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Wolfgang
Wolfgang, VW Master Technician
Category: VW
Satisfied Customers: 4656
Experience:  Senior VW Master Tech 15 yrs
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I have a 2001 Jetta, 4 cylinder AVH engine. It has been

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I have a 2001 Jetta, 4 cylinder AVH engine. It has been intermittently misfiring on cylinders 1 and 2. In addition to Codes P0300, P0301 and P0302, it will sometimes return Codes P0351 and P0352. Misfiring usually occurs in 10 minutes after engine is fully warmed and will usually go away in a couple of minutes only to return again intermittently. There is no backfiring or smell of raw fuel. Spark plugs, wires and ignition coil were replaced in 2011 when this came and went the first time. I have recently replaced the fuel filter and spark plugs. Wires and ignition coil survived water spray, so they have not been replaced. Oxygen sensor returns normal voltages and fuel system remains closed-loop until the misfire begins. Fuel trims are normal as are throttle position sensor and mass air flow sensor readings. Not sure what to try next. Injector cleaner seemed to help for a week or two. When it isn't misfiring, it runs like a new car.
JA: Have you located all of the vehicle's oxygen sensors? Are the wires leading to and from each intact and in good shape?
Customer: They look OK and voltage readings are normal.
JA: Are you fixing your Jetta yourself? What have you tried so far?
Customer: I have recently replaced the fuel filter and spark plugs. Wires and ignition coil survived water spray, so they have not been replaced. Oxygen sensor returns normal voltages and fuel system remains closed-loop until the misfire begins. Fuel trims are normal as are throttle position sensor and mass air flow sensor readings. Not sure what to try next. Injector cleaner seemed to help for a week or two. When it isn't misfiring, it runs like a new car.
JA: Anything else you want the mechanic to know before I connect you?
Customer: no

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i do need a vin # to assist! second on the coil plug is there a yellow wire that goes under the battery tray?

thanks

Customer: replied 11 months ago.
3VWSK69M71M097804
There is no obvious yellow wire going under the battery tray from the 6 pin plug that goes to the coil. All the wires are enclosed in a flexible black plastic tube.
I have been looking for the TSB that talks about the extra ground wire but it isn't listed for my car. As for my skill, I have been working on cars since 1969 in the driveway. Over these years, there isn't much I haven't done. I have several scan tools but no clue yet as to what's wrong with this Jetta.

There is a tech bulletin where the brown wire of the coil connector gets eliminated from the loom and a new terminal and wire goes to the ground stud under the battery tray!! the p0351 and p0352 are coil activation faults. that needs to be rectified first .

what is the compression test of all cylinders hot . may have low psi when hot compared to 3 and 4 . that is also needs to be considered

Customer: replied 11 months ago.
Do you know the number of the tech bulletin or can you send me a copy?

let me get that!!

tb 01-08-27 note the codes may be different because of the factory scan tool interprets the code differently than obd scan tools.

anything else?

if not.....

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Wolfgang

Customer: replied 11 months ago.
I have installed SB 01-08-27 and in the process, I checked all the grounds and cleaned the battery terminals. After driving the car on the highway for about 20 minutes, the engine started shaking violently for about 30 seconds and then smoothed out for another 5 minutes and then started shaking again. The codes are: P0300, P0301, P0302, P0304, P0351, P0352, P0354. This is a very intermittent problem but makes the car almost undriveable. I'm looking forward to another suggestion.

the coil is it a genuine VW factory coil?

Customer: replied 11 months ago.
I'm using an after-market coil which was installed in 2011 when, at that time, I was having mis-firing problems with the P0351 codes. The new coil, along with new wires and plugs, seemed to stop the problem, but not completely. When it came back, I replaced the plugs again. No difference. While the car is idling and misfiring, I have sniffed the exhaust trying to confirm raw gas fumes typical of bad ignition. Smells normal. (no, I didn't do this too long...). Additionally, I have yet to hear a back fire, indicating a ignition problem. My conclusion is that it's a fuel injector problem but the scanners I have used, show a normal fuel trim and oxygen sensor voltage. When misfiring occurs, the system goes into open-loop. I do have another ECM which I plan to try.

i have seen alot of aftermarket coils when hot they do break down. my recomendation use a factory coil and retest !!

Customer: replied 11 months ago.
Good advice. I just ordered a Delphi GN10383 less than 1/2 hour ago. I think they make great coils. It will arrive Thursday and hopefully, I can have it installed by Friday.

being a dealer tech seen alot of chinese coils and they are not worth a darn . some delphi coils are made from china so be aware!!

Wolfgang and other VW Specialists are ready to help you
Customer: replied 10 months ago.
After driving 50 miles, I have had no misfires. It may take a little getting use to not having a "check engine" light on but I don't think I'll miss it. Thanks for your help. The Delphi coil did the trick.