Pull the plates out, check the ground strap, clean clean clean, new grease on the ball.

Watch out for the ball flying across the room....not a cool thing.

Hard to tell from that picture, but you should be able to see the contacts and where they are touching or not.
Might need to reset it.

Rich

If both of the tubes in the plenum spin, that means you have 4 potential leak spots. I fear you're spinning your wheels until you address them. Bite the bullet?

Looked at the simple test on pelican and it confirms that when you set it at idle correctly, you have no connectivity on that circuit, which is the idle circuit.

It also says to turn it CCW one hash mark on the mount, now I am not sure what he means by that, nor what it would do....but that is about as much variable as any switch has, many have less.

See what happens when you move it clockwise till you see ohms on that circuit, what finger is the out most contact touching, then go CCW until the ohm meter stops, then go a bit further.

There is a correct place for the outer finder to reside, as well as the middle finger.
Sometimes bending the fingers makes them shorter or longer to meet the needs.

Rich

Yup, I agree... It's at that point... I'm just doing the prelim stuff - checking it out as I go.

I know the AAR is fine. Been there done that.

TPS - is still an open subject.

Dizzy is gonna get a bath.

Anyone know if the plenum can be taken out (and replaced) without taking off the intake tubes? I can easily cut the rubber hose connecting the plenum to the tubes, but putting them back on would seem difficult.

Onward ho!!!

It's not very hard to remove a few bolts on the head and pull off one intake runner tube....it's ten minutes work.
It's a whole hell of a lot easier getting to the one bolt underneath the plenum that holds it in place also.....
Pick that side.

If it was me, I would pull them both off and remount them clean so I know it's not leaking at the head mount.

Me...

Head---RTV---spacer---rtv----intake manifold

Well, I'm tempted to put the dizzy back in and give it a try.

Before I cleaned the plates - I tried to move them by sucking on the vacuum and they did not budge.

Now that they are cleaned and back on - I can easily move them by sucking on the vacuum.

HMMM???

they should move freely in order to snap back to zero at idle...it can happen too fast for the plates to get there and it causes all sorts of wierd things to happen.

rich

These guys know their stuff Len. Try those fixes first, then we can tackle the plenum if need be.

Well, plenum is out.

I'm too tired and sore to do any more tonight. It's time to start drinking!

Initial inspection of the plenum - it looks fine. What I thought were loose support rods must have been on something else. It was a long time ago - so I may have the parts confused.

In any event, the support tubes do not wiggle.

Interesting, I removed the left side manifold to get to what I needed so the plenum would come out. The middle nut - wasn't a nut on a stud at all. It was a bolt. I don't know how deep the stud hole goes - maybe the bolt was bottoming out and it wasn't sealing well? IDK.

Anyway, tomorrow I'll check the other manifold - see if it has something similar.

Manifold gaskets, injector gaskets - still like new.

BTW - how do I test the plenum (now that it is out) for leaks? Was thinking of putting some light inside and plugging all the holes - see if any light comes out in a dark room.

Is there a proper way????

Thanks,

Len

Tape up the holes, sink in water.

Well that worked. What I learned - I'm not that good at taping up holes.

Lucky for me, I left the cold start injector and it's mounting plate on. That's where the leak was. The outer gasket (NLA) was hand made..... poorly I might add. Bubbled up like one of those fake treasure chests in a fish tank.

Anyway, I'm a bit peeved at a) myself for not finding it without going to such an extreme, and b) my motor builder that made the gasket. I never thought to second guess him.

As far as going to the extreme - well at least I can rest easily that my support tubes are in good order. Should I tape them now that I have the plenum out? Seems to me the tape on the bottom side would just melt?

One of the side intakes has a small ding on the lip - so it's a bit out of round. I'll crimp that out - and anyway, I'm putting clamps all around.

I have some honey-do things I need to get done around the house today. So not sure if I'll get some bench time or not.

I'm happy to have found a leak. Maybe I can get some good forward motion going on.

