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A Mechanic's Life - Tales From Under the Hood

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  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,353
    Did it have a title card on it called "L'il Profit-Maker"? :P

    The problem with this concept is that so very few engines will benefit from "engine cleaning", whatever that means. Or, more precisely, so very few will RUN better after engine cleaning.

    first off, what exactly gets cleaned and more importantly, did the dirt even matter?

    I knew this guy--a transmission whiz, and he was...well...a bit shady...he was good at "overselling".

    The interesting thing was that he contended that the smarter and more technically minded the client, the easier to upsell them !

    Why? Because while they knew how to launch missiles or build oil refineries, they did not know that the "dirt" they saw on the turbine fins of an F16 didn't mean squat on certain parts of a Buick transmission.

    That engine cleaning machine could flush all kinds of gunk out of the demo engine and that gunk had nothing to do with how the engine ran.

    Let's face it, you could cut up the average oil filter, put the debris inside onto a napkin, then run over to the client and say---LOOK WHAT WE FOUND IN YOUR ENGINE---EEK!

    Of course, it's been in there for 10,000 miles already and doing no harm whatsoever.

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  • busirisbusiris Posts: 3,490
    edited January 2013
    Yep, that's my take on the N2-in-passenger-tires debate. There are circumstances (Space Shuttle, jet fighters and passenger airlines, off-road mining equipment, race cars) where the limited benefits of N2 in tires make sense. But the benefits of N2 for the general driving public is minimal, and not worth it IMM if one has to pay $5+ for the N2 fill up.

    Add me to the list. If one can get it for free, why not?

    But for the average automobile in which the owner regularly maintains optimal air pressure in the tires, it buys you nothing, and it certainly isn't worth paying extra to get.
  • thecardoc3thecardoc3 Posts: 1,526
    Twenty years ago people would just take their cars out to the highway and stomp on the gas and "blow them out

    Is it significant that time-frame coincides with the deaths of the majority of the carbureted engine vehicles?
  • steverstever Viva Las CrucesPosts: 41,318
    The Jeep Liberty Diesel folks still do that (or a few of them do, at least). Apparently so do a lot of diesel pickup owners.

    Back in the day, did most folks succeed in blowing out some carbon or just blowing out their muffler? :shades:

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  • thecardoc3thecardoc3 Posts: 1,526
    I once watched an old timer decarbon a Chevy V-8 with water.

    He carefully sprinkled water into the carburator


    snip...

    Afterwards, the compression was restored and the engine purred like a kitten

    When an engine needed decarboning there were deposits of carbon in the combustion chamber, and on the head of the piston effectively making the compression ratio of the engine be too high. That's why they would "ping" or detonate and to reduce that sound people would retard the timing. By decarboning, which reduced the compression ratio, the timing advance could be restored and the result was improved performance over what the engine had been recently producing.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,353
    Back in the "old days", when flathead engines were common, "decarbonizing" the head by removing it was considered "maintenance" !

    Of course, a flathead's cylinder head is nothing much more than a slab of steel--not very high tech---but a lotta head bolts to get off!

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  • thecardoc3thecardoc3 Posts: 1,526
    Back in the day, did most folks succeed in blowing out some carbon or just blowing out their muffler?

    Nothing blew out mufflers like failed secondary air control valves!

    With carbureted engines, during deceleration the idle circuit would still supply fuel, the problem is it would be driven extremely rich by the very high manifold vacuum. The mixture would be so rich that it would not burn in the engine, and would then be pumped into the exhaust. The bypass valve of the secondary air was supposed to dump the air to atmosphere when the manifold vacuum spiked, but of course occasionally they would fail and stick in the "normal" position. The combination of a hot exhaust (maybe even glowing carbon deposits), and the accidental combustable air fuel ratio that resulted was impressive to say the least! :)
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,792
    Nothing blew out mufflers like failed secondary air control valves!

    Oh, one thing did it better.

    On a carburated car with single exhaust all it took was the driver switching off the ignition, waiting about ten seconds and then turning it back on.

    Tunnels were best for doing this and some cars wre MUCH better than others!

    :)
  • thecardoc3thecardoc3 Posts: 1,526
    I remember that trick, we had a lot of laughs with it.

