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vwnewton
vwnewton, VW Owner,ASE Master and L1 Advanced
Category: VW
Satisfied Customers: 307
Experience:  25 years of VW obsession turned into a job, last 15 years as a VW Tech.
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I have a 1997 Jetta 2.0l The car idles rough but smooths out

Customer Question

I have a 1997 Jetta 2.0l The car idles rough but smooths out when the rpm is raised. replaced rotor, distributor cap, plugs, plug wires. coil checks good. it is showing a P0102 and P0303
Submitted: 1 year ago.
Category: VW
Expert:  Wolfgang replied 1 year ago.

Thanks for choosing Just Answer . I'm Wolfgang here to help!!
Below is my first answer or request for more information. If you do not understand it, or you need more information from me, or need me to go in more detail. Do not rate yet, just reply. Put yourself in my shoes, I can not see, smell, hear, feel or touch your car, nor do I know any history on it. So take into consideration I am doing my best based on what you tell me. Also understand fixing cars often requires sophisticated tools, that you may not own. So even if you can not do what is outlined in my answer, that does not mean my answer is wrong deserving to be rated negative.

can you tell me how did you verify that the coil is good please .

thanks

Customer: replied 1 year ago.
I checked the coil resistance it is .7 I also checked the plug outer pins 12Vdc
Expert:  Wolfgang replied 1 year ago.

please do this procedure . have the engine running and have a cup of water . while running splash the coil with water . does the vehicle run rough and even stall?

Customer: replied 1 year ago.
No real change with water. stays idling rough. if I rev the rpm and take my foot off the gas the engine dies. if i ease off the gas it will stay running rough
Customer: replied 1 year ago.
only current code is P0102
Customer: replied 1 year ago.
When maf unplugged no change in rough idle
Expert:  Wolfgang replied 1 year ago.

ok perform this step then door open , disconnect the battery both cables touch and hold for 10 minutes , ignition on then hook up positive cable then the negative cable . you will hear a beep and noises normal. start the car does the idle become better?

Customer: replied 1 year ago.
Did it. Still rough. Check engine cleared and came back p0102. Only code shown
Expert:  Wolfgang replied 1 year ago.

ok i do need your vin # ***** pull up factory info!!

Customer: replied 1 year ago.
3vwxa81h7vm123987
Expert:  Wolfgang replied 1 year ago.

ok on pin 3 when the car is running on the mass air flow sensor what is the voltage please?

Customer: replied 1 year ago.
14 volts
Customer: replied 1 year ago.
All other pins 0v to neg terminal
Expert:  Wolfgang replied 1 year ago.

ok disconnect the ecu then measure resistance of pin 1 to ground . then check the reistance of the same pin to ecu pin 1. then measure resistance pin 2 of the maf to pin 16 of the ecu and then pin 4 to pin 17

Customer: replied 1 year ago.
Pin 1 to ground 0.5
Pin 1 to pin 1 plug open
Pin 2 maf to pin 16. 0.2
Pin 4 to pin 17. 0.2
Expert:  Wolfgang replied 1 year ago.

just to make sure pin #1 at the ecu is a brown wire and pin #1 at the maf is brown /red wire . please double check the resistance on those 2 please

Customer: replied 1 year ago.
Wire color is correct
Pin 1 Ecu harness to pin 1 maf sensor is 0.3
Customer: replied 1 year ago.
Replaced maf sensor. Runs better. But still rough at idle. Code p0102 cleared.
Customer: replied 1 year ago.
Car ran better for about 20 miles and now running really rough again like before
Expert:  Wolfgang replied 1 year ago.

what scan tool are you using please . make and model

Customer: replied 1 year ago.
Innova 3020b
Expert:  Wolfgang replied 1 year ago.

can you get ecu sensor readings of what are the mixtures if it is running lean?

Customer: replied 1 year ago.
Not on this tool
Customer: replied 1 year ago.
P0304 keeps showing and clearing
Expert:  Wolfgang replied 1 year ago.

ok then you need to recheck the work make sure that the plug wire is on good and plug looks ok swap #3 and 4 plug and see if the misfire moves . if still on #4 then a compression check is needed to see if you have low compression or not

Customer: replied 1 year ago.
The misfire code has cleared. But still rough idle. Compression checked good. Mechanic who checked compression thought it might be a fuel injector. Tried a new one no change. The car runs aliitle better when cold and gets worst as it warms up
Expert:  Wolfgang replied 1 year ago.

when running rough what happens if you spray carb cleaner in the intake does it run better?

Customer: replied 1 year ago.
It actually ran worst and died
Expert:  Wolfgang replied 1 year ago.

there are readings needed to see what the ecu is seeing . and your scan tool is not right for the job. VAG com is needed to check these readings out . do you know some one that has vag com?

Customer: replied 1 year ago.
I have a innova 1003f. Will that work
Expert:  Wolfgang replied 1 year ago.

i'm sorry but no.

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