Not done yet, but I'm on the right path. Thanks Rich!!!!

If you go look for a leather punch set, Harbor freight has them, it helps in making gaskets....

Rich

Was thinking red RTV high temp.

Thoughts about taping the support tube ends? They are solid and did not bubble, it just freaks me out - seems like a weak link in the plenum. IMHO

I would make a gasket, they should sell gasket kit/ material at the local hardware store, parts store, or hobby shop.

If you are worried about the plenum tubes, clean the paint off the area and seal them up with JBweld, or caulking or whatever makes you happy, then paint it up.

You won't sleep right till you do that, so get it done.

Made a gasket, and used red high temp RTV on all contact sides for the cold start injector holder.

Plugged / covered the support tube ends with JB.

Waiting for the RTV to setup, then I'm putting the plenum back on. Sort of anxious to see what happens.

This is a picture of the gasket that was on the outside of the CS injector holder.

The water test showed the leak coming from the ends - DUH. The bolts go through and into the plenum. So air worked its way around the threads and out of the plenum (or into when mounted and the car at idle).

Click to view attachment

This is getting to the point of being a bad dream.

That middle "bolt" in the manifold that I found in place of a "stud"... well it came out just fine. But when putting it back on.. guess what? The thing was stripped (inside obviously). No way to get it tight. Builder used some thread glue to hold in it - so taking it out - I had no clue it was stripped. Putting it back however, well that was a different story.

I'll deal with that at some point. I think the manifold is on tight enough not to leak. I got as much on that middle bolt as I can for now. I wanted to see what the results of fixing the cold start injector port leak would be.

The surge is less but still persists.

For grins - with the car at idle, I tried to adjust the TB switch manually. I noticed that turning it full CW or full CCW - the surging got really bad. So what I did was turn it full CCW the slowly turned it CW until the surging either stopped or should I say "got way better". Perhaps not the best way to go about it, but there did seem to be a "sweet spot" - anywhere else the surging was wild.

I don't have a fog machine, but I'm gonna get me a 10 cent cigar to make some smoke and see if I can see where the leak is at.

Maybe it's been the manifold all along?

UGH

You can still test for leaks at the manifold first. Start it up without changing anything else. Then proceed with the carb cleaner/propane leak test around the manifold gasket.

If it's leaking, you might have to do a helicoil for that stud... or *might* be able to get a few threads tapped with a metric tap. But it's worth testing for leaks first.

surging always seems to be one of 2 things - lean running, or vac leaks. typically MSP and CHT failure are at the top of list , and a bad TPS but car should still run even without the tps hooked up , on mine i just found out that a back temp sensor- the one that screws into the top of the plenum right next to the TPS on the back side, can cause these symptons as well. Mine had gone bad and was causing some a lean situation aand resultant bad ilde, surging, and bad issues. i was sure i had an electrical problem the way it would cut out and go up and down. but after replacing the temp sensor, perfect idle. - once you have your manifolds and plenum taken care of, test that temp sensor.

At this point - it seems I may be near normal.

I reset the dwell and timing. I'm not sure why timing should be set with the car at or near 3,000 RPM? It's been my experience over the years to set timing at idle.

Thinking about that, it would be next to impossible to do, when at idle, the surging was nuts.

Anyway, with the help from my wife to jack the rpm's up to around 2500 - 3000, I set the timing. Ended up retarding the advance quite a bit from where it was.

That seemed to drop my idle way down to under 900 RPM - and the surging seems to be near gone.

I don't want to say it's resolved - it would be nice to know for sure if the timing may have been another part of the issue. (along with the leaking cold start valve).

I can FORCE the surging by doing one of two things.

1) advancing the distributor a lot

2) at idle muck with the throttle plate switch - take it off it's idle setting

Anyway, there have been times with I "thought" it was right - just to let it sit for a while and watch it go nuts on me.

Will test again later today. Keeping fingers crossed - that maybe it's settled down?

I'm at my wits end.

Every time I think it is back to normal - I'm wrong.

