The following topics are discussed in this article -
A question is often asked about why the engine “shakes” at idle.
Rob gives several possible reasons for the “shakes” -- those pertinent to wires and plugs are as follows -
A wobbling engine usually means one cylinder is not firing properly.
Here are some things you can check -
(Sometimes called a “power balance” test.) This test provides a good indication of how much each cylinder contributes to the overall power output of the engine. In addition, it also isolates which cylinders contribute little to manifold vacuum.
You can perform this test at home on any VW engine except those with electronic ignition. If there is a suspected burned valve or other major problem, this quick and easy test will indicate which cylinder it is. Because VWs have only four cylinders, a faulty one will show up relatively quickly.
To perform a cylinder mis-firing test -
If a cylinder is faulty, when it is disabled it will have little or no effect on the engine’s speed or performance, as it will not be contributing fully to the overall engine power.
A dwell-tachometer will give a more accurate indication of changes in engine rpm as you conduct the test.
From someone on the RAMVA Newsgroup -
I would stick with the stock type ignition wires as they often have a lower resistance than silicone wires with graphite leads.
Rob reports -
My original set (of spark plug wires) stayed in the car 18 years till they became hardened and brittle. (Dave, being obsessive and ultra-conservative, replaced his after only two years.)
Dave wrote to John Connolly (Aircooled.Net) with regard to ignition wires to be used with a CDI system -
I'm still not clear about the plug wires for use with the CDI system. Some say the sturdier wires (i.e., Jacob's or Megavolt) are necessary; others say the stock wires are just fine (mine are almost new -- I'm loath to replace them already).
John responded -
If they are almost new, don't change them. However, give them a check once in a while, because the additional spark energy can break them down quicker than with the stock ignition (weak).
Someone on the RAMVA Newsgroup wrote -
NGK's are the best of any commonly-available plugs, and can be cleaned with a wire brush for being re-gapped.
Dave wrote to Rob -
The Bug is starting to run rough. I think its those cheap Champion plugs I put in (just because they were hanging around my work bench) a few months ago. Tonight I'm going to let my fingers to the walking through the Yellow Pages and try to find a set of the NGK plugs--B5HS for the 12mm ones, if memory serves.
Rob responded -
B5HS is the standard electrode plug. These are the ones I'm using, and they are working well, but only 1000 miles or so on them, so time will tell.
B5HY is the equivalent grooved electrode version, and I'll try to find a set of these at next replacement time too, for comparison.
In NGK parlance, B is the thread size 14m (A=18mm, C=10mm), 5 is the heat range (2 is hottest, 13 is coldest), H is thread length 12 mm (# for 19mm), and S is standard electrode (Y=grooved, V=precious metals, VX=platinum, etc) and you might come across an additional letter for the plug gap (9 for .9mm, 10 for 1mm, 11 for 1.1mm, and 13 for 1.3mm; but not on the plugs suitable for VW as far as I know.)
Rob wrote regarding grooved electrodes -
The multiple electrodes tend to shield the spark from the mixture a little, which is OK in a slow revving aircraft engine, but not so good in a higher revving auto engine. Then they developed a "surface electrode" type, which had the cavity filled with bakelite or similar, and the spark jumped from inward facing 'bumps' on the rim to the inner electrode, all of which were flush with the bakelite filling the cavity. Supposed to be harder to clog, because there was no cavity to hold the gunk. Not even used in cars to my knowledge. NGK do make a grooved electrode plug though, and this is supposed to make the spark on the outer edge of the side electrode, instead of jumping to the center electrode right in the middle. Supposed to eliminate any possible shielding of the spark more exposure to the fuel/air mix.
Rob wrote in response to a query -
The VW engine works best with Bosch WA8C or NGK B5HS plugs. (Champion L87Ys are the right heat range too, but they have cut threads not rolled and tend to strip out the aluminium heads.) You can do a plug test by running down the road at a good speed (with the engine properly warmed up), and shutting off/declutching/tuning engine off in the middle of the run, and coasting to a stop. This is necessary so the reading is not contaminated by any idling.
