• đź’ˇ Fun fact. Whenever you start a thread, TCG Mechanic 5000 (our AI bot) will reply to you to start helping. It doesn't know everything and it will struggle with more complex questions but it can get the thread going and provide valuable information. You can choose to disable it prior to submitting a thread.

🔧 Technical Unusual issues and the last thing you'd think that causes them

SpeedSpeak2me

TCG Elite Member
TCG Premium
Aug 27, 2018
23,401
38,791
Real Name
Jim
So, wanted to start a thread for weird/odd/unusual issues people have had with their vehicles and the strange thing that caused them, which you wouldn't expect.


For example, the g/f's car (2013 Honda Fit) was getting an exhaust/fuel smell in the cabin when sitting idle. It progressively has gotten worse over the last few months. Last week I got the car up in the air and checked the entire exhaust system, of what I could see, for cracks/leaks/etc, and found nothing. Couldn't see the exhaust manifold because it was above the front crossmember and heat shield. Oxygen sensors were good as well.

Opening the hood while it was running you couldn't smell it from the front of the engine bay or driver's side, but could smell it on the passenger side and rear of engine bay. Went down the interwebz rabbit hole for others that had similar issues. All kinds of suggestions were given, but were primarily focused on the issue manifesting after a modification was made. In this case, the car is bone stock with only 77k miles on it.

Well, after going further down that rabbit hole I saw that someone suggested checking the plugs, as they are sometimes known to back out on their own. I'm thinking, "no way a plug is going back out after just a few years and 77k miles", so moved on to checking other things. Well, that and because getting to the plugs kinda sucks. The plenum on top of the engine blocks view/access to all plugs except for the one closest to passenger side, calling that #1.

Last night took apart the lower windshield cowl and its under tray so I could get to the coil packs and the plugs. Took off coil #1 and it looked fine, not exactly brand new, but in good shape. Proceeded to #2 and the boot was filthy, covered in residue, same with #3. Coil pack #4 looked the same as #1, so the outer cylinders were fine, the inner were looking pretty bad.

So now I'm thinking the loose spark plug thing isn't so cockamamy and might have some truth to it. Pull plug #1 and it's fine, just normal wear. Pull #2 and holy shit is it bad, so is #3. When I had the socket on #2 and started to loosen it there was no resistance. I thought maybe I wasn't on the plug, so I stopped. I then turned it to tighten the plug and counted the half-turns till the crush washer made contact.

#2 was seven 1/2 turns (3.5 full turns) from making contact and #3 was eight 1/2 turns (4 full turns) from making contact. That doesn't include the fact they're supposed to be torqued to 12-13 ft lbs. Well fuck me. I had never seen spark plugs back themselves out before. I can say at least they were gapped correctly at 0.050".

The crazy thing is no error codes or CEL were present. Just a rougher idle, less power, and worse mileage. She drives the thing with a heavy foot so didn't think much about the bad mileage (getting mid-upper 20's when it should be low 30's).

So here are some photos I took:

L-R (passenger side to driver side) 1 - 2 - 3 - 4 (new Hitachi replacement at bottom)
IMG_2473.jpg


And here with their corresponding plugs.
IMG_2474.jpg


Close up of #2 (left) and #4 (right):
IMG_2472.jpg
 

IDAFC21

WOW.
Staff member
Moderator
TCG Premium
May 23, 2007
56,950
24,190
Avondale, AZ
Well thats fucked up :LOL:

I could probably write a book on the GTO, but the one thing that comes straight to mind is the BCM wiring harness, which is located directly behind the glovebox in the cabin, and sits right alongside a metal bracket that over time, can rub into the harness and cause a number of issues. Not the least of which is that when I bought this car from the owner in 2008, the rear window defogger was ALWAYS on. You couldnt turn it off. Press the button and nothing would happen. It was always lit up. Couple years later, once I found out about the BCM harness, went in, taped it up w/ some electrical tape and and made sure nothing was cutting into it anymore, boom. Now the rear window defogger works as advertised. :LOL:
 

SpeedSpeak2me

TCG Elite Member
TCG Premium
Aug 27, 2018
23,401
38,791
Real Name
Jim
Friend of mine had a 93 Dodge Ram 2500 when the new models first came out. IIRC there was some kind of wiring harness/module under the seats that had issues. He'd hit the horn and the dome light would come on and the radio would shut off. Something funky like that. I'll get the exact symptoms in the morning.

I just recall he drove to/from Chicago to Sedona, AZ with no radio, and I think back.

