2000 Other Volkswagen Models Code PO102 + Rough running engi

Check fuel pressure see if it is in specs. Also clean MAF and throttle body.

I found a vacuum hose which was deteriorated and open. I trimmed it and put it back on and the car seems to idle fine at all speeds. I have cleared the codes and will be checking to see if the codes come back. I will then know if I still have a problem.

Great diagnostic work you have elevated the standinof all backyard mechanics.
Tell your friend it looks good runs good I can fix it and its paid for.

Oh well, not so good afterall. I drove the car a few miles and both codes came back... PO102 and PO134 and the car still runs very rough above 2000 RPMs. Drat.

Well, guess I will focus back on the MAF and O2 sensor. Could a code PO102 (MAF) be a secondary result of the PO134 (O2 sensor) code? The reason I ask is, the O2 sensor is less expensive than a MAF so I am willing to replace the O2 sensor right away. I'm not so willing to replace the MAF unless I absolutely have to because I hear that they are expensive.

Also, could a bad MAF sensor (plug) be the source of a PO102 code or is it more likely the MAF?

Thanks for your time.

[quote:3941125492="Docfixit"]Check fuel pressure see if it is in specs. Also clean MAF and throttle body.[/quote:3941125492]

Can you recommend a good cleaning solvent to use on the MAF and TB?

Maf can cause O2 to set so get some CRC MAF/throttle body cleaner clean both open throttle spray and scrub with a tooth brush any black areas.
Let me know

[quote:6f2459de45="Docfixit"]Maf can cause O2 to set so get some CRC MAF/throttle body cleaner clean both open throttle spray and scrub with a tooth brush any black areas.
Let me know[/quote:6f2459de45]

I'll get the cleaner tonight and will take off the TB/MAF tomorrow after the engine cools. I'll give it a good cleaning. How likely is it that it just needs a good cleaning? Can I expect this to solve the PO102 code?

If the cleaning doesn't solve the PO102 code, what next? Do I need a new MAF? Is that what I should buy or is it a particular sensor, etc.?

Thanks for your help.

First we do this carbon can effect many sensors in a bad way so before you start throwing parts we got some stuff to try first. I will be out of town till SAT
Leave me a post and I'll get to on Sat afternoon.
Also if you know where the EGR is take it off clean passages in valve and the manifold.
If I can get in touch with KHLow2008 I'll put him onto you he's good with VW

That will be good. I will locate the EGR in the mean time and give it a cleaning. I appreciate your help. Is this the EGR? (Sorry, my Haynes manual is practically worthless and the diagram in the engine compartment neglects to mention the EGR in the diagram).

Hi wscreate,

Docfixit has requested me to assist and I do not know if I would really be able to.

Firstly, the P0102 code came up first, so it takes precedence over the O2 sensor.

I am not really very familiar with VW so I am not sure if your car is equipped with MAF or MAP.

MAF uses air flow and should be attached to the air cleaner housing through air flows thru it to get a reading. Check for vacumn leakage between the MAF and throttle body. Any vacumn leakage would give a false MAF reading. It is risky to try to clean this as any type of force can damage the sensor. You should try checking the connectors for corroded or bad contacts.

MAP is installed after the throttle body valve and it uses vacumn to provide signals to the ECM.

Check out the above first.

I replaced the fuel filter today. Cleared the codes but they came back (PO102). Engine still runs rough after 2000 RPMS and it bogs down when I try to get RPMs over 2500.

I've done a visual inspection on the vacuum hoses and they all look intact.

I've checked the sensor connections, and they look fine... hardly any sign of wear and tear. I'm beginning to think that the MAF sensor needs to be replaced. It's an expensive part and I'm not happy.

Hi wscreate,

The MAF electrical is definitely giving the problem and if the wirings are ok, you have no choice but to replace it.

[quote:c0fa6def8c="KHLow2008"]Hi wscreate,

The MAF electrical is definitely giving the problem and if the wirings are ok, you have no choice but to replace it.[/quote:c0fa6def8c]

Thanks for the affirmation. I'm going to bite the bullet and buy one on Monday. I'll update this thread once I have it installed.

