Viper not running well...

[Scott E. Smith]

Ok here's the scene....took the Viper out last night ( 94 r/t) Iimmediately noticed it was runnung roug from 1-3k rpm brought it back home..next morning checking it out...would not start hat to go WOT to get it to start...running very rich, plugs appeared fouled ..replaced them ..same condition...no stored codes or chedck engine light...anyone have any ideas????? thanks!

 

[Steve-Indy]

Battery status ?? Coil packs ?? Plug wires ?? Throttle position sensor ?? ( not SURE if this would throw a check engine light)

 

[vettekiller]

how long was it sitting?

 

[BIGBADCJ]

Ok here's the scene....took the Viper out last night ( 94 r/t) Iimmediately noticed it was runnung roug from 1-3k rpm brought it back home..next morning checking it out...would not start hat to go WOT to get it to start...running very rich, plugs appeared fouled ..replaced them ..same condition...no stored codes or chedck engine light...anyone have any ideas????? thanks!

1. DOES IT IDLE? i had the same problem it ended up being the speed sensor over on the passanger side that hooks to the filters, it was not sealed properly.

 

[BIGBADCJ]

take it off the filter and stick your hand over it to see if it is sucking, you should be able to hear it.

 

[Steve Miehe]

I agree with Steve - check the battery.

 

[Scott E. Smith]

it has only been sitting for about a month,ran fine last month.wires about one year old (msd) it also has the Roe Racing VEC1 coil packs are roughly two years old, battery is new, air filters are clean.just pulled the plugs again...very black and sooty, all the same.maybe TPS? or coolant temp sensor? well any more ideas welcome!!

 

[SNKEBIT]

sounds like its flooding, does the viper have a fuel press. reg.??????

 

[Scott E. Smith]

ok this is strange....pulled all the plugs again, passenger side plugs are much more fouled than drivers side,even still a little wet with gas.drivers side not nearly as bad.

 

[KenH]

I'd check to see if your getting any spark on the passenger side plugs. Since there is a coil pack for each bank of cylinders, that would seem to be the most likely cuprit.

 

[GR8_ASP]

I'd check to see if your getting any spark on the passenger side plugs. Since there is a coil pack for each bank of cylinders, that would seem to be the most likely cuprit.

Not really true. Vipers have a 6 cylinder coil pack (left) and a 4 cylinder coil pack (right). Both coils have leads to each bank. The left coil pack supplies 1,2,3,6,8 and 9 while the right pack supplies 4,5,7 and 10. Confused? If you think you are just think about how the poor engine calibrators must have felt.

You could have wires grounding out or something like that. But doubtful all 5 on 1 side due to plug wires.

Not sure about any engine control issues that could affect 1 bank only. The way the the PCM operates can do strange things though. In general the PCM controls fuel directly for cylinders 2,3,4,6,7,8,9 and 10 (all the right bank and 3,7,9 of the right bank) while the ICM controls 1 and 5 (both left bank). I would check the fouled plugs to see if they follow either the fuel or ignition logics stated above. The plugs also fire on every TDC cycle and share an ignition coil with the opposite cylinder (there are really only 5 coils, 3 in the 6 cyl and 2 in the 4 cyl). Firing is not equal between the positive pulses and negative pulses, which could also be a contributor if your plug gaps are excessive or if the high tension leads have excessive resistance.

Gen I's are also famous for having throttle body adjustment issues. Try resetting them as it can only help.

Anyway, good luck in your diagnostics. Let us know what you find.

 

[Ulysses]

Check the battery, it's easy to do and the basis for a lot of problems. If not, cross it off the list. It's gonna take some diagnosis, might as well start with an easy one.

 

[RobHook]

Well, if we ignore the "single bank" clue for a second, I'd be sure to take a look at the MAP sensor too. In theory a bad MAP sensor (or, more common, corroded connector) will generate a check engine light but my '94 took a while to register that code for some reason. I'd say check it while you're in there.



--Rob

 

[Scott E. Smith]

Ok thanks for all the input thus far....plenty for me to check today....question about the battery, is it possible for it to be able to crank the engine etc and still have aproblem that may cause my scenario? because it did have to be recharged a month ago when it died for no appearant reason.bad cell maybe?

 

[Steve Miehe]

Probably so. If you have a cell going down, our cars will still start up but can act real funky on low voltage.

 

[Scott E. Smith]

well still no luck.....battery cheecked out ok. started and let run again,once again passenger side plugs fouled, #10 was the worst. driver side plugs still looked new.may have to take it to the dealer..a drb scantool would be the next step I guess.something weird going on here.

 

[Vic]

Do you have any junk in the throttle body or plenum on that side, that might be starving those cylinders for air?

 

[Scott E. Smith]

Ok new find.....removed smooth tubes etc. looked into runners for possible blockage...found raw gas pooling up in the drivers side runner(feeds passenger head)ok this explains the fouling only on pass side...but where did it come from????? I mean there's alot of gas in there!!!

 

[Vic]

The intake manifold doubles as the fuel rail. The fuel travels under pressure (60-100psi, or simular) down each side of the manifold, where it then branches off and feeds the injectors on that bank. There should never be gas inside the intake manifold, only the cylinders. It should be sealed, and pressure tight, right up until the injector itself, which only opens on command from the computer. The only thing that is suppossed to be inside the intake manifold is air. The only part I am not sure about is whether the injector sprays gas directly inside the chamber, or just ahead of the intake valve.

Maybe there is a crack inside the manifold, and gas is flowing in. Has the manifold ever been extrude honed, ported, or the like?

I'd say its unsafe to drive the car, because if that gas got heated by the engine, turned into a vapor, you could have a fire, or worse, an explosion. Park it, yank the manifold, and check for leaks?