Vanilla Ice Cream Allergy

I got this from a newsgroup:

I just got this in my mail box.

This is a weird but true story (with a moral) …

A complaint was received by the Pontiac Division of General Motors:

“This is the second time I have written you, and I don’t blame you for not answering me, because I kind of sounded crazy, but it is a fact that we have a tradition in our family of ice cream for dessert after dinner each night. But the kind of ice cream varies so, every night, after we’ve eaten, the whole family votes on which kind of ice cream we should have and I drive down to the store to get it. It’s also a fact that I recently purchased a new Pontiac and since then my trips to the store have created a problem. You see, every time I buy vanilla ice cream, when I start back from the store my car won’t start. If I get any other kind of ice cream, the car starts just fine. I want you to know I’m serious about this question, no matter

how silly it sounds: ‘What is there about a Pontiac that makes it not start when I get vanilla ice cream, and easy to start whenever I get any other kind?’”

The Pontiac President was understandably skeptical about the letter, but sent an engineer to check it out anyway. The latter was surprised to be greeted by a successful, obviously well educated man in a fine neighborhood. He had arranged to meet the man just after dinner time, so the two hopped into the car and drove to the ice cream store. It was vanilla ice cream that night and, sure enough, after they came back to the car, it wouldn’t start.

The engineer returned for three more nights. The first night, the man got chocolate. The car started. The second night, he got strawberry. The car started. The third night he ordered vanilla. The car failed to start.

Now the engineer, being a logical man, refused to believe that this man’s car was allergic to vanilla ice cream. He arranged, therefore, to continue his visits for as long as it took to solve the problem. And toward this end he began to take notes: he jotted down all sorts of data, time of day, type of gas used, time to drive back and forth, etc.

In a short time, he had a clue: the man took less time to buy vanilla than any other flavor. Why? The answer was in the layout of the store.

Vanilla, being the most popular flavor, was in a separate case at the front of the store for quick pickup. All the other flavors were kept in the back of the store at a different counter where it took considerably longer to find the flavor and get checked out.

Now the question for the engineer was why the car wouldn’t start when it took less time. Once time became the problem – not the vanilla ice cream – the engineer quickly came up with the answer: vapor lock. It was happening every night, but the extra time taken to get the other flavors allowed the engine to cool down sufficiently to start. When the man got vanilla, the engine was still too hot for the vapor lock to dissipate.

Moral of the story: Even insane looking problems are sometimes real.

Is this for real?

The Pontiac must have been bought many, many years ago. Vapor lock has almost been eliminated with fuel injection. This sounds like a story that was made up by one of those internet writers who have very little knowledge and way too much time on their hands. They take a grain of truth and turn it into a story of sorts.

If,in fact this did happen, I would guess that it happened in a Pontiac manufactured in 1954 or earlier. Most of these Pontiacs had a straight eight engine and these engines did have a vapor lock problem. The 1955 and later Pontiacs had a newly designed V-8. I owned a 1955 Pontiac and never had a vapor lock problem, but it had plenty of other problems.

I’ve seen vapor lock occur on fuel injected engines under these conditions.

When the vehicle is turned off and the engine is hot, the fuel in the fuel rails above the engine begins to boil creating vapor lock. This can be more of a problem if the gasoline contains ethanol as it makes the gasoline more volatile. One way to check for vapor lock under these conditions is to pour cold water over the fuel rails. If the engine starts after doing this you know it’s a vapor lock issue.

I guess you have to be in the auto repair business long enough to witness a fuel injected engine expierience vapor lock. Because I’ve seen it at least a half dozen times.


But this same reletive ‘wrong symtom / mis-direction’ happens all the time in diagnostics.
That part is very real.

Even at your medical doctor after three months of attepmted diagnostics with no relief
" Oh, your ear itches ? Why didn’t you say so before ? That means you have xxxx ! "

There is often an atribute that you don’t relate as being a symptom but is actually a piece of the puzzle.
AND many “symptoms” stated by a customer that have nothing to do with the repair.

I have seen a few incidents of vapor lock in fuel injected engines also so that’s why I said “almost”. Let me throw another monkeywrench in the engineers diagnosis: engines can get “hotter” after they are turned off. That’s why cooling fans can kick on and off after the engine is shut down. I think it’s called “engine percolation”. Vehicle carbs used to do this all the time which usually resulted in vapor lock. Unless the man bought ice cream in 20 below zero weather…the engine never had time to cool down in any event.

The engine itself doesn’t get hotter, the engine compartment does. The interior of the engine around the combustion chambers and the exhaust manifold are a lot hotter than the temperature in the water jacket at the temp sensor. Cylinder temperatures can get upwards of 2000 degrees and exhaust manifolds hundreds of degrees. Once the coolant stops circulating and the fan stops running, that internal heat and the exhaust heat dissipates through the coolant and the engine parts, radiating out into the engine compartment and heating it up. That raises the temperature of all the peripheral components including things like the starter motor assembly, the coil(s), and even the relay box. It also raises the temperature of the fuel lines.

