VW Beetle Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
17 Posts
Discussion Starter · #1 ·
Hey all!

It's me again. The guy with the mystical PO411 that just won't clear despite replacing the entire SAI system with expensive OEM parts. I've been getting by because it only does this after it's been started cold and driven to the first stoplight. If you let it idle, the SAI will come on again for a second or two and it'll throw the code. If you keep it up above 1500 RPM (or so) you can get through the three drive cycles needed to pass emissions (so far).

But that's not the end of our story. Now there's a new issue. This year when I started the air conditioning it began to misfire! Turning the a/c off cleared up the problem. A/c seems to work fine. Blows cold. Nothing overt going on with the compressor that I can see or hear. It seems to be worse in the rain, but that's not needed to make it happen. One day, driving to work in the rain it went into meltdown mode. Whatever happened, it caused it to suddenly run really rough. I pulled over, shut it down, and after a few minutes restarted it. After doing that it took me to work without any further complaints.

So what it does now is to occasionally misfire every so often if the a/c is running. She runs nice and smooth but just coughs every once in a while. My code scanner can't see anything happening, but after a test drive it threw a PO422 pending. It's got a brand new Warner cat in it so I know that's okay. I'm hoping that the multiple misfires and PO422 it threw during that horrible meltdown didn't break anything else.

I'd take it to a shop but after taking it to German Auto Group to get the fan switch replaced (because screw taking out the whole center dash) they took three days, $2200 of my money, and for that I got my master brake cylinder replaced (?? but okay...) and they broke my aftermarket radio. When I asked about that they said he didn't touch the radio and when I pointed out that he would have had to to to get the center console out they said he didn't touch the center console either. So that's the top rated VW shop in my area. When I picked it up it ran like crap but when I got it home I found out he just hadn't assembled the throttle body ducting properly. The ducts weren't fully seated. I seated them and she ran okay after that. I got a new radio (with apple play, yay) but the install manager at best buy said they didn't have a technician that had the skills to do the install. Turns out you need a master installer for that and none of his guys had that qualification. Even the VW dealers are super sketchy. I took it to one to find out once and for all what the issue was with the PO411 and they quoted me $522 to replace the vacuum hose from my brake booster. Of course, I ordered one for about $30 and did that myself in 5 minutes. They seem to be clueless otherwise. They did confirm that I have a strong vacuum and that the SAI system seems to be functioning as well.

So I'm leery of taking it to a shop. I'm not sure if there are any professionals around capable of diagnosing and repairing this issue. I might roll the dice and go with one last place that's treated me well, but in my area if you want it fixed right, you usually have to learn to do it yourself.

What's frustrating is that I know it's some small, stupid thing. I'm thinking probably electrical. If you've read my previous posts, you'll know I have that issue with the alternator harness that a replacement harness simply cannot be located for. I'm still trying to get around to doing the Alternator wire bypass thing (4 gauge vs stock 6 gauge) but COVID knocked out the only guy that will make one of those for you. Is it possibly a grounding issue? Hell, I don't know. A guy could go crazy just trying to figure it out, especially with this new a/c wrinkle.

So tell me. What say you? What stupid, simple thing am I overlooking? I welcome all opinions because I'm just about at the end of my rope.
 

·
5/23/10 <3
Joined
·
11,631 Posts
What fan switch did they replace that they removed the dash? Are you talking about for the interior HVAC fans?

As for the misfire, since it happens when it rains, my guess is the ignition coil. They tend to develop small cracks and moisture can cause arcing and misfires.
 

·
Registered
Joined
·
17 Posts
Discussion Starter · #3 ·
Yes, the HVAC switch. It's got Huco coils in it which I though would last the life of the car. I probably do need to replace the spark plugs, but the harness is Bosch, and was installed with the coils. What the issue is is that this only happens with the a/c running. Ran fine last year, and I can't seem to detect any issues with the compressor. Blows cold air and everything. It only recently started doing this.
 

·
Registered
Joined
·
17,697 Posts
For the misfires; what parts specifically, have been replaced and when? When, the a/c is turned on; you are adding a substantial load to the engine and so, that could exacerbate a preexisting problem. If something is wrong with the compressor or your clutch is failing; this could put a abnormal amount of load on the engine and feel like a misfire or substantial power loss.

Here is a diy: on adding moisture to the engine compartment with a water spray bottle and this can be a way, to diagnose, the cause of the misfires:

 

·
Registered
Joined
·
17,697 Posts
As to this trouble code; there are a number of parts of the sai system and the fuel pump relay, that can be a issue.


We have had some head scratchers over the years and one guy, had the vacuum hoses, to the combi valve solenoid, hooked up backwards or we have seen the vacuum hoses, have leaks or come off their connections. The vacuum hoses on these vw's; tend to get hard from heat, age and crumble, fall apart or crack, causing leaks, problems, etc.

As the ross tech page indicates; each aspect of the sai system, components; on the list, need to be systematically tested, one by one, a process of elimination to find the problem.

If you have access to VCDS by Ross Tech; there is a guided output tests, that will activate aspects of the SAI system, that way you can confirm they are working, when commanded by the ecu.

 

·
Registered
Joined
·
2,565 Posts
If you get misfires when it's really humid or rain then it's most likely the Ignition coil pack. The 2.0 is notorious for getting hairline cracks on that pack and shorts to ground. At Idle spray mist water with a spray bottle on the coil pack that's mounted on the engine, if it starts to misfire...............you found the problem. good luck
 
1 - 6 of 6 Posts
Top