    But there was this One Ton GMC Truck with a 454 in it that will forever live in my memory. When the muffler split from the backfire it felt like the truck lifted off the ground a few inches. I saw porch lights come on for two city blocks! (It's still funny today) :) :cry: :) (laughing so hard tears come to my eye's)
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,394
    >it felt like the truck lifted off the ground a few inches. I saw porch lights come on for two city blocks!

    I remember those days and have to laugh along with you. I didn't do that but other guys did. It was a great prank especially if the muffler survived with no damage.
  • thecardoc3thecardoc3 Posts: 1,526
    I remember those days and have to laugh along with you.
    :)


    I didn't do that but other guys did. It was a great prank especially if the muffler survived with no damage


    The truck I'm mentioning wasn't an ignition off prank, the truck did this trick all on it's own because of a secondary air system fault. It would have been a classic though had it been on purpose!
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,394
    >on it's own because of a secondary air system fault. It would have been a classic though had it been on purpose!

    Does that mean those in the truck did NOT expect this backfire waking up the whole neighborhood? If so, it was even funnier.
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,792
    That story made me laugh!

    Some cars were much better (louder) than others and some mufflers put up with dozens of backfires without blowing up.

    Other cars didn't fare as well. We taught the trick to one classmate who, in his first attempt to scare the hell out of a bunch of us standing in front of the high school managed to blow the entire exhaust system off his dad's elderly Buick.

    Another kid tried in vain to get his VW beetle to backfire without success until he finally blew off one of those chrome tailpipes.

    Todays cars just aren't as much fun...probably a good thing!
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,353
    Remember early Mazda rotaries? Man, they would let out a backfire that made everyone duck for 3 miles!

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  • steverstever Viva Las CrucesPosts: 41,318
    Kids these days use "flaming" led lights and their mp3 players to get the same effects.

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    Minivan fan. Feel free to message or email me - stever@edmunds.com.

  • thecardoc3thecardoc3 Posts: 1,526
    Does that mean those in the truck did NOT expect this backfire waking up the whole neighborhood?

    Yep.

    If so, it was even funnier

    Not to them..... :) :)
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,792
    Oh YEAH...those rotaries! I had forgotten about those.

    Those had a heavy iron "blast furnace" of sorts as part of the emission systems. Gas would sometimes slowly drip into that furnace AFTER the cars were parked. Some guy might park one in his garage and be un his house eating dinner when it went off! Talk about LOUD!

    When I was in the tool business I was once inside a shop that had one up on a hoist. There was a guy under it changing te oil or something when it went off.

    It made an M-80 sound like a cap pistol! The guy under the car didn't stop running for a half block. People screamed and we all ran for cover at first not knowing what it was! When I looked up I saw it was an early rotary and I started laughing. I have to admit, it scared the bejeesus out of me.

    No doubt payback for my misspent youth scaring people doing the same thing.

    Army trucks were pretty loud too especially in that one way tunnel that leads to Ft. Chronkhite right after the Golden Gate Bridge.

    I have personal experience on that one!
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,353
    Oh yeah, those rotaries backfired viciously. I mean, they were beyond LOUD--reminded me of light artillery in the army.

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  • thecardoc3thecardoc3 Posts: 1,526
    The one dealership that I worked in had the service desk right in the middle of the shop. It was essentially a trailer with one open side for the desk and a door on each end.

    My stall was right across from the desk and I had a Chevrolet Caprice in for it cutting out on the highway. As I was checking it over I realized that if I snapped the throttle it would occasionally cut out right in the bay. That was great because it meant I could test and prove where the failure was coming from. So watching my tools I snapped the throttle, and it revved up normally. I did it again and it revved up normally. The third time it started to wind up and it cut out, I saw that I had lost spark but I didn't lose power to the coil. Well it turns out I didn't lose fuel as was proven by the back fire it produced when it lit back up.

    It took the dust off of the rafters in the building.

    I did feel kinda bad for the two old ladies that were at the service desk, right behind the car. The service manager said they both about jumped the desk into the trailer with him.........
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,353
    Gee, good thing you didn't have some old war vets digging foxholes in the showroom....

