# 1997 VW Jetta GLS VIN A 2.0 P0304 CODE HELL



## JWaters9891 (May 5, 2012)

Please if absolutely anyone can shed some light on my current situation, I would be most grateful. I bought this car October last year, and have been dumping money into it ever since trying to get it back to ground zero. I am down to a P0304 OBDII engine code, Ive done everything that I know to do including taking the car to a mechanic (he had it for a month and a half and couldnt figure out the problem). Heres a list of work Ive done so far.

-New Bosch Double Platinum Plugs
-New Autolite Wires
-New Bosch Distributor, Cap, Rotor
-New Timing Belt
-New Ignition Coil
-New Fuel Injector (#4)
-New EVAP Purge Valve
-New PCV Valve
-New Oil Cooler Seal
-New Coolant Hoses (All Upper and Lower)
-New Thermostat
-New New Coolant Temperature Sensors (Both)
-New Brakes Front and Rear

Thats just the stuff I can remember off the top of my head. I am tired of throwing my time/money at it and already have about 3 times more invested in it than I paid for it! Please help, is there anything else that may be causing the misfire? Here is a little more information on it. I bought the OBDII reader from Advance Auto and when I clear the misfire code after the motor has warmed up, it will stay off for the rest of the day (as long as the motor is kept warm). However, when the motor is cold and i start it, the light comes on within 3 to 5 minutes everytime. If you need to know anything else then just ask. The Car has 182,500 miles on it. Thanks


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## greyhare (Dec 24, 2003)

Plugs; is the gap set correctly? 0.6mm (0.024") The platinum plugs shouldn't hurt but are expensive and gain you nothing. The ABA is quite happy with standard Bosch or NGK copper plugs.

Wires; do the Autolite wires have the correct connectors? Are they on tight?

Do a compression check cold and hot.


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## JWaters9891 (May 5, 2012)

The Plugs are gapped right, the wires fit snuggly on each connection. As far as the compression goes; the mechanic performed that test, came back and said that its as if the motor was brand new (suprised me seeing as it has such high miles). As far as doing the test when the motor was warm and/or cold, im not sure if he did both. 

I used to own a 1996 Acura Integra in which I did a tune up on with some plugs/wires from advance auto. When I got done with it the car ran like dog **** (for lack of a better word). I ended up taking it to the dealership and they told me that Acura's dont tend to play well with aftermarket plugs/wires? Is it possible that VW is the same way on this? 

Once my Jetta warms up, the motor seems to smooth out a good bit and run more like "normal". However, the CEL remains on. Once I replaced the PCV and the Purge Valve the motor smoothed out A LOT; and once every couple days it will turn the CEL off itself. But like I said before, as soon as the motor cools, it will come back on. The car has been throwing the P0304 code since I bought it, before I started dumping cash into it. It almost makes me think that there is some kind of sensor going out or possibly an electrical issue (not in the wires though I believe). Is there a sensor of some sort that involves ambient temp with the ignition?


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## Anony00GT (Mar 6, 2002)

First things first, DO NOT throw any more parts at this car until you've diagnosed it. You need a good scan tool capable of giving you more than fault codes, you've clearly reached the limit of a cheap AutoZone code reader.

I'll start by assuming all your replacement parts are verified good and installed correctly.

Let the car sit overnight, then turn the key on (DO NOT start the engine). Connect the scan tool, and read IAT and ECT. They should be within a few degrees of each other and ambient temp. If not, determine which sensor is implausible. If the ECT is implausible given ambient temp, replace it and retest.

Read/log MAF and O2 sensor data and post it up.

Verify fuel pressure with a mechanical gauge, and fuel volume.

I personally wouldn't use anything but Bosch wires on the ABA, but I wouldn't jump to your wires right away as the problem either. I will highly recommend, though, that you to check the coil. If it's not OE, Bosch, Temic, or Beru, chuck it and replace it with one of the above. Even if the coil isn't the cause of the misfire, a cheap made-in-China coil can, over time, burn down the coil drivers in the ECU. The coil can be verified with VCDS if you're unsure.


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## vdubtech398 (Jul 19, 2007)

Is cylinder 4 always misfiring?? If so and your compression test is okay, perform a leak down test on all cylinders. make sure fuel pressure is ok as well


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## JWaters9891 (May 5, 2012)

Well to start, sorry about it taking so long to get back to yall, just been busy for the last few days. Anyway, I hooked the scan tool up to the car a few minutes ago, after it had been sitting for about two hours. Heres a list of the readings/measurements that I got.

