Hey group. driving down highway today and once i exitted the engine started to miss and wanted to stall. so i limp home to investigate. the car would run but it was way down on power.

i pulled the plugs and none looked bad or fouled. replaced anyway. however smoke came out of #1 when the plug was out? any ideas.

started car...same problem so i used boot pliers to pull off each spark plug boot to try and isolate to a specific cylinder. all cylinders drop a similar amount of rpm's. i also checked timing and was where i had previously set it. 15 base 36 total. now i am at a loss.

i believe it to be carb related. the car seems real rich. at idle(i had to turn up just to get to idle) could it possibly be a power valve? carb is new(500 miles) filter new . i dont think i have a vacuum leak either. checked all of one hose and it was fine.

Please help. thanks tommy

ps i have 7 psi of fuel pressure

anybody?

Tommy,

I would also, based on your cylinder power drop being even, suspect the carb.

You most likely picked up some dirt,(how is your filter), or maybe got some moisture in the carb, (did you just refuel?).


Do your idle mixture adjustment screws affect the idle or are they dead?

You might want to pull a bowl and check to see what evil lurks there.

Bill

Bill this is my camaro and i did not flush out the tank(my bad) but i have run 4 tanks through. was running low when it started miss so i filled up and that did not fix. i was going to look at the filter and carb tonight. the filter is after the mechanical pump and before the carb. it is one of those -an types with the stone in it. so it is easy to check.

and since i was suspecting the power valve i was going to take off the bowls also. maybe blow some compressed air through things. the idle mixture screws had some impact on tuning or trying to tune but not a lot.

the carb is less than a year and i have heard there is power valve protection or blow proof valve? what exactly does that mean? how can one tell if a power valve is bad, is it obvious(ripped rubber) but just trying to figure if i should buy any parts on my way home, pv's are only 5 bucks and i might just get a spare. thanks tommy

Tommy,

I would not worry about the power valve at this time. It is not something that goes bad just driving down the road.

I would go in the direction that you sucked up some dirt or moisture from your low tank.

I would as carefully as you can, drain some fuel out of your primary, by putting a little very clean cup under one of the bottom bolts as you loosen it and see what you get. If you have water in the system it will look like little air bubbles rolling around in the bottom of the cup. Then pull the bowl off and do a carefull visual inspection. What you do next will somewhat depend on what you find.

Don't tear into any more than you need to. Its always the best rule.

I am assuming this is a rough idle (miss) problem.

How does it run if you get into it under power?

Good Luck Bill

I see that this happened after running the fuel low could have been some debris in take that collected on the fuel sock in the tank,you could have fuel pressure still just not fuel volume.Or as has been said water,but if you filled the tank back up water will usually dilute and wouldn't be as much of a factor.The question has already been asked does this happen at idle or is it everywhere in the rpm range,and have you check the float level?

Bill and Jr at first it would kinda clear up at some throttle but as the limping home got closer it just didnt want to run right. and yes bill you are correct to assume it was a rough idle...wanted to stall so i would put into neutral at lights to rev up.

once i got it home i upped the idle to just keep the pig running. i will do as you both advised and check the bowls carefully as well as have a looksie at the fuel filter. hopefully i will find something there. i will post back with my findings. thank you both for your input. tommy

ok. cleaned the filter took the bowl off and the metering block for the primarys. they was some junk in the filter...not enough to restrict, imo. pulled the air/fuel mixture screws and there was pooky on the ends of the needles so i cleaned and blew out the metring block. put back together and its better. but still kinda seems down on power. any more ideas?

it almost reminds me of a vacuum leak on a fuel injection car.

i did return carb and set float bowls and as i said it does run better. maybe i will just keep driving and see if it cleans out. at least run the tank of gas down and refill. all ideas welcomed. thanks tommy

I used to have the same problem from time to time with my old Holley 650dp. I'd pick up a piece of dirt into an idle bleed, and it wouldn't idle right, sometimes not at all. I ran a 14x5" k&n filter, but no gasket at the base of the air cleaner, probably the cause. When you pulled off the metering block, did you blow out all of the passages in the main body? Use a rubber tipped gun when you do. Once in a while, I could actually hear whatever was in the idle bleed passages "pop" when it came out. Aerosol carb cleaner usually didn't work as good as compressed air. And always wear your safety glasses :cool: and point the exit point of the air passage away from you.

Darren i did just as you said with the air and rubber tipped nozzel. did not find as much yuck(just a speck and it could have come when i pulled the needle out of the rubber gasket) in the rear metering jets/block so i just blew out the mixture holes lightly.

like i said it runs alot better but it still seems a little down on power. maybe gas or maybe a little piece of yuck that will hopefully blow through. i will drive and hope. thanks all. tommy

ps i run a circle air filter housing with a rubber o ring on the base of the filter pan.

you mentioned the carb was new. What carb are you running and what cam. I don't think it is a fuel or delivery problem. I had a similiar problem when running a 650 vs demon on a big cam. It wouldn't idle to save its life, no matter what i did. It made so little vaccum that it really messed with idle circuit. I put on a 750 mechanical mighty demon and problem solved. With the other carb it ended up running so rich that it would foul out plugs in a heartbeat, then run really rough. I also changed the heat range on the plugs. Hope this helps.