accelaration problem ..exhaust

[laurie88]

guys

I live in middle east , Dubai and the dealer here is of no use, they do not even have the diacom software this is why it took so long to get hold of someone (mastercraft) who had the software so i could check the cam retard

cheers

[Andy3535]

guys

I live in middle east , Dubai and the dealer here is of no use, they do not even have the diacom software this is why it took so long to get hold of someone (mastercraft) who had the software so i could check the cam retard

cheers

Hi Laurie
You should buy your own hand held scan tool from Rinda Technoligies, The Techmate scan tool will do everything you want and at 500 dollars including the cable for your boat it is well worth investing the money. It is also very easy to use,your problem with the cam retard would have been quickly found!!I have the same problem with my 206 crossfireing at certain temperatures and loads and I hope changing the cam retard will cure this ,it is bloody cold here in Germany and my boat is winterised so I will have to wait untill next year to alter the distributor.
I have a link here for you guys that I found with PCM dealer recalls and updates,I printed out most the things of interest to me. here is the link https://www.pleasurecraft.com/dealer...s-recalls.html

have a good christmas all of you
best regards Andy

[laurie88]

Hi Laurie
You should buy your own hand held scan tool from Rinda Technoligies, The Techmate scan tool will do everything you want and at 500 dollars including the cable for your boat it is well worth investing the money. It is also very easy to use,your problem with the cam retard would have been quickly found!!I have the same problem with my 206 crossfireing at certain temperatures and loads and I hope changing the cam retard will cure this ,it is bloody cold here in Germany and my boat is winterised so I will have to wait untill next year to alter the distributor.
I have a link here for you guys that I found with PCM dealer recalls and updates,I printed out most the things of interest to me. here is the link https://www.pleasurecraft.com/dealer...s-recalls.html

have a good christmas all of you
best regards Andy

Thanks Andy

I will get hold of this for myself

cheers

[Mikeski]

Well maybe I'm a little old school... I would probably just stab the distributor, roll #1 over to TDC on the compression stroke, then set it by eye. Start-it, run-it, if it backfired, I'd give the distro a little twist one way, run it again, etc. until I got it running well. Sure the computer reader would be extremely helpful but I believe this particular problem could have been fixed without it.

[Andy3535]

Well maybe I'm a little old school... I would probably just stab the distributor, roll #1 over to TDC on the compression stroke, then set it by eye. Start-it, run-it, if it backfired, I'd give the distro a little twist one way, run it again, etc. until I got it running well. Sure the computer reader would be extremely helpful but I believe this particular problem could have been fixed without it.

This is an informational update in order to provide you with some information that may assist you in setting the CAM
retard on ALL 2002-2004 PCM 5.0L (Pro Ski) and 5.7L (Excalibur) engines.
The ignition system on the affected engines is unique to any ignition system PCM has built in the past. There could
be a misunderstanding as to what a technician is doing to the engine when the distributor assembly is rotated. In
the past, rotating the distributor would advance or retard the ignition timing. This was done in order to properly set
the base ignition timing.
However, when rotating the distributor on the affected engines, you are not setting ignition timing. The ignition timing is
not affected by rotating the distributor. The ignition timing is 100% computer controlled on these applications.
When rotating the distributor on the affected engines, you are adjusting what is called “CAM Retard.” This parameter
represents the position of the distributor rotor relative to the proper terminal in the distributor cap when the spark
is delivered. This parameter MUST be 43-47 degrees or driveability problems will exist. Some of the symptoms, but
not limited to, are as follows:
• Backfi re
• Loss of power
• Sluggish
• Hesitation
In order to properly set the CAM retard, one of the following scan tools MUST be used:
Hand-held Scan Tool: PC Based Diagnostic Software:
Rinda Techmate Diacom
(Purchased through Rinda (Purchased through PCM,
Technologies, P/N 94040) P/N RT0086)

[scuff97]

Some other things that can happen if not set properly are premature cap and rotor wear, coil failure, as well as spark plug wear, even though the engine may run ok.

