Mechanical/Automotive/Electrical WTF!?

a_kelley

a_kelley

mechanical fixer
Joined
Jan 26, 2010
Location
Rutherfordton
Thread to post up your weird, crazy, no way possible noises/actions/faults/failures.

4.0 Jeep engine - rotational steel on aluminum cyclic, constant screech/warble - checked starter, TC bolts, cracked flex plate.. no. Distributor shaft was the source.

Dodge omni. - key off position, hazard lights on, turn signal on, and wipers on. The radio, wipers & lights would turn on and off with the hazard lights - from the factory - all factory wiring. It was a factory wiring bug.

98 zj - no o2 codes, only a bank 1 lean - yielded mid single digit fuel mileage. Unplugged o2, reset ecu, instantly doubled fuel mileage. Still hadn't changed the O2 on it.

More if I can remember them....

What's your mechanical/electrical/automotive WTF!? Story?
 
The one I never figured out:

My '90 Grand Wagoneer (FSJ)...once in a while, would not start. Crank and crank and crank, but no fire. Turn the heater/AC control to off, and it would fire right up.

(That thing went thru three or four of the ignition control boxes in the last 100k miles I had it. $90 for Jeep application, same part except plug $13 for an '85 Ford p/u. I can solder. I figure that a bad ground somewhere was contributing to the failures and the relationship to the heat/AC control).


An 04 Mercury Montego...drove to grocery store, wouldn't restart. Finally figured out brake switch was bad (no brake lights = no start condition). Metered switch, definitely bad. Replaced switch, blew brake lamp fuse. Replaced fuse, blew again. One rear taillight was half full of water.
 
My night with my son last night on the 60 Catalina. Spent two hours trying to sort out the wiring. One of us under the hood and one under the dash pulling wires and trying to figure out where it goes. He's nine and could figure it out better than the previous owner. Random abandoned wires, everything twisted and taped, spade connections and eyelets just taped on with no crimp, etc. He even had the new 1-wire alternator wired up with an old piece of knob and tube wiring that was completely bare about halfway down. There was an old household extension cord wrapped up and abandoned in there plus about an 8' long piece of 2-wire loom attached to the hot side of the coil and then wrapped up and abandoned into an opening in the frame. I'd say we are MAYBE 2/3 done now.
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Strangest I've seen lately was a 13 or so Ford focus. Wipers either wouldn't cut off or would randomly start wiping if they were off then wouldn't quit.

Turns out the battery amp sensor (monitoring sensor) on the negative cable was full of that blue powder corrosion. It isn't directly wired to a module, instead it transmits directly over a LIN (local interconnect network) to any modules that need it's info. The wiper motors are also on that network so the crazy signals the battery monitoring sensor was outputting on the network were upsetting the wiper motor.

That car the body control module sends a signal over the LIN to the left hand wiper motor to tell it what speed to run and then it sends a signal over a separate wire to trigger the right motor. There's two separate motors and no wiper linkage transmission like the old days.
 
Also last week I had a cylinder 5 misfire p0305 code on a Hyundai Santa Fe. It's under the intake plenum. So I pull the intake, replace the coil on 5 and go ahead and do all 6 plugs while I'm in there. Put it back together, the dead skip is gone so I only cruise it around the grocery store parking lot next door figuring it's obviously fixed since it runs smooth. Lady picks it up and is back in 10 minutes it has a miss at idle that goes away with throttle. And now a p0401 egr insufficient flow code.

While pulling the plenum off the brittle rubber vacuum hose to the egr cracked. I had replaced it with new hose. I tested the egr system and everything was working correctly by the manual except the egr world barely crack open at idle. This car has full manifold vacuum going to the egr and an electric solenoid that's computer controlled teed into that hose. Then another hose comes off the solenoid back to the intake boot before the throttle plate to bleed off vacuum when the egr should be closed. Which is sort of back assward from the way most egr systems get plumbed.

After pulling my hair out for an hour my boss says it's almost like it's getting too much vacuum now but just changing a hose wouldn't cause that. For some reason it clicked and I grabbed the old vacuum hose from the trash can. Pressed halfway down inside it (about 4") was a tiny brass restrictor not much bigger than a pellet gun pellet. I put it in the new hose and all was well. Usually bwhen you find a restrictor in a vac hose it's externally visible looking almost like a plastic union. Not Hyundai though.
 
