98 3.0 rough idle

stampsc31757 · 12-28-2012, 10:14 PM

I need help with this problem as smog is coming up in a couple of weeks and need to get this sorted. It runs fine if the ecu has been reset. Once it has had time to read the sensors for about 15-20 miles it starts to have a rough idle. The idle air control valve, egr valve, dpfe sensor, egr solenoid, spark plugs, plug wires have all been replaced. I have looked for vacuum leaks and dont find any. I am running out of ideas. It only idles rough once it is warmed up. I dont know if it could be the coolant temp sensor. My gauge reads perfectly. Please help. I do not know where to take it next.

monsterchuck · 12-29-2012, 07:03 PM

Any codes? The check engine light does not need to be on for a code to be in the system. If you're disconnecting the battery to reset the PCM, you may have to drive it a few times to get anything to show up.

stampsc31757 · 12-29-2012, 07:13 PM

I know you have to drive it around after you reset the ecu. It still has a rough idle. I dont have a vacuum leak unless its in the brake booster or an area like that. I still do not have any codes pulling up. Its been about 50-60 miles of both highway and city driving. No codes stored or pending. I just replaced the intake air temp sensor, fuel filter, and pcv valve. I haven't reset the ecu in a couple of days and i do get out and drive it around for about 15-20 miles a day to try to get the ecu to throw a code. It doesn't have any power loss, cold idle is great, normal driving is great. Just a very rough idle once it is warmed up. It does it stopped at stop signs while in drive or neutral, as well as in park. I haven't checked reverse or any of the other gears. I did put some fuel system cleaner in to see if that can clear it up. I also just put 91 in it to see if that helps any. Any help will be greatly appreciated.

stampsc31757 · 12-31-2012, 01:31 AM

I found my problem. The vacuum line going from the valve to the solenoid was mixed up with another vacuum line.

12-28-2012, 10:14 PM	#1
stampsc31757 New Member Join Date: Dec 2012 Posts: 9 Rep Power: 0	98 3.0 rough idle I need help with this problem as smog is coming up in a couple of weeks and need to get this sorted. It runs fine if the ecu has been reset. Once it has had time to read the sensors for about 15-20 miles it starts to have a rough idle. The idle air control valve, egr valve, dpfe sensor, egr solenoid, spark plugs, plug wires have all been replaced. I have looked for vacuum leaks and dont find any. I am running out of ideas. It only idles rough once it is warmed up. I dont know if it could be the coolant temp sensor. My gauge reads perfectly. Please help. I do not know where to take it next.

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12-29-2012, 07:03 PM	#2
monsterchuck Member Join Date: Jan 2010 Location: Michigan Posts: 156 Vehicle Year: 1984 Vehicle Make: Volkswagen Vehicle Model: Jetta I use this vehicle for: Prius-shaming fuel mileage Rep Power: 11	Any codes? The check engine light does not need to be on for a code to be in the system. If you're disconnecting the battery to reset the PCM, you may have to drive it a few times to get anything to show up.

12-29-2012, 07:13 PM	#3
stampsc31757 New Member Join Date: Dec 2012 Posts: 9 Rep Power: 0	I know you have to drive it around after you reset the ecu. It still has a rough idle. I dont have a vacuum leak unless its in the brake booster or an area like that. I still do not have any codes pulling up. Its been about 50-60 miles of both highway and city driving. No codes stored or pending. I just replaced the intake air temp sensor, fuel filter, and pcv valve. I haven't reset the ecu in a couple of days and i do get out and drive it around for about 15-20 miles a day to try to get the ecu to throw a code. It doesn't have any power loss, cold idle is great, normal driving is great. Just a very rough idle once it is warmed up. It does it stopped at stop signs while in drive or neutral, as well as in park. I haven't checked reverse or any of the other gears. I did put some fuel system cleaner in to see if that can clear it up. I also just put 91 in it to see if that helps any. Any help will be greatly appreciated.

12-31-2012, 01:31 AM	#4
stampsc31757 New Member Join Date: Dec 2012 Posts: 9 Rep Power: 0	I found my problem. The vacuum line going from the valve to the solenoid was mixed up with another vacuum line.