I'm slowly working through the 2500-3000 RPM shudder that I get in my 2.0 at part throttle cruise... It's a '76. The engine has 850 miles since the rebuild. Rings seated very quickly- no oil required from its 250 mile oil change to its 850 mile oil change.

Also, during the rebuild, ALL ground connections were carefully polished, and assembled with star washers on both sides of harness lugs. Also, injectors were rebuilt and calibrated by Marren Fuel Injectors in Connecticut. Cap, rotor, plugs, wires, coil all new. It's got a PerTronix pointless ignition.

The car runs better than new at all RPMs and load, except for this shudder. Sometimes its less noticable than others....

WHAT HAVE I MISSED HERE!?!

So far, I've gone through these steps-

1. checked and adjusted fuel pressure. Was running 34 psi. Reset to 29 psi.
2. checked and adjusted timing at 3500 rpm.
3. adjusted TPS at closed throttle using Pelican Parts procedure.
4. Tried warming up, then disconnecting TPS and test driving. TPS seems to be doing its thing... Ordered a new TPS anyway, since mine is old, and they may be hard to find in the future when I really need one, and I can use the old one for a spare. Not in yet.
5. connections through 270 ohm resistor and into TS2 are new and sound.
6. measured TS2 at 80 ohms hot, 2200 ohms cold. Engine had already cooled a bit before I could get my meter on it, so the 80 ohms may be a bit high, but looks fine. TS2 was new 850 miles ago.
7. disconnected vac retard and test drove. Aside from high idle, it still ran the same, ie still had the shutter. I thought that since rebuilding the dizzy the breaker plate could be moving TOO easily, and there was maybe an oscillation set up because the vac port in the TB was partly exposed to vacuum at 2500 rpm third gear cruise. Anyway, still ran the same.
8. New Bosch FI breaker points.
9. Since the '76 didn't originally have the 270 ohm resistor, I tried shorting around it. It ran very poorly across the range, especially cold or warm.

Also, I bought an inductance meter to check out my MPS. Mine was a rebuilt from AA that I got in about 1989. I have no idea which one it is or was, so I'm looking forward to finding out and adjusting if necessary to '74-'76 2.0 specs. (meter hasn't arrived yet)

So now I'm thinking that I may have screwed up the centrifugal advance. I built one good dizzy from two. I noted that the springs from the one were wound from two different sized wires, so when I assembled my composite one, I put two same size (smaller gauge wire) springs in.

So, I MAY be getting too much advance in the range where I'm having the problem. Looks like the '76 2.0 got a lot less advance until 3000 RPM than some of the other D-Jet dizzys. My original was '76, and my donar dizzy was a '74 2.0.... The easiest and most precise way to know what's going on is to take the distributor somewhere and get it plotted.

Can anyone recommend a place where I can send my dizzy to have the advance checked and calibrated? Preferable in the Boston area, but I'm glad to ship it if the turn-around is reasonable.

THANKS!

PS- ANYTHING I MISSED HERE??? ANY MORE SUGGESTIONS ARE WELCOME!!

Jim

Ok,

4. TPS-Did you disconnect it and run the car around? If it makes no difference then its not the TPS.
5. 270ohm resistor and TS2- What TS2 r u running?? 012 (74-76) or 017 (73 2.0L) You shouldn't have to run a resistor at all IF you have all the matching FI componets.
You should be running a 052 ECU, 043 MPS, 012 CHT as these match


AA rebuit MPS- Hmmm, several of their rebuilt MPS's I have seen have a soldered on copper diaphram soooo the stiffness of the soldering around the partload stop effects THROTTLE RESPONSE. They run but off idle and cruise is funky, kinda like "on/off" in the transion.
Also the need to run a 270 resistor makes me feel like the calibration is WAY OFF.

Borrow someone's good 043 MPS and try it.

the advance is set by the springs underneath so if you haven't mucked around with them it should be ok. How does the timing mark look when you time it with a lite?? steady? moves alittle? wanders a 1" or more?