Was working on a 04 grand am once that would only crank but not actually fire off, would start with starter fluid and run perfectly fine, could run it for a few minutes, turn it off, and it would fire back up.....let it sit for 5-6 hours, no start, just turn over and over.

turns out when the AC would get turned on, it would blow the fuse for AC compressor, but somehow this was linked into the BCM which would send the signal to pulse the injectors, with the fuse blown, the injectors wouldn’t receive signal. Replaced fuse and everything worked fine.

never dug into the AC issue, just decided not to turn the AC on, no more blown fuse
 
My 05 Saab 9-3 old original coils, it has a mis at 3/4 throttle under load, but no code.
New coil packs run great with no miss, but throw a misfire code. So. I’m swapping coils once a year for inspection.


Sent from my iPhone using Tapatalk
 
Walmart battery flipped polarity on me. Took a week to figure that one out. Kept popping the 80A main fuses. Battery showed 12v. About the 50th time I put the multimeter on the battery, I noticed the - hiding in the shadow. Walmart auto guy didn’t believe me when I asked for the refund.
 
BrianGreen said:
Walmart battery flipped polarity on me. Took a week to figure that one out. Kept popping the 80A main fuses. Battery showed 12v. About the 50th time I put the multimeter on the battery, I noticed the - hiding in the shadow. Walmart auto guy didn’t believe me when I asked for the refund.
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I've flipped polarity accidentally by jumping my charger on a dead battery with the wires backwards. Oops. Killed the battery dead again and recharged it. It was weak before that though.
 
Samurais o_O:eek::shaking::confused:

When the some of the dozen er so ground wires to the frame start corroding and loosing ground the things do some absolutely baffling crap!

Death wobble on Samis .... stupid engineering has a felt wiper on the knuckle covering a rubber seal. It's bad enough these can age and cause wobble .... convincing the owner of this is practically impossible. Just tooooooooooo simple.

Nice, simple, single over-head cam engine.
Them: Why is my 200,000 mile engine skipping? I've changed and checked everything!
I've owned it 10 years ..... never had this problem.
Me: Have you checked or set valve lash?
Them: No! That's not it .... valve lash sounds ok.
Me: ???
 
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Constant problem in the 4.0 in my 94 ZJ. Have just given up on figuring it out and live with it.

To start it: turn key on and let fuel pump prime, turn key off, push starter button and slowly turn the key until it fires. Very very rare that it runs right on the first start, sounds like its running on 2 cylinders and makes a awful sucking sound through the intake, dies if you put any load on it. When it finally catches after 5-20 times, runs like a top. Plenty of power and aside from a skip above 3200 rpm it runs great.

I have changed every sensor I can find and nothing helps. Put a new ignition switch in it and it does the skippin and missin.
 
JSJJ388 said:
Constant problem in the 4.0 in my 94 ZJ. Have just given up on figuring it out and live with it.

To start it: turn key on and let fuel pump prime, turn key off, push starter button and slowly turn the key until it fires. Very very rare that it runs right on the first start, sounds like its running on 2 cylinders and makes a awful sucking sound through the intake, dies if you put any load on it. When it finally catches after 5-20 times, runs like a top. Plenty of power and aside from a skip above 3200 rpm it runs great.

I have changed every sensor I can find and nothing helps. Put a new ignition switch in it and it does the skippin and missin.
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you try a different ecm? I've got a few here if you want to try one. Any 4.0 sbec will run the engine, whether from an xj,yj, or another zj.
 
a_kelley said:
you try a different ecm? I've got a few here if you want to try one. Any 4.0 sbec will run the engine, whether from an xj,yj, or another zj.
Click to expand...

No, sure havent. Might have to take you up on that. Main reason I didnt is all this started after an engine swap.
 
Oh. Try tightening up the terminals at the ignition coil(pull yellow piece out of the end and squeeze the terminal sightly with needle nose), and check for codes after trying to start it one time unsuccessfully. (Disconnect battery first to clear the codes) lmk what you find.
 
Tim C said:
Strangest I've seen lately was a 13 or so Ford focus. Wipers either wouldn't cut off or would randomly start wiping if they were off then wouldn't quit.

