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flyboat
Samba Member
Joined: April 21, 2010
Posts: 2752
Location: Bath NC
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 Posted: Sun Apr 21, 2013 6:10 pm Post subject: Major hesitation (bucking) at highway speeds:UPDATE |
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This is one I can't diagnose. Bare with me while I give you the details. After the engine (1600 dual port bone stock aftermarket build) gets warm, it starts hesitating at high way speeds. I first thought Vapor Lock. As I was removing the intake manifolds to replace the ruber boots, I noticed the #2 intake port was sooted up. Afer replacing everything I could to prevent vac leaks, the problem still persists.
I have replaced the dizzy as teh old one was a chinese 009. I went to the factory 34 svda dizzy. I replaced wires, plugs coil, condenser, points, and carb. No change. It is my guess that the soot in the intake port of the #2 cylinder is due to a sticking valve or a burnt valve. However teh engine runs fairly well as for power and smoothness. except for this anoying bucking. I can dial the carb in so it is less but then the carb is too rich.
Please help This is a friends car and he gave it to me to repair because he pulled out all his hair. i still have hair and want to keep it.
Cheers
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Last edited by flyboat on Thu Apr 25, 2013 5:52 pm; edited 1 time in total |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Sun Apr 21, 2013 8:04 pm Post subject: |
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what throttle position is this hezitation? light load? medium load? all of the above?  |
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jfats808
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Joined: December 10, 2007
Posts: 5022
Location: oahu hawaii
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| Posted: Sun Apr 21, 2013 8:25 pm Post subject: |
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Hows the fuel pressure coming in?
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Check your oil levels routinely! |
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LeviMan2001
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Joined: April 11, 2009
Posts: 3855
Location: Alaska
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Slow 1200
Samba Member
Joined: July 02, 2004
Posts: 2105
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| Posted: Mon Apr 22, 2013 1:56 am Post subject: |
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| do a compression test, a burnt valve will show then |
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flyboat
Samba Member
Joined: April 21, 2010
Posts: 2752
Location: Bath NC
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| Posted: Mon Apr 22, 2013 2:14 am Post subject: |
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The hesitation is under load. I can play with the carb to get it to usually only do this in 4th gear. But when the carb isout of adjustment just the smallest amount, the hesitation shows up in 3rd gear also. It is usually in the higher rpms of 3rd gear and anywhere in 4th.
Installed a small fuel pump set to run 3 psi because I suspected the mechanical fuel pump.
It has all the tin, hoses, pipes etc.
I'll do teh compression test tonight.
Thanks
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62 Ragtop Bug
66 tintop Westy
Porsche 914
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Cptn. Calzone
Samba Member
Joined: June 27, 2007
Posts: 1855
Location: S>E>Alabama
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| Posted: Mon Apr 22, 2013 7:04 am Post subject: buckig |
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Could be junk in the rank or some type of fuel delivery problem.May have to drain the rank and pull the sock see ift cruddy
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scottvw
Samba Member
Joined: November 17, 2004
Posts: 2821
Location: Centennial, CO
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| Posted: Mon Apr 22, 2013 7:26 am Post subject: |
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| Change your fuel filter....regardless if it looks ok. |
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flyboat
Samba Member
Joined: April 21, 2010
Posts: 2752
Location: Bath NC
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| Posted: Mon Apr 22, 2013 7:32 am Post subject: Re: buckig |
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| Cptn. Calzone wrote: |
| Could be junk in the rank or some type of fuel delivery problem.May have to drain the rank and pull the sock see ift cruddy |
Pulled the tank and it was spotless. Pulled the hose off the mechanical fuel pump and fuel flowed freely. I'm fairly confident its not a fuel delivery problem.
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flyboat
Samba Member
Joined: April 21, 2010
Posts: 2752
Location: Bath NC
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| Posted: Thu Apr 25, 2013 5:51 pm Post subject: |
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UPDATE:. I have finally figured this hesitation out. I had two problems. When your chasing something, usually your looking for one thing. The first problem was vapor lock. Solved that with an electrical fuel pump.
The second problem as some suggested was/is a burnt valve. I mentioned seeing soot in the #2 intake port. I checked compression peer your suggestions. when cold it was 70 psi. Low but not horrible. when hot is was less than 30 psi. So the engine is coming out in a few weeks. When I get it opened up, I'll post pics of the culprit.
Thanks
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62 Ragtop Bug
66 tintop Westy
Porsche 914
09 Z06 Vette track car |
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