Hi wscreate,

Hope you have checked and confirm the wiring circuit from ECM to sensor is ok.

Good luck.

Interesting that you say that. I did check the connector yesterday and found a potential problem.

So, that concerns me, but I have no idea if the connector is supposed to have 5 metal pieces or 4 with a dummy hole. However, the sensor male plug does have 5 prongs. As for testing the connection from the PCM to the plug, I have an electrical tester, but have no idea how to use it to test this.

Hi wscreate,

Check if there are 4 or 5 wires behind the connector.

Some do have dummy points.

If any connector pin is not aligned or is contaminated, it could be having a high resistance thus the wrong reading.

Clean and blow dry it with a contact cleaner or rust remover.

There are 4 wires behind the connector. The female connectors, two of them are loose and seem out of place a bit. I am not sure if that is creating a problem. I was thinking about finding some dummy wire to plug into each of the connectors individually, and all at once to test the MAF sensor with. In other words, instead of plugging the connector in to the MAF sensor, jump 4 wires from the connector to the MAF sensor. I will also give the cleaning a try.

Hi wscreate,

Any loose connections can result in high or low resistance thereby sending the wrong signal to the ECM.

The MAF is a sensitive item and any slight changes would affect the ECM.

Try to tighten the female clips by compressing the clip area to make them tighter.

After plugging in connector, use a pointed object to push the female clips from behind the connector to tighten them.

Well, I can report some progress. I took the red part of the female connector apart and straightened the metal female prongs. They were bent and after I straightened them, and plugged the connector back to the sensor, the PO102 error did not come back. But, the engine continued to exhibit the same symptoms.

1. Engine idles fine at about 800 rpm
2. When giving the engine gas, it seems to rev fine until about 2000 rpms, and then the engine runs rough and shakes and wants to stall out. In fact, it seems it would stall unless I let up off of the gas.

I ran the codes again after this and found 2 new errors.

P0302 (Cylinder 2 misfire)
P0134 (O2 sensor, bank 1)

The consistent error is the PO134. It has been with me most of the time since the trouble began. The PO302 error is new.

I cleared the codes and ran the car again, and got only the PO134 (O2 sensor) error again.

I guess the question is, can a faulty 02 sensor cause the following problems...

1. Engine stalls, runs rough at RPMs greater than 2000
2. Can a faulty 02 sensor cause a cylinder misfire

Any help will be greatly appreciated. I feel like I am close to solving this problem. I am thinking I should replace the 02 sensor.

Thoughts?

Hi wscreate,

Yes, the O2 sensor can cause the misfire and vice versa. Since the O2 sensor had been there for a long time, I would suggest replacing it.

Misfiring could be due to injectors or spark plugs too but they would not be that consistent and can happen at any rpm.

One more item to check is the EGR valve and the exhaust passage under it. Clogging of the valve and passage will cause misrifing between 1500 to 2500 rpm depending on driving conditions, end result would be a faulty O2 sensor.

