Missing spark at low rpms

[cposk]

The issue I am having seems very similar to the problem dom was having a while back(link below) which ended up being his cam sensor.

(http://forums.viperclub.org/threads...-she-missing-spark-fuel)?highlight=cam+sensor).

98 GTS. I bought the car in October 2011. It supposedly has Hennessy 600 heads and cam. From what I can see, everything else is stock. 38.5k miles when I bought it.

At about 40k, I started to get what felt like the motor "coughing". This would happen in low rpms when throttle was applied. I mostly started noticing it when cruising in 6th gear. After about 500 miles, it was happening more often, but still was very intermittent. I figured that it was old plugs not firing. Went to autozone, they didn't have the Champion brand plugs the FSM called for so I got the autozone brand. After putting them in, it was worse. So I eventually picked up a pair of the plugs that the FSM calls for and put them in. For couple hundred miles, it still happens every once in a while.

This only happens below 2500-3000 rpms. Sometimes at idle, sometimes not. It feels like a "hiccup" and can be heard through the exhaust. As soon as a get over 3k, no issue. Smooth and scary fast. Oh and no CEL, all gauges read normal.

I am going to replace the plug wires next, then the cam sensor. My questions are: Should I be using a different plug? Is there anything else I should be looking at?

 

[Dom426h]

Oh No, not that thread...

Here is info on what sparkplugs you should be running.(unless the henny mods require something diff)
http://forums.viperclub.org/threads...use-on-a-gts?p=3038671&viewfull=1#post3038671

If your on original wires @ 40K then might-as-well replace them. This guy makes some nice wires that some of us run:
http://www.qualitywires.com/Qualitywires/Home.html

If that dosnt clear her up, pm me your # and i'll give you a ring to talk about your issue and determine if it is similar to mine. These things are much easier to describe with voice rather than words.

 

[cposk]

Took the car out last night and it ran horribly. The problem was constant for the entire 20 min drive, feels like a cylinder isn't firing/is missing. There was a Caymen S and Vette looking for some sauce and I had to let them run circles around me.

Quality Wires are on the way. Hopefully this fixes the issue.

 

[ViperTony]

Maybe a long shot but how old is the battery? When my OEM battery started to die my Viper ran horribly. The OEM plugs are fine, I believe they are Champion RC12LYC if I'm not mistaken. Hopefully it's a simple fix.

 

[Viper Specialty]

If you actually have missing caused by a failed spark, the most likely cause is a coil, PCM, or the wiring inbetween.

 

[DrumrBoy]

Try the coils last, they're more of a PITA than the other components and rarely go bad.

 

[cposk]

The reason why I am steering away from coil/wiring between is that it has been happening for a while, but very intermittently. In my experience with other motors, when a coil goes bad there is no in between, it fails completely (correct me if I am wrong).

Order of attack:

1) Plugs (done w/ Champ RC12LYC's)
2) Plug Wires (the boots look old and cracked, not sure if they have been replaced but car has 41k and it can't hurt)
3) Reset PCM
4) Sync Throttle Bodies
5) Battery (It has held a charge for 2-3 weeks in between starts without a tender.)

On to the bigger stuff from there.

 

[Ratical2]

Most likely not the source of the problem but it should be checked anyway. I had a similar miss problem that was the result of a loose intake manifold. It seems like the screws need to be torqued periodically along with the valve covers.

 

[cposk]

Most likely not the source of the problem but it should be checked anyway. I had a similar miss problem that was the result of a loose intake manifold. It seems like the screws need to be torqued periodically along with the valve covers.

Thanks, I will check this today while I change the plug wires. I could definitely see them working themselves loose with the cam.

 

[cposk]

Plug wires completely solved the problem. My 1500rpm idle hang is also gone. The idle is way less aggressive now and between shifts is much smoother.

Also found a nest in under my intake manifold. Fire hazard?

You must be registered for see images attach

 

[plumcrazy]

glad you got it fixed. i had a nest there one spring as well...lol

 

[CEJ]

Glad to hear AB's wires fixed the problem. I'm still running my original (2001) wires, so I need to get them replaced.

Freakin' mice. Check for wires with chewed/missing insulation. They did a number on an old car of mine by eating the insulation off the wires leading to a fuel injector (on a Park Ave). I wondered why the gas mileage had dropped, and when I popped the hood and pulled off the intake cover, there was a nest and the bare copper wires. Thank goodness for electrical tape.