HEI 8 pin Chevrolet 350 Misfire

[drholl]

MegaSquirt-2, 454 TBI’d, HEI 8 pin Chevrolet 350 Misfire

My wife doesn’t like me to mess with her 71 Monte Carlo with, as she says, the “Perfect tune”.
But 2 weeks ago, I decided to do a VE Analyse on a 30 minute datalog I got while she was out with friends.
I did the VE Analyse which made minor chances (2% in the VE table), loaded the minor changes and during my wifes easy driving it seemed fine. But one day my wife said, and I quote “It popped back when I stepped on it”. OK, she’s normally a very easy driver.
So I started to do a “compare” between the earlier “Perfect tune.MSQ” and my updated “Perfect tune +1.MSQ” which I loaded. I’d saved the “Perfect tune.MSQ” in 2 different locations, a working folder and a backup on a separate thumbdrive.

But this is what I get when I load the “Perfect tune.MSQ” file from either location in MLV.
(See Screen Shot.bmp)
Can I fix this by opening the “perfect tune.MSQ” in notepad and editing something?

I know cars, but computers hate me!!!

Thanks
Holl

[drholl]

OK, I went back to a much earlier MSQ, went over all my wires, installed a different distributor, etc. The engine runs fairly well for an old MSQ. But the Tach still goes to zero once in awhile.

My wife has a reasonably stock Chevy 350, (the ‘71 Monte Carlo in the avatar).

For years with MS-2, it had an 8 pin HEI. Now I’m getting zero (0) RPM readings when we step on it around 2,000 RPMs or so, and once in this datalog, a 7,000 RPM spike. The "zero" in turn drops the IAC towards the cranking number. And when the zero RPM happens, sometimes a “Pop” occurs back through the TBI.

Is there a way to turn next pulse tolerance “off” so the ignition fires whenever it sees the square wave pulse on pin 24?
Can I set the “Cranking”, “After Start” and “Normal Running” to 0% or 100% so it’s taken out of my testing? The problem only occurs when I accelerate. This is the second distributor that I’ve had in the car in the last 2 weeks.

Thanks, I’m kind of running out of ideas.
And remember, Computers hate me!!! They cry when I get near them.

Thanks guys.

Holl

[drholl]

In going through "all" of my settings, I found out somewhere along the line I changed "Cranking Trigger" from what the manual says "Trigger Rise", to "Trigger Return". I did a comparison back to March 2012 and that setting just screamed at me. Sorry for all the confusion.

And I want to thank any and all who thought about my issue.

I'll change it first thing in the morning and post my results.

Thanks Again
Holl

[drholl]

OK, HELP.

I found and fixed the trigger problem but it has had no effect on the misfire problem.
I took a datalog today and here it is. If you guys have some ideas as to what's causing this please let me know. Even ideas that are far fetched are welcome. I've replaced coils, distributors, plugs and have been leaning out the injector pulses.

It's driving me crazy.

Thanks Guys
Holl

[drholl]

Here's the same type pops. I broke the datalog into 3 sections.
149 - 157 Then a break until
181 - 192 then a break until
292 - 305 Ended.

I hope this makes sense.
And the MSQ that was leaned out to ensure I wasn't flooding out the spark.

Thanks
Holl

[Matt Cramer]

It's losing the RPM signal. Try bringing the HEI signal in through the VR conditioner - you can adjust the trim pots to get some noise filtering.

Also, where's the ground pin on the module connected?

[drholl]

