Horrible night. Car pissed. Never ran horribly like this before.

[Nascar83Fan]

The ecm will still have the error code stored and it'll show up as long as the error exists even if the service engine soon light isnt triggered by the ecm to turn on.
If the ecm loses power, such as the car battery being disconnected and then reconnected or the ecm orange wire fuseable link is unplugged and plugged back in would reset the ecm and clear any codes that were in memory. Unhooking the ecm from the car would also do the same thing, none of which should be done with car running or with the key on engine off position. Only under key off engine off position or key not in the ignition should one do any of the above to avoid possible damage to ecm and other eletronics in & on the car.
The scanmaster as long as the ecm hasn't lost power will be able to display what the last error code(s) are in the ecm's memory. The nal on scanmaster is where the mal codes would show up if any were being set by the ecm. The scanmaster itself doesn't store mal codes, it's only an interface to display what is being reported by the ecm and a couple other sensors are reporting to the ecm. It has no storing abilities, it's just a scan tool for diagnostic & monitoring functions for TR's and the TTA's. A modified version of the scanmaster was made for the syclone & typhoons that came later.




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[aminga]

The crank sensor tells the car when #1 is at TDC. The cam sensor tells the car when it is on the compression stroke.

Actually you have the crank and cam sensors reversed.

 

[pacecarta]

that gummed up connector has three contacts in it, one goes to the oil indicator bulb in dash , the other is 12v and the other is to the fuel pump, if the pump connector grounds it will stop the fuel pump

 

[Powertechn2]

that gummed up connector has three contacts in it, one goes to the oil indicator bulb in dash , the other is 12v and the other is to the fuel pump, if the pump connector grounds it will stop the fuel pump

Do you mean the one that is sticky dumdum'd up that I found just chilling down by the intake?

I'm not sure if it goes to ground if it would cause a cel, however I guess if the ecu saw a lean condition it might raise a cel.

 

[earlbrown]

Look down at the brass block the turbo oil feed line comes from. Is there a 3-pronged switch with nothing attached to it. (and does you oil light come on during KOEO?)

 

[Stage24u]

The car was stored for 10yrs you say........

Was it stored outside?

Is it a T-Top car? Sunroof instead?

Replace the ECM.

Chances are water could have hit the ECM, causing the intermittent backfire/stop/die/ feeling.

Same thing happened to my 1st GN, and recently to a buddy's Limited.

Water hit the ECM and never acted right since, throwing out weird symptoms from backfiring to bucking, to dying, then running fine....rinse and repeat.

Replaced the ECM and that seemed to solve the problem.

 

[BuickMike]

The car was stored for 10yrs you say........

Was it stored outside?

Is it a T-Top car? Sunroof instead?

Replace the ECM.

Chances are water could have hit the ECM, causing the intermittent backfire/stop/die/ feeling.

Same thing happened to my 1st GN, and recently to a buddy's Limited.

Water hit the ECM and never acted right since, throwing out weird symptoms from backfiring to bucking, to dying, then running fine....rinse and repeat.

Replaced the ECM and that seemed to solve the problem.

Take out the ECM and open the case. You will know right away if it has water damage because the board will have corrosion on it. At least the ones I've seen did, especially on the connector and top part of the board.

 

[haywire4130]

Actually you have the crank and cam sensors reversed.

Not true- he was right, the crank sensor only knows when it is on tdc. Theres 2 rotations (and tdc's) of the crank for one of the cam. the cam sensor shows "which tdc"- compression or exhaust

 

[BuickMike]

Not true- he was right, the crank sensor only knows when it is on tdc. Theres 2 rotations (and tdc's) of the crank for one of the cam. the cam sensor shows "which tdc"- compression or exhaust

Yep. Think about it. The window in the crank wheel is going to trigger the sensor when it hits TDC on the compression stroke and the exhaust stroke. The camshaft spins only 1 rotation for every 2 rotations of the crank, and therefore is used in conjunction with the crank sensor to figure out which one of those triggers is actually the compression stroke. If your cam sensor is having issues, the ECM still knows when the top of the strokes are and can just go into batch fire mode. If the crank sensor loses signal, then it is just going to fire who knows when, causing the motor to run like crap, backfire, etc....just like if you left your distributor loose and it spun around a bit.