What cam was installed?

what shape is your FI harness in?

i had a similar problem with mine and it wasn't until i cut into the hard and brittle plastic covering that i discovered that some of the wires had become brittle as well and were broken inside the protective wrapper ...

specifically, i had 3 white wires that go to the injectors broken where you could not see it ...
Andy

Usually, the TPS is the culprit for this. Mine did this and new TPS fixed it. As the contacts wear, you can get a dead spot due to wear and/or corrosion.

Thats why the "test" for TPS is to unplug it and drive around to see if it clears up.

If the studder or bucking is gone then its the TPS adjustment or worn out.

If unplugging the TPS doesn't fix it then its another problem!

Thanks a ton for the help. You've got me thinking in some new directions! I'll update when I have more info.

Jim Kelly

An update. I think progress is being made...

To test my theory about distributor advancing too quickly vs. RPM, I retarded the timing. The shudder is still there, BUT! the engine runs much more smoothly and is quieter at idle. Plus, at WOT and >3000 RPM, it actually seems to be pulling stronger.

Still looking for a place to check my distributor advance.....

Next steps here- verify that the paint mark on the pulley aligns with the groove on the fan casting at 27 degrees. This fan is not the original, because the original one to my engine had 3 or 4 broken blades. Though I had the replacement one balanced and it's pulley trued on a lathe, AND I verified that the TDC mark on the fan was good, I never verified the paint mark on the pulley. To verify the TDC mark, I found TDC with a vernier depth gauge before the head went on. The TDC mark aligned perfectly with the fan housing, as did the TDC mark on the flywheel..... Anyway I'll do that this weekend... use a mirror to see the fan markings, align TDC and put a new paint mark on the pulley, and then find 27 degrees and put another new paint mark on the pulley....

Also, my LC meter arrived yesterday. I did a quick check on inductance at 0 inches Hg, and whatdayouknow? 1.45 H. EXACTLY the inductance Paul Anders specified for a -043 MPS (after correcting his 1.39 H for sea level, where I'm at).

That was great news, but that's at 0 inches, and my problem is at part throttle, probably 6-12 inches. But at part throttle, the inductance is varied only by the aneroid cells, and if one or both were leaking, I think I would see less than 1.45 H, so I think my aneroid are OK, and since the MPS holds a vacuum overall, it should be adjustable if it's out at the other vacuum levels.....

Those are the next steps, which will have to wait for the weekend....

Does this make sense or is it just my imaginative misinterpretation of the engineering involved????

Comments are welcome!
Jim

Ok, WOT is good on the MPS for a 2.0L stock.

What is the inductance at 4 hg?? This is the reading for partload as the outer screw is set against the stop plate for this reading. This then sets the inductance scale from 4 to 15hg which is the transion phase from idle to partload where most of us do our driving.
This is why the "flex" of the diaphram is so critical for smooth running and soldering stiffens up the diaphram giving it problems. I also think this is why OEM MPS's run smoother than even the Brett rebuilt units as they have a different pleating on the diaphram than OEM.


The shudder could just be the dizzy adv plate sticking as it spins up the adv.
or the MPS partload setting isn't right for your car. Most of the driving occurs at 2500to3000rpms normally, so that is where the critical setting occurs.
The old Kjell Nelson article had you adjust the center screw at 2500rpms but that changes the idle settings too which I don't think he understood. But, it does give you a better partload setting/running for a quick fix.

With the hydro cam I am not sure what problems it coud cause with the djet as the hydro cam I have seen are pretty steep ramps compared to the stock solid cam.

Here's the plot. Mine is Red, Paul Anders' is blue/black.

Not sure the hydro cam would do the shudder. It's almost exactly stock timing- 2 degrees more duration at 1mm, which may only be longer ramps. People use much more aggressive cams than this with D-Jet, I think.

