[doradidit]

99 New Beetle
2.0, 5spd MT
107k, stock w/ cone filter on MAF

A few weeks ago I noticed some stumble if I ran the revs past 4200 rpms. Being the notorious 2.slo, I figured ehh, a low powered 8v has no business being tached out, I just wont take it that high. Well starting this week its been gutless anywhere after 3000 rpms and hardly reaches 4000. Pushing for more flashes the cel. I ran the codes at AutoZone and found...

*misfire cyl #1
*o2 sensor

starting cheap I replaced the wires&cleared cel, it came back.
plugs are Bosch, getting NGK asap,
replaced coil pack, still no luck.
I have a few more things to check but so far I'm stumped... What could be the cause? Any help is appreciated Thanks in advance!

 

[red99]

A plugged fuel filter or failing fuel pump can cause your symptoms. Not enough fuel flow to keep up with the high load conditions.

 

[doradidit]

Thanks! I'll start checking fuel system next, I'm not sure how this would cause the isolated misfire though. Should I try running injector cleaner first?

 

[red99]

If the fuel flow is limited then at a certain point as you open the throttle the mixture will lean to the point where it won't ignite and you get the misfire. It could cause the O2 sensor code as well since the ECU can't tell if the reason the mixture is too lean is because of the O2 sensor malfunctioning or the fuel flow being too low. You could confirm this if you can monitor the fuel trim as you drive.

 

[doradidit]

Okay, thanks a lot for your help. I think I'm going to change the plugs and fuel filter and maybe clean the MAF and o2s. any other suggestions are greatly appreciated!

 

[doradidit]

Okay so I changed the fuel filter(those clips were a blast) and cleaned the MAF with electronic cleaner twice. Before cleaning the MAF,the engine completely stalled when I tried to get it past 4k. the first start after unplugging the MAF I could rev it past 5K no problem, so I cleaned it, plugged it back up, and it continued to do well. Went for a test drive and she started acting up again and the cel came back(had it scanned and cleared after the coil pack). ...I pulled over and disconnected the MAF, and drove to AutoZone. I could get it past 4k with less hesitation than usual in 1st and 2nd gear, but in 3rd it was just too much load and it wouldn't go past 3500 rpm. Scanning the cel gave three codes...
P0301- cyl 1 misfire ..no idea what could still cause this
P0422- catylist below threshold bank 1 ..heated o2s?
P0102- MAF circuit low input ..bad MAF?

Can someone please help??
Thanks in advance!

 

[esse10]

throttle valve

Okay so I changed the fuel filter(those clips were a blast) and cleaned the MAF with electronic cleaner twice. Before cleaning the MAF,the engine completely stalled when I tried to get it past 4k. the first start after unplugging the MAF I could rev it past 5K no problem, so I cleaned it, plugged it back up, and it continued to do well. Went for a test drive and she started acting up again and the cel came back(had it scanned and cleared after the coil pack). ...I pulled over and disconnected the MAF, and drove to AutoZone. I could get it past 4k with less hesitation than usual in 1st and 2nd gear, but in 3rd it was just too much load and it wouldn't go past 3500 rpm. Scanning the cel gave three codes...
P0301- cyl 1 misfire ..no idea what could still cause this
P0422- catylist below threshold bank 1 ..heated o2s?
P0102- MAF circuit low input ..bad MAF?

Can someone please help??
Thanks in advance!

You forgot to recalibrate the throttle valve and maf sensor. Everytime you do work that involves gas/air mixture you need to recalibrate the system by disconnecting battery power for a while, then reconnect, then put key to on position without starting the car(20-25 seconds), you can actual hear the throttle valve recalibrating itself. put key back to off position you're done. Happy driving ............never clean the actual maf sensor with anything other than the spray cleaner, never touch the actual sensor with anything.

By coil pack you mean to say Ignition coil? cause the 2.0 is notorious for the ignition coil getting hairline cracks and causes all kinds of problems like you are describing.

 

[doradidit]

Thanks I'll be trying this soon! And yes I meant the ignition coil. Sorry about that, I've never clearly understood ignition outside of a typical distributor haha. And I checked the old coil, no visible issues compared to the new one.. might consider taking a volt/ohm meter to it and seeing if I can sell it.

I forgot to mention that I've been hearing a rattle under the car since I got it(about 3 months ago)that only occurs when I'm decelerating/off the gas. I wrote it off as a heat shield rattling around but now I'm thinking maybe the cat is broken apart inside. This could explain the acceleration "wall" if all the bits are getting blown to the exit of the cat and creating back-pressure. I'll have to reach under there and whack the thing a few times to confirm this. My main concern is spending all the money to have it replaced and still have the misfire. It will miss pretty badly at idle if I push it to break 4k rpms (with MAF unplugged). I'm not sure what to do next at this point. If anyone has any questions or suggestions feel free! All help is appreciated, Thanks guys

 

[nighttrain1974]

First of all, 2.slo? Lol.

