why do vehicles pick the worst times to give problems? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

86Scottsdale · 01-06-2003, 05:46 PM

Well, my X-Mas break is just about over and by this time tomorrow I'll be back down at school (hopefully). Of course, the truck has picked a rather poor time to start acting up, and since it's been snowing more or less nonstop here for the past few days it's not going to be feasible to work on it since I have no garage. Here's the problem, maybe somebody can help me out since I have a few vague ideas but not really the time or place to work it out. As of late it'll start up and idle fine on all of the fast idle cams, but after this is where it gets screwy. Sometimes when it's warmed up enough to come off the cams, it'll drop to about 500rpm in park (I have it set at ~800) and idle roughly, sometimes it'll stick right at 800 and be nice and smooth. And sometimes it'll go to 800 and idle, and suddenly just drop to 500 without me having touched anything. In the worst cases it'll fall to 500 and slowly die out, idle slower and slower and stall. It does it when fully hot, cold, anytime. It's been a little colder here (about 30 deg), so I switched back to the stock air cleaner from the open element, although it used to do fine with the open element even at 15 degrees. That fixed nothing. I put some drygas in both tanks in case I had ended up with water in 'em. That did nothing. Today for instance, I warmed it enough to get to the lowest cam on the fast idle, and drove off. It did fine. I went about 8 miles down the highway at ~55mph, running perfectly, came up to temp. I pulled into a gas station, and as I was circling the pumps it went from it's normal ~500rpm in drive to about 300 and running quite rough, I kicked it into neutral, thinking taking off the load would stabilize it but it still was right down at about 300. I filled the tanks and started it up, started fine, but idled slow, but I managed to drive off. After about 30 min more driving it was back to running smooth again. So, I am rather puzzled. It almost seems like I'm getting a vac leak or something that's intermittant since it'll drop real low like that at a "flick of a switch" for lack of a better term. The only vac lines I have anymore are for the dist, pcv, and brakes, but all are in good shape. There's strong vac if I hold my finger over the end of the pcv valve at idle. Whenever it does stall I can start it right back with no problems. Hopefully I'm making some sense here and not too drawn out. What are your thoughts? My parents are starting to pressure me towards getting a new truck (actually went to a chevy dealer today), but I'm insisting I can get it fixed. It's an Edelbrock 1406 carb, 305 engine, just so you know.

Thanks for any help.

**old Rusty C10** · 01-06-2003, 07:43 PM

are ya sure the choke aint screwin up?

Tom · 01-06-2003, 08:11 PM

My vehicle never chooses times that are worst, it just contantly gives me problems

It sounds like you have some sort of vaccum leak. What "cams" you are talking about on the 1406 I have no idea. My carter dosent have any.

86Scottsdale · 01-06-2003, 08:21 PM

Tom:

The cams are the different steps on the fast idle, maybe a bad term to use, but I'm sure you know what I mean now. When you start it up it'll be like 1800rpm, then you can tap the gas and it'll drop to ~1400, then after it warms up a bit more (electric choke opens more) you can tap it down to ~1000, then tap again when it's completely off so the throttle linkage is then stopped by the idle screw.

I had the air cleaner off the one time and the choke was completely open and it was dying on me.

It seems like a vac leak to me too, but I don't know of any that'd be on and off like that.

I went out and replaced the pcv valve this evening, since I'm betting it was the original (still rattled though), and drove it for about an hour and had no problems, but since it is something that doesn't happen every time, I'm not convinced that did the trick. We'll see what happens when I head back to school tomorrow (100 mile trip). I'll keep everybody posted.

bill_ont_canada · 01-08-2003, 03:59 AM

Hey 86Scottsdale

In answer to your question...

why do vehicles pick the worst times to give problems?

Anything that can go wrong will go wrong, and always at the worst possible time.

It's one of Murphy's Laws you know !!!!