As Ron White would say, "listening to the sound of wind".
 

nytebyte

Not Politically Correct
Mar 2, 2004
13,627
20,958
Had a 2002 Mustang GT that had several odd symptoms which didn't occur all at once, but followed one after the other over a period of months.
First, it became hard to start when the engine was warm. I tried all the basic solutions to fix that issue, such as replacing the IAB valve with no success.
Second, the engine would occasionally stall when backing out of the garage on a cold engine. After it stalled, it would start right back up like nothing was wrong.
Lastly, it started throwing camshaft position sensor codes, which made no sense since it ran and idled fine.

That last one was the clue. I borrowed a friends oscilloscope and took a measurement from the battery terminals. Instead of showing a mostly steady and flat line at about 13 to 14 volts, like you'd expect, the resulting graph looked like a kindergartener scribbled it with a crayon. I was getting some wicked AC bleed through from the alternator which clearly had some badly fucked up diodes.

I replaced the alternator which immediately corrected all the problems.
 
  • Like
Reactions: SpeedSpeak2me

Z28Camaro

TCG Elite Member
TCG Premium
Jun 25, 2015
2,177
8,199
Metamora
Bad electrical grounds. The first 4th gen Camaro I owned years ago had a strange hesitation issue and I checked/replaced all the usual suspects without luck. Found some pretty major corrosion on the main electrical ground point on the body under the hood. Cleaned everything and replaced the stud and it went back to running strong again.
 

DEEZUZ

NO PUKESTERS
TCG Premium
Nov 20, 2008
82,325
94,412
NWI
I had a 6.4(only made for 2 years, so not alot to go off of experience wise at the time).

This truck first start in the morning would die. But after that, entire day would start and run fine. If you gave it throttle while cranking it did keep running.

I had about 20 hours into testing before I said it might be the high pressure fuel pump. I was totally unsure of it but couldn't think of what else.

This is after 20 hours of back probing sensors and running miles of clear fuel hose to check for airetion, had this hooked up like a cancer patient...

Next day same thing, after $3500 fuel pump job... Well we just ate that... Mind you, I am in contact with A D S members across the world. Some of the best instructors and technicians... Nobody has a thought. No help. Nothing. Ford engineers didn't have a guess.. I was completely fucked... My dealer tech buddies... Nobody...

Alone...
giphy.gif


I'm data logging every morning I had graphs and charts and data flow numbers. I've got highlighters I've got data streams 5 pages long taped together... I'm stumped man... Threw a few hundred dollars in sensors in... Nothing...

Had this truck here for a few months.....

I data log one morning... Before I turn the key, I notice my THROTTLE position sensor is reading PT for partial throttle... Hmm... That's weird... I lifted the pedal up and it went to CT closed throttle... Hit the key... Started up and ran perfect... A fucking throttle pedal.... Nobody ever believed me... I kept that throttle pedal incase I ever wanted to test/sabotage someone... Fuck me.
 

Intel

TCG Elite Member
Oct 28, 2009
5,889
3,357
Palatine
Friend bought a WRX that was "built" by the previous owner. Huge downpipe, bigger turbo, triple disc clutch, just stupid loud. Friend thought he was going to get into cars. Just ended up driving the thing and never got it tuned like I said it needed. The odd thing was whenever he filled the car with gas it would basically not start for 5-10 minutes after a fillup. He brought it to at least one shop and they couldn't figure it out and just dealt with this "feature" for about 5 years.

Finally brought the car to my house to do a brake replacement and I looked over the Evap system and found out the hoses were backwards. Everytime he was filling up it was filling the intake with gas vapor and the car was "flooding" and wouldn't start. I rearranged the lines and we filled it with gas and the car started right up ever since.

Maxima Clutch job lead to a hard/no start condition.
Did the clutch on my Maxima and put it back together. Car ran and drove fine for like 2 days. Then became harder and harder to start. I couldn't figure it out and threw a CPS at it thinking it was having a hard time syncing on startup. This was before I had most of my scanner/software stuff to look into problems. Sent it to a shop who couldn't figure it out. Eventually ran a ground straight to the starter and it worked better. So I ended up having to take off the manual trans again and sanding the whole mating surface on both the engine and the transmission so it could get a better ground connection. Car started and ran fine after that for 3 more years.
 