Hi Matt.
The wifes ’71 Monte Carlo is still popping and stopping for no reason that I can figure out.
I’ve been pulling my hair out for 6 weeks looking for this problem. My wife’s ‘squirted ‘71 Monte Carlo had been running fine for years then it started to have a miss when it was “stepped on" fairly hard at 2500 RPM (TP=60%). I couldn’t figure out what was causing it. Datalogging it more, I began to notice that it was going to “Zero” RPM instantly from the 2500 it was running at. Then in a couple weeks it started to “just stop” at traffic lights, no notice at all, idling fine, the light gets ready to change and the engine just stops. Throw it in neutral, hit the key, and it starts right back up (5 seconds tops, with people honking, waiting for the “crank to run taper time” to drop so it doesn't chirp the tires). I’ve gotten lots of datalogs of this. Now it’s started to die while driving down the street. My wife won’t drive it anymore, it’s unreliable. But if I’m going down the street at 40-45 MPH (1700 RPM) or faster, the engine RPM goes instantly to zero, the fuel stops, the engine is still spinning and after a couple seconds, it gets fuel and starts running again. Usually I get a reset but sometimes just a yellow line saying “Time gap” for 2 and a half seconds or so.
Here’s a 7 minute drive datalog with it happening 6 or 7 times. I was going to the freeway for a short logging session but I have to go through a busy intersection to get there and I chickened out with it quitting so much. The long “Zero RPM” times are when I waited for a signal light to get ready to go green. I’ll start it and hope it will take off. It’s gotten so bad, sometimes it will only run for a couple seconds and quit again.
If you can, look at the datalog and tell me if the power is momentarily being shut off or the Hall/VR wire would be doing this type of symptom. But I’ve replaced both already.
Here’s what I have done. I replaced the 8 pin HEI with a new one, and replaced that one with the one out of the ‘squirted ‘59 Caddie (a known good one). I tried 2 different coils. I replaced ALL relays. I replaced the Hall/VR wiring. I spliced in a second power wire and put that power on a dedicated relay, straight to the battery. I bought, and installed a new MS-II 3.57 ‘squirt. I’ve installed “connector savers” on both ‘squirts to ensure good contacts. I have bought, but not yet installed, a new DIY harness.
Nothing I have done has made ANY change to the symptoms. NOTHING.
This weekend the guys are coming back to help me and I need some more ideas to try ! ! !
Could my tach masking or next pulse tolerance do this? But these are normal settings on the Caddie.
This has been the problem from, well, down below……
I'm trying to use any knowledge to try and troubleshoot this problem.
I know “What” the resets are but not all the reasons that cause them. I believe resets are caused by inputs “TO” the ‘squirt or the lack of a required signal. I thought it was either power coming “on” or the tach input coming up from zero or going down to zero.
Is it when; you have “0” RPM, engine code “0”, and the tach becomes active as the RPM signal goes up, or is it when the power comes on? Or is it when the RPM signal “Goes” to zero? Or some similar sequence?
These resets are most noticeable when the engine stops for no reason and I have to hit the starter to get it running again. I think it’s as the engine stops, not when it restarts, but I’m not sure. I've never had this problem before.
Are there any other causes of the resets (vertical red line)? Is the ‘squirt losing power or Hall/VR signal?? Or something else?
Please give me some ideas. The wife is really getting on me about her car. She dearly loves this car!!!

Thanks Matt
Holl

[Matt Cramer]

It's losing the RPM signal. You can try reducing the normal running next pulse tolerance to 25% in case 50% is too aggressive, but beyond that, most of the causes I'd look for would be in the ignition system or its wiring.

[drholl]

Thanks Matt. I knew you knew more about this than I would.

I will let you know what turns up or not.

Holl

[drholl]

Well, there was a post that I read, must have been removed, as I did read it earlier. But, since I spent the time writing a reply I'll put it in anyway. He said he also had a miss at idle while waiting for a traffic light and the engine would die immediately.

Well, that's the way mine started. But it then progressed, over a period of 2 weeks, to the electronic RPM signal quitting while cruising on the highway. This caused a "dead" engine (just spinning), which after 2 seconds, started running again. I have not found the cause. At a traffic signal, the engine would just instantly shut-off once in awhile.

Well Matt tried to help as best he could with good ideas. But to no avail. I still can't find what's causing the RPM to instantly go to zero, even while the engine is still spinning in gear on the highway.

I believe that it's a problem with my harness wireing to the car or the car itself. I have just ordered a new harness. At present, I have removed the TBI (put a carb on), changed 3 distributors, the last one is old points style with a Crane XRI points eliminator in it connected directly to the coil on the tach-in wire, changed the coil twice and changed the 'squirt to a known good one from my daughter's 59 Cadillac. It's not the 'squirt as the symptoms are 'exactly" the same. NOTHING I have done has changed the symptoms.

It's not the 'squirt. It may be in the car wireing. But we've had the car for 40 years, it has always run well for a 40 year old car and my wife "Loves" this car.

