I am helping Brian with Lew's car. As most of you may know, it is a 2056 with djet.
The car was running fine, he drive it to CT one day and when he came back he noticed that the MPS was hanging. The car starts to run on 3 cylinders with #4 not firing. We checked for spark and injectors they are all fine, but if you remove spark wire #4, it had no effect.

The strange thing is if you elevate the mps about 6 inches up, it's all fine, even that 4th cyl works. All the electrical wires on the unit are fine

?

Dies the 2056 uses 1.7 or 2.0 MPS?

He would like to make it to Hershey.

If he lifts up the MPS it runs fine?
Is there oil in the plenum from the long highway run?
Look inside the hose that goes to the mps and see if there is oil in there.

a 2.0L MPS is necessary for the 2056 recalibration. The 1.7L MPS does not have enough room to adjust.

If #4 is intermittent it has nothing to do with the MPS. Check either the rest of the harness for wiring issues or perhaps the FI grounds at the top rear of the case.

I wouldn't say intermittent, it only runs right when holding the MpS about 6 inches up from the mounting location.

Rich, I will ask him to check the system for water.

Jeff is there a general guidance for or someone that does the recalibrating the MPS for the 2056? I have read Paul Anders MPS article but I am not sure that I am experienced enough or have the equipment to attempt the adjustment. I am running FJ67 injectors that are slightly higher flow than stock.

I'll check for water in the line. I did take the line off to check for obstructions/leaks and found none.

I found this on the buildsheet for the engine:

"043 MPS replaced with 037 to achieve richer mixture"

The engine did seem to lean out a bit at higher revs under load...some faint pinging was noticeable...

But the car has been perfect until now. Driven local and to NJ CT without issues. Idles slightly high even when warm but that is it.

Click to view attachment

I have always thought the two MPS bodies of the 1.7 and 2.0 liter are the same.....the only difference was in the calibration and adjustment of the diaphragm?

That looks like a Fuel Injection Corp rebuilt MPS.

My bet is that the MPS came off the mounting bracket and cracked one of the harness wires.

I would check those first.

EMF. It's sensitive to spark plug wires. Reroute #4 plug wire under the runner. IIRC, that is a rebuilt MPS.

Edit: post a pic of the engine psg side.

Harness was checked and is intact.

Those exposed wires in the harness concern me. Brittle or cracked? Is that red wire to the TS2 or is it added to the harness?

The 2.0L MPS has a spacer ring that the 12.7L MPS do not have, which allows greater diaphragm range and adjustability...a 2056 adjustment is at the limit f the 2.0L MPS range.

That is a rebuilt MPS...not one of the new Tangerine diaphragms...all bets are off on how it performs. All MPS with new diaphragms need to be calibrated with an exhaust gas analyzer, there are too many variables to determine a single calibration for every engine, even the factory calibrated every MPS to the specific engine. I have found Brad A's published calibrations are lean, I always must richen them up.

Early 1.7L MPS's have a WOT stop ring cast in the cover while 2.0L and late 1.7L MPS's don't. You need all the adjustment you can get for a 2056 using a exhaust O2 meter for the calibration. Using a stock 037 MPS will help get you closer but that's a rebuilt one so it's calibration is suspect IMHO.

One curious thing that I found--the MPS can be sensitive to shocks and sometimes even to orientation. It is an electro-mechanical device, and the core inside it can be moved by external forces and change the mixture.

I found this out by accident with the engine idling while messing about with the MPS mounting--the sensor fell down onto the engine tin, and the engine hiccupped when it hit. Naturally, I tried it a few more times, and tried jarring it a few other ways. It was most sensitive to being hit on the end.

That part was what led to the realization that the core could be moved relative to the windings by thumping on the MPS body...

--DD

Hey Dave

This all started when I came home from a drive to NJ and popped the engine cover and found the MPS laying in the engine compartment on the tin. It had been jury-rig mounted and came off...but the car ran fine. issues started when I remounted correctly. So is the MPS toast?

You need a vacuum pump and volt/ohm meter ..............

See if it holds 15" of vacuum for 5 mins.

4 pins on the MPS. Should be 90 Ohms between the two outer pins and 350 Ohms between the two inner ( or could be visa versa, don't remember but the values are correct). Check each pin for continuity to ground (the case).

No idea! I don't think the core inside the MPS should be able to get to where it won't move unless the MPS body is in a certain orientation, but it may be possible.

Do you have access to another MPS for testing purposes?

--DD

He does not and I only have a few 1.7,s

Pretty bummed, but looks like I may be taking the normal car to Hershey. Where can I get a 2056 calibrated MPS?

I would talk to Jeff Bowlsby....

Try and have him hook up a 2.0 core or the FIC rebuilt one with one of Chris Foley's replacement diaphrams. He can calibrate it for a 2.0 and then you can road test it.

You can play with the fuel pressure to try and up the mixture if you think it is lean. Maybe someone at Hershey has an portable Innovate AFM they can bring?

I personally think you are giving up too soon. Are you sure you "rung" out all the input wires on the harness for continuity?

Are you sure it isn't the connector on the trigger point in the harness as well?

