11
votes
4answers
4k views

Difference between high octane and low octane?

What is the difference between high octane and low octane fuel? I'm not asking if one is better than the other for my vehicle, specifically, but rather what occurs differently both scientifically and ...
11
votes
2answers
10k views

2005 Dodge Ram: easy way to diagnose code P0420?

My truck is reporting a code P0420, which apparently is "Catalyst System Efficiency Below Threshold (Bank 1)" which can either be the catalytic converter or the rear O2 sensor. The code came on at ...
9
votes
3answers
232k 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 ...
8
votes
4answers
21k views

Automatic transmission: Is shifting to neutral while approaching stops bad?

This is not with the intention of saving fuel (as I have seen many answers assuming savings in fuel while doing this). But I have this habit of putting the vehicle into neutral before approaching ...
7
votes
5answers
278 views

Fuel consumption at same speed of different engine

I am wondering why two car running at 100 km/h for example with a 100 hp consume less fuel that an engine of 300hp. Even if I take a supercar lighter and more aerodynamics it will consume more. But ...
7
votes
3answers
433 views

Calculating MPG from MAP sensor (or converting MAP data to MAF data)

My 2002 Honda Accord V6 has a Manifold Absolute Pressure sensor (MAP). I understand that this sensor gives out information in pressure units (psi or equivalent). After doing a bit of research, I ...
7
votes
5answers
130k views

What is the meaning of BHP and torque in bikes or cars?

BHP = Brake horse power. It says that it is brake horse power but it is generally relates with high pick up (your bikes reaches top speed in lesser time). So what does this actually mean?. Torque = ...
7
votes
3answers
5k views

Why don't FWD cars have rear differentials?

This confuses me. The point of a differential is to make it so the wheels don't slip when one needs to be turning faster than the other, such as during turns. So if the rear wheels are directly ...
7
votes
3answers
62k views

Check Engine code P0420 Catalyst efficiency below threshold bank 1

After months of normal driving with no problems, my 2003 Honda Civic EX check engine light came on during a long trip. Got it scanned and it's P0420: Catalyst efficiency below threshold bank 1. They ...
6
votes
1answer
311 views

Oily Sludge in the Intake Manifold

When taking off the throttle body to clean my IAC, I noticed that there was a thick layer of oily sludge coating pretty much everything inside the intake manifold: I have two queastions: How did ...
6
votes
2answers
11k views

Oil pan threads stripped?

EDIT Helpful links on how threads got stripped and by who: http://tl.acurazine.com/forums/showthread.php?t=878261 Seems to be a common problem with some shops, where they don't take good care. ...
5
votes
3answers
788 views

Should one fit the least-worn tires to the rear wheels?

According to the Owner’s Manual Saab 9-3 M2001 (front-wheel driven cars): WARNING When fitting just one new pair of tires, these should be fitted to the rear wheels, as these are more ...
5
votes
4answers
21k views

Cheap way to fix peeling clear coat?

The coat on my car is peeling away something like as shown in following picture which I just pulled up from google as an example: This is my first car and I have never done any car work myself ...
4
votes
3answers
2k views

Realistically, how much can I expect to improve cloudy headlights by polishing?

The headlight lenses on my vehicle (a 2001 Ford F-150) are cloudy, and presumably as a result, the headlights are not terribly effective. (I could post a photo if you want.) I bought a polishing kit ...
4
votes
3answers
14k views

Low beam headlights don't work, High beam headlights do

The vehicle is a 2003 Chevrolet Trailblazer. The low beams aren't working. High beams are. The fuse is perfectly fine (tested and swapped out). The bulbs are fine too. A mechanic told me it could be ...
3
votes
2answers
495 views

Writing CAN Messages

I want to know what should I write with the CAN ID to send it to ECU. I am using ELM327 and Raspberry Pi with all connections to OBD-ii. initially for sending general PIDs to the ECU through ELM327 ...
3
votes
3answers
56k views

Possible reasons for loss of power, engine shaking, and smell of liquid fuel (not burning)?

