Idle rough at stop lights
#1
Idle rough at stop lights
After cleaning the maf, tb, new plugs, and new pcv my sisters 99 still idles rough at lights. She has a cel w a p0138 code. I am not certain but is this the rear most o2 sensor? Also would a bad o2 sensor cause rough idle at lights( does not stall out)?
I have done an extensive search therefore the remaining questions. TIA!
I have done an extensive search therefore the remaining questions. TIA!
Last edited by domano 68; 09-08-2011 at 08:31 AM.
#2
After cleaning the maf, tb, new plugs, and new pcv my sisters 99 still idles rough at lights. She has a cel w a p0138 code. I am not certain but is this the rear most u2 sensor? Also would a bad u2 sensor cause rough idle at lights( does not stall out)?
I have done an extensive search therefore the remaining questions. TIA!
I have done an extensive search therefore the remaining questions. TIA!
0510
Diagnostic Trouble Code 0510 points to a problem with the Rear Heated Oxygen Sensor. This sensor is mounted in the exhaust stream, just downstream of the Catalytic Converter. When the two Front Heated Oxygen Sensors are operating properly the Rear Heated Oxygen Sensor is not used for engine control operation. It is used to monitor the condition of the Catalytic Converter. If either or both Front Sensors fail the Engine Control Module uses the signal from the Rear Sensor to maintain a correct fuel/air mixture.
DTC 0510 is detected when the signal from the Rear Heated Oxygen Sensor does not reach the expected maximum voltage threshold value. The possible causes include ...
- Harness or connectors (the sensor circuit is open or shorted.)
- Rear Heated Oxygen Sensor
- Fuel pressure
- Fuel injectors
- Intake air leaks
Since you're getting a rough idle I would check the injectors, FPR, and for a vacuum leak.
A bad downstream O2 sensor has no effect on idle, but a faulty upstream O2 sensor would effect it.
Last edited by jholley; 09-08-2011 at 07:50 AM.
#4
If you read the 'Check Engine Light' sticky you could of confirmed that P0138 (0510) does pertain to the downstream O2 sensor after the CAT. This is the info it contains regarding that cel code:
0510
Diagnostic Trouble Code 0510 points to a problem with the Rear Heated Oxygen Sensor. This sensor is mounted in the exhaust stream, just downstream of the Catalytic Converter. When the two Front Heated Oxygen Sensors are operating properly the Rear Heated Oxygen Sensor is not used for engine control operation. It is used to monitor the condition of the Catalytic Converter. If either or both Front Sensors fail the Engine Control Module uses the signal from the Rear Sensor to maintain a correct fuel/air mixture.
DTC 0510 is detected when the signal from the Rear Heated Oxygen Sensor does not reach the expected maximum voltage threshold value. The possible causes include ...
- Harness or connectors (the sensor circuit is open or shorted.)
- Rear Heated Oxygen Sensor
- Fuel pressure
- Fuel injectors
- Intake air leaks
Since you're getting a rough idle I would check the injectors, FPR, and for a vacuum leak.
A bad downstream O2 sensor has no effect on idle, but a faulty upstream O2 sensor would effect it.
0510
Diagnostic Trouble Code 0510 points to a problem with the Rear Heated Oxygen Sensor. This sensor is mounted in the exhaust stream, just downstream of the Catalytic Converter. When the two Front Heated Oxygen Sensors are operating properly the Rear Heated Oxygen Sensor is not used for engine control operation. It is used to monitor the condition of the Catalytic Converter. If either or both Front Sensors fail the Engine Control Module uses the signal from the Rear Sensor to maintain a correct fuel/air mixture.
DTC 0510 is detected when the signal from the Rear Heated Oxygen Sensor does not reach the expected maximum voltage threshold value. The possible causes include ...
- Harness or connectors (the sensor circuit is open or shorted.)
- Rear Heated Oxygen Sensor
- Fuel pressure
- Fuel injectors
- Intake air leaks
Since you're getting a rough idle I would check the injectors, FPR, and for a vacuum leak.
A bad downstream O2 sensor has no effect on idle, but a faulty upstream O2 sensor would effect it.
#6
How much does a set of coil packs go for and where in the fsm does it describe how to test ( what section)?
The car has 70k miles (didnt mention before)
Thanks!
The car has 70k miles (didnt mention before)
Thanks!
Last edited by domano 68; 09-08-2011 at 10:56 AM.
#8
Sounds like you don't know that the downstream O2 sensor just measures the CAT. It can only effect the air/ fuel mixture if one of the upstream O2 is defective along with his downstream O2 sensor that is already defective.
Last edited by jholley; 10-03-2011 at 01:20 PM.
#9
my 96 is doin the same thing except im throwing codes its not the maf tb iacv or coils so i decide to check the fpr and the 2 screws holding it i were striped so i was just gona buy a fuel rail anyone kno how much one is and whee to get one they dont sell em at autozone
#10
my 96 is doin the same thing except im throwing codes its not the maf tb iacv or coils so i decide to check the fpr and the 2 screws holding it i were striped so i was just gona buy a fuel rail anyone kno how much one is and whee to get one they dont sell em at autozone
#13
and my tach is always goin up and down it hasnt worked since i got the car, its an auto, and i cleaned the iacv and yes it does seem to miss while driving but no codes
#14
Just a thought.. It is fairly straight forward to check coils. With engine running at idle, one disconnects each coil connector one at a time reconnecting after test and noting engine behavior changes. Each coil should contribute power, so engine should get rough as any one is disconnected. If no change is detected, it is likely that that coil & plug combination is not contributing power.
#15
i had the same problem on my 95 for a looooong time. switched the ignition coil on two cylinders and the problem was fixed. check your coils. it sounds like its acting like mine did after i got new spark plugs.
#17
Without CONSULT-II
When disconnecting each injector harness connector one at a time, is there any cylinder which does not produce a momentary engine
speed drop?
Yes or No
When disconnecting each injector harness connector one at a time, is there any cylinder which does not produce a momentary engine
speed drop?
Yes or No
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