At this point I really don't think I have a air leak. Maybe there is still an issue, but I can't find it.

When cold, the car does just fine, then as the AAR valve begins to close and the idle goes lower - as it should - that's when all the surging starts.

In fact - and for what it's worth - when I first start it and PLUG the AAR valve, it still idles fine (no surging) - so it seems to me the surging is only AFTER the car is hot.

IDK, I'm really close to just living with it. Aside from idle - car runs great.

BTW - the adjustment knob on the ECU - I've yet to notice it making any difference, at total CW or total CCW - the car (idling) just behaves the same.

If anything earth moving happens - I'll follow up. At this point I'm just gonna

You're still just walking around in the dark until you can isolate entire component systems. You haven't told us whether you've tested for leaks yet or not...

The computer is working against you at this point because somethin ain't right and it's trying to make it right. Once we know for certain there are no leaks, then you can begin to narrow things down. The next step at that point is probably the CHT sender, as others have mentioned. Think about the symptoms - it runs fine till it warms up, right? You need to follow that logic through.

You're a smart dude Len, don't get frustrated. Isolate systems first, and then rule them out. Changing parts and turning dials is not a great way to troubleshoot IMHO.

Timing is set at 3500 rpms to guarantee you are setting the timing with full advance on which at that speed is purely based upon centrifugal force and not vacuum.

Its a unique way of timing, and if you use a zip tie you can easily pull the throttle to the right speed and set the timing accurately.

Now, when you change the timing by ear, or by hand, you WILL screw things up.
So, STOP doing it. its not right and it will certainly create an issue.

Go back, set the timing by the book.
I know you changed it again, so go back and reset it properly.
Then, and only then will things sort out.

1) set Dwell
2) set timing at 3200 rpms steady, not blipped (watch for variation in timing when the rpms are steady, that will define a new issue....if it wont hold steady)
3) turn the ECU knob to full rich
4) set the TPS to the only correct spot it can be set....(again, its not a tuning aid and its not adjustable...stop messing with it)

If you do all of these things, you are now setup properly.

See if that works.
If it is close and idle moves a little bit let me know.
If the timing mark moves while you are watching it with the light at 3200 rpms, let me know.

You need to stop messing with three things at once.
Set them all properly so this can be diagnosed and fixed.

Proper diagnosis involves changing one single parameter at a time, not two or three.

you stated
I can FORCE the surging by doing one of two things.

1) advancing the distributor a lot

2) at idle muck with the throttle plate switch - take it off it's idle setting

Number one, yup, so set it right
number 2, yup, so set it right.

Rich

I just ordered a new TPS switch. But I can and will follow your guidelines to the letter and report back using the one I have. I believe it to be set correctly at this point.

Thanks,

Len

nice write up rich. concise and to the point.

So, I set the timing... had wife hold RPM (using the dash tach) at 3200. I did not notice the timing mark moving. Seemed to hold steady on mark.

Clamped down DIZZY, shut car off.

Turned ECU knob all the way clockwise (rich I think)?

Started the car.

No surging, but the idle is now LOW - like maybe 400 RPM. The generator light comes on. She does stall out sometimes. At times it will catch itself and stay running. If I get on the throttle and let go, that will usually result in stalling.

Turing (opening) JUST the air bypass does little for the idle. It makes a LOT of noise (sucking wind), but has no to very little effect. I turned it back to almost closed, which is where it was to start.

So that's where I'm at. No surge, low idle. ECU fully turned clockwise.

Thanks,

Len

Why full rich? Turn it back half way. Did you have the vacuum hoses disconnected and plugged when you timed it?







Edit: just saw that Rich had you do that ? Why full rich, Rich?

Well, I'm just following Rich's routine to the letter, as I said I would. His bullet point number 3.

Yes I had the vacuum hoses disconnected and plugged... at the throttle body.

I saw no need to plug the vacuum on the dizzy.

I'm cool until Rich has had time to chime back in. I'm sure there's a method to what he's asked me to do.

