Anyone running stock plugs on a blown car?

[ChicagoGTS]

I've been having some cold start issues with my bosch supers since day one and after talking to Dave (Roe Racing) this afternoon he said give the stockers a shot. I just wanted to know if anyone has had success with this.

~Matt~

 

[RedGTS]

How often do you drive your car? My car frequently stumbles around for a few seconds when I first start it cold too, but I usually don't drive the car but once every couple of weeks, and I figured out it didn't do it if I charged the battery first.

 

[ChicagoGTS]

I drive it every day, also I just put a new battery in 2 weeks ago hoping that would be the cure; but it didn't change anything.

 

[PRVT JET]

try a different colder plug, I started using the autolite 3923 with the nitrous.

 

[ChicagoGTS]

How many steps coder than stock would you guess those (3923) plugs are.

 

[PRVT JET]

Sorry matt, I don't know how much colder. check with tooofst on those plugs. 847-657-8689


isaac

 

[pullshard]

3923's are 2 steps colder.

 

[Sean Roe]

Hi Matt,
The 3923's are colder, like the Bosch FR8DC plugs in the kit. They're the desired plug for wide open throttle runs, racing, etc.
If you start the car an immediately drive away cold, it can stumble leaving the first or second stop sign with cold plugs. After it gets a little heat after a mile, they are usually ok.
However, for better idle and low rpm cruise characteristics, the stock hotter plugs with extended tips run smoother. I just wouldn't do a lot of boosted runs or race with them. It's hard to find a plug hot enough for street driving, yet cool enough for wide open throttle under boost.
Regards,
Sean

 

[ChicagoGTS]

Thanks Sean, I appreciate the input. I'll try the Autolites and post my results. I will say that my current plugs have endured quite a bit of tuning, so maybe there just tired. I've checked the plugs and compared them to the photos on Bosch's website and they appear to have a little soot on them but nothing like the carbon covered ones they show. However, I've noticed a consistent stumble on startup recently. It's nothing too alarming but I can tell after I turn the Key that it definitely doesn't start as smooth as it used too. However it's always been a bit jerky on a cold run and lower RPM's.

 

[Sean Roe]

Hi Matt,
As a test, try turning your key on and letting the fuel pump run once or twice before going to start. If the fuel pressure check valve has failed (it happens), the pressure at startup would be low and the engine would run rough while the pressure builds up to 55. When you turn your key to "on", the pump will run for 2 seconds, then shut off if the engine isn't started.
Regards,
Sean

 

[VIPR GTS]

My car has a very bad stumble the first few blocks I drive it unless I let it sit and idle before driving. I would rather spend a little time warming up the motor than give up the full boost performance. The stumble is only a minor inconvience.

 

[ChicagoGTS]

I don't want to give up boost either, but I guess I'm a freak that way. I want the best of both worlds. My car runs awesome otherwise, it's just a little irritating as an every day driver during "idle and low rpm cruise". But after I floor it I tend to not be as irritated . Sean, I've tried letting the pump motor stop before engaging the starter but it doesn't seem to make a difference. I'll start with the plugs and hopefully that will do the trick.

 

[PRVT JET]

Hi Matt,
As a test, try turning your key on and letting the fuel pump run once or twice before going to start. If the fuel pressure check valve has failed (it happens), the pressure at startup would be low and the engine would run rough while the pressure builds up to 55. When you turn your key to "on", the pump will run for 2 seconds, then shut off if the engine isn't started.
Regards,
Sean

Hey sean, I have noticed my car will start rough after starting cold. it starts as if it's flooded, than it starts normal. I did try something different, when cold I would crank once real quick and stop, then I would start the car and it starts fine. Where is the fuel pressure check valve? and how do I know if it's bad? thanks in advance, matt, sorry for a slight hijack!

Isaac

 

[Bob D]

I tried a lot of plugs and wasn't happy with any until I tried the NGK 6418 Iridium. The heat range seems perfect for my tune. My car fires right up and they aren't too hot. They were recommended to me by NGK, I was trying find a plug one step cooler than a 7252. I hope they last as long as they claim because they cost around $7 each.

Bob
612rwhp, 647tq, 7 lb pully

 

[ChicagoGTS]

What autolite plug is a step hotter than the 3923's?

 

[Sean Roe]

Hi Isaac,
Dang computers. I wrote a reply, it locked up on me and closed internet explorer before I could hit continue.
Anyway, The fuel pressure test port is on the passenger side. It's a brass fitting. Be careful.
If you turn the key on, the pressure should go to 55 psi, then hold after the pump has shut off. If it doesn't hold, you have a bad check valve or leaking injector.
Also, I've see two cars exhibit your symptoms when they had low oil pressure at startup. This was due to the lifters being bled down and the oil pressure not coming up quick enough.

Hey Bob,
Good info on the plugs. How long have you been running them now? How do you compare to the Platinums?

Regards,
Sean

 

[PRVT JET]

Ok sean, one more I guess. How is the lifter problem fixed and how do I know if that's the case? thanks again.

Isaac

 

[Bob D]

Sean,
Iv'e got 5600 miles on the NGK 6418 plugs. I pulled them today and they looked perfect. The Platinums ran good under boost but looked too cold whenever I checked them, plus my idle was a little rough. Some of this difference could be due to changes in my tuning too. My A/F is a flat 11.8

Bob