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  • thecardoc3thecardoc3 Posts: 1,526
    We got a call from a new customer who said someone had reccomended us. His Jeep Grand Cherokee had a mis-fire and they couldn't figure out what was wrong.

    The diagnostics were straight forward, #1 cylinder wasn't firing. It was easy to confirm that the cylinder had spark with the secondary coil on plug lead for the PICO scope. The next check was for injector pulse and the injector wasn't triggering. Connecting the scope, there was power to it, but the PCM wasn't grounding it. A quick glance around the engines wiring harness revealed a wire that didn't belong under the hood. Sure enough it was a poor splice for a remote start system that needed to see the injector pulse to know if the engine was running or not. Repairing the damage to the wire caused by the way the remote start was attached to it restored the injector's operation.

    When we called the customer to report what we had found and that the car was ready to go, the owner voiced both surprise and pleasure. For us we solve issues similar to this all of the time and we really try to always have a straight in at the problem and straight back out approach. Customers like him make what we do worth the effort.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,353
    Ah interesting. So if I had hooked up a simple NOID light I would have been fooled, right?

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  • thecardoc3thecardoc3 Posts: 1,526
    edited January 2013
    Ah interesting. So if I had hooked up a simple NOID light I would have been fooled, right

    Fooled? No, not this time. But no matter what a noid light shows you, you're not done yet, and that's just one of the problems with that approach. The light would not have flashed with this failure. But was the problem no power to the injector, or a loss of injector command? Was the loss of injector command a wiring issue, or was the computer not commanding the injector to trigger? Was the computer not commanding the injector because it has failed, or because it has intentionally turned the injector off because of a misfire detection?

    Noid lights trick techs (people) when they make it look like an injector trigger command is present but the circuit has actually failed sufficiently that it cannot carry the current required to open the injector. In those cases the noid shows a pulse when in reality you don't have an injector command pulse. A stethoscope is a much better tool to determine if an injector is triggering or not as long as it's possible to reach the injector. But even it still doesn't tell you why but at least you didn't disturb the harness and have risked temporarily restoring the circuit. Today especially with gasoline direct injection you cannot always reach the injectors easily, nor is it safe to try and test them with traditional routines anyway.

    By taking the right approach the first time, a tech actually spends less time locating the problem and never get's tricked into believing that the circuit is functional when it really isn't. Noid lights are/were notorious for setting that trap and have caused many a misdiagnosis.

    The extra wire for the remote start system was obvious to me, but it was shielded with corrugated wrap just like the rest of the harness and was routed rather nicely so if you weren't real familiar with what the vehicles harness should look like it might not get your attention. With the schematic in hand and the scope already connected, we can use the scan tool set to command the injector to be triggered via the ASM tests. This way all of the checks are done at a high level of safety, and that means without the engine running.

    A solid diagnostic approach is one that doesn't have to be changed by a vehicle's characteristics. This injector and it's circuit just happened to be easy to reach. A few weeks ago the #2 injector on a Ford Escape was proven to have failed mechanically without having to remove the intake manifold first. Both failures are diagnosed with the same fundamental, repeatable routine.

    BTW, Remember why I visited here, NBC's "sting" operation? If I was going to rig a car to test someone's ability to diagnose, I would easily set a trap where diagnostics done with a noid light would fail and people would be condemning injectors and computers falsely. That wouldn't happen with the right approach, and it really doesn't take any longer.
  • steverstever Viva Las CrucesPosts: 41,318
    You really should pitch your shop to the cable networks for a reality show.

    Maybe we could arrange for Oprah to break down in her old Pontiac G6 near your shop for a segment.

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  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,394
    >Oprah to break down

    Oprah could add the shop to her show of favorites. Some people seem to live and die vicariously on what she has on that show. The repair shop would be overrun with women wanting their car repaired at Oprah's Favorite Shop.
  • thecardoc3thecardoc3 Posts: 1,526
    You really should pitch your shop to the cable networks for a reality show.

    Since when is anyone interested in hard work, done correctly, while doing everything possible to try avoid getting involved in a train wreck?