It feels like ignition. Or lean miss maybe I guess. My curve is slightly leaner than Anders', but then I also have that ballast resistor that I'm not supposed to have which would probably more than make up for it. I suppose the ECU could be hosed. Fuel delivery is OK, because it runs great >3000 RPM.

Dizzy advance plate WAS sticking. That's why I rebuilt the two dizzys I had into one. Very smooth and lubed now. Centrifugal advance seems to come in very smoothly when I speed it up under the timing light. Still don't know if it's too much too early, though.

Next things to check are the timing marks, and the dizzy advance curve. When I get my new TPS, I'll swap, but unplugging mine didn't change the symptom. Plus, I think TPS mainly tells the ECU that the throttle is closed, or that it's moving in the open direction.....

Thanks again for your advice....

Click to view attachment

Here's the newest news- this is starting to get me down.

1. confirmed it's the correct ECU for '76. Didn't realize it, but I could read the sticker through the hole in the mounting bracket and it's a -052. That hole saved me a boatload of time and aggravation pulling the ECU.

2. MPS- in addition to the inductance vs. vacuum curve above, the primary coil is 86 ohms, the secondary coil is 340 ohms.

3. checked the timing marks. I printed out the the Pelican Parts scale, aligned TDC using a mirror, then checked and remarked TDC and 27 degrees on the pulley. Unfortunately, my previous marks were OK, though smudged, but I sharpened them up with a permanent marker.

4. reset the timing to 27 degrees at 3500 RPM. Started to get strange here... it was off, maybe 10 or 12 degrees advanced. The car now idles at about 900 RPM without the vacuum retard (never did that before, always too fast until I hooked it up). It even requires the idle bleed screw to be out a bit to hold it to 900.

5. checked the idle vacuum- it's now down to only about 7-8"!!!! Was always a bit low, but at least it was 14".

6. set the idle mixture. Don't have a meter, so I used the old chevy carb approach of setting it to "peak steady vacuum", which is where I hit the whopping 8".

By now the car was idling OK, but rough. Not lumpy rough, but rough as in it feels like there's a vibration.

7. pulled the plugs. All four look OK- light tan ceramic, light tan side electrode. black dry fluffy deposits on the end of the steel casing, though, like it's running rich.

8. checked the compression. Looked good- 140-145 on each cylinder. Took about 3 cranks to get to the 140. I haven't personally seen an engine this even.


Now, the engine is running WORSE than ever. I don't want to even take it around the block any more- the shudders have progressed to jerks, and even above 3000 rpm it sounds and feels like something serious is going on....

Engine has about 900 miles since rebuild. Fuel pressure set at 29psi, injectors were cleaned and matched by Marren FI, new 8.0:1 euro piston sets, new TS2... plus all the other things in my earlier posts....


Only thing left is the ECU??? But even that wouldn't explain all these symptoms....

Oh me oh my. And the weather finally got ideal for cruisin'...

My 1.8l shudders too at about the same range (3000-3850). I've been told that it's my dizzy. I've also been told that it's an old fuel line that is collapsing at just that rpm.

I dunno. I just drive up to 3000, upshift drive to 3000, downshift to 4000 and drive to 6000, then upshift again. Easy. It would be nice to fix it though....

At sea level you should be at 0hg 1.45, 4hg 1.19 and 15hg .76 as those are the readings I get with my NOS 043's using a Wavetek meter. Yours is adjusted to 037 spec.

Long story short, you are running rich at partload and idle. Aw, its only a little bit off but its a lot in terms of A/F ratio if you put a LM1 w/o2 sensor to test in.

Pull the MPS apart and adjust it to spec. You can just remove the WOT stop by burning the expoxy off and screwing the stop in all the way and cleaning the thread until the stop comes out cleanly. Then adjust the inner and outer screws to spec and reinstall the stop to spec. Put a piece of tape over the wot stop and drive around to test it.

