: NorthStar Missing?



N0DIH
05-11-07, 07:04 PM
I searched and searched and haven't found too much to help.

Got a friend's 96 N* Deville with a traction control fault, so it starts in 2nd, but it also has a off the line misfire and also when medium and harder throttle is pressed. Wires ohm good, coils ohm good. Disconnecting EGR, no change. Injectors ohm ok, but unknown on flow. New GM recall fuel rails (so o-rings should have been replaced). New spark plugs also.

Pops up the P300 fault. Can't seem to pin it down. Fuel Press reg vacuum port (in manifold) was sooooo carboned up it wouldn't work, that has been fixed, but reg is the same and IIRC, pressure did seem to change properly. Rerouted vacuum to a new source (for climate control I think, at least on the pass side rear bank heading to firewall).

Intake inside is BAD, really needs to come off and be hot tanked or some how cleaned, but I don't see it being the major misfire problem.

Ideas on where else I should look?

I don't have a FSM on N*, so I am at a loss there, I know the LT1's mainly not the N*'s (trying to learn!)
Thanks!

Ranger
05-11-07, 07:25 PM
My money is on plug wires. Search for my "Stutter, Engine or Trans?" thread.

AJxtcman
05-11-07, 07:39 PM
Torque Management
Torque Management is a function of the PCM that reduces engine power under certain conditions. Torque management is performed for three reasons:

To prevent overstress of powertrain components.

To limit engine power when brakes are applied.

To prevent damage to the vehicle during certain abusive maneuvers.

The PCM uses manifold vacuum, intake air temperature, spark retard, engine speed, engine coolant temperature, A/C clutch status, and EGR valve position to calculate engine output torque. It then looks at torque converter status, transaxle gear ratio, and brake switch inputs and determines if any torque reduction is required. If torque reduction is required, the PCM retards spark as appropriate to reduce engine torque output. In the case of abusive maneuvers, the PCM may also shut off fuel to certain cylinders to reduce engine power.
There are five instances when engine power reduction is likely to be experienced

During transaxle upshifts and downshifts.

Heavy acceleration from a standing start.

If brakes are applied with moderate to heavy throttle (input supplied by the Extended Travel Brake switch).

When the driver is performing stress-inducing (abusive) maneuvers such as shifting into gear at high throttle angles.

In the first two instances, the driver is unlikely to even notice the torque management actions. In the other cases, engine power output will be moderate at full throttle.

When the PCM determines that engine power reduction is required, it calculates the amount of spark retard necessary to reduce power by the desired amount. This spark retard is then subtracted from the current spark advance. In the case of abusive maneuvers, the fuel injectors for cylinders 1, 4, 6, and 7 will also be disabled for a period of time.


Traction Control
Traction Control is a function of the PCM and the EBTCM that reduces front wheel slip during acceleration by applying the front brakes and reducing engine power. Refer to Brakes for an explanation of the EBTCMs role in traction control. The PCM continuously sends out a PWM signal that indicates the torque output of the powertrain. This signal, referred to as the Delivered Torque signal, is used by the EBTCM to determine what action is required when it sees the front wheels slipping. The EBTCM may decide to apply the front brakes only or apply the front brakes and request reduced torque output from the powertrain. The EBTCM requests reduced torque using another PWM signal. This signal, referred to as the Desired Torque signal, is used by the PCM to determine if the EBTCM is requesting reduced torque output from the powertrain. If the EBTCM requests reduced torque, the PCM will disable between one and seven fuel injectors to achieve this.

Desired Torque will normally be a 90 percent duty cycle signal to the PCM. When the EBTCM decides to request reduced engine power, it decreases the duty cycle of the Desired Torque signal by the amount of torque reduction required (90 percent duty cycle means no torque reduction, 10 percent duty cycle means 100% torque reduction). The PCM responds by shutting off fuel to one or more cylinders depending on the percent torque reduction requested. The PCM will not shut off any fuel injectors if any of the following conditions are present

Coolant temperature is below -40C (-40F) or above 131C (268F).

A low coolant level is present.

Engine speed is below 600 rpm

The disabled fuel injectors will be re-enabled one by one as the need for traction control ends.

Several DTCs disable traction control when set. They will also trigger a TRACTION OFF light or message. The PCM traction control override also disables traction control and triggers the message. To diagnose a Traction Off light/message, diagnose any DTCs set first. Then check the traction control override and, if active, deactivate the override. If the TRACTION OFF light/message is still present, refer to Brakes for further diagnosis.