 

[aminga]

If you have a waste spark coilpack then The plugs actually fire on the compression and exhaust stroke anyway. 6&3, 1&4 and 2&5 are paired up and fire together. You need The cam sensor is locate the #6 cylinder in the ignition squence. When the cam signal goes low the next rising edge of the crank signal is #6.

Ignition timing is drive off of crank sensor only. No crank sensor no fire.

Fuel injection timings is driven off the cam sensor. So it can be out of spec and afect the injection events.

http://www.gnttype.org/techarea/ecmsensors/camsensor_FAQ.html

 

[BuickMike]

Thanks for the link. I didn't realize how the cam sensor will affect timing if it is off far enough. OP, on that note, check your cam sensor alignment if you haven't done so already. Looks like maybe checking out the timing chain would be a good idea. Heck, that should be a first for everyone buying these since they have the lovely nylon coated upper timing gear. I learned my lesson the hard way on my '68 Buick GS 400.

 

[RmvBfrFlght]

That gnttype article is confusing. The cam sensor only sets up the ignition and SFI injector sequencing.

The actual spark and injection events is triggered by the crank sensor. Rotating the cam sensor some doesn't change the injection timing.

RemoveBeforeFlight

 

[haywire4130]

(Foot in mouth) I retract my previous statement... In my defense, I work on diesels every day at work. In the case of a diesel they use the cam sensor to determine which tdc the crank is at to sync the cam and crank like I described above. To the best of my knowledge (on large cummins engines anyway) you can unplug the cam sensor once it's running since it is already in sync.

 

[Powertechn2]

lots of posts....

Yes, the car was stored outside, not a t-top car.
Ecm showed no signs of moisture.

The issue started before the car was parked. This is one of the reasons the person who did the frame off resto kinda gave up. He only had a backfire, he never had the car run poorly like I have had happen. Tomorrow somewhere between trying to repair the fubar driveway and doing some mods on an ar for a buddy I will get a chance to check the codes in the scanmaster.

As for the crank vs cam sensors. Assuming as said before that you can unplug the cam sensor and the car will still run that makes me think it is a crank sensor issue.
Whatever it is it seems to be confusing the ecu/ecm and I think it is throwing off the injector time. This is only based on the fact that when this issue started I could watch the O2 mv change while even at a steady speed/throttle. I don't mean change minutely, I mean change from 600/700 to 100, 90, etc. Would go outlandishly low. The car wouldn't build boost when this would happen... You need combustion to make power, and on the same hand, no combustion, no boost. Judging by how rich the car would run before to how the plugs looked when I pulled them and how it felt it seems like it is throwing off the injector timing.

I have not replaced the injectors yet, nor the chip.

When I say stored, it was still ran, just maybe 1 tank of fuel ran through it a season. It was not just left there to rot, it was driven still, just not regularly.

It seems as if the injectors are intermittently spraying between bdc and tdc on exhaust stroke, then being as from what I can tell it uses waste spark system it is then firing at tdc on exhaust which could be causing the backfire.

Previously the backfire would only happen if you were heavy on the throttle then let off. Before this issue it had only backfired on me maybe 8 times total since I have owned the car. Whatever the issue it it is getting worse, which should at the very least make it easier to pinpoint.

I will report back with the codes tomorrow sometime.

Before the car out of nowhere started to run poorly I had just thought that maybe an injector was failing as it would only backfire on me after heavy throttle then letting off, as if an injector was sticking, and the fact that the car had a rich running condition, especially noticeable at idle. I started reading that these cars have rough idle, more noticeable with reds chips, which I have so I had started to think that the idle was normal. Till now.

I will also seal off the connector that was just dumdummed up as it should be sealed and insulated better. I would laugh if this was the issue all along.

Also, the timing chain was replaced when the engine was rebuilt, along with the cam. I forget the grind of the cam, either 212/212 or 220/220... I am only going off of memory. I lost most of the build info when my phone went on the fritz as it was stored in my text messages. I can easily find out what cam is in it, it is a common cam used.

From what I can tell he had built the engine properly, ARP used throughout, he did his research. I do know when he had first gotten the car before doing a frame off that it didn't run right and was a dog. I can only assume by looking that the cam and crank sensors were never replaced. This might have been an underlying issue all along. Whatever it is he never figured out.