Readings (MOTOR OFF, IGNITION ON):

MAF (LB/M) --> 3.66
IAT (DEGREES/F) --> 113
MIL STATUS --> ON
ABSLT TPS (%) --> 3.9
CALC LOAD (%) --> 28.6
COOLANT (DEGREES F) --> 113
IGN ADV (DEGREE) --> 0.0
SECOND AIR --> ATMOS
ST FTRM1 (%) --> 0.0
LT FTRM1 (%) --> 0.8
FUEL SYS 1 --> OPEN
FUEL SYS 2 --> N/A
ST FTRM11 (%) --> 0.0
02 BANK 1 SENSOR 1 (VOLTS) --> 0.445
02 BANK 1 SENSOR 2 (VOLTS) --> 0.645 ** Changed to 0.445V after about 30 seconds

I could not find anything for an ECT reading though. Is there a physical sensor that I could disconect and test with a multimeter? As far as the ignition coil goes, I ordered that from autopartwarehouse.com and all it said there was OEM Replacement (no brand listed). I believe it is fine though. How can I verify it? I dont have a mechanical gauge or compression gauge, I'm sure advanceauto has a compression gauge for rent; maybe they'll have the mechanical fuel pressure gauge too. Anyway, the car has been running about the same for the last week or so. It hits a rough spot every once in a while if I leave it idling while I run into the store. The RPMs will fluctuate toward 0 and about 800, and if I rev the motor a couple times it will typically even back out at idle, wierd. 

And to put the icing on the cake; all of my windows stopped working a few days ago, in the middle of a rain storm (2 of which were all the way down when the rain started). So I cut the cables to the windows so I could get them back up. Now the motors will work every once in a while (but of course they dont go up and down because of the cables). So I obviously need two regulators/tracks, but where should I start looking for troubleshooting? And would it be cheaper/easier to just install manual crank windows? 

Thanks for all yalls time and hope to hear back.


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## Anony00GT (Mar 6, 2002)

So I take it this car runs smoothly (except for that occasional stumble at idle), yet keeps throwing a P0304?

You already have an ECT reading. Look at your data post again 

Change scale on the scan tool to metric.

What is MAF reading (g/s) at idle? Note, then watch MAF while doing a WOT redline blast in 2nd or 3rd gear. How high does it go as engine approaches redline?

Where is LTFT at idle, operating temp? Where does it go with engine held at 2500 RPM in neutral?

The integrity of the coil can be verified with VCDS, but there is no test you can perform with a generic OBDII scan tool to check this.


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## germancarnut51 (Mar 23, 2008)

Some people insist on having power windows.

Some people want windows that work.

People who are serious about having windows that work have manual windows, because they work.

Converting to manual windows is easy. All you need is the manual window regulators, window crank handles, and holes in the door panels for the handles to attach.


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## Anony00GT (Mar 6, 2002)

Germancarnut is dead-on balls accurate about the windows. I converted my old a3 Jetta to cranks because crank regulators were a fraction the price of new power ones. It's a straightforward bolt-in replacement. Just add a crank and drill a hole. Done.


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## Geeked (Nov 20, 2006)

Sounds like a fuel enrichment problem at this point. The misfire seems to only occur when the ECU is running the car in open loop (when cold) - so the o2 sensor data is not being used in the air/fuel mix. My guess is it's running rich in open loop, causing the misfire.

Can you pull the spark plug from cyl 4 and let us know how it looks? If it's got carbon cover, that would confirm the running rich scenario.


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## germancarnut51 (Mar 23, 2008)

How did the oil look when you got the car? You could be looking at a sticky valve or lifter due to poor oil change/extended oil change intervals.

I've found this type of problem on used cars that I've bought, and found that after replacing leaking vacuum hoses and coolant hoses, inferior replacement parts installed by POs, with quality parts (don't use any more chain auto parts store parts, and replace any that you installed), and a number of oil changes with a quality brand of oil, the problems go away if the engine is sound as the gunk is washed and changed out.

Think about doing two-three rounds of quality fuel/fuel injector system cleaner, and a engine oil system cleaner (don't bother with any Lucas products, LubroMolly or Redline is the way to go).


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## JWaters9891 (May 5, 2012)

Alright guys; I've not been able to work on the car lately due to rain. I will post up what I find as soon as the weather breaks a bit. As far as the question about oil, I have been changing it every 2800 to 3000 miles with Mobile Clean 5000 (10W30) and Fram filter. It usually comes out dark, but no chunks/metal shavings. I believe the car was just let go by the previous owner as far as the maintenance goes (single mom w/ two kids). I have run 'seafoam' through the gas tank about 2 months ago, it didnt make much of any difference. 

With the windows I have to agree with just having windows that work. I believe I will be putting manual cranks in place of the power. Especially with what I have read about VW track record with the power windows. 

Anyway I think the rain is supposed to slow up for the weekend, so I'll be updating yall soon hopefully. Thanks


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