SpeedSpeak2me

TCG Elite Member
TCG Premium
Aug 27, 2018
23,401
38,791
Real Name
Jim
My dad told me of one when he was a teenager back in the early 60's. His dad had bought a new car (he can't remember if it was a Buick or Caddy), but after a few months it was running rough. So he (my dad) decided to give it a bit of a cleaning and tune up. Went over everything, changed plugs, wires, etc.... went to clean the carb and used lacquer thinner since it was a great solvent for cleaning gas. residue

Does all the work, goes to start car, it sputters and dies. Oh shit. Goes over everything he did, can't find a problem. Friends come over and they start going over it. Nothing.

My dad pulls the carb thinking something plugged up a hole or maybe the floats were stuck.. Upon further inspection he found that the seats for the main jets were melted. At some point GM stopped using metal seats and went to plastic, which the lacquer thinner promptly turned to goo. Lesson learned.

He was able to get new seats and replace the mains before his dad knew what had happened.

He introduced the problem himself, but based on prior wrenching he, nor his friends, had heard about the changes to the carb. These guys would have no problem tearing down a new engine just to see what changes were made, then put it all back together. Plastic seats. Cheap bastards, LOL
 

Mr_Roboto

Doing the jobs nobody wants to
TCG Premium
Feb 4, 2012
25,676
30,570
Nashotah, Wisconsin (AKA not Illinois)
My dad had an S10 that would stall randomly when making a turn in '94. Took the dealership a week to figure out an AC wire was causing the issue.

My first Astro had an issue with the fucking dash light. Basically there was a short between it and the ground to alternator. It wouldn't ever let the alternator charged. I ended up fixing that by having a bulb in series with the pink/black wire in the alternator connector. Jank but I got juice!

Lastly, the Escalade kept draining the battery. The 6 disc changer was keeping the amp on and draining the battery. Also, the CAN Bus noise from the radio setup kept me from using HPT at all with the stock box until a couple months back when I figured THAT out. I could see how LS Swaps are easier than having it in an OEM car in a way because you don't have any BCM shit to worry about.
 

SpeedSpeak2me

TCG Elite Member
TCG Premium
Aug 27, 2018
23,401
38,791
Real Name
Jim
My dad had an S10 that would stall randomly when making a turn in '94. Took the dealership a week to figure out an AC wire was causing the issue.

My first Astro had an issue with the fucking dash light. Basically there was a short between it and the ground to alternator. It wouldn't ever let the alternator charged. I ended up fixing that by having a bulb in series with the pink/black wire in the alternator connector. Jank but I got juice!

Lastly, the Escalade kept draining the battery. The 6 disc changer was keeping the amp on and draining the battery. Also, the CAN Bus noise from the radio setup kept me from using HPT at all with the stock box until a couple months back when I figured THAT out. I could see how LS Swaps are easier than having it in an OEM car in a way because you don't have any BCM shit to worry about.
My dad has a 2011 Silverado that kept eating batteries, and went back to the dealer three times (under warranty). He finally took it to a different dealer and they said it was an issue with the wiring harness in the dash that goes to the fuse block. Didn't know specifically what, so they just replaced it all. Has been fine ever since. Still don't know the exact cause, they just used the spaghetti method and threw everything at the wall to see what stuck.
 

smug

Please go back to eating crayons
TCG Premium
Aug 4, 2007
8,087
3,751
Cedar Lake, IN
Real Name
Dan Erickson
Currently I have a 2011 Fusion Sport 3.5L that like to randomly stall at stop lights or low speed in a parking lot. I have replaced a couple suspect sensors, scanned it and no CEL, all EVAP test have passed, took it to a mechanic and he came up empty. Also, replaced the throttle body and wiring because some Fords were known for that. If I ever figure this out I’ll be happy.
 
  • Like
Reactions: SpeedSpeak2me

SpeedSpeak2me

TCG Elite Member
TCG Premium
Aug 27, 2018
23,401
38,791
Real Name
Jim
Currently I have a 2011 Fusion Sport 3.5L that like to randomly stall at stop lights or low speed in a parking lot. I have replaced a couple suspect sensors, scanned it and no CEL, all EVAP test have passed, took it to a mechanic and he came up empty. Also, replaced the throttle body and wiring because some Fords were known for that. If I ever figure this out I’ll be happy.
Vacuum leak somewhere? Had similar symptoms in a loaner POS buick from an actual dealer. Vacuum line going to the brake booster was cracked. Was okay above idle and low-RPM, but would die out at stoplights. I did the troubleshooting on it at work. Capped the vacuum line coming out of the intake going to the booster, ran fine. I drove it back to the dealership when my car was ready, undid my cap, told them to fix their loaner cars before they start stranding people.