OK, so the Anders numbers of:

So, for a 0 280 100 043 MPS, the 0, 4, and 15 in. Hg calibration values would be, 1.45, 1.24, and 0.75 H, respectively.

are incorrect? That would be good news, because at this point, anything that fixes it is good news....


I'm relieved that the spark plugs and compression look as good as it does. Less likely that it's internal to the engine now.

Jim

His numbers are based on using a correction factor and taken off 2 rebuilts and one used factory 043.

My number is based on 2 NOS 043 units at Sea Level. (well, my house is maybe 50ft in elev.) Paul's house is at 1280ft.

Try my numbers and see how it runs.


Everyone remember, the best and surest way is too measure the A/F ratio on your own car with a wideband. Either on a dyno or doing test runs with a LM1 meter. The Wavetek method is a via electronic standardization similar to what Bosch did. The Factory states the A/F ratios to be 13.7 to 1 for partload and 12.5 to 1 at WOT. We don't know exactly what the numbers the Factory used other than measuring the units we have.

The NOS units I have tested on a couple of cars just to see how they run compared to old units. They run crisper, meaning the idle/partload transision is much smoother than the Brett rebuilts or god forbid, AA units.

My Raby cammed 2056 MPS runs at .81,1.44,1.74 to set the A/F ratios of 13.6 to one at partload and 12.4 to 1 at WOT. Makes good power too.

This is great information, Geoff!

I'll try adjusting the MPS soon. First, I have set up to try the fuel pump under load. I'm trying to focus on the fact that I've seen degradation over the past few weeks. Could be the fuel pump is on the edge, especially for the periods when the injectors are only open very briefly. At WOT, the ECU enrichment PLUS that ballast resistor (that I shouldn't have) may be masking everything. As the fuel pump continues to deteriorate, the situation has degraded.

It's the original pump. 98k miles and 30 years (the car's birthday is next month!). I have an NOS backup, but I want to test the pressures first, while the car is bucking- lookin for the smokin gun.

I donno. But I'll try that first. My daughter's Cabrio pump went similarly- misses, then OK for a few days, then stalled. Static pressure OK, but it wouldn't back out the driveway. New pump, and away we go.

Strange the plugs look fine, but anyway...

Thanks again. This info is much appreciated! I will make good use of it!
Jim

I have never tried to tune a hydro camed djet 914 only ones with duals.

That could be causing some of the problems.

29 lbs is pretty good fuel pressure.

The ballast resistor will throw the idle mix way the f*ck off so take it off (rich).

The shudder is the A/F being off IIHO....so

either reset the MPS to my numbers or due to the hydro cam try to adjust it by ear. Take off the WOT stop

1. warm up the car
2. have a friend try to hold the rev's at 2500rpms via the gas petal
3. adjust the inner screw to the best running you can as your friend battles to hold the rpms steady at 2500. (its tough cuz its gonna go up and down as you adjust the screw slowly). You will find the "sweet spot" if you go slowly, this should be fairly close to 13.5 to 1.
4. shut off the engine and check your readings via the inducance meter, reset the WOT stop to spec. tape it.

go for a drive....and see if it improves any. This is the shadetree MPS adjustment method and will "get you home". To really set it up you have to use a wide band meter to set the A/F.
Djet is hardwired for a specific set of engine VE and tossing in a variable such as a hydro cam IIHO makes for problems that require lots of tuning.

Why did you install a hydro cam??? Have you read any of the work and postings by Jake Raby on hydro cams.

Hi Geoff,

I'll start by setting to your numbers using my LC meter. That way I can get the feel of setting it off the car, and maybe get it closer. I'll follow with the test drive and the reset by ear, as you suggest.

It'll be next weekend before I can try it. I'll be shot if I'm found in the garage again for a while...

The car has always had the ballast resistor. Well, at least it came on it back in '83 when I bought it. It wasn't shown anywhere in the Haynes manual, so I tried removing it back then- ended up bucking on acceleration and rubber banding on cruise. Called AA and talked to George, who recommended putting it back on. Ran fine up to when I shut it down to rebuild it in '02.

