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Sat Oct 31, 2009 7:28 pm

78 2.0 FI - Was running like a champ. I was driving around all day. Great. Idle was a little high, so I was turning the little adjustment screw in when I noticed a drastic sucking sound (it had been there the whole time, I just noticed it though). Thinking it must be a vacuum leak, I started feeling around the throttle body with my fingers, and I was able to make the sound stop by covering the seam between the throttle body and the air box. Sounds like confirmation of a vacuum leak, right?

So I took the throttle body off, and cleaned the black seal, and put a thin bead of silicone on there, both sides. I know - give me shit for that, I WILL order a new seal - no silicone. But for now, that's where I'm at. I'm just resurrecting this bus from previous neglect.

I put it all back together and now it runs TERRIBLY, barely at all. Sounds like a timing issue - but that's just me going by ear. I can't imagine that I even touched anything that sensitive. Here's my theory: You think that it DID have a vacuum leak, and now I DON'T - so my timing is way too advanced? Just a guess.

I know I can easily test this by pulling the vacuum line off the distributor, but it's late now, I have lots of neighbors and I just thought of this. I'll try it in the morning. Any other ideas? What could taking off and re-installing the throttle body possible do to make it run so poorly? I checked all hoses and wires very carefully.

It's going ka-chug, ka-chug, ka-chug, very slowly and very rough, some blue smoke.... no amount of throttle open or close makes much difference. I thought I was just making a quick/easy fix.

What else could FIXING a vacuum leak do to mess it up?

Sat Oct 31, 2009 7:31 pm

Your engine was using that extra air for the idle mix. Now that you've fixed it, you're going to have to adjust your idle air. Go thru' your Bentley. Peace!

Sat Oct 31, 2009 7:46 pm

It could definitely be a timing issue, but wouldn't the easiest thing to do be to grab your light and see where it's at?? You'll probably have to make several adjustments now that you sealed off the vacuum leak...idle, check your points, your timing, etc etc.

Sat Oct 31, 2009 7:54 pm

VDubTech wrote: It could definitely be a timing issue

Not to start an argument, but how did his timing change? idle vacuum?

And what with that "BLUE SMOKE"? rich is black, oil is grey/blue

Personally, I think his bus just got tired of being painted "Baby Blue"...Go Orange!

but I'm not a FI guy. :wink:

Sat Oct 31, 2009 7:59 pm

Daverham wrote: 78 2.0 FI - Was running like a champ. I was driving around all day. Great. Idle was a little high, so I was turning the little adjustment screw in when I noticed a drastic sucking sound (it had been there the whole time, I just noticed it though). Thinking it must be a vacuum leak, I started feeling around the throttle body with my fingers, and I was able to make the sound stop by covering the seam between the throttle body and the air box. Sounds like confirmation of a vacuum leak, right?

So I took the throttle body off, and cleaned the black seal, and put a thin bead of silicone on there, both sides. I know - give me shit for that, I WILL order a new seal - no silicone. But for now, that's where I'm at. I'm just resurrecting this bus from previous neglect.

I put it all back together and now it runs TERRIBLY, barely at all. Sounds like a timing issue - but that's just me going by ear. I can't imagine that I even touched anything that sensitive. Here's my theory: You think that it DID have a vacuum leak, and now I DON'T - so my timing is way too advanced? Just a guess.

I know I can easily test this by pulling the vacuum line off the distributor, but it's late now, I have lots of neighbors and I just thought of this. I'll try it in the morning. Any other ideas? What could taking off and re-installing the throttle body possible do to make it run so poorly? I checked all hoses and wires very carefully.

It's going ka-chug, ka-chug, ka-chug, very slowly and very rough, some blue smoke.... no amount of throttle open or close makes much difference. I thought I was just making a quick/easy fix.

What else could FIXING a vacuum leak do to mess it up?

How long have you had this bus?

It sounds like a PO may have enriched the mixture to compensate for the vacuum leak. If they did this troughout the rpm range it means they probably moved the wiper and/or spring in the airflow meter. Could be a bitch to readjust.

I would pull the cover off of the airflow meter and see if there are any marks showing previous settings.

Sat Oct 31, 2009 8:18 pm

73kombi wrote: VDubTech wrote: It could definitely be a timing issue

Not to start an argument, but how did his timing change? idle vacuum?

Well, sealing up a vacuum leak in and of itself will change your idle speed, which always changes your timing. You make all of your adjustments to idle speed, points, etc and then the last thing you set is the timing. Any adjustments of those prior settings can and will alter the timing. It only takes a minute to check it, so if there was a question of timing I would think it much easier to throw a light on it than to start a post here and wait for answers. It's only 8:18 on the West coast as we speak, it's not like adjusting the timing is gonna keep anyone up.

Sat Oct 31, 2009 9:13 pm

I'm pretty sure Daverham was involved in a big timing discussion a few weeks back and timed to 28 deg@3500 with the hoses off so I'd say leave the timing alone for now. My vote is for dramatic mixture change after fixing the leak or he didn't plug the AFM back in.

Sat Oct 31, 2009 9:28 pm

concur with BusDaddy. Check to see the AFM plugged back in.

Is the bad running at all rpms or just at idle?

