Workin through the 2500 RPM shudder on my 2.0..., Next steps???? Running out of ideas! Options

[jk76.914]

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

[Bleyseng]

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?

[jk76.914]

Ok,

4. TPS-Did you disconnect it and run the car around? If it makes no difference then its not the TPS.

It made a difference in how the car ran, but NOT in the shudder. Very flat spot on any acceleration, even mild. Plus, when I shifted to neutral to coast to a stopsign, the RPM undershot the idle speed, but then recovered. Neither were a problem with the TPS connected.


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

It's either an 003 or 012 CHT, not sure which. Resistance checks out OK hot and cold.

ECU is probably original to the car. I guess I should pull it to find and record which I have. I wish I'd thought of that when it was out- how dumb is that???

I know I shouldn't be running a resistor, technically. But the car came with one, and when I tried removing it many years ago, when it had its original MPS, and again after the rebuild, it runs like a piece of (IMG:style_emoticons/default/stromberg.gif) without it. Lean miss I assume. I've seen other postings in the club from people who had the same problem... Maybe when I get this shudder problem straightened out it'll work without it!


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.

This was bought in 1989 or so, so the correct spares may have still been available back then... but I can't assume it. The original failed one day on my way to work. Wouldn't hold a vacuum. So I exchanged it. Seems to me they had one part number of rebuilt MPS for both 1.7 and 2.0. Anyway, I'm also dying to get my inductance meter and check it out. You bring up a good point for sure though. Even if the inducances check out, it doesn't mean the MPS has a smooth transition.....

Borrow someone's good 043 MPS and try it.

I'll have to post a request and see what I come up with... I'll hold off though, until I check the calibration on mine. Also until I can check the distributor curve....

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?

I may have mucked up the distributor, which is why I need to find somewhere with a machine that can plot the advance for me. Then I'll know for sure. I mixed and matched springs from my two distributors when I rebuilt them into one good one.... I know the set integrity was not maintained. There were three different type springs in the four total in the two dizzys, so I reassembled with the two matching ones. Coincidentially, these two were made from the smallest gauge wire, which probably gave the lowest spring constant, and therefore the earliest advance....

As far as stability- it's rock steady at any RPM. Doesn't budge. Advances smoothly with RPM.... Stability was a problem before the rebuild. And the breaker plate was sticking....

What cam was installed?

You're going love this one- it's stock timing, but with an hydraulic profile. Hydraulic lifters, special pushrods.... Smooth idle, good mid-range torque, pulls strong through 4500 then begins to taper off. Feels like stock, but quieter.

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