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Common problems with automatics; need help setting up school workstations
Topic Started: Oct 3 2012, 04:15 PM (1,165 Views)
DieselGuru
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I'm a relatively new automotive technology instructor at a post secondary school, and we have a 1995 Geo Metro 1.3L automatic as one of our trainers. I've been setting up bugs for my students to diagnose to help reinforce what I teach them in lecture, but I'm starting to run a little dry...

I've been trying to choose bugs that are realistic, require no test drives to replicate, don't take long to set up and restore, and do not require permanent damage. So far I have used this transmission for leak diagnosis, TV cable adjustment, transmission range sensor R&I and adjustment, and speed sensor theory of operation.

I have a Ford background, so I am not very familiar with pattern failures on these vehicles. Any suggestions you may have will be appreciated.

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Stiffchezze
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Sir Metrologist

Welcome DieselGuru ! :banana

So let me get this straight. :hmm You are teaching students how to trouble shoot Metro's and you are looking to induce problems with them to make new Metro Guru's?

AWESOME!!!! :rocker

I assure you, you have come to the right place! :thumb Between the members on this forum, I think we know these things better than most of the engineers that built them! ;)

I'm going to figure out some good ones and get back to you. :evillol

:hmm In the mean time, If you can get a Factory Service Manual. They are VERY detailed on trouble shooting ECM issues. Work the problem trees backwards; your students will hate you! :lol

OHH, just thought of a good one. Its not transmission related, but "kink" the fuel return hose. It'll throw a fuel system too rich code. It'll drive 'em crazy! :banghead
Details in my build thread below.
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Coche Blanco
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The brains of the automatics do die a bunch...
Edited by Coche Blanco, Oct 3 2012, 07:49 PM.
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Memphis metro


Jam something in the exhaust pipe.

Disconnect slightly the wire harness to the TCM.

Put a break switch in the ground circuit to the TCM breaking the ground to it.

Unfortunately you are limiting yourself a great deal making it a none driveable situation. Most automatic trans failures are driving failures. And your top notch student is internet savvy and will look up everything we suggest on this website and have it figured out before he even cracks open the hood.

When I was in the AirForce we were trained on equipment that the instructor could flip switches to create issues.
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G.O. Joe
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Good luck finding problems! My auto tranny has almost 250,000 miles and not a hitch (knock on wood)!

Now that I've said that it'll probably crash tomorrow!
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DieselGuru
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Thanks for the input so far. To let you know, I have access to Motor Alldata, not the best source in the world... I have done the kink the fuel return hose trick for my engine performance class - checking fuel pressure and diagnosing incorrect fuel pressure readings...

I have used the ignition system extensively - scoping the pattern with good plugs and wires, then scoping again with improperly gapped plugs and wires that have excessive resistance. Performed ignition system timing adjustments, crossing two wires to cause severe engine misfire, etc.

I have also used the lighting system quite a bit - bugging headlamp and taillamp circuits, opening grounds, and simply removing fuses.

Best one of the lot so far - air conditioning class... Diag an inop air conditioner, A/C will not cool. Problem is the A/C fuse under the hood is blown - 5A fuse in place of a 15A. One sharp eyed student noted that the diagram called for a 15A. Restore circuit with a 15A fuse, A/C now cools. Next week, same car, same concern, as if it were a comeback. Now the 15A fuse is blown. Replace, and the new fuse blows. Inspection of the harness shows chaffed wiring around the timing belt cover, and missing bolts in the timing cover - as if the vehicle had a timing belt replaced by a shadetree... Fix the harness, replace the fuse. Here endeth the lesson.

Anyway, about the transmission, I'd like to come up with a problem that results in a no drive or reverse engagement (so it can be verified in the stall) that does not require the use of a scan tool to diagnose. This would compliment the lecture on diagnostic methodology that makes a comparison between code driven diagnostics and symptom driven diagnostics. (I have a 2002 altima that will have a P07xx code in it for code driven diagnostics)

Again, thanks for the help, and I'm open to suggestions concerning other vehicle systems, too I teach all 8 ASE areas with this car. Feel free to PM about non transmission system ideas to keep this thread relevant to the forum...
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Shinrin
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You could loosen the lock cable that only lets you shift when the key is turned and the brake is depressed. Loosen it so you can't shift out of park
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DieselGuru
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Shinrin - I used an electrical failure to kill the shift lock system once before, but I hadn't considered a mechanical failure. Which end do you recommend?

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wizard 03


Its a shame you don't let them test drive it. Best common problem on an automatic is the TCM trash's out on them. It literally will not shift gears, however if you put them into a selected gear, it will go into that gear.
For instance 1 gear will allways be in fist gear no matter how fast you drive the car, or as what most people seem to experiance, 3'rd gear will stay in 3'rd gear, even if your trying to move from a dead stop. {car revs up slightly, but barely moves anywhere like its stuck in third gear.}

Even if you was to allow them to try and drive it in the parking lot, or through the garage, this problem would be very interesting to try because it will not throw a check engine light, or be very obviouse as most TCM's are in with the ECM nowadays......All you gotta do is unplug the TCM under the dash just a little.
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Deckers
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You could plug the tranny filter output hole with a glop of junk and let them try to figure out why it doesn't get pressure. :scared

You could plug the breather and see how many notice that when it starts to pee fluid all over the floor. . . . :coffee

You can pull the halfshafts out on each side and they'll look like everythings okay, it just won't go anywhere. :rofl

My favorite "What the Hell ?" moment was a mechanical advance distributor on an electrical advanced model. :die
Edited by Deckers, Nov 5 2012, 09:19 PM.
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