    Reality shows live by the train wrecks, and even when it comes to doing a live radio show the only thing it really does is attract the nightmares, "the ones nobody else can fix". The publics perception of what we are supposed to do day in and day out doesn't allow us to charge correctly for the time that they eat up. So in the end it doesn't matter if we are the last stop for many problems like that, we can't be profitable and stay in business fixing them.
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,792
    edited January 2013
    I'm still laughing.....thanks for making my morning!

    One more rotary story...

    Years ago, I guy I knew bought a well used but nice (and FAST!) Mazda rotary pickup truck. The person who sold it to him said nothing about it ever backfiring.

    Well, this guy lived in a very upscale apartment building that had underground parking. For the first few days his new truck behaved itself. Then one night after working the night shift, my buddy pulled into his stall at about 2AM and went straight to bed.

    About ten minutes later, this tremendous explosion shook the building!

    He heard curses and screams and running feet. He looked out his window...nothing.

    About three or four nights later the same thing happened! People were very upset and they all figured someone was going by and tossing a M-80 or simlar devise into the underground garage.

    So, several days later the owner was at a strip mall, sitting in a barber chair when another loud explosion shook the building. People ran out of nearby stores to hopefully catch whoever did it.

    " IT WAS THAT GREEN TRUCK!!" he heard somone yell. huh???

    Sure enough, someone walked in and asked if anyone owned a green Mazda truck. IT JUST BACKFIRED AND SCARED THE HELL OUT OF US

    Bewildered, he stopped by a nearby Mazda Dealer and asked a Service Advisor if such a thing was possible. A couple of Service Advisors looked at one another and smiled. they told him if he could leave it for an hour they thought they knew what it was.

    They replaced some valve I think and didn't charge him even though the warranty was long expired.

    A couple of years later he sold it to a co-worker who loved to play pranks on others. I remember him saying he wished he had kept to old valve so he could have had it reinstalled.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,353
    This is true....TV likes car fires, fist fights, screaming, explosions, etc. It does not respond to anyone exhibiting modest behavior.

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  • roadburnerroadburner Posts: 6,689
    Oh yeah, those rotaries backfired viciously. I mean, they were beyond LOUD--reminded me of light artillery in the army.

    Back in 1973 the first Mazda dealer opened in Louisville. Dad and I received an invitation to a private introductory event(and it really was private I think that we were invited because I subscribed to Road & Track). They had several RX2s and RX33s that you could test drive in a huge parking lot- the place sounded like the howitzer firing range at Fort Knox...

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

  • roadburnerroadburner Posts: 6,689
    Thursday afternoon my friend called me; the battery in his 2005 X3 had died in his driveway and he had a "mechanic" come over and "fix" it. Now the 4X4(DSC) warning light was on- and the "mechanic" had left him with a printout from the store where he bought the battery that said that the battery might not function properly.
    This time the situation was an easy fix. When the battery is removed the DSC defaults to "Off" and the DSC/xDrive warning light illuminates. The fix? Push the DSC button.
    As for the battery function issue, the "mechanic" failed to read-or possibly understand-the entire printout. The warning concerned newer BMWs(basically from the E90-on) that have an Intelligent Battery Sensor(IBS) that adjusts the charging system to the age of the battery. BMW's with an IBS have to have the new battery registered-and in some cases the IBS has to be reprogrammed. The dealer and some Indie BMW shops are able to do this. The thing is, a 2005 X3 doesn't have an IBS.
    At this point I suspected that the R&R of the battery may not have been performed properly either- and I was right. The "mechanic" pulled the old battery out without disconnecting the vent tube, breaking the plastic vent elbow that plugged into the battery. So the battery was sitting under the load floor without being vented to the exterior- and the plastic plug provided to close off the redundant vent port on the other end of the battery was just laying in the battery storage compartment(along with the unopened instructions that detailed how to connect the vent tube). Friday I stopped by the dealer and picked up a new vent elbow(it cost less than fifty cents, but my friend at the parts counter provided it at no charge) and I'll install it tomorrow.
    Anyway, it turns out my intervention also saved the "mechanic" a few dollars; he was sure that he had damaged the 4X4[sic] system and was preparing to have it flatbedded to the dealer.
    And I have told my friend to CALL ME FIRST the next time the X3 has a problem....

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

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