The plugs should have a grey/black thin coating on the rim of the threaded section. The centre porcelain insulator should be off white, turning darker deeper into the plug (about 1/2 way down the insulator) and the tips of the outer electrodes should be grey/white, turning darker on the bend, to blend into the dark grey of the rim of the plug. Black/oily is a good indicator of a worn engine. Black/sooty means it's running too rich. Brown /whitish insulator and a 'white all over' outer electrode usually indicates lean running, often accompanied by a light coloured rim on the plug. If the rim has a speckled "pizza" appearance, the engine is detonating (even if you can't hear it), and you try a different brand of fuel of go to the next higher octane fuel. And of course if the centre electrode has rounded edges instead of a 'squared off' end, and the outer electrodes are looking thin and burned, the plugs are past their best and should be replaced.
If you can avoid using oxygenated (MTBE) fuels do so, your engine will run smoother. Oxygenates result in less "fuel" in the fuel, and make old carburetted cars like the beetle run lean, which means running hotter, and they don't like running hotter since they are a hot running engine anyway. If you don't have a choice, try switching brands, and DO use a "pump octane" of at least 87 maybe higher if it needs it to avoid detonation.
Rob responded to another query -
Just to check, are your old plugs the 1/2 thread, or the longer 3/4 inch thread? If your car has the newer style replacement heads (they are interchangeable), they will need the 3/4" plugs B5ES ("E" for "extended" thread).
With the engine out, it might be possible to shine a torch down a plug hole and check. If the heads are the newer 3/4 inch type, and you have 1/2 inch plugs in them, you'd see a blackened section of unused thread at the bottom of the hole. The short plugs will fire in the newer heads, but less efficiently, as they will be "buried" inside the heads.
Dave asked of John Connolly (Aircooled.Net) -
I'm running NGK plugs that are less than six months and 1000 miles old -- can I clean them up, gap them to 0.040", and reuse them (with a CDI system)?
John's short response -
Yes.
Rob wrote in response to a query regarding spark plugs in CDI systems -
The regular plugs should be OK. B5HS is right. Widen the gap a little from the normal, and there is a possibility that the STANDARD plug leads will occasionally arch, since they are running at 38,000 volts in lieu of the normal 20,000.
As a start, make sure the distributor cap is clean and dust free, but before you clean it, have a look at it at night with the engine running. It's a common arching point (between the rubber caps) - you can see any arching at night.
If it's arching there, it may just need the thicker (insulated) leads, and an occasional wipe of the distributor cap.
Dave asked -
I wonder if I don't need to be running hotter plugs, since the CDI system almost doubles the voltage across them.
Rob responded -
The plug "heat" is actually a function of the cylinder head temp more than anything. A "hot" plug retains heat in the centre electrode longer than a "cold" plug. A hot plug has a long centre electrode - the join to the shell of the plug it deep inside the plug. VWs need a coldish plug to counter the fact that they are shedding heat into a hotter than normal head. So is the NGK B5HS a "coldish" plug.
Dave's question continued -
The bottom line on the spark plugs, then, is NGK B5HS with a .040" gap. Just wanted to make sure that you concur.
Rob responded -
Yes. But as I said, if the misfire continues, suspect the leads and a dirty (doesn't have to be much) cap first. Oh - and clean the inside of the cap too, if it doesn't look shiny clean.
Rob wrote -
There is a possibility that the STANDARD plug leads will occasionally arc.
They are sometimes described as high tension plug leads, or 8mm plug leads (thicker insulation) - but I don't know what they'd call them in the US.
You had new standard leads I remember, and these SHOULD be OK, so hopefully a good clean around the cap and maybe the leads too might be enough.
