I have a 1973 2.0 built to a 2056 running stock fuel injection. I am running points and I have verified the dwell and timing are correct. The air temperature sensor on the throttle body is disconnected due to it causing the engine to hunt excessively at idle. The valve were set less than 500 miles ago.

The car starts and runs fine on initial start. It at times has a little hesitation on acceleration due to the wear on the TPS board I think. As the engine warms up into the normal range, I experience a significant loss of power. The temp never goes past the "M" on the temp gauge. There is never any pinging. But there is just no instant response to pressing the accelerator that is present when the engine is cool. At times pushing the accelerator results in little or no engine response for a brief period and the engine almost stalls.

I have checked numerous times for vacuum leaks, lose wires, and made sure the grounds are good. Checked the plugs and it does not appear to be running rich or lean.

I tried to calibrate the TPS according to the Pelican article but never really got the readings as indicated in the article.

I am going to go back through it one more time but I need some suggestions as to what I should check next?

did you recalibrate your MPS?

Do you have a knob on top of the ECU?
If you do, turn it off, all the way.

Rich

I don't think idle CO adjustment is gonna solve his problem ....................

The Cap'n

Have not redone the MPS. But while I am sure that will help overall, it does not seem like the MPS would cause this issue.

If you don't get that tps adjusted right, you'll always have that hesitation. The knob on the ecu will have no effect either. Do you have a wide band O2?

Here's a quick fix on that tps:

Use 1000 grit wetordry and sand the traces on the board where the marks are. They are thicker than they appear. Use polishing compound and alcohol to finish up. Then try again to calibrate it.

It would if it was too lean or too rich at WOT

or at transition.

OK just to be clear, I am asking the following question because I don't know the answer. I am not doubting your response. If I understand the MPS it essentially controls the length of the injector pulse based on manifold pressure. While there is a temp component in the overall system, the MPS does not change the pulse based on temp. Because this only occurs when the engine is warm, the MPS should be functioning correctly?

Are you still running those fuel injectors with more flow? It would really, really benefit you to have a wideband AF meter in your car; it will give you an eye into what your mixture is doing when you have the loss of power happening.

Yes on the injectors. Don't have access to a AF meter.

All the engine FI sensors are used to calculate he pulse width, including temperatures (TS1 and TS2).

The TPS must be calibrated correctly, it has the idle switch and 'accelerator pump' functions that are also ECU signals.

It apparent that your MPS needs adjustment to adjust the air:fuel mix to the characteristics of your car, which can only be correctly done with an exhaust gas analyzer or wide band O2.

Mike, what cam?

Stock cam.

To add to what Jeff said.

if your car is too hot, you would get more fuel....to keep it from melting.
This is the case with any fuel injection system.

More nowadays....you get limp home mode which is super rich.

Like jeff said...everything in the system, all the sensors are there to tell the ECU how long the pulse width needs to be.

The FI trigger points just tell it when to do it.
Everything else is for mixture.

So.....
The best way to figure it out is with an Air Fuel gauge stuffed up the tailpipe.

I use a portable one with 8 feet of cable.
Its an O2 sensor inserted in the tail pipe with a metal clip and a screw clamp to keep it in place (lost one on the road once)

I use masking tape and run the wires up to the gauge which sits on the passenger seat so I can see it...along with my tools.

I drive the car slow, fast, transition, long highway runs.
I drive and stop , tune the MPS, drive some more....

That is how I do it.

You can also ask for someone that has the more expensive equipment and knowledge to setup your MPS properly and bolt it back in place....

rich

Ok so I took a closer look at the plugs and decided it was running lean. Made a few adjustments and now have a much nicer plug color. Runs much better but I will have to seek out someone with a AF meter to get it exact.

Ordered a TPS board and I think that will solve the hesitation as currently the injectors do not fire when the throttle is moved as they should.

And just for fun I hooked up the temp sensor on the throttle body. For some strange reason it runs fine now with it attached.

That depends on how well it really runs when it is cold. The enrichment part of the system could be masking problems that are caused by the MPS. A rich engine for example might run OK cold, or a lean one might be OK when the cold enrichment circuit is on and then not well when the engine warms up.

Did it run ok before? People are suggesting the MPS because often a 2056 needs a tweak at the MPS to go with the non-stock engine. But, if it ran fine before with the stock MPS then that isn't an issue for you.

So what is your fuel pressure?

Watching this thread carefully, maybe it will help solve my high idle/low idle/pinging at higher rpm etc. etc issue

What is the correct advance to set timing on a 2056?

31 PSI.

I have mine at the stock 27.

You can rent an AFM is you don't want to buy it.

Check it as Rich suggests under WOT, part load ,and idle and check back.

31 should be okay if your CO checks out and you have the 2.0 injectors that have been flow checked.