:) A bad extended brake switch will cause Misfires on accel, But it should not set a DTC.
I could take a look at it I have a tech 2 in hand and I have one most weekends

chazglenn3
05-11-07, 07:48 PM
Sure wish you lived in the Seattle area. It is very nice of you to offer your time, tools, and experience.

AJxtcman
05-11-07, 08:36 PM
Sure wish you lived in the Seattle area. It is very nice of you to offer your time, tools, and experience.

The bad thing is....... I lived in bellingham until I was about 10 years old. Then I moved to the Portland area for about 3 or 4 years. I then moved to Washougal. I know the Biffe #16 very well. I moved out to WI in 93 and have been stuck here ever since. This state sucks and I love Washougal area. My mom lives in Federal Way. My soon to be wife works for bechtel, so we will see where the next job is. I about 4 years we will move. My grand parents live in bellingham on the ocean. We get out ever other year or so

Ranger
05-11-07, 08:47 PM
This state sucks
:histeric:

AJxtcman
05-11-07, 09:37 PM
:histeric:

At least I don't pay tolls.
:nyanya:

Ranger
05-11-07, 09:40 PM
And you have better roads.

P.S.
I was laughing WITH you, not at you.

AJxtcman
05-12-07, 09:50 PM
And you have better roads.

P.S.
I was laughing WITH you, not at you.

I don't know about the roads, but my Northstar has a bad misfire. Broke a piston. Pictures soon.

Ranger
05-12-07, 09:55 PM
:eek: First time I've heard that. Are you sure? How'd it happen?

AJxtcman
05-12-07, 10:30 PM
Long story. Very fast car. I was doing a 0 to 130mph run for a new fast time. I had an abnormal down shift into 2nd at just over 100mph, but I pedaled the gas. I have an altered program in this car, so maybe timing. This is a newer crate engine with less than 5000 miles on it. The car would misfire for 20 seconds or so. This may be since I welded the bock the second time. http://www.fiero.nl/forum/Forum2/HTML/078978-2.html
I welded the other bank. The injectors had been in my garage attic for a few years and I thought it was a bad injector. #7 only. swapped plugs, wires, coil
assembly, and injectors. I have not had a problem in a week or so. I did take a customer on a test drive and I told him the right Exhaust pipe sounded off. The misfire happens on U turns after doing a test run most of the time. I can start the car and pull around to the overhead door at work (about 100 feet) and it will start to misfire, but by the time the door opens it has cleared out.

Back to the U turn. 96 to 99 rear valve have problems with a baffle for the PCV system. If it is not sealed up the PCV valve will suck up the oil. The intake manifold passage for the PCV tube drops the oil above #6, #7, #8 runners. The vacuum increases on decel and it sucks in the oil. Turning left should cause the oil to run to the #1 and #2 runners. The PCV system may have oil building up in it and then dumps it into #7. I am not sure. This time it started to misfire and the it knocked hard. After that it rattled as the parts of the piston left out the exh. It may have too much tuning in the PCM. I have a Nice Boroscope it cost me $1400 in 96. I can see the large chunk missing. :crying2: :crying2: :crying2:

Ranger
05-12-07, 10:38 PM
The car is not stock. No wonder we have never heard of this before. Sounds like a good argument for not messing with the PCM.

Only 5K on a brand new crate motor? That really sucks.

AJxtcman
05-12-07, 10:48 PM
The car is not stock. No wonder we have never heard of this before. Sounds like a good argument for not messing with the PCM.

Only 5K on a brand new crate motor? That really sucks.

The engine was free. the trans was free. #2 Pcm was free. #1 and #3 PCM cost me.

AJxtcman
05-12-07, 11:03 PM
The base program may have been a 99 SLS korean or it may have been a 99 SLS non stretched limo/taxi or I have too many programs going and I have no clue unless I check it. I may have installed a new one last week. I remember looking at one to load, but I don't remember if I put it in the car.
.
.
Wait I did not load that program. It has a 99 SLS based program in it.
.
I was looking at some others for someone else, but my re programing adapter is still on a test PCM next to me.
.
I need a break from PCM's I am losing it :ill: :bonkers: :bonkers:

AlBundy
05-13-07, 04:43 PM
Loss it after we get the program.:D :alchi: