Last post on Jun 09, 2013 at 10:49 PM
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Volkswagen New Beetle, Coupe, Hatchback
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#893 of 1141 Re: 1973 Beetle Carburetor Condensation Problem [bpeebles]
Oct 19, 2007 (4:27 am)
Thank you, BPeebles. I don't know if he adjusted the carb lean or not--but he did talk about adding a tube which sounded a lot like what you're talking about--this intake-tube that preheats intake air. He said he has a lot of old bugs on his farm that he could search around for one that has this intake tube and give it to me for no charge. He may charge me for labor, which is okay. I don't know why the new carb doesn't come with this intake tube if this is a common problem? Where it stands now, is that I am supposed to call him to see how his last adjustment was (the third one)and talk about him searching for this intake tube. How do I ask him about the lean issue? I don't want to sound like I think he doesn't know what he is doing. I think he does know what he is doing as he is a respected Beetle mechanic. One issue he raised, sort of, was when I took him driving, he noted that I drive slower than him. He guns the gas pedal, I slowly push it down. So he pushes thru any hesitation while you can clearly feel the Bug buck/hesitate during the early parts of the acceleration while I drive. I still didn't think that should happen despite it being a carb engine. Am I unrealistic? I found the followin info on-line. What do you think?:
"Fuel: According to Rob Boardman, the hesitation problem is almost certainly a lean-burn thing. VWs like a fractionally rich mix -- they don't like lean burn conditions. A larger main jet in the carburetor will provide a richer mix and may help the problem. Also, Rob advises the use of a brand-name fuel with at least 91 octane (more aromatics and less methyl tertiary-butyl ether - MTBE - to achieve the higher octane. Only the 1200cc engines and the newest low-compression factory (Mex/Brazilian) engines are happy on 87 octane gasoline. Carburetor: Spitting/sputtering/cracking is an indication of the fuel/air mixture being too lean. The engine speed (RPM) at which the problem occurs tells which jet needs to be changed. Test the engine's performance through the range of 1000-4000 RPM, paying attention to steady throttle position through this range.
• If the engine runs good at 3000-4000 rpm but stumbles elsewhere, the correct main jet is being used, and the problem lies somewhere else. If the hesitation problem occurs at higher rpm (2500-4000), a larger main jet needs to be installed. If the main jet doesn't solve it, try the accelerator pump (see below).
• If the stumbling occurs at 2000 RPMs and lower, a larger idle jet may need to be installed to enrichen the mixture. (Don't go much beyond 65, however.)
• If you have an 009 centrifugal-advance distributor, a larger main jet may sometimes help to compensate for the flat spot inherent with this distributor. The standard jet is 127.5 (in a 34PICT/3 carburetor); try a 130 or even larger.
What are these "jets" that you are talking about, are they part of the carb or part of the engine? You mentioned "main jets", The article above talks about "idle jets" and "larger jets". Since I experience the hesitation when I first accelerate, am I correct that the article suggests my "larger idle jet" is the issue? I really appreciate your help with this. Oh yeah, and am I interpreting the meaning of "flat" correctly? I am thinking that refers to no acceleration while I have the pedal to the floor in the third gear.
#894 of 1141 Re: 1973 Beetle Carburetor Condensation Problem [elisa2]
Oct 19, 2007 (4:31 am)
BPeebles, we haven't even touched the issue of distributors.
#895 of 1141 Re: 1973 Beetle Carburetor Condensation Problem [elisa2]
Oct 19, 2007 (8:53 pm)
To answer your question about what is a "jet" which we are talking about...
The carberator contains small orfices thru which fuel is metered. These are precisely-sized holes usually drilled in brass. These are called "jets" which are a critical part of the tuning process of any carberator.
I do not have the space here to teach you every nuance in the art of carberator operation...but here is a synopsys
The role of a carberator is to precisely mix automized fuel droplets with air as the engine sucks the air thru it. All carberators have a venturi. This is an area where the airflow is forced to flow thru a narrowed opening. The laws of physics says that faster-flowing air has less pressure. This lower pressure sucks fuel thru one or more jets into the airstream. The fuel is also atomized into droplets at the same time.
Most carberators have at least 3 "circuits". Each circuit may have its own jet.
Each of these circuits are "tunable" usually by adjusting the size of the jets thru which the fuel is meterd. There is also some amount of overlap between these circuits so changing one jet can affect the other settings. Some jets are adjusted with a screw... other jets are "fixed" and must be replaced with larger/smaller jets to make an adjustment.
