Car seems like it misfires when driving after cold startup with s/c...

[BlackFox5.0]

I have 36# injectors, and a Pro-M 80mm, for s/c and the injectors. a 255lph HP fuel pump, and an A-trim. Timing at 10* base. 93 Octane. Autolite 23's @ .035"

When I take my car to work right after I start it I let it idle for a few seconds, then I roll out of the driveway, but when I give it gas and let the clutch out, it seems like it misfires....I was thinking maybe it was because the engine is cold and it's pouring a lot of gas in the cylinders to warm up the engine, but it's dumping too much fuel...If i can find out whats wrong, I'd like to fix it.

Any suggestions?

 

[ponycar17]

Since you're in the communist republic of MA, I'm assuming you still run emissions stuff... If so, and you have your smog pump connected, try taking the hose off that goes to the vacuum actuated valve on the passenger side of the engine. This valve goes to the metal pipe that connects in front of your catalytic convertors on your H-pipe... Clog the hose up somehow so you don't have an exhaust leak. My guess is, that valve is sticking open like mine was, causing some seriously loud popping as cold air is allowed to enter a fuel-rich exhaust while you're warming up (even if you have no cats)... Usually, the popping will go away when you warm up and go out of open-loop operation...

And if you have no emissions stuff, scratch what I just said...

 

[PRO50SC]

Did you do all these mods at the same time? What did you change when this problem started to happen? Need to be a little more descriptive. I had a similar problem and it was the sorry a$$ 75mm pro-m bullit I was using. Took it off and the problem went away. Sent that POS back for a refund. Have you tried rotating the clock position on the mass air. They are very suseptible to turbulence from the blower.

Here is something I posted a while back you may want to try as well.

I put a 75mm Pro-m bullitt on my car a couple of months ago and the car ran like crap. Poor idle quality, surging and detonation. I took it off immediatly and sent it back for a refund. Last week I put in 30# injectors, C&L 76mm mass air and a Kirban afpr. The car ran great except for a funky surge at just off idle throttle and lousy cold start. I cured this problem by buying some window screen from a hardware store and intalling a piece in front of the mass air inlet. Since the stock units have this I figured it must be for a reason and felt I had nothin to lose. Too my surprise it worked. Any of you guys that have had this issue should give it a try.

 

[BlackFox5.0]

I still have the smog pump, but the vacuum line that goes to the valve along side where the alternator "used to be" snapped off so that valve is not operating. I wasn't having problems before I put in the injectors and MAF.

One thing i forgot to mention is that we had like a monsoon here a few weeks ago, and I had to drive the car, and the filter got a bit wet becuase of where it is positioned because of the power pipe. So maybe the MAF sensors got dirty?

I have been getting a lot of backfire when coming down from the RPMs going down a hill in gear....I'll try hooking up that smog valve, those plastic lines are so brittle, lol

 

[PRO50SC]

Oh yeah, how does it run when it's warmed up?

 

[mr_tinkertrain]

hey, my car does that EXACT same thing only its bone stock except for flowmasters. could that be whats wrong with mine too? has emissions, stock h-pipe gutted cats, pops in low rpms when its cold, WON'T idle when cold, and has been this way for o.....100,xxx miles or so. Could it be this too? someone give me a detailed explanation of how to find the hose?

 

[BlackFox5.0]

Oh yeah, how does it run when it's warmed up?

It's actually pretty good, runs fine when it gets a around 140*

 

[Demented4.6]

mine is similar when cold... almost like a carbed car

 

[Legendary]

I have the same problem but I think it has something to do with my spark plugs. I don't have any smog junk on the car.

 

[BlackFox5.0]

I too might think it's my plugs. I have Autolite 23's gapped at .035" they are 2 steps colder than stock. Maybe I should have went with 24's at the same gap?

 

[Legendary]

Are the Autolites 764 a colder plug? Thats what I have in the car now.

 

[astronut1885]

I have to run 764s because of my P heads, and I think they are the same heat as stockers. Chris, one thing I can think of is maybe your cam isn't really blower friendly. I know some cams work better than others, like mine is touted by FRPP to be "great with superchargers". That's all that's coming to my mind is the cam.