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71 votes
6 answers
396k views

Why does my A/C blow foul smelling air when it first turns on?

Most of the time when I first turn on the A/C in our 2008 Toyota Sienna, the air that blows out has a very distinct chemical - nasty smell. After a while it seems to go away. I'm not sure if I just ...
polarbear's user avatar
  • 813
51 votes
4 answers
89k views

Reviving a vehicle that has been idle for a long time

Some related topics: How to maintain a sometimes-used vehicle? How long does it take for gas to go bad? The first related topic addresses preparing a vehicle for long-term disuse, and maintaining ...
Iszi's user avatar
  • 2,591
16 votes
3 answers
15k views

How can I tell if I have bad cats?

No, not that cat! Catalytic converters - or "cats" - have a nasty habit of failing with age. What are the symptoms associated with a cat that's gone bad? Are there any tests that could definitively ...
Zaid's user avatar
  • 39.2k
43 votes
4 answers
160k views

How far can I drive with 1 gallon too much oil?

I have way too much oil in my Acura TSX. Do I need to take care of it without turning it on or can I drive it to a service station? If I need to do it in place, I don't have the ramps or a pan or ...
Jason Kleban's user avatar
28 votes
4 answers
19k views

How do I test my car battery?

My car still starts fine but when I turn off the car (just the motor . . the key is still in and "on") I noticed the headlights dim to almost off. It's and older car and the headlights don't turn off ...
tooshel's user avatar
  • 1,051
105 votes
17 answers
275k views

Does Downshifting (Engine Braking) Cause Extra Wear and Tear?

Does the act of downshifting to slow your vehicle down have any negative side affects? I don't downshift more than one or two gears at a time and I let out on the clutch slow enough that I don't rev ...
Gary's user avatar
  • 1,203
14 votes
1 answer
108k views

Do I have to rely on wire color to correctly wire up an O2 sensor?

It seems that everyone and their grandmother has a different color-code convention for 4-wire O2 sensors, which complicates matters when one is trying to wire up a replacement "universal" O2 sensor. ...
Zaid's user avatar
  • 39.2k
68 votes
7 answers
23k views

What to check when buying a used car?

I'm looking to buy a used car. What do you think I should check (mechanically) before buying it (especially if it's diesel)?
Reed's user avatar
  • 1,021
62 votes
6 answers
313k views

How long does it take for gas to go bad?

Approximately how long does it take for unleaded gasoline in the tank and fuel lines to become unusable in a car that is not being used? What causes this, and what can be done to prevent or remedy ...
Iszi's user avatar
  • 2,591
34 votes
8 answers
430k views

Running with straight water as coolant in the summer. Is it fine?

I grew up flushing the coolant twice yearly. In the Spring, you drain the antifreeze and fill with straight water for the summer. In the Fall, you drain the water and put in a 50/50 antifreeze/water ...
Wulfhart's user avatar
  • 705
25 votes
4 answers
471k views

Symptoms of Lean or Rich carb settings on a motorcycle

I have a 1981 Yamaha XS650. I recently put in K&N stock replacement filter (ie, they are in the airbox and conform to the size of the original), however they may be leading to a leaner mixture ...
user avatar
66 votes
9 answers
816k views

What actually happens when there is not enough oil in a car engine?

When a car is topped up with oil, it clear to most people that you are supposed to fill it to the recommended amount as specified by the manufacturer (normally on a dip stick). What exactly are all ...
Max Goodridge's user avatar
26 votes
4 answers
509k views

What actually happens when there is way too much oil in a car engine?

I saw the answers to a question I posted recently highlighting the disadvantages of having too little oil in an engine, but that got me wondering what if the complete opposite were to occur! I know ...
Max Goodridge's user avatar
19 votes
3 answers
59k views

Lugging the Engine (Manual Transmission)

So...lugging the engine obviously isn't something that is good. But why? For example when you feather a clutch to get the car moving, it lugs for a quick moment when you hit the catch point (When ...
user avatar
82 votes
10 answers
46k views

What are the benefits of premium (high octane) petrol?

Here in the UK it's common for petrol (gas) stations to offer both regular and "premium" unleaded petrol. The premium stuff is (naturally) more expensive, and I've often wondered what the actual ...
Simon Whitaker's user avatar
31 votes
9 answers
362k views

Is it okay to leave a car for 5 months without driving it?

I need to travel to the east coast and work from there for a duration of 5 months. I can leave my car in covered parking here and ask a friend to start the car for a few minutes every week. What ...
vivekian2's user avatar
  • 649
22 votes
6 answers
374k views

I drove with my Parking Brake on for 30 mins: should I be worried?

Yesterday, I was driving my car for about 30 minutes on the highway at speeds of up to 60 mph. I felt my brakes weren't really working and looked down to notice my emergency brake had been on the ...
Siena's user avatar
  • 221
9 votes
3 answers
228k views

Oil in coolant - how much trouble am I in?