I put the hydro cam in to-
a. quiet the engine
b. have a solution that self-adjusts for temperature and wear
c. not have to frequently adjust the valves.

I didn't know this club existed in '02. I did talk to Jake, however. He quoted a rebuild price of about $4500 or so IIRC, but wasn't interested in doing the hydro cam. At the time, as I recall, his main argument centered around losing touch with the condition of the car if you didn't get under there and do the valves from time to time. Implied (or came out and said, I don't remember) that people who do hydro cams are lazy.

He was obviously VERY knowledgeable, and we had a great chat one Thursday evening on the phone. The real reason I didn't go with him was that he couldn't offer any warranty on his work. It made sense, because he couldn't control how it was installed, broken in, used, etc. But he was still pretty much an unknown to me, a voice on the phone, and that was a big chunk of what I'd saved to do the entire car....

Also, I had a lot of experience with Corvairs. My first 4 or 5 cars. Rebuilt the engines in three of them- a 110, a 140, and a 150. My last one was the 150hp turbocharged Sypder. And every Corvair made left the factory with an hydraulic cam, and I never had any problems at all with them. The only reason I can see not to go hydraulic is if you're going to rev over 5500 or so fairly often, and I don't. Most (all?) car manufacturers, including Porsche, have ultimately gone hydraulic. Partly because, IMHO, they need to maintain settings, for emissions purposes, over time, as the engine wears. Same reason, I think, most manufacturers went to optical or hall effect ignition in the mid '70s..... But whether for emissions or performance, maintaining settings is a good thing. Or so I reasoned. Even VW went hydraulic with the TypeIV/Type 2 in '79. Though not with DJet, I know.

So I picked one from a knowledgeable hydraulic cam guy, one that is extremely close to stock timing, and bought the set.... lifters, pushrods, cam w/ gear.

I sure you're right about it having some effect, and that I'll need to tune around it.

Still can't figure out why it's degraded, though, over the past 100 miles... It was running better than EVER from about 200 miles AR (after rebuild) to about 750 miles AR. oh well. It'll come together.

Thanks again. I hope others are getting something out of this thread. I've seen other postings about a similar symptom that seemed to end inconclusively.

Jim

Another thing to look at is the lifters and excessive cam wear. Pull the lifters out and check them for wear and mushrooming. There were a ton of bad cams out there on the market and even now.
Cam timing is really important with Djet too so we'll see if you can work around it.

The resistor should only be on there if the CHT is one for a 73 2.0L. There is no reason to fatten up the idle mix that much unless there is some other problem like a vacuum leak

I would practice the KISS rule here and pull and plug all unecessary vacuum hoses like the AAR, decel, etc to rule them out. The only vacuum hoses that should be hooked up is the MPS and the PCV hose to the plenum.

Low idle vacuum can be several things but I am concerned about the valve timing or that they aren't closing properly. Back off the hydro adjustment some so there is alittle noise.

I don't like hydros cuz they seem to wear so much faster due to being under constant pressure from the lifters.
The setup I like is the Porsche swivel feet on early rockers. Fairly quiet at start up and quiet when hot. On my car I have never had to adust them although I still check them every 6 months since I do race at times.

Here's the latest.

1. I checked fuel pressure whilst driving. Teed a 6 foot piece of fuel hose in and drove around with the gauge in my lap. 28-29 PSI at all times.

2. Relashed the valves. Opened them up to one turn from zero lash. Everything seemed OK. Still no valve noise. Next step will be to open them up to .006", but I've seen articles that because this type of lifter has a hairpin style retainer, vs. a circlip, it can't take too much of that. Still an option, if I don't figure it out soon.

3. Checked TDC again! This time I confirmed that the "0" on the fan casting is indeed aligned to the mark on the flywheel. Used mirrors and flashlights at both ends to see the marks.