I have left the 'squirt in the car so that it "thinks" it's working, but the outputs are not connected, as it now has a carb and a points eliminator kit. The 'squirt says "Zero" RPM but the car still runs on the carb and Points Eliminator. The computer is there for datalogging the "miss". I have the Tach-in connected to the coil negative with the points eliminator as a datalogging trigger. I no longer have the coil driver connected but the input still goes to "Zero" once in awhile, 20 seconds to 10 minutes. I have tried the "VR" and the "Hall" inputs, no difference. The problem must be in the car or the harness, so I'm getting the new harness. I'll wire it "over the top and out the window. That's my last hope.

I would like to know how to tell the 'squirt to just "FIRE" the coil, and injectors, if it even "THINKS" it "SEES" an ignition event. I don't want the "squirt" to go into "resync" or to "reset" the CPU. I think this can be done by turning "Next Pulse Tolerance" to zero or 100%. But I don't know for sure. I asked about it once, but didn't get an answer. I wish I knew what else could cause the ‘squirt to miss the points trigger???? And how to ignore the Next pulse Tolerance.

Yeah, it's been a terrible issue.
Holl

I thought I knew cars, but computer hate me. They cry when I get near them.

[trakkies]

Sounds very much like you have a problem on the ignition +12v circuit. Possibly the switch or connectors? Most problems come down to fault connectors or switches or relays.

What you could do is rig up an indicator (LED or similar) fed from the actual coil +12 terminal. If that goes out when the engine dies, you have your answer.

[drholl]

Thanks to both you and Matt. I'll give it a shot. I have rewired the entire power circuitry including new relays throughout.

Holl
This issue is Killin' me.....

[drholl]

Thanks Matt and Trakkies for your earlier help on this problem.

I’m still having major ignition problems on the ’71 Monte Carlo. My wife won’t drive it until it’s fixed (It's been over 2 months now. I'm in hot water!).

I want to make sure I’ve connected the ignitions properly for all of my old cars. So I have 3 short questions.

I don't see a particular location that Pin 1 of the DB-37 should be connected to, when using points or similar on a regular dizzy.

SO-
1) Right now, on the ’71 Monte Carlo, I have reverted, from 2 different GM 8 pin HEIs, back to an old style vacuum and mechanical advance timing with a Crane XRi (points eliminator kit) connected to the negative side of the coil (Black/Yellow) along with the trigger input, pin 24 of the DB-37. The Crane power (Black/Red) is connected to the positive side of the coil along with the 12V input. Where should pin 1 of the DB-37 (the black wire, i.e. return for the trigger input) be connected on the engine or distributor? If on the dizzy, where specifically???

2) On another old style ignition, the ’59 ‘Vette, the Cranes’ (Black/Yellow) is connected to the Trigger input, pin 24, (which has a pull-up resistor). So specifically where, on the engine, does the black wire of pin 1 on the DB-37 pin connector, get connected? Same as #1 above???

3) And on the ’59 Caddie with an 8 pin HEI, exactly where on the engine or dizzy, does the black wire of pin 1 of the DB-37 pin connector, get connected? The engine ground or the ground output of the HEI (Pin 1 of the 4 pin connector) or someplace else???

I don't want to go to MS-III until I fix this ignition problem so that it won't ever come back. This issue is killin me...

Matt or Trakkies, If you can please answer as quickly as you can. My wife has been without her car for 2 months as I try to figure out what's happening. This deserves a personal Thanks from me.

Thanks Guys
Holl

If any of this doesn't make sense please let me know. Thanks.

[Matt Cramer]

I know the feeling - my wife's been asking when I'm going to have that LS swap into her '72 Chevy pickup done for a while!

Thanks Matt and Trakkies for your earlier help on this problem.

I’m still having major ignition problems on the ’71 Monte Carlo. My wife won’t drive it until it’s fixed (It's been over 2 months now. I'm in hot water!).

I want to make sure I’ve connected the ignitions properly for all of my old cars. So I have 3 short questions.

I don't see a particular location that Pin 1 of the DB-37 should be connected to, when using points or similar on a regular dizzy.