I have oil in my coolant reservoir. Could it just be the head gasket or is it almost certainly the entire engine or might it be something else entirely? Thanks in advance...
ConsultUtah's user avatar
5 votes
1 answer
6k views

What is a stress riser?

What is a stress riser and why is it important to avoid them during engine construction or rebuild?
Pᴀᴜʟsᴛᴇʀ2's user avatar
16 votes
3 answers
2k views

Multimeter - Basic Functionality and Howto

Multimeters I'm looking for some responses regarding multimeter basics for the site tag-wiki to point OP's at when we want them to use one. The question is; What are the basic functions of a ...
DucatiKiller's user avatar
  • 32.9k
13 votes
5 answers
150k views

Tire SideWall Damage. Replace?

Yesterday I bumped into a curb and my tire has sidewall damage. Is this tire safe to drive on? or do I need to replace this tire?
M.Bolt's user avatar
  • 131
46 votes
4 answers
28k views

Jump starting a dead battery: Connect black wire to negative pole of battery or grounded metal?

Most of the advice I've seen for jump starting cars instructs to connect the black wire to a bare piece of metal on the car with the dead battery. However, I've always just hooked up both poles to the ...
JohnFx's user avatar
  • 768
38 votes
3 answers
376k views

What does a water-like drip coming out of the exhaust of the car signify?

Sometimes while driving in the traffic, I come across a car or two which would be dripping water-like drops from its exhaust steadily in 4-5 second intervals. I tried to ask a couple of people at the ...
Sandman's user avatar
  • 685
22 votes
4 answers
787k views

Will Putting An Extra Quart of Oil In My Car Ruin It?

I put too much motor oil in my car's motor. About a quart - have I ruined my car? I've been driving it. I know I need to get the oil drained. But I'm worried that I've ruined my car which has been ...
Nancy's user avatar
  • 221
21 votes
9 answers
104k views

Battery drains by itself when vehicle is parked (parasitic draw)

A 1998 Jeep Grand Cherokee has gone through 3 batteries in the last 3 months. While they have all been replaced by warranties, it'd be nice to get the problem solved permanently. I've tested the ...
PearsonArtPhoto's user avatar
18 votes
2 answers
5k views

What is a leak down tester and what can I do with it?

Background There are quite a few head gasket related questions on the site. Coolant or water in the oil, oil in the coolant or water in a radiator, etc. I'm thinking that some instruction on howto ...
DucatiKiller's user avatar
  • 32.9k
29 votes
9 answers
129k views

Will higher octane fuel improve gas mileage?

I've heard from some people that high octane fuel will increase gas mileage. Around here, we have the basic unleaded(87), mid-grade(89), and premium(93 or 91). I've been using the basic 87 unleaded ...
Earlz's user avatar
  • 927
24 votes
4 answers
8k views

Will engine braking damage my transmission? How can I tell?

I drive a manual transmission '08 Honda Fit. On my daily 17 mile commute to work, there are three long hills that I can coast down, each about a half mile long. Going down these hills, I've done two ...
yhw42's user avatar
  • 347
23 votes
3 answers
157k views

Must I Replace All 4 Tires on an All Wheel Drive (AWD) vehicle?

I have a 2005 Subaru Legacy 2.5i Wagon. I just destroyed the passenger-side rear tire. The tires have approx. 6/32" tread remaining, per an informal measurement with a coin (I used this guideline ...
qxotk's user avatar
  • 414
18 votes
11 answers
32k views

What's the best gear to leave a manual vehicle in when parked? [closed]

I've been told that reverse is the "strongest" gear, so in a manual transmission vehicle you should park your vehicle and leave it in reverse in the event of a parking brake failure. Others have said ...
William's user avatar
  • 651
16 votes
6 answers
100k views

Can coasting in neutral damage an automatic transmission?

When I drove a manual transmission, I got in the habit of shifting to neutral on long, shallow grades to save fuel. Now I'm driving an automatic (specifically, a recent Corolla) and still doing it. ...
Michael Myers's user avatar
14 votes
1 answer
4k views

What exactly are fuel trims?

What is meant by the term "fuel trim"? Why are they so important in diagnosing engine operation issues? How do short-term fuel trims differ from long-term fuel trims?
Zaid's user avatar
  • 39.2k
11 votes
10 answers
105k views

Will different tread depths hurt my 4 wheel drive?

I have a Ford F150 4x4. The front 2 tires treads measure 12/32, one rear is 6/32 and the other is 10/32. The dealership told me I should replace the rear 2 tires because the big difference in tread ...
NotDan's user avatar
  • 211
19 votes
6 answers
124k views

Engine power specification at different rpm?