The car (Renault Megane 1998 1.6e hatchback) lost power (about 500rpm in a bursty rhythm) after I re-ignited on a traffic light, the engine started shaking, and I could smell liquid fuel. There was no ...
22
votes
3answers
98k views

What does a water-like drop 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 drop from it's exhaust steadily in a break of 4-5 seconds. I tried to ask a couple of people at ...
18
votes
2answers
27k views

Is starting your car with the A/C on bad?

I was always yelled at by my father when I was first starting to drive when I left the A/C on when I turned off the car, and then later turned it back on, with the reasoning that I was ruining / ...
15
votes
8answers
2k views

Will having a radiator full of engine oil do damage to the motor?

I've got one question; I was looking over this car that I was going to buy and there was engine oil in the radiator. I asked the guys why it was in there and he said he didn't have enough coolant to ...
15
votes
10answers
156k views

How do I loosen stuck lug nuts in order to change a tire?

How do I loosen car tire lug nuts (so that I can change a tire) when they are really really stuck? I have tried turning the provided wrench, even standing and jumping on it. This worked for 4 of the ...
14
votes
2answers
1k views

Should a mechanical “click” Torque Wrench be set to zero when not in use?

I have a standard click torque wrench. I was told I should set it to zero when not using it in order to keep the accuracy high. Is this true? Secondly, I have not been doing this since I purchased ...
13
votes
6answers
2k views

Why or why not increase engine efficiency by running the car “fuel-lean” (using a turbo or supercharger)?

Everyone wants their cars to use less fuel, right? I read the following passage about running the car fuel lean from this website: Run the engine fuel-lean, that is, use excess air. It is well ...
13
votes
1answer
156 views

LTFT and STFT values are off and don't make sense

Car is a 2015 BMW M5 and it has an aftermarket CAI and a catback (slip on) exhaust. No other performance mods or tunes. About 6-7 months ago, I bought a Kiwi OBD-II reader, simply out of curiosity ...
13
votes
4answers
4k 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 ...
13
votes
2answers
11k views

Why would a new gas cap cause the “check engine” light to shut off?

This happened to a friend of mine: The "check engine" light came on in his truck (Toyota). He replaced the gas cap and the light shut off. Then I also had a "check engine" light come on in my 1994 ...
12
votes
1answer
6k views

Where can I find my car's colour code?

I'm currently shopping around for a touch-up pen to repair some very light scratches on my car. I've found out that our local hardware automotive store can mix the exact colour for any vehicle. ...
12
votes
6answers
11k views

How to fix leaky tires after 2 shops couldn't

I have an SUV with factory 16" steel wheels and P235/70R16 tires. The tires have just under 30,000 miles of gentle driving on them. Two of the tires have been leaking quite a bit (about 10 psi per ...
11
votes
2answers
400 views

What is valve float and how does it impact engines?

The Wikipedia entry is hard to grok: Valve float is an adverse condition which can occur at high engine speeds when the poppet valves in an internal combustion engine valvetrain do not properly ...
11
votes
5answers
116k views

Why would there be transmission fluid in the water overflow reservoir?

The car is a '98 Buick Lesabre with the 3800 engine and about 170k miles. It appears as though some oil was in the radiator, but I haven't seen any signs of coolant in the oil. The water pump recently ...
11
votes
3answers
1k views

Are there any advantages of idling a vehicle vs. turning it off and back on again?

I was sitting outside, eating my lunch the other day, and a small bus (you know, one of the short ones) pulled up to the sandwich shop I was eating at. I noticed that the driver got out of the bus, ...
10
votes
1answer
185 views

How do lambda sensors work?

Virtually every modern passenger vehicle today utilizes lambda sensors from the factory. How critical are they to a vehicle's operation? How do they work?
10
votes
11answers
34k views

Couldn't start my Volvo due to Key Error. Called assistance and he fixed it by hitting the key with a screwdriver. What could be the error?