SO-
1) Right now, on the ’71 Monte Carlo, I have reverted, from 2 different GM 8 pin HEIs, back to an old style vacuum and mechanical advance timing with a Crane XRi (points eliminator kit) connected to the negative side of the coil (Black/Yellow) along with the trigger input, pin 24 of the DB-37. The Crane power (Black/Red) is connected to the positive side of the coil along with the 12V input. Where should pin 1 of the DB-37 (the black wire, i.e. return for the trigger input) be connected on the engine or distributor? If on the dizzy, where specifically???

Pin 1 is a plain ground wire. In this particular setup, there's nothing in the ignition that should be grounded through the MS, so leave it floating.

2) On another old style ignition, the ’59 ‘Vette, the Cranes’ (Black/Yellow) is connected to the Trigger input, pin 24, (which has a pull-up resistor). So specifically where, on the engine, does the black wire of pin 1 on the DB-37 pin connector, get connected? Same as #1 above???

Same as above - nowhere.

3) And on the ’59 Caddie with an 8 pin HEI, exactly where on the engine or dizzy, does the black wire of pin 1 of the DB-37 pin connector, get connected? The engine ground or the ground output of the HEI (Pin 1 of the 4 pin connector) or someplace else???

The HEI ground pin.

[drholl]

Thanks Matt for the quick reply.
But of course one more question.
In Base Ignition settings, How do I turn Next Pulse Tolerance "OFF"?
Set Cranking, after start and normal running to 100% or 0%.

I know engines but computers hate me.

And this zero RPM problem is just killin' me....

Thanks
Holl

[Matt Cramer]

IIRC, 100% tolerance = no filtering.

[drholl]

OK, I found it. It was a corrupted MSQ evidently. One that was missing a ">" or something like that, I guess.

I ended up taking a MSQ from the Cadillac and put it directly into the Monte. Yeah, it wasn't correct, but it ran OK at an idle. Real rich, but it ran. It didn't hic-cup or anything. So today I used it to re-enter all the settings that I had from the previous MSQs and it ran GREAT.

I will delete all the earlier Monte Carlo MSQs so I don't ever use a bad one by mistake.

Trakkies and Matt, I want to thank you for all the time, ideas and information that you sent to me to help on this problem.

Thanks Guys, you do a great job.
Holl

Remember, I know engines, but computers hate me.

[drholl]

OMG, I'm back.

The car ran fine yesterday. And I was ecstatic, BUT...
Today after idling for 5 minutes, just to be sure it was OK, I then left for a buddies house and about a mile away from the house, it started shutting off so badly and often, I had it towed rather than drive it for 50 - 100 feet and have it stall in traffic again. The engine would almost always start up quickly. But eventually I noticed something that appeared a little different from earlier times. As it would quit while safely on the side of the road where I could watch the laptop, I noticed that sometimes when I tried to restart it, with the laptop running, it had a "dead" screen. The power appeared to be off to the MS-II. But yesterday I ran a power lead directly from the battery to the MS-II, nothing in between. I had to disconnect the wire to kill the MS-II. I did it just to be sure the key switch wasn't faulty. And a 10 Gauge ground directly from the ground on the battery, to the same clean location on the intake manifold where the 5 MS-II grounds are located. A single point ground. Could the varistor be sensing too much current? What in the MS-II draw more than 0.5 A continuously? The two varisters that are in the MS-II are rated for 1 Amp peak, and 0.5 Amp continuous, kind of like a slow-blow fuse.

When you look at the datalog and see the Batt Voltage drop to 9 volts or less, that's when I'm cranking to start it up.
I cut much of the data out to get the datalog well under 1 meg.

I'm wondering if the battery voltage is OK, as shown by the datalogs, but the 5 Volts is dying. Does this make any sense?

Please offer some advice. I need it. This MS-II is practically brand new. I bought it as the original CPU was doing this same thing, dying, and I wanted to eliminate the CPU.

Thanks Matt and Trakkies
Holl

[drholl]

I forgot to add the last datalog that I butchered to shorten it.
It just seems like the MS-II is just powering off. But it's wired directly to the battery. No relays, no nothing between the CPU and the battery.

Thanks guys
Holl

[trakkies]

Well, by that log, MS isn't loosing power when is looses sync. Battery voltage is pretty normal apart from a couple of spikes. The TPS need calibrating, though. And the AFR is bouncing all over the place. Fix the TPS (callibrate) and post another log.