4. On the lifter front- I also checked the oil drained from my last oil change for metal. I poured it from the pan to a bottle for recycling, and checked the bottom of the pan with a magnet. No metallic particles found. When I changed the screen, it had droppings from the case sealant that had oozed out, nothing else. I dried them between rags and inspected under magnification and with a magnet.

5. removed two fuel injectors. When I back-flushed, both had debris in the inlet screens. I blew them out with pressurized alcohol into a white coffee filter. One gave up a particle that looked like a fly sat there, and I'm not too worried about that. The second one had a piece of cured blue RTV about the size of an dry oatmeal flake, and paper thin. That one could be a big problem.

So I'm in the market for a set of 4 new fuel injectors. These were cleaned and calibrated at Marren FI in Connecticut. Only two are original- 95k miles old. One is about 40k miles old, and one is only 950 miles old. Time for a complete new matched set, in my opinion. Putting these in was like putting in a set of rebuilts...

Also, I'm going to add a real EFI fuel filter in the engine compartment. My daughter's '99 VW Cabrio has one downstream from the pump (handles about 50 PSI). It's in a steel can, and it has nipples for 7mm hose in and out. I happen to have one in hand, as a spare for her car- not any more!

Although the fuel tank was cleaned and treated, and the rubber hoses are all new, the plastic lines underneath the car are original. The ends were taped shut for four years, but any deposits in there went nowhere. And now with the gasahol, they probably just washed downstream to the injectors.

This winter, I'll replace the plastic with stainless. Once this crisis is past.

I found that the PO used blue RTV on the metal fittings on the ends of the plastic lines to seal the hoses when he replaced them. As if the barb and clamp wasn't enough!

Not driving it now. Shopping for fuel injectors and installing the rear filter.

If new injectors with filter don't do the job, I'll pull the lifters and take a look. I want to get back to where I started, with just the shudder at part throttle, and then I'll go after that with an MPS tuneup using and AFR meter.

Oh yeah, meanwhile, I won a complete '75 2.0 fuel injection setup on eBay. It's shipped and should be here this week. Then I'll have an MPS to practice on, as well as duplicate parts to try swapping things around. Of course, who knows if this setup works any better than mine.....

Progress at last.

I replaced all four injectors with new ones. Took a chance on Niehoff injectors for MB 450SE. Couldn't resist them at $50 each-

Click to view attachment

Also added a modern EFI fuel filter. "Borrowed" the spare I had for my daughter's VW Cabrio. Happens to have 7mm inlet/outlet nipples-

Click to view attachment This is a temporary mounting location.
While I waited for my the injectors to arrive, I spent A LOT of time checking curves on MPS, but in the end, I test drove with my original one. In fact, every thing I've tried has been one change at a time, so I could see what happened.

Anyway, when I got the filter and the new injectors installed, I took it out for a test drive. The mid-range shutter was GONE! The bucking was GONE!
They were replaced with a high end miss. Such a miss that it felt like a rev-limiting rotor kicking in, only at about 3500 RPM.

So I came home, and replaced the plugs. And then the miss disappeared too!

I'm not done... The idle is a bit lumpy. I improved it by turning the idle mixture full lean, but it's still a bit lumpy. Next steps- careful relash of the hydraulic lifters, and elimination of the ballast resistor. I tried the latter briefly, and it ran fine in the mid range. I'll try taking it out permanently after I relash the valves. Then, assuming it's running OK, I'll take the plunge and get the WB O2 AFR gauge and tune the MPS.

I'm thinking the original shudder was marginally lean mix at part throttle cruise, aggravated by the gasohol. The 450SE injectors are probably flowing a bit higher, either because they're new or because of a different design or because they're supposed to flow more. A 2nd problem was the plugs, but that developed later and accounts for the degradation.....

Thanks to everyone who gave inputs, expecially Mr. Bleyseng! Geoff, your posts and PMs have really helped steer me through to this point, and it's appreciated. You must have a Doctorate in D-Jet-ology!

Good news!!

Tune that MPS as soon as possible!