Erratic idle
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Senior User
Joined: Aug 2014
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From: Florida
Erratic idle
97 shortie. 3.0 245,000 miles.
I've already cleaned the throttle body and the idle air control valve. Throttle position sensor reads 5 volts, good ground, and a smooth voltage increase from idle to wide open throttle and back down.
Which of these codes is most likely to cause erratic idle? Mostly in the morning.
P0340 Camshaft position sensor.
P1443 Evaporative purge flow sensor.
P0401 Insufficient EGR flow.
P0171 Air/fuel ratio is too lean or rich for PCM to correct.
I doubt it's number 1, and number 4 seems too general to be any use.
I'm leaning toward number 3. Seems I read somewhere that the tube from the exhaust gets plugged up.
This started when I disconnected a plug from the blue air bag box to get rid of that beeping. Coincidence?
Any thoughts?
I've already cleaned the throttle body and the idle air control valve. Throttle position sensor reads 5 volts, good ground, and a smooth voltage increase from idle to wide open throttle and back down.
Which of these codes is most likely to cause erratic idle? Mostly in the morning.
P0340 Camshaft position sensor.
P1443 Evaporative purge flow sensor.
P0401 Insufficient EGR flow.
P0171 Air/fuel ratio is too lean or rich for PCM to correct.
I doubt it's number 1, and number 4 seems too general to be any use.
I'm leaning toward number 3. Seems I read somewhere that the tube from the exhaust gets plugged up.
This started when I disconnected a plug from the blue air bag box to get rid of that beeping. Coincidence?
Any thoughts?
Posting Guru
Joined: Jul 2004
Posts: 2,416
Likes: 1
From: Mitchell, SD
P0340 Camshaft position sensor.
Your cam sensor is going out, I would replace this before it dies completely before it leaves you stranded. This is where the computer gets its info to fire the coil.
P0171 Air/fuel ratio is too lean or rich for PCM to correct.
This also indicate a vacuum leak which would also cause the throwing of the EGR flow code and possibly the Evap code.
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
Hot unplugging of PCM connected components can cause false codes and damage expensive PCMs.
Disconnect both battery cable leads and touch them together for 10 seconds to bleed off charge in system capacitors. Dumps volatile stored codes memory, also learned parameters for your systems sensor variations and drive style.
Check to see what codes come back.
Any of those common Aero codes will cause idle issues.
Disconnect both battery cable leads and touch them together for 10 seconds to bleed off charge in system capacitors. Dumps volatile stored codes memory, also learned parameters for your systems sensor variations and drive style.
Check to see what codes come back.
Any of those common Aero codes will cause idle issues.
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Senior User
Joined: Aug 2014
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From: Florida
[QUOTE=93nighthawk;17141855]Your cam sensor is going out, I would replace this before it dies completely before it leaves you stranded. This is where the computer gets its info to fire the coil.
Do you mean the black cap with the three wires? I have an old one from when I had to replace the complete assembly because it was leaking oil up the shaft seal.
I read somewhere on this site that the engine would run even without the cam sensor.
Do you mean the black cap with the three wires? I have an old one from when I had to replace the complete assembly because it was leaking oil up the shaft seal.
I read somewhere on this site that the engine would run even without the cam sensor.
Cross-Country
Joined: Aug 2015
Posts: 78
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Nah,baby,Nah! Vacuum leaks appear and disappear with engine temp a lot of times. Do n't rule out vacuum leaks OR MAF sensor dirty or bad. don-ohio
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Senior User
Joined: Aug 2014
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From: Florida
Bought some CRC MAF sensor cleaner and sprayed the MAF sensor as per instructions.
Changed the cam sensor with the one I had on hand. Like to never got the engine cover back on.
Replaced the Evaporative Purge Valve. Evidently this is a pretty generic part. Even Walmart sells it.
Seems to be running okay now.
Had the codes checked again. Only one.
P0402 EGR flow at idle fault.
Pretty much the same as P0401 insufficient EGR flow.
This vehicle rarely goes more than 5 miles from the house.
I think I'm done.
Changed the cam sensor with the one I had on hand. Like to never got the engine cover back on.
Replaced the Evaporative Purge Valve. Evidently this is a pretty generic part. Even Walmart sells it.
Seems to be running okay now.
Had the codes checked again. Only one.
P0402 EGR flow at idle fault.
Pretty much the same as P0401 insufficient EGR flow.
This vehicle rarely goes more than 5 miles from the house.
I think I'm done.
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