Thanks for sticking with me on this KHlow. I decided to check the codes again today before doing anything. I idled the car and tested the car at 2000 rpms... the rough running still persists at 2000 RPM (engine shakes, bogs down, wants to stall). Checked the codes and did not get a PO134 code immediately. Instead, I got a PO301 error (misfire cylinder 1). I let the car cool down. Came back and checked the codes and the PO301 was the only one there. I cleared the code and cranked the car and let it idle. I pushed the idle up to 2000 rpms and the shaking was still there. I got a PO301 again... cylinder 1. I decided to check the plug wire for #1. Popped off the end, did a visual, and then plugged it back on. Interestingly, the car idled perfectly up to about 3500 rpms after I did this. I decided to drive it. I took it up to about 3000 rpms on a couple of stop and gos... and everything seemed fine. I thought... the darn plug wire wasn't on tight. But then, on my way back to my house, the rough running happened again, only this time it seemed to happen at a lower rpm... about 1500. Got back to the house... checked the codes and got a PO301 error again. So, I decided to let the car cool and then I changed the #1 spark plug. The old one was fouled. I thought... AHA! But, no, after I cranked it, I got a PO302 code (Cylinder 2). What the???? It migrated to cyl 2? I let the car run for a bit, and it ran rough at almost any speed now. I checked the codes after a few minutes and got these codes.... PO300 (Multiple mis-fires detected) PO301 (cyl 1) PO302 (cyl 2) Later, the PO134 code came back into the picture. So, now I am a bit frustrated. I corrected the original problem with the MAF sensor (Code PO102) and that code has not come back. But since then, I have multiple misfires. In light of this new info, I decided to change out the remaining 3 spark plugs tomorrow. Do you think that this new info still indicates a bad 02 sensor like the code says, or does this sound electrical in nature? For the record, I replaced the coil on this monster of an automobile back in April. These 2000 Cabrios seem to have a problem with the coils and the aftermarket coils are not all that dependable. I appreciate any advice you can give me on this. I'm considering buying plug wires. Could it be the distributor cap? I guess what I'm saying is, maybe I should replace the plug wires and dist. cap tomorrow along with the spark plugs. Of course, if it is likely that the O2 sensor would create multiple mis-fires and the other symptoms I have described, then maybe I should replace the 02 sensor first. What do you think? As for the EGR valve... where would it be according to this diagram. VW doesn't use the EGR terminology...

hi wscreate,

You are correct, the diagram does not show an EGR.

The problem did change when you replaced 1 spark plug, so I would suggest replacing the others and see if it improves.

Btw what was the color of the spark plug tips? Sooty? very white? Any sign of something like an air brush at work?

The spark plug was sooty. It was coated and in a black residue.... carbon I assume. I also assume that is from a too "lean" condition.

I replaced the remaining 3 plugs and they were all black, but not as dirty as plug #1. The car continues to run rough and at low idles now. I checked codes and got 3 misfires.

PO300 Multiple misfires
PO302
PO304

So, I have received misfire codes on cylinders 1,2 and 4 at different times...

Before I changed plugs
~~ Misfire on Cylinders 1 and 2

After I changed plug 1
~~ Misfire on cylinder 1 and 2

After I changed plugs 2, 3 and 4
~~ Misfire on cylinder 2 and 4

I did check the plug gap, and these Bosch Platinum Plus plugs require a .040 not adjustable gap. There is one thing.... each plug came with an extra top piece... the metal prong that the plug wire connects to. They are different sizes, the one which came installed on the plug and the one which was the extra. The extra one is longer. I am going to wait until the car cools and remove the plugs and change the metal piece. I believe the one that is installed may be shorter than the ones on the plugs which I took out. I didn't think to check before I installed the new plugs. I'll wait until the car cools and will update when I have completed the change.

Hi wscreate,

Sooty plugs mean too rich mixture or misfiring which would cause unburnt fuel to be present int the chamber.

Hoep the new plug caps solves the problem of misfiring.

I guess the air flow electrical problem had been solved but it might be faulty and not giving a correct reading.

The only way to find out is to plug in a diagnostic analyser and get all the data performance to see if any is out of specs.

Faulty injectors can cause rich mixture.

The plug tips were fine. They were the same size as the old plugs. No problem there.

I have decided to replace the plug wires just on a hunch that their doesn't seem to be enough fire coming through. The plug wires look old and dried out and somewhat brittle. These are just hunches of course. If not the plug wires, I will replace the distributor cap also. If it is not the plug wires and dist cap, then I suspect I might have a bad coil... another bad coil. This model vw has a problem with coils according to one mechanic I spoke to.

I have ordered the plug wires online and it will be a few days before they get here. Will update this thread after they are installed.

Hi wscreate,

Thanks for the reputation points. :)

Yes , if the wires are old, they can cause misfires, especially when cold, it would be worse.

Ohm them out and see if the resistance is very high or no contuinity.