At this point, I'm surely not in any rush. And it's becoming more obvious that I'm clueless!

Running rich will cause a slower idle. Slowly one click at a time turn back and you shod see the idle change while making it more lean.

Recap 75 2.0 d-jet - was a California car, cat deleted by some PO, new (used) FI harness for a non California car.

Latest update...

Following Rich's guidelines....

Day 1:

1) Set idle - motor warm, RPM's at 3200, pulled vac lines off dizzy, plugged the holes to the throttle body. Timing mark did NOT move - held steady.

2) Turned ECU knob full clockwise - to full rich position.

3) Adjusted TPS - per the Pelican site.

Car now idles very low - most times it will eventually stall out.

Day 2:

Today the motor was cold. I didn't know what to expect, but leaving everything as was, I just went for it.

Car started. It took a few tries - maybe three. But it had a hard time staying running. The AAR valve was full open because I could here it sucking air. The extra air had NO effect on the idle at all.

After a while the car will run, but the idle is just above stall point - and it catches itself most times, but eventually will stall out.

I have a new TPS coming in. Most likely it will get here sometime next week.

For what it's worth, I've never seen the ECU knob have any effect on the idle - ever. I laugh every time someone tells me to adjust it, because I know it's not going to do anything. Maybe it is broken, or the idle circuit is fried, or the TPS is shot. I think when the day comes that the knob actually has an effect on the idle, I'm gonna fall over.

And yes I did try to turn ONLY the ECU knob (day 2). I'd turn the motor off, move the knob like 1/4 turn - restart. I went from full rich to full lean - no setting had any effect.

I've put the knob back now to full CW (rich) position - as it was this morning.

Once you have it warm and running, set the idle using the air bypass screw in the throttle body.
Sounds like you are almost there, but you may have closed that idle air screw long ago to get it to stop fluxuating.

Rich

That does nothing. Even when the AAR is wide open (when the motor is cold) the idle is low low low.....

Adding more air - regardless of how I do it has no effect on idle.

Air bleed screw in throttle body not having any effect on idle is typically caused by a very lean condition. I would definitely check fuel pressure and see what you are getting....an air/fuel ratio gauge would be a good investment also.

Fuel pressure is steady at 28 PSI

Double triple checked and reset:

• Fuel Pressure 28psi
• Dwell @ 50 Degrees
• Timing correct
• TPS - set per Pelican's site

Idle is about 600 when warm (when read with multi meter on coil). I don't know about when cold - will be able to tell tomorrow.

Knob on ECU - no noticeable effect.

Air valve - little to no effect.

Worth noting I have a new TPS board on the way. I'm keeping my hope up that may have some positive results.

???

What did you figure out with the missing manifold stud?

George,

A while back when I took the manifold off I noticed that the stud had been replaced with a bolt.

I didn't notice that it was stripped, until I put the manifold back on.

It's back together as it was. The bolt is still stripped. It's in as tight as it can be at this point. Again as it was. I've not revisited that issue, but using your propane test there are no leaks around that area.

I may tap it out this weekend.

If that is an intake stud, it's going to make tuning the car very hard to do.
It's leaking air.

I'm dealing with the intake stud this week - hopefully. Haven't done much else - except put a new TPS board on.

But I agree it makes no sense to plod on when I know there are other issues to deal with first.

Just for grins, I did pull up a picture of the motor AFTER the rebuild and in this shot if you zoom in on the intake, you can clearly see there is a BOLT in the middle where it there should be a nut on a stud.

That's the oddity that I discovered when I pulled that intake off. I was expecting a nut and came out with a bolt. Putting it back on that puppy was for sure stripped and needs to be resolved.

There will be an ending to this saga. Sadly for now, it lingers on.

Click to view attachment

Is that the regulator on the black bracket at the rear tin?

Yup, and yes I know the mount point is just below it. I may move it at some point, but that's how it was installed.

Did you tap that bolt hole for a larger stepped stud?

