Plug fouling?

[ViperBite]

On my way home today I had a chance to open it up a bit. In second gear I nailed it. However at 5500 rpm it felt like a shutter to redline. I backed off thinking it was my fuel cutoff but then realized that is programmed at 6250 rpm. Backed off and did it again in second gear and again at about 5500 it shuttered. By this time I was having to take my exit. So my last chance was a 1st gear run. However this time nothing abnormal till I hit the fuel cutoff at 6250, of course went through 5500-6250 pretty quick. Is it possible for the plugs or ? to foul up if the car is babied for awhile, or is there a difference in 1st versus any other gear of acceleration in the fuel mapping or spark control? I will try again later (several days) but want some opinions. And next question, if I just run the car up to 5500-6000 while sitting, would it exhibit the problem if it still existed or does the engine need a load?

Car has 7350 miles on it. Wires are 8.5 mm (blue, Mopar) which I don't think are stock. Plugs are stock champions. I run 93 octane.

 

[Sean Roe]

Hi ViperBite,
Are you familiar with how to use the VEC2 logging software?
If so, log a run where it does the hiccup / shutter.
It may be hitting 100% duty cycle on the injectors.
If it's hitting 100%, we will suggest a resistor to get the duty cycle under 100%.
It appears that PCM tries to overdrive the injectors when the weather gets hot, instead of taking fuel out.
This is another one of the quirky things we've learned about Vipers electrical systems (and the most recent).
If you're on stock fuel injector connectors, I suggest you replace them with better ones also. We have premium ones for $14.95 a pack of 10.

Regards,
Sean

 

[ViperBite]

Sean,

I could not see any sign of a Premium connector on the car, meaning I saw no splice on the wire, assuming you are talking about the black connector. Also, the temp today or during the run was around 80 or less. Really cool here today.

I have not done any logging yet as I have not had the time. I did "log" a few seconds of sitting in the garage watching the idle RPM plot, just to make sure I could communicate and hit the right buttons on the SW. Is the injector duty cycle different or based on the load of the engine or just based on rpm? Can I log the cycle from the garage or does the car need a load? Hope that question was not stupid.

Can't I change the injector duty cycle with the VEC2?

 

[Sean Roe]

Hi again,

To clarify my post above (since I've already received one e-mail and had to explain this), the 100% duty cycle problem with hot weather is something I've recently found on 2000-2002 cars, not all Vipers. However, it seems that all exhibit a similar symptom of richening the mixture in hotter weather, which is backwards, unless you are the warranty provider for the car.

I don't know if the MSD brand injector connectors we stock are on our website (we have over 300 products in inventory now, so I can't tell 1/2 of what's going on sometimes). Flat out, the stock ones are garbage and should be replaced.

Regarding injector duty cycle, yes, you can change the duty cycle delivered to the injectors, but that's not the problem. The problem is the stock PCM hitting 100% duty cycle, which it shouldn't do. The VEC2 is timing a pulse form the stock PCM, creating a new pulse and sending that to the injectors. When the pulse goes away, the VEC2 doesn't do anything and waits for the next pulse.

Duty cycle is the percentage of time an injector is held open relative to the RPM of the engine. The higher the RPM, the shorter the time the intake valve is open to squirt the fuel in. 20ms at 6,000 RPM is 100% duty cycle. 20ms at 3,000 RPM is 50% duty cycle.

If the weather was cool, you may not have hit 100%, but I wanted to at least mention it in an effort to help diagnose the hiccup.

At the least, change those dang connectors.

Regards,
Sean

PS. Logging off to go home. Will be back at 7:30 am.

 

[ViperBite]

Sean, thanks.

Will call tomorrow to order the connectors. Understand your comment about the PCM/VEC2 interface. I need to re-read your documentation with the upgrade kit. Still have alot ot learn.

Any other thoughts about possible clues? I can't believe the plugs or wires are the problem, fuel filter does not make sense. Any other thoughts?