Question -
When I couldn't start the car the other day, I had to leave the car at the wash. I disconnected the spark plug wires to deter thieves. When I got there the next morning I put them on the wrong cylinders! So, I pushed the car 1/2 miles to my house over mixed up wires!
Response -
I'm not laughing -- it's easy enough to do, and a hell of a good lesson in the school of hard knocks.
One trick I found useful for this was to put a twist of copper wire around the spark plug leads near the plug ends. One turn for No1 cylinder, twice around for No2 and so on. Can't mix them up then unless you remove the wires from the distributor too.
Question -
I own a 1968 model beetle which is a 12V one. I would like to enquire regarding its spark plugs and hope that you don't mind.
In one of your articles, I noted that you mentioned NGK plugs B5HS. Here in my home town, I can't get them but the dealer told me to use B6SS. Is it OK and what does the figures on the plugs indicates such as 5 or 6. My plugs also appears to be black/oily and what does it indicates.
Response -
I have the NGK Spark Plug Guide in front of me...
The NGK letters and numbers mean -
B - 14mm plug (A-18mm, C-10mm etc)
5 - heat range - 2 is very hot, 13 is very cold.
H - thread length 12.7mm (E for 19mm)
S - "standard" electrode type (Y for grooved, P for platinum etc)
The 6 heat rating should be OK - it's just a fraction "colder" than the 5, and should be OK in your hotter climate. "Colder" for a spark plug means that it gets rid of heat faster than a "hot" plug.
But you said B6SS - the character after the number should only be an H or E indicating the length of the threads. There is no S length - only H and E. If you really meant B6HS, then yes - that should be fine.
Black and oily usually means that the engine is starting to burn a little oil (starting to get worn). If you use a colder plug (the B6HS) there is a possibility that they will oil up more, but there's no way of telling untill you try them and see if they oil up too fast and stop working.
If the deposits were black-sooty I would say that it's just running a little rich, but black-oily usually means it's burning a little oil, so you might keep a check on the oil level too, just to make sure it's not using too much between oil changes.
Rob commented -
I changed the spark plugs on the weekend.
The old ones are Bosch W8AC and all were in quite good condition for 12000+ miles. Nice to see that all plugs looked the same - all cylinders performing about the same.
I might take a close up photo as an example of the correct heat range (clean ceramic centre post, black rim and colour change from grey to black on the outer electrode, right on the bend.)
It will be interesting to see if the NKGs (replacements) look any different after they have done the same miles.
Question -
After I had picked up the vehicle I noticed it pinging under acceleration… (Mechanic) sent me on my way stating that if I was not happy to bring it back to him again and he will try a different set of spark plugs.
Response -
Changing spark plugs will not cure pinging/detonation. Only timing and choice of fuel would have any effect there, since we are not talking about altering the compression ratio (the only other consideration in eliminating detonation).
You can get a lot of other useful information about Type 2 VWs at VintageBus.Com and Type2.com.
Our friend Leo in Venezuela wrote -
So now I'm in a new little project on my car..... he spit away a spark plug, so I had the thread fixed an made the job on three sparks.
The fact is that the fourth one had already this job done, and spit last week the spark plug again but with the copper threaded insert, so I think it was a rebuilt head....
Response -
That's unfortunate, but it can happen with old heads - the thread is only aluminium so rough handling in the past could have damaged the threads. I always use Bosch or NGK spark plugs because of this - they have smooth threads. Some other brands have sharp threads which damage the heads more easily.
Disclaimer stuff: Rob and Dave have prepared this information from their own experiences. We have not assumed any specialised mechanical knowledge, but we DO assume that anyone using this information has at least some basic mechanical ability.
We hope you find this information useful, but we don't take any responsibility for anything which happens to you, other people, your VW or any other property or goods resulting from your use of this material.
Feel free to print off any of this information for your own use. If you intend to link this material to another site, reprint it, or in any other way redistribute it, please leave the information complete, including this disclaimer section, and provide a link to this Web site.
Last revised 6 May 2004.