I really should have called the dealer to have it towed, but had shit I needed to get done and didn't feel like dealing with it.
 

smug

Please go back to eating crayons
TCG Premium
Aug 4, 2007
8,087
3,751
Cedar Lake, IN
Real Name
Dan Erickson
Vacuum leak somewhere? Had similar symptoms in a loaner POS buick from an actual dealer. Vacuum line going to the brake booster was cracked. Was okay above idle and low-RPM, but would die out at stoplights. I did the troubleshooting on it at work. Capped the vacuum line coming out of the intake going to the booster, ran fine. I drove it back to the dealership when my car was ready, undid my cap, told them to fix their loaner cars before they start stranding people.

I really should have called the dealer to have it towed, but had shit I needed to get done and didn't feel like dealing with it.
That’s worth a look. I seem to remember vacuum numbers on the scanner being normal but you never know.
 
  • Like
Reactions: SpeedSpeak2me

Mr_Roboto

Doing the jobs nobody wants to
TCG Premium
Feb 4, 2012
25,676
30,570
Nashotah, Wisconsin (AKA not Illinois)
Vacuum leak somewhere? Had similar symptoms in a loaner POS buick from an actual dealer. Vacuum line going to the brake booster was cracked. Was okay above idle and low-RPM, but would die out at stoplights. I did the troubleshooting on it at work. Capped the vacuum line coming out of the intake going to the booster, ran fine. I drove it back to the dealership when my car was ready, undid my cap, told them to fix their loaner cars before they start stranding people.

I really should have called the dealer to have it towed, but had shit I needed to get done and didn't feel like dealing with it.

Rented a Verano once, got low oil pressure alarm on it. That went back pretty quickly.
 

Mr_Roboto

Doing the jobs nobody wants to
TCG Premium
Feb 4, 2012
25,676
30,570
Nashotah, Wisconsin (AKA not Illinois)
My dad has a 2011 Silverado that kept eating batteries, and went back to the dealer three times (under warranty). He finally took it to a different dealer and they said it was an issue with the wiring harness in the dash that goes to the fuse block. Didn't know specifically what, so they just replaced it all. Has been fine ever since. Still don't know the exact cause, they just used the spaghetti method and threw everything at the wall to see what stuck.

fuuuuuck that if this Escalade's harness is gone chances are that it's either getting traded or I'm on the hunt for an AWD subframe to stick the LQ9 and 4L65E in for an Astro Van. I'll ditch most of the harness at that point so problem solved, right?
 
  • Like
Reactions: SpeedSpeak2me

IDAFC21

WOW.
Staff member
Moderator
TCG Premium
May 23, 2007
56,950
24,190
Avondale, AZ
So i bought my 02 WRX used back in 04, and while I'd done a lotta research on these cars prior to buying it, it was still my first turbo car and I didnt know ALL the in's and out's of it, and I'd never actually driven one prior to the one I'd bought. So over the first few months of ownership I was learning lots about it, and finding either mods that the previous owner had left on the car, or evidence of mods that the previous owner had removed prior to trading the car in.

Since the car came with the optional boost gauge installed, I soon realized the car wasn't hitting it's full 14.5 PSI of boost or whatever it was supposed to be. It was closer to like 7. This obviously concerned me, especially as I was still discovering things the previous owner did/had done to this car. My mind went to places like is it a tune issue, did the previous owner mess w/ the ecu? is there a bigger problem? I was scouring the forums every night, and finally stumbled upon a thread where someone had experienced a similar issue. The culprit, for them, turned out to be a little brass pill thats supposed to go in line w/ the boost line and regulates the boost. Without it, the car just runs at wastegate pressure, which was........7 psi!

So I went out and check out the boost line where it was SUPPOSED to be, and low and behold.....no pill! This means the previous owner probably had a manual boost controller on the car at some point, and then when they were putting it back to stock, either lost or just didnt have the brass pill anymore. I don't remember how much this little pill cost, but it was practically nothing, and its literally the size of a BB. I had a picture of it once but I can't currently find it anymore. Put that in, and BOOM. I was finally getting full boost out of the car. One of the best mods i ever did! :LOL: It was literally like 3 months of racking my brain tho thinking something was really wrong w/ the car.
 
Old Thread: Hello . There have been no replies in this thread for 90 days.
Content in this thread may no longer be relevant. Consider starting a new thread to get fresh replies.

Thread Info