If any of these guys who post replys here dont know it already, I can absolutly confirm your moral to this story, even if the story is not for real, the moral is.

I doubt of the story is real, but I agree with others that the moral of the story is valid.

I can add another thought. Never assume something will act the way your theory says it must.

I was once involved with failure analyzing a lab hydrocarbon remover. Its function was to remove hydrocarbons from “house air” down to a specific ppm. We used heated rhodium coated ceramic spheres, which were a proprietary process of our supplier’s. The performance of our units suddenly dropped. The first thing we looked at was the spheres. It turned out that the average diameter was larger than previous batches. We all commented that the surface area per volume would be lower (true) and patted one another on the back for our genious.

Until I ran a test using new spheres of the same average diameter as our old ones. No improvement happened. We ultimately discovered the problem, a difference in the spheres themselves making them smooth rather than porous had affected the performance of the spheres. Smooth surfaces have much less surface area than pourous ones.

We all have stories like this. The obvious answer often is not the correct answer. Never assume. Well, perhaps only over the internet…

Another misdirecting symptom story.

“Go drive my truck ( 1991 ford Explorer ). I think there’s something wrong with the transmission, it barely goes and slows immediately when I let off the gas. Like it’s struggling to get going, all the way home ( two miles ).”

Transmission problem ? parking brake on ?

Nope, flat right rear tire !
No, the flump flump flump rough ride was no clue.

What if one of the times “Dad” went to get ice cream there was a line and even though vanilla was the flavor it still took as long or longer to get the vanilla?

Who gets in the car every night after dinner and drives to get ice cream (ever think of buying a freezer?) this chain of events has “scam” written all over it.

Myself I have not come across the vapor lock situation, just lucky I guess.

The story is useful in that it teaches you that your customers may link events to their symptons and that link my only exist in the customers mind.

Allow me to suggest that the term “myth” might be more appropriate than “scam”.

This old chestnut has been around since the days of carbureted cars and homes with no freezer worthy of the name–thus the nightly ice cream runs and the vapor lock issue.

Most likely this fable was invented in the early '50s, and closely resembles the problems solved by “Gus”, the friendly old mechanic featured in Mechanics Illustrated (or, was it Popular Mechanics) who figured out all manner of odd automotive issues and charged something like 92 cents to repair the problem.

However, its vintage does not make it any more valid as a genuine experience. It only serves to show–as oldschool said–that people link disparate events with actual symptoms. Only a true Sherlock Holmes could unravel such twisted clues, and I am sure that GM has never employed any detectives of that ilk.

The clue that this is just another old wives’ tale is that GM allegedly detailed an engineer to shadow the complainant for several days in order to deduce the source of his no-start problem. Trust me–no car company would do that–especially since so many consumer complaints are not valid in the first place.

Sending an automotive engineer to someone’s home town for several days to determine the origin of one person’s no-start problem? I don’t think so!

Learning how to both not get mislead by customer reported symptons and not reducing the trust factor with your customer when you must somehow find a way to tell them that a parameter they link to the cars problem is not connected is a skillful activity.

The money that “eccentric” customers bring to the shop pays the bills just as well as those who don’t present such linkages. The answer is to find a way to humor the customer and make them think you are onboard with the connection but not to let it influence the diagnosis. This works as long as you the mechanic are not equired to give a logical or technical linkage between what the customer thinks is causing the problem and the actual fix.

Here on CarTalk we can try as hard as we want but we still will not break the idea that using preminum in a car that does not require it is some how benefical, and if you pick this subject to impress upon your customer you just may lose the customer.This is just one example where it is best to just knod your head “yes” and keep writing up the repair order. If the customer wants to say the car runs poorly while transporting vanilla icecream, well you have to decide if it is a fight you just have to win.

Some of the worst and most dangerous are the ones that start with "My Father, Uncle Brother, etc says that… and you know it is utter nonsense but you have to decide, do you want the customer or not.

This reminds me of the (true) story of the guy whose computer would reboot whenever he flushed his toilet.

After some head scratching, it was determined that when he flushed the toilet, it would cause the well pump to kick on. (he lived in the country) Apparently either the local power supply was pretty weak, or the computer’s was marginal, but there would be enough of a voltage drop to cause the computer to crash and reboot.

I wonder why the pressure tank did not supply the water the toilet needed which would only cause the pump to kick on if the tank flushing (or other water drain) dropped the level of the pressure tank below a pre-set level. This is another story that does not hold up to even the most simple of analysis.

I grew up in a house with a well pump. The pump kicked on when the pressure dropped to 20 psi and turned off at 40 psi. I think that almost every time the toilet was flushed, the presure dropped low enough to trigger the pump. Many pump installations today have a very small tank and start up almost every time water is drawn.

Mine did too. It’s normal for the pump to start when the toilet is flushed.

I love this discussion… from vanilla ice cream to toilets!! LOL!!