idle would jump around and drop, if you gave it gas, it would correct itself and idle normally.
Perhaps what I was seeing was the transition from open loop to closed loop?
Maybe when this happens and the IACV switches, it created some sort of fuxor?
#7
07-11-2006, 11:37 AM
RE: Weird idle and strange bogging
does it have ac. if so, when you get it warmed up and idling correctly, turn on the ac.
what happens to the idle.
if no ac, then turn on the lights.
what happens to the idle?
does it return to it's correct value - 750 to 800 , i think.
what happens to the idle.
if no ac, then turn on the lights.
what happens to the idle?
does it return to it's correct value - 750 to 800 , i think.
#8
07-11-2006, 12:09 PM
RE: Weird idle and strange bogging
.5v is what is known as the threshold for the O2 sensor. Any voltage above .5v indicates a rich mixture and any voltage under .5v indicates a lean mixture. The primary O2 sensor (the first one) should go between lean and rich. The way the computer works, it cannot create a stoic mixture so what it does is look for the when the mixture is lean then adds fuel. When it adds fuel the mixture become rich so it takes away fuel. THrough this cycle you get a stoich mixture. The O2 sensor should not be around .8v, it should switch between lean and rich. It should pretty much look like a sine wave. The x-axis of this sine wave should be the .5v line. If your confused about that at all just tell me whats confusing and i will try to explain it. The second thing is if the first O2 sensor is showing a constant .8v after the O2 sensor has warmed up then there is a definate problem b/c it should not be doing this. In fact, you would prolly have a check engine light. Next time you have the scan tool have some1 remove a vacuum line from any where on the engine. This will put more air into the engine and the O2 sensor should lean out (go towards 0v). If this happens than the O2 sensor is fine. If this does not happen, either the O2 sensor has not yet heated up or there is a problem with the O2 sensor. What i just realized is that at idle you should have a slightly rich A/F mixture so the first half of this post might not be correct. However, the test for the O2 sensor should still be valid. If the engine is completly cold, liek when you turn it on in the morning, will it ever die out? Also, when you anticipate that the engine is about to die out, check how many steps the IACV is at. The computer should be increasing the steps when you feel the car is dying out. If the computer is increasing the steps but the motor is not moving then you might just have a bad motor. I wouldn't be so quick to change the motor, but that is also a possibility. The problem here is that i still don't know exactly what it takes for your engine to die out. You say that it only happens when you start the car warm, but what about when you start the car cold and let it warm up. After it is warmed up will it die out at idle? Remember that when the car is completly warmed up the coolant temp should be around 200 F, but it looks like your car is pretty close to that so you can rule out a bad coolant temp sensor.
#10
07-11-2006, 06:29 PM
RE: Weird idle and strange bogging
ORIGINAL: AgentofDarkness
.5v is what is known as the threshold for the O2 sensor. Any voltage above .5v indicates a rich mixture and any voltage under .5v indicates a lean mixture. The primary O2 sensor (the first one) should go between lean and rich. The way the computer works, it cannot create a stoic mixture so what it does is look for the when the mixture is lean then adds fuel. When it adds fuel the mixture become rich so it takes away fuel. THrough this cycle you get a stoich mixture. The O2 sensor should not be around .8v, it should switch between lean and rich. It should pretty much look like a sine wave. The x-axis of this sine wave should be the .5v line. If your confused about that at all just tell me whats confusing and i will try to explain it. The second thing is if the first O2 sensor is showing a constant .8v after the O2 sensor has warmed up then there is a definate problem b/c it should not be doing this. In fact, you would prolly have a check engine light. Next time you have the scan tool have some1 remove a vacuum line from any where on the engine. This will put more air into the engine and the O2 sensor should lean out (go towards 0v). If this happens than the O2 sensor is fine. If this does not happen, either the O2 sensor has not yet heated up or there is a problem with the O2 sensor. What i just realized is that at idle you should have a slightly rich A/F mixture so the first half of this post might not be correct. However, the test for the O2 sensor should still be valid. If the engine is completly cold, liek when you turn it on in the morning, will it ever die out? Also, when you anticipate that the engine is about to die out, check how many steps the IACV is at. The computer should be increasing the steps when you feel the car is dying out. If the computer is increasing the steps but the motor is not moving then you might just have a bad motor. I wouldn't be so quick to change the motor, but that is also a possibility. The problem here is that i still don't know exactly what it takes for your engine to die out. You say that it only happens when you start the car warm, but what about when you start the car cold and let it warm up. After it is warmed up will it die out at idle? Remember that when the car is completly warmed up the coolant temp should be around 200 F, but it looks like your car is pretty close to that so you can rule out a bad coolant temp sensor.
.5v is what is known as the threshold for the O2 sensor. Any voltage above .5v indicates a rich mixture and any voltage under .5v indicates a lean mixture. The primary O2 sensor (the first one) should go between lean and rich. The way the computer works, it cannot create a stoic mixture so what it does is look for the when the mixture is lean then adds fuel. When it adds fuel the mixture become rich so it takes away fuel. THrough this cycle you get a stoich mixture. The O2 sensor should not be around .8v, it should switch between lean and rich. It should pretty much look like a sine wave. The x-axis of this sine wave should be the .5v line. If your confused about that at all just tell me whats confusing and i will try to explain it. The second thing is if the first O2 sensor is showing a constant .8v after the O2 sensor has warmed up then there is a definate problem b/c it should not be doing this. In fact, you would prolly have a check engine light. Next time you have the scan tool have some1 remove a vacuum line from any where on the engine. This will put more air into the engine and the O2 sensor should lean out (go towards 0v). If this happens than the O2 sensor is fine. If this does not happen, either the O2 sensor has not yet heated up or there is a problem with the O2 sensor. What i just realized is that at idle you should have a slightly rich A/F mixture so the first half of this post might not be correct. However, the test for the O2 sensor should still be valid. If the engine is completly cold, liek when you turn it on in the morning, will it ever die out? Also, when you anticipate that the engine is about to die out, check how many steps the IACV is at. The computer should be increasing the steps when you feel the car is dying out. If the computer is increasing the steps but the motor is not moving then you might just have a bad motor. I wouldn't be so quick to change the motor, but that is also a possibility. The problem here is that i still don't know exactly what it takes for your engine to die out. You say that it only happens when you start the car warm, but what about when you start the car cold and let it warm up. After it is warmed up will it die out at idle? Remember that when the car is completly warmed up the coolant temp should be around 200 F, but it looks like your car is pretty close to that so you can rule out a bad coolant temp sensor.
.5V is right around stoich...so the car shoots for that, but overshoots and corrects and so forth. So if I log the 02 sensor voltage I should see a sin wave that hugs .5V.
At idle it sits at about .8V but can vary up to .2 or .3V
If the 02 sensor is bad, should it be throwing a heater code for slow response or...shouldn't the trims be way off?
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