Also, there is usually an accelleration pump. When the gaspedal is pushed down, a small amount of fuel is squirted into the carberator to assist in accelleration. (reduce sudden lean condition because air changes speed easier than liquid gasoline during changes in throttle openeing) Yes - this is often called a "flat spot" during accelleratin.
The above is just a simple explanation... Some carberators may have emulsion-tubes, power jets, slide valves, Constant-vacuum, constant-venturi, float-level settings, idle-bypass circuit, dashpot adjustments, multiple 'barrels', air jets, tickler valves, needle valves... the list goes on.
(Yes... I have been working on carberators since I was about 8 years old)
#896 of 1141 Re: 1973 Beetle Carburetor Condensation Problem
Oct 21, 2007 (5:38 am)
Thank you, that helps a lot in conceptualizing what is happening. On Friday, I told my mechanic to go ahead and find the tube for intake air issue and then he said, "you mean the air filter?" Now what is he talking about it? What does the air filter have to do with pre-warming the air to prevent condensation? And for clarification, I should use the term "flat spot in 3rd gear" when I tell the mechanic that I have very little umph/accerlation in that gear? Thanks again!
#897 of 1141 Re: 1973 Beetle Carburetor Condensation Problem [elisa2]
Oct 22, 2007 (5:22 pm)
The intake-air heater is usually fed into the airfilter housing. (Air is heated BEFORE it reaches the airfilter.)
Note that heating the intake air was often used to improve running in cold weather. It is most often considerd BAD for power to heat the intake air. (because colder air is more dense... thus has more oxygen in it)
Most intake-air heating systems only operate for a short time... then thermostaticly close off the heated air to allow cold air into the engine for most of the time.
Yes - "flat spot in 3rd gear" would tell most mechanics that it is lacking accelleration in 3rd gear.
Also, be aware that all carberator tuning must be done with plumbing and air filters installed.... the tuning will change each time somthing else changes. Carberators are VERY sensitive to any changes in the intake-air plumbing because they operate based on pressure-differental.
#898 of 1141 Re: 1973 Beetle Carburetor Condensation Problem [bpeebles]
Oct 23, 2007 (6:04 am)
I can't thank you enough for the education. Yes, that is exactly what my mechanic was talking about. Heating the air prior and then it automatically shuts off. I have to assume he knows to readjust carb after installing this intake air heating system. I drive myself crazy enough by doubting people's abilities all the time. Thanks, again.
#899 of 1141 Re: 98 VW Speedometer & Cruise control [fgrayaz]
Oct 24, 2007 (4:45 pm)
I boughtsrame car for my daughter speedo does same thing tranny also slips when cold and sarting usualy first time you move. The HAynes vw manuel says you can access the speedometer by jacking car up. I couldn't find it, Looks like transmission range swnsor is below airbox, an danother one sits on transaxle in front side of transaxle. I hadn't thought much abouy cluster. I have learned that the speedometer sensor also part of engine control system
Check engine light goes on and off Po422, and P1582,p0102,p0112. No help from dealers they want to scan and repair only themselves.
#900 of 1141 2003 Turbo Beetle Shimmies upon acceleration
Dec 07, 2007 (12:14 pm)
(2003-turbo betle-17" low profile tires)I've noticed a shimmy that becomes more pronounced when I accelerate (60 - 65 mph). I have replaced the tires but the problem still exists. I have also begun to notice a squeaking sound that comes and goes as well as a new "click" (metal to metal) when staring from a stop (this too is sporadic). A 2nd appointment with the dealer has been made but I would appreciate any information.
#901 of 1141 Re: 2003 Turbo Beetle Shimmies upon acceleration [indigojack]
Dec 08, 2007 (8:40 pm)
#902 of 1141 Passengers Banging Heads in the Back Seat!
Jan 08, 2008 (8:51 am)
HI, I was hoping someone can give advice on this problem that my backseat passengers keep having in my 2006 New Beetle (TDI . Everyone who sits back there bangs their heads on the pillar behind the rear side window. The Insurance Hiway safety institute has crashtest photos of dummies hitting their heads on that same pillar, http://www.iihs.org/ratings/rating.aspx?id=246. It makes me feel really guilty knowing this to let people sit back there, so I'd like to know what others are doing about this problem. I called VW customer care and they told me to talk to the dealer and there's nothing they could do (some customer care!!!). My current plan is to take it to a body shop and have padding installed up there. Any other suggestions?