Car companies advertise the power of an engine at different rpms. Car 1: 80 PS at 6000 rpm Car 2: 85 PS at 6500 rpm What does the power at different rpm mean? Does it mean Car 1 has better power ...
user3041058's user avatar
14 votes
4 answers
80k views

Why should I connect the red/positive terminal first when jump starting?

So, it's fairly popular consensus online that it's red/positive clips to the positive/red posts, then the black/negative clip to the frame One site mentions sparks, but you'll still get a spark when ...
QueueHammer's user avatar
8 votes
4 answers
85k views

What is the proper way to extract a broken sparkplug?

When dealing with a car with aluminum head(s), what is the proper way to extract a broken sparkplug?
NoCarrier's user avatar
  • 2,902
8 votes
3 answers
95k views

Rough Low Idle and Engine Shakes, Hesitation and Lack of Power

On a 98 Mazda 626 GF 2L I'm working on the engine seems to shake / wobble for about a second / second and a half when going to WOT from any starting rpm. It also almost sounded like maybe one of the ...
Robert S. Barnes's user avatar
7 votes
1 answer
17k views

I drove with the handbrake on for 1000 metres

I left my handbrake on for about 1000 meter when driving this winter. I smelled something burning when I opened the front door. Since then there is often a burning smell back right wheel after ...
Jenny's user avatar
  • 71
29 votes
3 answers
14k views

Static vs. Effective compression: Why does higher effective compression not require higher octane gas?

Background I've been trying to do a lot of research on boost lately because I'm planning on running a moderate turbo setup on my daily/light-duty-autox car in the future. I'm trying to get into the ...
Annath's user avatar
  • 643
20 votes
2 answers
83k views

How is engine load determined?

I'm struggling to find information on how engine load is defined. Is it really just a fancy word for torque demand? There are three parts to this question: Is there a theoretical equation that is ...
Zaid's user avatar
  • 39.2k
14 votes
2 answers
4k views

How to determine exactly what's wrong with my alternator?

My 98 Mazda 626 GF 2L uses an 80 amp fp34 A2TB0191 alternator with an internal voltage regulator. I did a little test where it I turned on the bright lights, AC, radio, rear defogger and opened the ...
Robert S. Barnes's user avatar
12 votes
1 answer
93k views

What is seafoam? What does it do? How do you use it?

Mech's seem to get a real rubbery one about Seafoam. Is it just fuel additive, like something similar to Lucas Oil? Do I just pour it into my gas tank as a gas treatment? What will it do/help ...
rhill45's user avatar
  • 257
11 votes
2 answers
5k views

BSFC (Brake Specific Fuel Consumption) - How is this a beneficial measurement?

Brake Specific Fuel Consumption or BSFC Measuring various attributes of an ICE (Internal Combustion Engine) and how it performs certainly gives a greater understanding of how a particular ICE ...
DucatiKiller's user avatar
  • 32.9k
11 votes
4 answers
68k views

How to understand different engine oils?

When I went to shop for engine oil, I found many types as such: 5W-30 A5 5W-30 A1 5W-20 SAE 5W-30 10W-30 Also I see other information such as: Fully Synthetic Semi Synthetic Oil Synthetic ...
malhobayyeb's user avatar
11 votes
4 answers
2k views

Starting a 2 stroke jet boat after several years

The parents in law gave me a jet boat, it hasn't been started in 5 years. The boat resided in NH on a trailer on their yard for 5 years, so it has seen freezing temperatures frequently. From what I ...
Calvin's user avatar
  • 489
9 votes
1 answer
723 views

Excessive Coolant Expansion: Part 2

This is a continuation of my excessive coolant expansion question regarding my 98 Mazda 626 2L. When I drained the coolant I noticed this black sediment which settled to the bottom of the container I ...
Robert S. Barnes's user avatar
8 votes
3 answers
137k views

Can I reprogram a used Mercedes smart key?

I want a new key for my Mercedes Benz and I've heard that you can get a used smart key for much cheaper than a new one from a licensed Mercedes mechanic. Can I reuse an already programmed Mercedes ...
Ben Brocka's user avatar
8 votes
1 answer
23k views

What are some Seafoam Alternatives

I read this procedure for using Sea Foam ( also listed on their website ) to clean the intake manifold, injectors and crankcase. I think this would be useful for my vehicle, however Sea Foam isn't ...
Robert S. Barnes's user avatar
6 votes
1 answer
2k views

How does a torque converter work?

I am still in the learning process and I am okay with torque converter but there are some things I can't understand very well: Why does the impeller and turbine have vanes in opposite directions? ...
user3407319's user avatar
77 votes
16 answers
534k views

Should I resurface or replace my rotors everytime I replace brake pads?

I have heard it is proper practice to replace or resurface your brake rotors every time your do a brake pad replacement. Does this need to be done every single time or is it overkill? Maybe it is ...
Troggy's user avatar
  • 2,106

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