Strange MPS issue, Lew's car Options

[achman_73_2.0]

"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?

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.

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.

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.

[achman_73_2.0]

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

Maybe that's not what you read? (IMG:style_emoticons/default/beer3.gif)

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

[achman_73_2.0]

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

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.

[914_teener]

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

Maybe that's not what you read? (IMG:style_emoticons/default/beer3.gif)

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

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.

[r_towle]

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...

[TheCabinetmaker]

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

[achman_73_2.0]

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

Maybe that's not what you read? (IMG:style_emoticons/default/beer3.gif)

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

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.

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.

[achman_73_2.0]

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

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!
(IMG:style_emoticons/default/WTF.gif)

[worn]

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

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!
(IMG:style_emoticons/default/WTF.gif)

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. (IMG:style_emoticons/default/pray.gif)

[achman_73_2.0]

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

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!
(IMG:style_emoticons/default/WTF.gif)

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. (IMG:style_emoticons/default/pray.gif)

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...