 

[Nascar83Fan]

When you do get a chance to look at it,
i would start with checking to see if the crankshaft sensor mounting bracket was securely being held in place by the 2 bolts and haven't loosened some allowing the crank sensor to move around.
I'd unhook the connector from the crankshaft sensor and would carefully pull the wiring going to the crank sensor up top to where you can inspect it completely without being under the car. I would also see if the contacts on the sensor itself and on the connector had any debris or something causing there to be intermittant contact issues.
You can also check for any hidden breaks on any of the wires that go to the crank sensor connector while you have it unhooked at eye level by using a small thin paperclip to probe each pin opening on the connector without messing it up to see if you gently move the wire around if there are any signs of intermittant wire connection issues on a volt meter or other testing device.
Verify the crank sensor hadn't made contact with any of the rings that pass through the sensor ears, if it has made serious enough contact then the ears get smacked and it'll run weird cause of damage.


Hope you get a chance to look at it in between your to do list items you mentioned.
Hope it's just something as simple as the crank sensor needing to be changed or fixing a simple wire intermittant connection issue scenerio.

Ever since the previous owner had it rebuilt, when they had picked it up was it having any backfire issues? Before it was torn down, did the previous owner have any backfire issues?
Wonder if the grounds that connect to the block under the ignition control module area possibly aren't tightened down enough.

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[aminga]

lots of posts....

Whatever it is it seems to be confusing the ecu/ecm and I think it is throwing off the injector time. This is only based on the fact that when this issue started I could watch the O2 mv change while even at a steady speed/throttle. I don't mean change minutely, I mean change from 600/700 to 100, 90, etc. Would go outlandishly low. The car wouldn't build boost when this would happen... You need combustion to make power, and on the same hand, no combustion, no boost. Judging by how rich the car would run before to how the plugs looked when I pulled them and how it felt it seems like it is throwing off the injector timing.

Rapidly changing O2 in closed loop steady state driving is perfectly normal. That's how the ECM adjusts fueling by switching rapidly between lean and rich.

 

[Powertechn2]

Ok, so managed to look at the code... It is 42:C3I EST or Bypass Circuit Failure.
Not sure what that is. The car started and ran fine after reading the code, no light on. Then started to run poorly again, then cel came on, but no new codes were shown.
Didn't have time to do much more than that.
Worked on driveway, spread between 4800lbs and 5800 lbs of limestone depending on who's calculations you go by. Some say limestone is 171lbs per cu/ft... Some say 2800lbs per yard for 3/4", some say 200lbs per yard for the 1-3 inch. I did one yard of 1/2 to 3/4 which definitely weighed more on my trailer than the 1-3" which I did a yard of as the base. I am rambling. tired.

Anyways,
Typical causes for this code include:

1) BYPASS line is open or grounded
2) EST line is open or grounded
3) PROM or CALPACK not seated properly in the ECM
4) Poor connections between ignition module and ECM
5) Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
6) Faulty or incorrect ignition module
7) Faulty ECM

So, I had already replaced the coil, plugs, and the ignition module. I am assuming this is pointing to either a harness issue, ecm issue which could be the connection or the ecu, or is it possible that the ecu is not getting correct reading from the crank sensor to throw this?

On a possibly unrelated note, the tach in the cluster doesn't read right, and never has. The wire for tach signal is disconnected and melted. I am assuming it reads rpm from the alternator judging by where the connector that I was told was tach signal is .
As for the O2, I just never saw it drop below 150-200 when it would drop/rise/drop while not under a load.

Also it would do this while trying to apply throttle with no response.

 

[Pronto]

The green plug near the alternator that is a tach signal is for an external tach, not the dash one. The O2s should move around even at idle. If you check the CC on the Scanmaster it should be moving at a fairly quick pace, not stuck on a number or slow moving. If it's not moving the O2s not working right.

 

[Raeban]

As for the tach not working, it gets its signal from an output on the ignition control module. The wire runs from the ignition control module down to a diagnostic connector by the alternator and then back to the firewall connector on the drivers side.

In regards to the Code 42 and the typical causes, check/clean the ECM terminal and ignition module terminals first

 

[Raeban]

And pronto with the holeshot!