01-06-2003, 05:46 PM	#1
86Scottsdale Registered User Join Date: Oct 2002 Location: Mechanicsburg, PA Posts: 8	why do vehicles pick the worst times to give problems? Well, my X-Mas break is just about over and by this time tomorrow I'll be back down at school (hopefully). Of course, the truck has picked a rather poor time to start acting up, and since it's been snowing more or less nonstop here for the past few days it's not going to be feasible to work on it since I have no garage. Here's the problem, maybe somebody can help me out since I have a few vague ideas but not really the time or place to work it out. As of late it'll start up and idle fine on all of the fast idle cams, but after this is where it gets screwy. Sometimes when it's warmed up enough to come off the cams, it'll drop to about 500rpm in park (I have it set at ~800) and idle roughly, sometimes it'll stick right at 800 and be nice and smooth. And sometimes it'll go to 800 and idle, and suddenly just drop to 500 without me having touched anything. In the worst cases it'll fall to 500 and slowly die out, idle slower and slower and stall. It does it when fully hot, cold, anytime. It's been a little colder here (about 30 deg), so I switched back to the stock air cleaner from the open element, although it used to do fine with the open element even at 15 degrees. That fixed nothing. I put some drygas in both tanks in case I had ended up with water in 'em. That did nothing. Today for instance, I warmed it enough to get to the lowest cam on the fast idle, and drove off. It did fine. I went about 8 miles down the highway at ~55mph, running perfectly, came up to temp. I pulled into a gas station, and as I was circling the pumps it went from it's normal ~500rpm in drive to about 300 and running quite rough, I kicked it into neutral, thinking taking off the load would stabilize it but it still was right down at about 300. I filled the tanks and started it up, started fine, but idled slow, but I managed to drive off. After about 30 min more driving it was back to running smooth again. So, I am rather puzzled. It almost seems like I'm getting a vac leak or something that's intermittant since it'll drop real low like that at a "flick of a switch" for lack of a better term. The only vac lines I have anymore are for the dist, pcv, and brakes, but all are in good shape. There's strong vac if I hold my finger over the end of the pcv valve at idle. Whenever it does stall I can start it right back with no problems. Hopefully I'm making some sense here and not too drawn out. What are your thoughts? My parents are starting to pressure me towards getting a new truck (actually went to a chevy dealer today), but I'm insisting I can get it fixed. It's an Edelbrock 1406 carb, 305 engine, just so you know. Thanks for any help. __________________ Dan '86 C20 Scottsdale, 305-H w/all the smog controls removed, Weiand Action Plus non-egr intake, edelbrock 1406 carb, dual 2-1/4" exhaust w/Flowtech Afterburners, and all the factory HD options to make it run cool and ride rough

01-06-2003, 07:43 PM	#2
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	are ya sure the choke aint screwin up? __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

01-06-2003, 08:11 PM	#3
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,748	My vehicle never chooses times that are worst, it just contantly gives me problems It sounds like you have some sort of vaccum leak. What "cams" you are talking about on the 1406 I have no idea. My carter dosent have any. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

01-06-2003, 08:21 PM	#4
86Scottsdale Registered User Join Date: Oct 2002 Location: Mechanicsburg, PA Posts: 8	Tom: The cams are the different steps on the fast idle, maybe a bad term to use, but I'm sure you know what I mean now. When you start it up it'll be like 1800rpm, then you can tap the gas and it'll drop to ~1400, then after it warms up a bit more (electric choke opens more) you can tap it down to ~1000, then tap again when it's completely off so the throttle linkage is then stopped by the idle screw. I had the air cleaner off the one time and the choke was completely open and it was dying on me. It seems like a vac leak to me too, but I don't know of any that'd be on and off like that. I went out and replaced the pcv valve this evening, since I'm betting it was the original (still rattled though), and drove it for about an hour and had no problems, but since it is something that doesn't happen every time, I'm not convinced that did the trick. We'll see what happens when I head back to school tomorrow (100 mile trip). I'll keep everybody posted. __________________ Dan '86 C20 Scottsdale, 305-H w/all the smog controls removed, Weiand Action Plus non-egr intake, edelbrock 1406 carb, dual 2-1/4" exhaust w/Flowtech Afterburners, and all the factory HD options to make it run cool and ride rough

01-08-2003, 03:59 AM	#5
bill_ont_canada Nobody is perfect... Join Date: Dec 2002 Location: London,Ont,Canada Posts: 200	Hey 86Scottsdale In answer to your question... why do vehicles pick the worst times to give problems? Anything that can go wrong will go wrong, and always at the worst possible time. It's one of Murphy's Laws you know !!!! __________________ Have a fabulous day. Bill... (ö¿ö) " Loud Pipes Save Lives "



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