Secondly get rid of the cone filter, it's doing zip for your engine. It's probably the cause of your maf dying.

Then replace your maf, it's dead. If it runs better unplugged then that tells you it's done. But the ecu won't let it rev past a certain point to protect the engine,
Also when you get it running again, pease take it round the tacho, they love it, trust me. There's power aplenty above 4000rpm but if people continue to drive them like v8s or diesels then you'll never see their true character. Remember the 2 previous generations of golf had a variant of the 2.0 8v in them, and in GTI models to boot.

Live a little, plant that foot down every once in a while.

 

[Jeff2]

Secondly get rid of the cone filter, it's doing zip for your engine. It's probably the cause of your maf dying.

Then replace your maf, it's dead. If it runs better unplugged then that tells you it's done.

I personally stick with stock air filters in my cars for this reason. Unless you're modifying the engine itself to go faster, you aren't very likely to get much performance gain from an aftermarket air filter anyway.

 

[Smileybug]

First of all, 2.slo? Lol.

You've never heard it called that before? I've heard it for years.

 

[doradidit]

Theres lots of mixed feelings about cone filters doing anything for German cars especially, but I personally prefer it way more than stock, I was very pleased with the throttle response I picked up. I'm very particular about my driving and using as little clutch as possible(floated gears in my old civic lol), so being able to spike the throttle for downshifts was also a plus. Anyway I'll be looking into a new MAF here soon, not writing off the cat just yet, it could def be OE looking at the rest of the car maintenance wise. Thanks again guys!


And yes, 2.slo haha

 

[red99]

I had the cat rattle for a couple years before I finally got the P0422 code. Never noticed any power loss due to the failing cat.

 

[doradidit]

Thanks for the input. I guess the MAF is first on the list then considering price. Would a cam/crank/temp sensor throw a code? I feel that if one of these is failing the ecu could go into limp mode.

 

[Jeff2]

If that cone filter is an "oiled" type, you'll likely keep ruining, and replacing, MAF sensors. The temporary, perceived, gain in throttle response isn't worth it, IMHO.

If you don't actually dyno the car before and after a change like this, any perceived "gain" may actually be the placebo effect, plain and simple.

 

[doradidit]

I've switched back and forth between the air box and the cone and every time the motor just had a better feel all together. I've never oiled it but It may have came lightly coated. It's a spectre filter from oreilley. I think I'm going to pick up a new MAF tonight and recalibrate throttle valve and if this doesnt help I'm double checking everything Iv done so far and looking deeper into the issue. Has anyone ever experienced limp mode with a 2.0?

 

[nighttrain1974]

You've never heard it called that before? I've heard it for years.

I've heard it called that many times before. I must be driving a different engine then.

And as so rightly said above, placebo effect is exactly what these cone filters are about. It's been well documented that the stock air box on a VW can be good for up to 400bhp. The oil from the wretched cone things gets onto your Maf sensor causing it to fail, a lot.

I tried one myself for a while from K&N and tbh the only thing it gained was heat soak.

 

[doradidit]

You could put thick sock right over the MAF thatd hold up to 400hp, doesn't necessarily mean it's getting as much air as it wants lol.

 

[Jeff2]

You could put thick sock right over the MAF thatd hold up to 400hp, doesn't necessarily mean it's getting as much air as it wants lol.

Possibly, but 400hp is quite a lot and would require substantial mods to the actual engine.

On a stock engine, an aftermarket cone style air filter may sound different (cone filters tend to be noisy), so the louder sound from the engine compartment may make you think that you've got better "trottle response". Unfortunately, more sound doesn't necessarily mean more horsepower. Again, if you don't put the car on a dyno before and after a mod like this, then you really have no clue if you actually gained any horsepower.


My other car is a '91 Ford Crown Victoria with the stock, low output, 5.0 liter V8. The silly flat snorkel looking stock intake on it is actually a very well designed cold air intake. We have the same problem on the Crown Vic forum with people putting aftermarket cone filters on the cars expecting a gain in horsepower with the stock low output engine. Most of the time, they just succeed in turning their stock cold air intake into a hot air intake since there really isn't any better way on those cars to get cold air into the engine. Dyno and drag strip runs confirm this.

 

[doradidit]

Don't get me wrong here, I know what you mean, and I completely agree in some cases, but it made a difference that I notice and like, so I'm for it. I am considering removing the lower screen and putting the box back in. Hopefully it will have a similar/safer effect. But first on the list right now is getting the poor thing running again,