Ok so I finally bit the bullet and ordered a wideband AF meter. Going to replace the TPS board, add electronic ignition, and try to adjust the MPS.

Anyone know what I should be looking for at idle, crushing and WOT?

Search the word "stoic".

I have mine set at 12.5. Once you bring in down under 14 you'll know you're on the right track.

Found this from Chris:
Using a wideband O2 meter that reads in A:F ratio, you want to see:

13.5-12.9 on the gauge while accelerating or climbing,

12.8-12.5 at WOT,

and 16-17 while cruising, going downhill or decelerating.

What about idle?

Based on what Chris has 12.5 would be pretty rich.

So because a lower AFR means a "richer" mixture, you want rich mixtures on acceleration and leaner on deacceleration.

Rich on accel, lean on DECEL....

Idle will be what it is.
If you setup the TPS properly ( look closely at the new board) there is a special circuit for the idle mixture.

The MPS settings are for part load, and WOT...

Those two settings are what matters with the MPS...the rest of it works based upon those two screws...

Oh so I got the AF Guage installed.

So under acceleration I am at 13.4 to 14.7.

WOT I am at 14 to 15 plus.

So that tells me I am running lean. With the additional displacement that seems to make sense.

What is the best way to overcome the lean condition? I am assuming MPS adjustment?

Is there a tool for holding the outer screw that will allow you to adjust the inner screw out to richer up the mixture?

is it lean all over the place?

If so, I have had good luck getting a 1000 ohm potentiometer (volume knob) from radio shack and placing that inline in the CHT wire.

turn it up until you AFM reads correct in all ranges, then measure the POT with an ohm meter to see where it is set.

From there, got back to radio shack and buy a resistor that is the same as you measured the POT...and replace the POT with the inline resistor.

This works on the whole range..so if you are only lean in one spot or another, it may not be a good solution and adjusting the MPS is really what you need to do.

rich

In another thread you posted the location of the welded bung. Why did you pick that location?

Well it was easy to get to and it met the installion guidance of placing it in a location and angle that would not collect water.

Best? Any way that works.

Try bumping the fuel pressure a few PSI. It looks like you're already over the stock spec by a bit, but you can go a bit further IMHO.

You can add resistance to the CHT circuit. That will make the FI think the engine is always cold, so it will add extra fuel. It can be a bit fussy.

You can unplug the intake air temp sensor. That will richen the mixture across the board slightly.

You can adjust the MPS. It is definitely fussy--you can make large mixture changes with little tiny physical adjustments. You'll have to hold things in the right place as best you can when you go to adjust stuff.

--DD

You may be able to get away with just adding some extra resistance to the CHT circuit like Rich mentioned.
Obviously, there's a line where it would create a problem if it's too much but you could try that and
experiment with various resistors or try the potentiometer idea.

Wow having the AF gauge made all the difference. Adjusted the MPS inner screw out a bit and upped the fuel pressure to 31 and I am running in the high 12s under acceleration and 11 to 12 on WOT. Will have to fine tune it a bit more but what a difference in performance.

Thanks for the info guys. Will keep posting updates.

As a redneck engineering fix I cut a small slot for a screwdriver in the outer MPS adjuster which with some effort will let you adjust the inner screw while holding the outer in place.

Right on!!

yes, the best way is to adjust the MPS to your engine.

Well I am getting closer to the ranges Chris suggested and I just keep findind more power!

Making small adjustments and driving for a bit then adjusting again as suggested.

I am really impressed with how much cooler and more powerful the car is now that it is not constantly lean. Not sure the AF meter will be a permeant gauge but it will stay for the time being.

I think now I am getting close to getting the performance out of the 2056 build that I wanted.

The thing that I learned is that very small adjustments in the MPS can have a huge impact on the mixture. I was making way too large changes when trying to do it by trial and error.

Still have a small idle hunt issue as the engine goes very lean for a moment and slows but the goes back to rich and runs well. Will have to think about that one.

Do you know that there are 3 adjustment screws?
Do you have a hollow hex tool to hold the outer diaphragm screw from turning while you turn the slotted inner screw?
The plug on the end of the housing is the third adjustment screw. It sets mixture at WOT after the other adjustments are completed.

Yes I know about the full load stop. But have been focusing on getting the others set. Don't know if it is right or wrong but I assumed that the ful load stop,would be the last setting after you had the others correct.

Can you turn the WOT stop? On a MPS the first thing I do is remove the epoxy and clean the threads so I can unscrew it. Then I run it without the WOT until the adjustment is correct for part load. Then I install the WOT and set it's adjustment...
Finally I epoxy it so it's not going to move just like oem.

I don't like the drill a hole in it method....

This one was drilled but I am making the adjustments as you noted.