Turns out the battery amp sensor (monitoring sensor) on the negative cable was full of that blue powder corrosion. It isn't directly wired to a module, instead it transmits directly over a LIN (local interconnect network) to any modules that need it's info. The wiper motors are also on that network so the crazy signals the battery monitoring sensor was outputting on the network were upsetting the wiper motor.

That car the body control module sends a signal over the LIN to the left hand wiper motor to tell it what speed to run and then it sends a signal over a separate wire to trigger the right motor. There's two separate motors and no wiper linkage transmission like the old days.
Click to expand...

Glad you shared that. My aunt's 13 Explorer is doing weird shit with the wipers!
 
Croatan_Kid said:
Glad you shared that. My aunt's 13 Explorer is doing weird shit with the wipers!
Click to expand...

I'm not sure if explorer uses the same system but it's something to check. I'd need to look up the wiring diagram first to know for sure. I think those have issues with the switch too. On the focus while the wipers were acting screwy you could unplug the batter sensor and they'd stop. If you catch it acting up try it.
 
05 wrangler alternator not charging, customer request new alternator (just to make sure of reliability), problem didn't start until an engine swap. It took an hour to find a bad ground wire on the block, it was corroded inside the insulation.
 
I have a somewhat friend, that has a Buick Road Master. Probably around a 96 model, with the 3600 engine, I believe.
He drove it for a year after getting it, & it's around 100K mileage. Then the starter went out. With someone helping him [he knows nothing about cars], he went through 3-4 AutoZone & Advance starters. They run about 3 weeks & go out. Since, he's been taking it to a local Mount Holly Electrical shop, which has a trusted reputation. I bet there's been 8 starters put on, & all end up the same way. He keeps threatening to sell it as soon as he gets a starter on it, but never does! He Loves the car, but no one has found the problem! I've asked him about the ring gear, starter drive, shims, flex plate? As far as he knows, it's all been checked, & double checked. He just tells me it's good for 2-3 weeks, & then he hears it grinding? I think it was the original 100K starter, that first failed. Now nothing will last on it. Wth?
 
rodney eppes said:
I have a somewhat friend, that has a Buick Road Master. Probably around a 96 model, with the 3600 engine, I believe.
He drove it for a year after getting it, & it's around 100K mileage. Then the starter went out. With someone helping him [he knows nothing about cars], he went through 3-4 AutoZone & Advance starters. They run about 3 weeks & go out. Since, he's been taking it to a local Mount Holly Electrical shop, which has a trusted reputation. I bet there's been 8 starters put on, & all end up the same way. He keeps threatening to sell it as soon as he gets a starter on it, but never does! He Loves the car, but no one has found the problem! I've asked him about the ring gear, starter drive, shims, flex plate? As far as he knows, it's all been checked, & double checked. He just tells me it's good for 2-3 weeks, & then he hears it grinding? I think it was the original 100K starter, that first failed. Now nothing will last on it. Wth?
Click to expand...
I'd check the starter relay & ignition switch to see if it's not hanging the starter on and killing it..
 
josh m said:
My 05 Saab 9-3 old original coils, it has a mis at 3/4 throttle under load, but no code.
New coil packs run great with no miss, but throw a misfire code. So. I’m swapping coils once a year for inspection.


Sent from my iPhone using Tapatalk
Click to expand...

Odds are good you have the wrong spark plugs or a bad ignition cassette. I went through 4 out of the box before I bought one from a licensed dealer and got a REAL OEM part. The saab cassette is your ignition coil, knock sensor AND for some reason it cleans the spark plugs by doing a 30 sec. discharge. The aftermarket units are JUNK. If you have driven any appreciable amount of miles with a bad cassette, you probably have a clogged or partially clogged converter.
 
My first car was a Peugeot 505 Turbo, pulled the engine to do a cam swap, new turbo and head replacement. After install I could not get the car to start, it would crank and crank and never fire. checked and rechecked timing, dizzy install, every single connection.....nothing. Out of frustration while unplugging and re-plugging in all the connections, I swapped the two leads on the temp sensor (measured value across a resistor) and the car fired up.
My only guess is there is a diode on one side of the sensor.
 
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