Slight hesitation

|What can be the cause of a flat spot in accelerating at about 3k rpm? |When I gas it goes hesitates and then takes the gas again!

depnds on the car - FI or carb? Rex in Fort Worth

Yes it is possible.

Has it always done this, or is it just starting to??

I used to own an old Chev Nova with a 250 CID straight six. This thing had a Rochester MV carb on it. These carbs were a pain in the ass. Wistles, Dips, Flat Spots, choking out, stalling, you name it!

I don't know how many re-builts I went through. They were ALL the same.

I eventually purchased a Holly Economaster Carb. It was cheaper new than a GM rebuilt. It did NOT get me any more gas mileage. What it DID do was make that old six run PERFECTLY. No more flat spots or stalling. A wonderful carb.

IME, carbs are a black art. They can get dirty, but they can also wear. Also, as your engine wears, the mixture it requires to run properly changes. Without "tuning up" your carb, the carb does not change the mix, so as your engine ages, it wont run properly until you adjust the carb. Many carbs have a nasty tendency to fall out of adjustment too!

And if you have dual carbs or a six pack, then you have between carb balancing to worry about too!

A properly designed, rebuilt, and adjusted carb is a wonderful thing. They are just REAL HARD to come by. And I dont know many mechanics that know how to do the job correctly. There are a few around, but definitely not the newer machanics you find in a lot of shops.

Tell us what car, what engine size, what year, and what kind of carb you have. Perhaps there are some known bugaboos that can be fixed on your carb.

It is actually an engine on my boat but in research I found it is the same engine used in a 72 Vega. So it is a 140 hp general motors engine with a Rochester 2GC carb. It only started this now after not being used for a year. That is why I think it is gummed up a bit even though I winerized it. I think I will look for some kind of gas treatment that may clean this out. Otherwise do you think taking out the idle adjustment screws and spraying carb cleaner in there can help?

From: Cloaked ( snipped-for-privacy@NOSAPM.yahoo.ca) Subject: Re: Slight hesitation

View this article only Newsgroups: rec.autos.tech Date: 2003-08-21 12:56:47 PST

Yes it is possible.

Has it always done this, or is it just starting to??

I used to own an old Chev Nova with a 250 CID straight six. This thing had a Rochester MV carb on it. These carbs were a pain in the ass. Wistles, Dips, Flat Spots, choking out, stalling, you name it!

I don't know how many re-builts I went through. They were ALL the same.

I eventually purchased a Holly Economaster Carb. It was cheaper new than a GM rebuilt. It did NOT get me any more gas mileage. What it DID do was make that old six run PERFECTLY. No more flat spots or stalling. A wonderful carb.

IME, carbs are a black art. They can get dirty, but they can also wear. Also, as your engine wears, the mixture it requires to run properly changes. Without "tuning up" your carb, the carb does not change the mix, so as your engine ages, it wont run properly until you adjust the carb. Many carbs have a nasty tendency to fall out of adjustment too!

And if you have dual carbs or a six pack, then you have between carb balancing to worry about too!

A properly designed, rebuilt, and adjusted carb is a wonderful thing. They are just REAL HARD to come by. And I dont know many mechanics that know how to do the job correctly. There are a few around, but definitely not the newer machanics you find in a lot of shops.

Tell us what car, what engine size, what year, and what kind of carb you have. Perhaps there are some known bugaboos that can be fixed on your carb.

I think that's the standard in-line 6? If so, I had several, though time has clouded my memory. Isn't that when they had the 'Air Injection Reactor', and other early emissions controls? One thing I found with mine was that the screws in the top of the carb would work loose, and this seemed to cause it to stumble on turns. At least, that was how it seemed to me; no one else ever seemed to have that problem.

My other bit of wisdom is to make sure it's not an ignition problem, before messing with the carb.

Approximately 8/29/03 20:47, ge uttered for posterity:

Vega was an inline 4 banger aluminum block. In the cars, the carb had an extremely unfortunate tendency to come loose from mountings and leak, due to a beancounter style decision not to use any lockwashers.