If it is just at idle, you can turn the AFM screw in 1/2 turn at a time and count the turns, 1/2, 1, 1 1/2, 2, 2 1/2, 3, and a bit etc. Make a mark with a sharpie before you begin where the slot is and don't lose count. Write the number down. Then open it back to where it was and turn 1/2 turn more open at a time and see if that helps. If it does, get someone with a CO sniffer or A/F meter to set the idle CO. If it is through out the entire range, it is hard to put an AFM back to factory without a good understanding how it works and the equipment to set it.

Sat Oct 31, 2009 10:20 pm

Thanks guys. Glad to have some support. Clear a few things up:

1. I live in a townhouse, lots of echos, and a LOT of neighbors, just being a nice guy by waiting (still assembling my stock exhaust, this system is loud).

2. I have Pertronix ignition.

3. I do have a tach and timing light, will check that in the morning.

4. I did set my timing to about 28 deg. @ 3500 RPM a couple weeks ago, I think I forgot to remove the vac hose at that time, so it is likely out now I guess.

5. I double checked the AFM conn. That's all ship shape. BTW, I have looked inside there, the resistive strip looks super clean, no worn out marks, not sure how to see if that has been messed with before.

6. I have had this bus for about 6 weeks. Just getting it dialed in. Did the fuel tank (POR-15), did Pertronix, did (ALL) the fuel lines - lots of other stuff.

7. Not just at idle. It's running terribly at any rpm, although I can barely get above an idle anyway.

8. Yes, I know she's tired of blue. Going back to original color as funds permit!!

Not sure what screw is on/in the AFM, I have not touched that and don't intend to - but I'll look for "marks" as evidence of tampering by PO. Like I said, it was running beautifully this morning. I don't think that has been tampered with. Is that a common fix? Sounds dicey. I HAVE had the mixture screw ALL OVER the place, not sure where to begin with that. Maybe Bentley knows. I'll have a look in there.

I'll mess with it in the morning - hopefully figure it out. I'm new to FI. Not trying to waste anyone's time. Just looking to see if I missed anything obvious. Anyone reading/writing here must want to, so I figure you're interested.

Thanks again.

Sun Nov 01, 2009 3:35 pm

Well, my quick hose-off, re-adjust timing didn't do anything. It's running worse than ever, won't even start now. last time I had it running, the timing was so far out, I couldn't even find the little mark on the pulley. I tried going really far both ways, never brought it into view. Now what?

I'm gong back out there to try again...

Sun Nov 01, 2009 3:44 pm

Bring the engine up to TDC on #1, then put the mark on the distributor so it lines up with the rotor. This will get your Bus right around 0 degrees and it should start from there and then you can adjust to the proper spec.

Sun Nov 01, 2009 3:47 pm

Could you have installed the distributor cap backwards? IT only really fits right one way.

Is it possible that the S boot has a tear in it?

Order up a new throttle body seal also. http://www.germansupply.com/home/customer/product.php?productid=16922&cat=&page=1

Those 2 screw that hold the throttle body on need to be tightened as a team so that it will seal well.

Sun Nov 01, 2009 4:12 pm

Update: Fixed.

Thanks for the input guys, I will be ordering that seal today, and a spare temp sensor II just to have on board.

Half the reason I'm documenting this is to help others learn by my mistakes and this is a good/stupid one: When setting your timing, look carefully that you clip the timing light to the right plug wire! :roll:

I know it goes on #1, but I think they criss-crossed on me, and that is why I couldn't even find the timing mark.

Overall, I think my assessment was correct, the fixed vacuum leak did affect the timing, but when I tried to correct it with the timing light clip on the the #2 plug wire, naturally I made it worse - DUH! A new day, a fresh perspective and I figured it out. By the way, it DOES run better than before now, idling right at 850RPM, 7.5 deg BTDC, and 28-32 degrees BTDC at about 3000RPM. Balls on - and no sucking sound. Live and learn, what a moron. Oh well, the bus is running the best ever since I've owned it, so that's good. Moving forward...

As far as getting it running today in the first place, I just set everything back to where I thought it should be, by eyeball. That was enough to get it running so I could dial it in. Credit me that, at least I have a good "feel" for it, even if I do hook up my test equipment incorrectly! :D

Happy November.

Sun Nov 01, 2009 4:28 pm

Awesome.....sometimes the best thing you can do for your Bus is to walk away and come back with a clear mind and a fresh perspective. Nicely done.

Sun Nov 01, 2009 4:33 pm

seems like i see more cars these days with the dist. installed weird or with number 1 in the wrong place than i see correct ones....just more stuff to sort out

Sun Nov 01, 2009 5:47 pm

Well, my dist is in the right place. I just clipped the wrong plug wire, they cross over each other a couple times, and I just got the wrong one. Not being careful enough.

I picked up a few tips along the way - so thanks for that. Good advice:

- Tighten the throttle body screws evenly. Good call.
- Rotate engine to #1 TDC and align rotor to mark. Also good. Thanks.
- And I checked out that adjustment on the AFM wiper, inside. I never realized that was moveable. Now I know. I'm not going to move it, but one day, that info might come in handy. I also discovered the CO adjustment screw in my Bentley... not sure what that is. I'll read up on it.

I'll keep all those ideas in mind next time I'm in there.

Thu Nov 05, 2009 11:23 am

Don't feel bad, I have a number 1 marked with sharpie on the dist...you don't need to ask why :roll: