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The VIPER Garage  |  Generation-specific Viper Forums  |  SRT10 Viper Discussions  |  2008 sputter/misfire help.
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Author Topic: 2008 sputter/misfire help.  (Read 1674 times)
lmcgrew79
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« on: October 02, 2013, 07:00:59 PM »

2008 with mopar pcm, high flow cats, catch can and corsa exhaust. Around the 1800-2200 rpm mark the car sputters for a bit then goes, more in light to mid throttle applications. It seems like a misfire, but no codes are being thrown. Spark plug wires and plugs was changed last year, the car gets used on track quit often. It seems like it started on track during the warm up laps about a month ago, its not happening in higher rpms or on track at wot. Any Pointers on where to start would be great.
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Viper Nation - ezine
« Reply #1 on: October 02, 2013, 07:54:32 PM »

Change the spark plugs first thing.  You said Mopar pcm ... that program was written for headers and cat delete I believe.  If so you should be running fat without the headers and through the cats ...  Changing spark plugs and gapping them to about .040" should solve the problem.  I would suggest adding the headers and removing the cats.

I presume you checked the air filters? 
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
lmcgrew79
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« Reply #2 on: October 02, 2013, 08:03:20 PM »

Ill change the plugs tomorrow and check again. I have random tech cats I guess I can just knock them out.
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Viper Nation - ezine
« Reply #3 on: October 02, 2013, 08:32:47 PM »

Can you find out exactly what the pcm is programed for and make sure the car is that way? 

I don't remember if the 08s came with cloth airfilters ... think they did and your's may need cleaning?  The SRT engineers at VOI X told us that a thin layer of insulation under the airtubes and airbox was worth 18bhp at racing temps.  It didn't add the hp - it prevented the heat from raising the intake air temp and reducing the power ... Have you upgraded to that?  It must be a huge difference at the track ...
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
Taillights
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« Reply #4 on: October 03, 2013, 10:32:27 AM »

Hey 79, does it missd at a certain RPM? Or possibly at a certain throttle position ? Something I would try is check your throttle position sensor. Unplug it and hook up an ohmmeter up to the TPS. Then slowly open the throttle and look at the ohmmeter, you should see a nice smooth curve. Good luck.
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lmcgrew79
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« Reply #5 on: October 03, 2013, 07:11:34 PM »

Well i replaced the plugs and it fixed it. The plugs all looked ok except for cylinder #5, it had backed out, it was loose as soon as i put the socket on it. Wondering how long its been like this and how much compression i was loosing, or it just recently did it.
I went with the colder 7437's this time. We will see how they do.

Here is a photo with the exhaust/carbon on it.
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Viper Nation - ezine
« Reply #6 on: October 03, 2013, 11:28:24 PM »

Those look like crap.  I have one friend that read the heat on his plugs by the amount of thread that was discolored.  His "Hot" was three threads.  Not sure that pertains to your particular case, but maybe remember the color of the threads each time you pull your plugs so you'll know if there is changes in the way the engine runs. 

Without seeing the electrodes I can tell you anything about your running/idling mixture ...

Anytime I have a misfire I pull the plugs and look at the electrodes for problems.  Vipers are awesome for driving/cruizing plug life (I've gone 40,000mi. on a set of plugs gapped at .032"  Glad it fixed the mis.  You sure you didn't want to go hotter plugs? 
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
lmcgrew79
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« Reply #7 on: October 04, 2013, 06:04:35 AM »

That may not be the best photo. Here is a plug in the light.

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Viper Nation - ezine
« Reply #8 on: October 04, 2013, 09:54:31 AM »

Since that's low throttle where the computer/02 sensor adjusts the mixture it looks ok

To check the pcm adjustment tables you would run the car full throttle for a couple gears, then keeping your foot on the floor, shut off the key, coast to a stop and pull the plugs.  That would show you the a/f mixture under WOT. 
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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