[DanielC]

We generally think that the rotor inside the distributer cap is exactly under the tower that connects to the plug we want to fire. It is not. If the ignition timing on the engine can vary from 5 to 45 degrees before top dead center, depending on engine rpm, and manifold vacuum, and what the computer thinks it should be, the rotor can be plus or minus easily 20 degrees away from the tower on the cap of the plug you want to fire.

A V-8 engine has a tower every 45 degrees. If the distributer is incorrectly located, when the timing goes to the extreme far end of the timing range, the rotor may be closer to the wrong tower. That is where the spark will go, and your engine will misfire.

[91xl]

if the timming is out that far it will likely not start, even thought the cap posts are 45 degrees apart timming is mesured at the crank making the actual spread 90 degrees since the crank turns twice to the cam and distributors 1 time

[DanielC]

"if the timming is out that far it will likely not start, even thought the cap posts are 45 degrees apart "
On an engine that does not have a computer controlling the timing, this is true.

On an engine with computer controlled timing, in many cases the computer will just compensate, and the engine will start. It may throw a trouble code, but it might start just fine.

However, if your distributer is installed so that the rotor is exactly under the correct tower when cranking, the engine may start just fine. The ignition timing is probably around 10 to 12 degrees advanced. Rev the engine up, and add some vacuum advance because the engine is now running, and the rotor now has moved a long way from being exactly under the proper tower.

If it requires less voltage for the spark current to get to ground, by jumping to the wrong tower, it will. The engine misfires.

It takes a lot of voltage to fire the spark plug in the cylinder coming up on compression. It does not take that much voltage to fire the other spark plugs.
This voltage requirement is higher when the engine is under a heavy load, with an open throttle, because the cylinder pressures are highest at this point.

[91xl]

actually the computer and only compensate so much. i am an ase certified master technician and driveability specialist and mostly work with computer controls thats why he had the issue. the ecm couldnt advance it far enough for the few degrees it was out and caused the backfire throught the intake

[DanielC]

I am going to suggest that maybe the reason it was backfiring out the intake is this. The rotor was closer to a tower on the distributer cap that had a cylinder with an open intake valve.

Since the computer controls the ignition timing, it caused the ignition coil to fire, at the proper time. The distributer on the engine does not control the ignition timing, it is just a high voltage switch that hopefully connects the ignition coil to the proper spark plug. If the distributer is not located properly, (cam retard is out of spec) the rotor can be closer to a wrong tower, and misfires can happen.

Back in the "good old days" of points, ignition systems would not allow the engine to start unless the position of the distributer was close enough to the correct location, for the ignition timing to be correct. When the ignition timing was correct, or close enough, the fact that the points were physically connected to the distributer cap, by the distributer body and parts, automatically put the rotor in the right location under the cap.
On modern engines, the distributer no longer controls the ignition timing. That is why you have to set the cam retard.

[91xl]

cam retard is actually the reading the ecm uses for injector timming it is the cam sensor inside the distributor, on this motor the ignition module is bolted to the same bracket as the coil the backfire is caused by the ignition event happenning at the wrong time, the flame travels to slow in the combustion chamber and re ignites the new fuel mixture when the intake valve is open. the ignition timming would need to be more than 45 degrees off to reach the next tower, remeber timming is off the crank not the cam 45 degrees on the crank is only 22.5 on the distributor

[AirTool]

cam retard is actually the reading the ecm uses for injector timing....

Finally we have the right answer.

I have not put a lot of thought into laurieXX's problem and especially the bulletin from PCM. I am vary curious why PCM made this change. i suspect it is related to a change in the injection software and map of the engine performance.

I have the same engine (although different ECM, etc) in my 99 Tahoe and I've moved the distributor around significantly and did not see any degradation until the distributor was WAY off. (There will, however, be valve/cylinder damage over time if run too far our of spec.)

Basically, this feature is just a ("bad") way to monitor camshaft position.

For "spark", the spark from rotor to tower can jump a good distance and the rotor doesn't need to be that close to the respective tower. It just needs to be closer to the proper tower than the wrong (adjacent) one. As others have said, ignition timing is controlled by the computer and the key measured variable is from the crank position sensor. (Unplug that one and see if she still runs

When I set this on my Tahoe, I just gradually moved the distributor one way until the MIL came on....then reset it and marked the distributor. Then I moved the distributor the other way until the MIL came on....then reset it and marked the distributor. Then I set it between the marks and "shazam" ....no MIL. IIRC, the the throttle (TPS) has to be moved and the engine has to go over 1000 rpm before the OBD2 internal reset/test is made. (This applies to autos....I dunno about the PCM biz....and I guess the check engine light doesn't come on in the boat. )

For more info, google "vortec trouble code P1345" and you will learn more. Ignore any threads where people suggest setting the "timing"....I think we are past that now.

[DanielC]

Kind of my point. The distributer on a modern computer controlled engine does not really affect or control the ignition timing, The computer has taken over that function.
Because of that, you can move the distributer a lot, and the ignition timing will not change. In some cases, it can be moved so far, that the rotor points to the wrong tower. Since the towers on a V-8 engine are every 45 degrees, you only have to turn the distributer body 22.5 degrees and the wrong tower can become closer.
In some cases, with the distributer this far misaligned, the engine will not start, in other cases it will. When this thread began, Laurie88 said the engine started, and idled fine.
Injector firing is not really that critical of a timing event. Many V-8 engines "bank fire" the fuel injectors. A GT-40 engine only has two banks. So, if a GT-40 V-8 engine has an ignition "event" every 90 degrees of crankshaft rotation, it stands to reason it has a fuel injector firing for each cylinder every 180 degrees of crankshaft rotation. Since each cylinder needs 720 degrees to complete the entire 4 stroke cycle, it seems to me that three out of the four times the fuel injector fires for each cylinder, it is squirting gas at a closed intake valve.

[AirTool]

DanielC

I hope you don't think we are arguing. Instead, we are all just trying to get smarter.

.... In some cases, it can be moved so far, that the rotor points to the wrong tower. Since the towers on a V-8 engine are every 45 degrees, you only have to turn the distributer body 22.5 degrees and the wrong tower can become closer.

Splitting hairs here....but if the roter was pointing 22 degrees towards one wrong tower but still okay, you could rotate 44 degrees the other way and still be on the same (proper) tower.

....Many V-8 engines "bank fire" the fuel injectors. A GT-40 engine only has two banks. So, if a GT-40 V-8 engine has an ignition "event" every 90 degrees of crankshaft rotation, it stands to reason it has a fuel injector firing for each cylinder every 180 degrees of crankshaft rotation. Since each cylinder needs 720 degrees to complete the entire 4 stroke cycle, it seems to me that three out of the four times the fuel injector fires for each cylinder, it is squirting gas at a closed intake valve.

I don't know the GT-40 systems, ...but maybe the GT-40 bank is firing continuous (and varying) pulses to deliver the proper average lb/hr of fuel and the intake valve is doing its job just as if the engine had a carb or TBI. Maybe Shane can comment if he is following this one.


Back to laurie88

1. At one point, the op reported the distributor was never moved. I'd like an update on that and would like to understand how the foul up occurred.

2. I'd like to know if the check engine or see dealer or whatever light came on. I think the op reported it didn't but can't remember and didn't double check. I've wondered and posted before that I'm not sure cam retard will throw the light on the PCM system.

3. I was holding back, but having read all the details and (especially) that the distributor had not been adjusted,....my fear and theory was that one or more of the cam lobes had rounded off. I've seen that before and the result was smooth idle and rough higher engine speeds. Lucky it was only a distributor adjustment.