Did you test it as Slit's suggested?

You are not looking for water in the plenum, you are looking for oil
Oil may get into that line, caused by high pressure in the valve covers, high pressure in the case, filling the intake plenum with oil that would migrate and get sucked into the mps.

It may drain when you lift it up the six inches...

Or, you may be making the wiring harness happy in one position and not happy in another position.

Try strapping it up high, under the engine lid....drive on the highway and see if it happens.
Rich

FIXED!

So I was finally able to go to the garage and look at the car yesterday.

I narrowed it down in my mind to the wiring. Either the wiring of the #4 injector to the MPS, or the #4 injector itself.

I pulled the plug to the injector, and closely examined it.

It seemed intact, until I noticed one of the two wires seemed to not be seated as far into the connector as the other one. I investigated further and found that the metal connector in the plastic connector was broken in half on that wire. The other one was fine.

Thinking this would explain the intermittent miss when we held the MPS up (it made the connection when held up and stressed) I clipped the wire, and soldered another one on the end‎ which already had a connector on it. My patch job is definitely mediocre and not permanent...but I fired it up and it ran perfectly! I let it warm up, then took it around the block...all seemed good, so I took it on a 45 minute drive, and it ran great!

Still idles way too high (around 1800rpm) but at least it runs correctly.

Now, just need to fix the idle, figure out why the fogs stopped working all of a sudden, and try sometime to get the MPS calibrated for the 2056 so it stops pinging under load/full throttle. The octane boost actually seemed to help a bit, but it still pings.

I read your email late last night. That's great need! We can certainly look at the high idle when you have the time .

Glad to hear it !!

too high of an idle speed and pinging are both signs of timing that may be too advanced.

Sometimes the advance plates stick on the old distributors, so they never let off at idle.

Sometimes the timing is set wrong by the tuner...which may be your situation.

Check your timing...

The MPS will have little to do with pinging...that is all about timing.

rich

Also make sure you are connecting the vacuum correctly. I did it incorrectly and hooked it to the wrong side of the dizzy. I have an advance and a retard on my dizzy. Switch the and you get good idle with them plugged and very high when connected. I think the Cap'n corrected me on this.

Also check that the injectors are seated and that the do not have leaks. Yea I did that too!

Been playing with my MPS to adjust for my 2056. No air meter but I have it so it runs pretty well. I have two MPS's. One that I don't change and one the I adjust and see what changes. Be interested to seem what you come up with.

The oddest thing I have is what seems to be not pinging exactly but valve clatter when I start out slowly. Not there at higher rev or if I give it a good amount of throttle on the start. I think my TPS board is worn as I get a little bit of a slow start at times.

in the end, it was not intact.

Rich

I went through the recalibration process last summer for my 2056. It is a trial and error process, and I would not attempt it without an air fuel gauge. But now it pulls real strong all the way. I could maybe calibrate one for my engine and send it. I have a webcam though. Not sure how much difference it makes.

There is no way for the MPS to affect the firing of only one cylinder. No way. However, the wiring for the mps, the hoses, the fuel injection, the spark plug wires all conspire to want to be right where the fuel injector wires plug in on the right side. I can easily imagine the MPS dragging one of the FI trigger wires out or out of whack by breaking one. It is a PITA, but the MPS has to be held down. It is like putting your iphone in the engine compartment tied to a string for heavens sake!

I did a lot of inductance graphing and I suspect a 1.7 body can work. Good luck! Let me know if I can help.

"I did a lot of inductance graphing and I suspect a 1.7 body can work. Good luck! Let me know if I can help."


I'm going to start a thread on this subject. Depends whom you talk to.


Glad you got it going to the OP.......still think you might want to consider replacing the harness and checking the dizzy for correct functioning prior to any MPS recalibration.

Good luck

We pulled the FI on the #4 cylinder, and unplugged the coil and tested it by cranking. The FI squirted fuel, so it appeared that the harness was intact.

It was partially intact, as I found out.

I am going to make a better repair on the wire, then try to set the timing, then maybe even attempt to adjust the valves, as I don't know when they were done last. Definitely might have to have some help on the last one.

After doing timing and valves, I will re-evaluate the pinging. If it is still there, I will look into calibrating the 037.

Thanks for everyone's help

I will text you later.

set your valves 1st, then time it. good job!

Mps has no impact on pinging or detonation.

"Either the wiring of the #4 injector to the MPS, or the #4 injector itself."

Please explain which wire goes from the injector to the mps? Do you mean the ecu?

The valve clatter also changes as the cylinders heat up, so that may play a role here.

Sorry, I mean one of the four wires which is plugged into the MPS through the connector. I really don't know where it leads...I'm not really electrically savvy.

It's not valve clatter, pretty sure of that. I used to run a turbo Miata, very experienced with the sound of pinging...but on someone else's car, not mine. Mine is living happily in Florida right now, 12psi 245/whp.

I think it is the timing...but I will adjust valves and then set timing as suggested

When I read the post and suggestions......there are two that suggest checking the distributer first....

Maybe that's not what you read?

The wires go to two coils, one inside the other. So there are 4 ends. All 4 wires go to the ECU aka brain to be used to set the length of injector pulse. It is one really cool analog system for measuring engine load. Incidentally, the plug to the MPS works in either orientation.

The MPS can affect detonation. An overly-lean mixture will detonate easier than a proper, or overly-rich, one.

As Worn just mentioned, there is no one-to-one correspondence between MPS wires and injector wires. There is just one "signal" produced by the MPS, and it is used as a basis for the injector pulse of all four injectors.

--DD

Thanks for explaining.

Odd, as when I unplugged MPS and flipped it over and plugged it back in, the car died and wouldn't run.

Not sure what you mean, as this had nothing to do with the dizzy

Seems logical. If the MPS is calibrated for a stock 2.0 engine, and you increase displacement, you may have issues.
Based on what I have read in the archives with people with 2056 engines, it has been an issue running lean and trying to calibrate the MPS.

I mean this:

You first suspected your MPS and then it turned out to be your wiring.

Now you have a high idle and you still suspect the MPS?


High idle and pinging could mean several issues. Don't forget the FI system is a System. Therefore you need a systematic approach. The FI system is also an electromechanical system.........so I am suggesting you check the mechanical stuff first to rule those out....otherwise you will be chasing your tail.

High idle could be a vacuum leak which could also cause the detonation due to an overly lean mixture and or timing.....the MPS can also cause the lean mixture as Dave has mentioned....or it could be comorbid.....meaning all the above.

Rule out one thing and then check the next component.

So you MAY want to check out the dizzy to make sure it is functioning correctly for arm movement, correct vacuum hose routing, and vacuum leaks at the advance and retard diaphrams............

That"s what I mean.

Detonation, or pre-ignition, is typically cause by timing of the combustion event.
Not a faulty MPS.
Too much advance will create a few results
Pinging or detonation ( you have this)
High idle ( you have this)
To much heat, and more pinging when super hot.... (You have this, though you may not know it)


A lean condition, what a faulty mps will do, will create just the hot condition.
A broken mps with a vacuum leak will run super rich, so richer eyes will water.

I still would suggest that your timing may be wrong, your advance may be sticky.

Just reading all your conditions at once...


I will add one disclaimer...
bowlsby makes new wiring harnesses because many of us have chased our tails for months to eventually find out the harness if fubar...

You've had several very knowledgeable people tell you to check your diz,
so why don't you? One thing to rule out.

No offense meant.

I don't remember saying anywhere that I suspect the MPS for the high idle.

I said I would adjust valves and check timing, as I don't know when this was last done or if it was correct before I got the car.

There seems to be a debate as to whether the MPS can't affect the car running lean. Some say yes, some say no way. It seems that if the MPS is determining injector pulse length, and you have a larger displacement engine than stock, and the injector pulse length is not long enough at max load, then you will not get enough fuel into the cylinders, causing it to run lean, which could result in pinging.

Does this not seem logical?

Of course this is determined also by timing, injector size etc.

On a supercharged car I built, I went with slightly larger than stock injectors and then had a "band aid" controller which lengthened injector pulse under boost to add extra fuel. The injectors were near 100% flow, so the pulse was lengthened which added fuel and prevented leaning out and detonation. Sounds crappy, ran perfectly, and works for low boost just fine.

I will try to adjust the valves, then set the timing, and re-evaluate the idle. If it still runs high, I will know that the timing and valves are correct and that it the issue lies
somewhere else. I will then check the dizzy, vacuum lines, dizzy advance etc. and see what I come up with.

There clearly seems to be a misunderstanding here.


The initial problem (engine running on 3 cylinders) had nothing to do with the dizzy. Read the thread.


The high idle may ABSOLUTELY have something to do with it.

I have not had any time to go to the garage (I live in NYC, remember, my garage is not connected to my house--it is 15 minutes away) and my work has kept me incredibly busy.

I'm not resistant to checking the dizzy! Sheesh!

Actually the MPS can have an impact on both even if it isn't a prime suspect.

The MPS can make the car go lean. Somewhere during the adjustment of my own 2056 MPS I went way lean and produced an explosion that tore open a previously healthy muffler. I suspect a backfire, cause I heard popping at the time.

Any vacuum leak will cause high idle. The engine will respond to more air by giving more fuel and that will be that. The MPS hose is one of several that go to the manifold downstream of the throttle butterfly. If my idle will not go down the first suspect on my list is a vacuum leak.

When I first got my car it ran horrible all the way from Baltimore to Madison. I ended up stripping down and cleaning the entire induction system. It certainly needed it - the car had sat for almost 20 years. In my case the fuel regulator was stuck shut so the injectors were seeing 90 psi pump pressure. A bit, uhmm rich. The car ran for several years quite well even though I ultimately discovered the diaphragm in the MPS was cracked. Thank heavens for Racer Chris.

Thanks for all the great tips and info.

This car has a pretty newly rebuilt 2056 from SchantzMD that runs very strongly. I am not sure how much of the wiring was replaced, or if the dizzy was rebuilt, I will try to look at the papers.

The MPS is an 037 that was rebuilt by FI corp. So who knows if the calibration is correct anyway...