hesitation from stand still

[minibagel84]

got an '84 Minnie Winnie with 350 Chevy. During warm up accelleration from a stop is just fine. There is a moment when I can hear the engine reach a warmed up state and the idle slows down. Pretty normal with a 4bbl Rochester carb. However, after the warm up the engine hesitates when taking off. I think there may be a vacuum leak from one of the components such as EGR, cruise control, brake booster, etc. Could be something else. Open to suggestions. Tried advancing the timing slightly and raising the idle. No luck. Also considered a worn timing chain. But, that doesn't feel right. Weigh in please. Thanks, Rusty

[M & J]

30 year old rubber hoses? Easy and cheap to replace. Wouldnt hurt and might help.

[Rickf1985]

My guess would be a dirty carb. After many years all kinds of stuff makes it's way into them and clogs up main jets and idle passages. Not to mention vacuum leaks throughout the carb from dried out gaskets. The vacuum lines you mention probably are also bad but don't generally cause that symptom. That is a lack of fuel during acceleration. If it is very abrupt when you mash the gas then the accelerator pump is bad or going bad. Your best bet is to rebuild or buy a rebuilt carb from a reputable rebuilder. Try to stay away from the big box parts stores. Even the small stores like NAPA buy there rebuilds from the cheapest places anymore.

[tiinytina]

yes on the above... a "quick" fix may be to add the appropriate amount of Seafoam to your tank prior to your next fill up, which will help clean out buildups, fuel inlets etc.  Remove the snorkel cover and look over all the linkages on the side of the carb to ensure they are all free moving etc.  From good high/cold idle to Low/warm idle but bad initial acceleration may a fuel availability issue, thus also change out any and all fuel filters.  I'm not sure if the 350 has an inline filter also between the tank and the engine located in the chasis as the 454/P30 does or not.  Vacuum lines also that EASY button change out, just make sure you use the correct ID/OD lines. 
tina

[LJ-TJ]

Well we're all kind of on the same track. My suggestion would be to put some Marvel Mystery Oil in your gas. A week or two a go I was having one heck of a time with the genny in the motorhome and was pi#$. Some where along the line someone said to put some Marvel Mystery Oil in the gas. RRRRRight and I'll find it right next to the glass hammer and canvas nails. Well at this stage of the game why not. Nothing else is working. So I pulled the gas line, put some Marvel Mystery Oil in a gas can with gas and fire up the genny. Well it ran like crap. As I was sitting there with it running trying to figure out my next move was going to be...... like night and day she let out one big bang. Scared the Crap out of me and she ran true as true can be. Haven't had a lick of trouble with here since. So my suggestion would be to put the appropriate amount of Marvel Mystery Oil in your gas and see what happens. i??


http://www.marvelmysteryoil.com/

[Rickf1985]

I will second the Marvel Mystery Oil BUT, the carb will still need to be rebuilt if it has not been done in the last 15 years. MMO is the only additive I would use in my oil or gas. I used to do independent testing for a rather well off individual who owned a large fleet of antiques and high performance cars. This was the only additive that ever did anything noticeable. On old engines in cars he would buy that had been neglected for many years I would add this stuff to the oil, no oil change, and just grab a chair and wait. In 20 minutes or less the lifters would quiet down and stuck rings would start to loosen up. This was a consistent result too. I tested many, many additives for him and this was the one that worked. To be fair, Seafoam was not out back then. I still stand buy what I know works though. I have tried the Seafoam on some of my own things and while it did no harm it didn't impress me either. Your results may vary.

[minibagel84]

Thank you all for the quick replies. Here's the things I failed to mention. The carb is a newly rebuilt from a small company out of Florida. I did do a valve job recently. New lifters, new push rods. All that and I may have overlooked some of the vacuum lines. My bad. MMO couldn't hurt. I'm going to look for vacuum leaks. Think I'll pull the molded plug off the vacuum tree and start running them down. Any and all advice is still welcome. Rusty

[Rickf1985]

New lifters and new pushrods? Just curious, why the new parts. New lifters should always be used with a new cam unless they are roller lifters on a roller cam. If the lifters were replaced due to being worn out then the problem may well be a worn cam. Lifters do not wear without taking the cam with them.

[circleD]

I had the same issue last year. I put on a new Edelbrock 1411 with all new fuel lines and filter. Replaced the vacuum lines with new ones since I only have 3-4 now. It cost more due to the Edelbrock but a great piece of mind. Very responsive and nicer to drive.

[TerryH]

Vacuum lines/hoses and fuel lines and filters should be your first check.
Possibly the most likely problem.
Definitely the least costly as well as the first to begin with should you start with replacement.
Unfortunately your problem may require a "replace and test " situation.
If so, begin with the easiest and least costly, then continue on.
Suggestion only.
Terry

[minibagel84]

No, the lifters probably didn't need to be replaced. While I was there with the heads off I just decided to replace them.

[minibagel84]

Well the good news for me is the problem showed itself and I got it fixed. Took everyones advice and started chasing down the vacuum lines first. Disconnected the vacuum trees and plugged em' all. One at a time until I got to the EGR. There's the biggest pain. The EGR is relatively new. Maybe 14 months. Pulled the vacuum line off, capped the valve and I'm back in business. I guess it really is not safe to assume anything. Not sure where the EGR was made, but I will do my best to buy the upgrade next time. Thanks for all your help. Rusty

[Rickf1985]

EGR should not be opening that early, I would suggest that something else is wrong. A vacuum line in the wrong place maybe. You should not be getting a EGR vacuum signal during acceleration. Disconnecting is the easy solution as long as you do not have to pass emissions laws. You may end up with some preignition.

[ramit]

had same issue on my 454 last year after sitting put a can of sea foam in the fuel tank fixed mine right up...http://seafoamsales.com/sea-foam-motor-treatment/