Haven't yet... game plan is to tap it out to 9mm - use a VW exhaust stub (9mm / 8mm). Think it will need to be cut to length as I believe the exhaust stubs are long.

Maybe middle or later in the week. I have a friend that works on the older VW's and we're trying to get together this week.

Once that's done, we'll seek out leaks and deal with what we find after the stud situation is put to bed.

OK, finally got that stud fixed today.

So, put the manifold back on hooked everything up, reset the timing again. Issue persists.

Sprayed carb cleaner all over every nook and cranny - nothing seemed to be sucking it in. Sprayed the intakes at the manifold, at the plenum connections, cold start valve, every hose, and the throttle body.

No leaks to be found.

New TPS board - adjusted per Pelican's doc.

Idle is way low, to the point it will stall out. Adjusting either the ECU knob or the air bypass has no effect.

If I pull the hose off the MPS - the car idles better. As soon as I put it back on - no dice.

The TB has two hoses that go to the vac on the dizzy. Not sure which is which, but one is high up on the TB and the other is smaller and lower on the TB. If I pull the larger hose off the TB (on top of the TB) the idle goes way up.

I haven't adjusted anything. Timing / dwell / leaks / valve adjustment are good.

NOW that said. Reminder that this was a CA car and had CAT at some point and speed limiter. Both removed by some PO and I have a replacement FI harness from a 2.0 NON-CA car hooked up. I don't see where that should be an issue, just mentioning it again. I don't know if the ECU is different for one or the other - or if it matters.

Finally, I know that at one point there was a short in the FI harness. It was up around the TPS area. I know this because the wires on the old harness were fried. I wonder if that short may have cause a board issue in the ECU.

Lastly, I'd love to beg, borrow, steal, (maybe even buy) known good ECU and MPS, to try. I really don't know what else to do.

I'm no expert, but since I've started on this issue, I've learned it really is a simple setup. Ain't much going on here.

if you remove both the advance and retard vacuum lines from the distributor, and put a bolt in each one so there is no leak at the intake, does the problem resolve?

Starting to suspect your distributor here.

rich

Negative. Actually it made it worse - that is if it would start and run at all.

With them off, if it does manage to start and stay it surges and will die out.

With the hoses on - it starts, idle is maybe 300, or less - and eventually dies out. The idle is so low, it's hard to determine if it is surging at all.

Started to wonder if the timing mark is correct? After the motor rebuild it came back with a bright yellow paint line on what I'm assuming is the correct timing mark.

Well I double checked the timing marks, and TDC is painted white, and the big yellow blade is @ 27 degrees... so timing appears to be set correctly.

I just wanted to double check that TDC was not yellow. The white on the TDC mark was on the back side of the fan, so you can't see it without a mirror.

Don't know if anyone is still following this or not....

Anyway, thanks to Carr914 I was able to borrow a MPS and ECU that he has as a spare to go with one of his cars that he's selling.

ECU looked old - mine has a nice shiny sticker on it (it may have been rebuilt).

I did notice however when I sucked on the loaner MPS, there was a distinct thunk and you could feel stuff moving about inside.

When I suck on mine, nothing feels like it is moving inside - so I was somewhat optimistic.... with caution.

So with just those two parts, I fired up my car - with my stuff to let it warm up and start acting funky. Didn't take too long.

After swapping out every combination of parts, the bottom line is that the MPS from the loaner is much more at home with my ECU.

I can get it to run at idle - with no surging. If I shut the car off and put my MPS back in, it starts - but dies - won't stay running.

Shut it off, put the loaner in and it starts and keeps running.

Shut if off, hook up my MPS, surge - sputter - die.

Will do more testing tomorrow morning when it's cold.

Maybe on the road to recovery..... we can hope.

Was your original MPS able to hold a vacuum test ?

I don't have anything to test that. So I can't say. It does offer up a lot of resistance when I just use my lungs. Not conclusive, but that's the case.

When I'd do the suck test on the loaner, there is a for sure sound that something inside is moving. Not so with my MPS.

That's all I got for ya.