My Volvo S40 (06) would not start when I turned the ignition key. I got a message that was somewhat like "Key Error, please try again". I tried with both my keys so it wasn't the key itself. I think I ...
9
votes
1answer
117 views

How does intake manifold runner length effect the power curve of a car?

Recently I learned that a number of things such as the cam profile, compression ratio and the intake manifold runner length and volume can all effect the power curve of the engine. Here is an ...
9
votes
1answer
192 views

A most intriguing cold-start misfire mystery

I'm trying to help a friend out with a CEL on his 2009 Merc GLK 280. Hooked it up to an OBD2 reader and retrieved a single code: P0300 - 'Random/Multiple Cylinder Misfire Detected', via the 'OBD ...
9
votes
3answers
25k views

Switching from Reverse to Drive - always stop completely?

I've been told by a couple people that it's really bad for a car to be shifted from Reverse to Drive while the car is still moving backwards. Is this true? In my experience: On automatic cars, this ...
8
votes
1answer
67 views

What is Lobe Separation Angle (LSA)?

What is Lobe Separation Angle (LSA) and how is it used in camshaft design? How is it measured? What difference does a long or short LSA make?
8
votes
2answers
235 views

My Ignition Timing is Retarded, no seriously, it's really screwed up

I logged some test data to try and help me figure out why my 98 Mazda 626 GF 2L ATX has a rough idle and is suffering from hesitation. (Speed k/h),(TPS_v),(MAF ...
8
votes
4answers
8k views

Is Paint Protection worth paying for?

I've just bought myself a new car, and as expected the dealer is trying to sell me extra items. The two options they are trying to push on me are Paint Protection nano technology paint protection ...
8
votes
6answers
15k views

What is the purpose of plastic engine covers?

I have a 2010 Toyota Corolla. What is the purpose of the large plastic cover that stretches over my valve cover? Does it have a particular function? Are they just for looks? Or are they designed by ...
8
votes
1answer
1k views

Car Suddenly Decides To Not Crank

Today I turned the key to start up my car and all the lights (headlights and instrument panel) came on bright and normal, but the engine made absolutely no sound. It wouldn't start, it didn't even try ...
8
votes
3answers
14k views

What can cause warped rotors?

I have a forward rotor on my '04 Chrysler Sebring causing a lot of pulsation when braking. I replaced the rotor- but within about a month the problem had re-appeared. The guys at Monroe noticed my ...
8
votes
2answers
460 views

All weather tires vs winter tires on well-plowed roads

I live in Minnesota. I've seen lots of people recommend changing to winter tires in the winter. However, what doesn't make sense to me is that the roads are plowed very well here. 90% of my driving ...
8
votes
4answers
89k views

Reasons for loss of radiator fluid

I've had to top up my car's radiator fluid twice in the last month after discovering that the expansion tank (plastic container where one usually tops up) had completely drained out (roughly a ...
7
votes
2answers
8k views

Is topping up the oil enough of an oil change?

If you use synthetic ester-based oil in a relatively new petrol engine, top it up regularly, and the engine runs very quietly and basically without any noise whatsoever (especially after another top ...
7
votes
3answers
2k views

How might I fix a dent in a Honda Rebel fuel tank?

In a silly move during an engine overhaul, I dropped my Honda Rebel's fuel tank and put a dent in the top side. Is it possible to pull this dent out? I've heard there is a method using heat and ice ...
6
votes
1answer
53 views

What exactly is a head gasket?

From what I have gathered, a "head gasket" is an important part of the engine on most cars, but that is about it. What is a head gasket? Where is a head gasket? Why is it necessary?
6
votes
3answers
2k views

Minimum RPM at idle speed

Looking at wikipedia, For a passenger-car engine, idle speed is customarily between 600 rpm and 1,000 rpm. For buses and trucks it is approximately 540 rpm. In case of many single-cylinder ...
6
votes
1answer
534 views

Can I break power steering by turning too far

Will I damage power steering in a 2008 Camry XLE if I routinely turn the steering wheel to its limits, i.e. where it will not move further?
6
votes
1answer
6k views

My 2005 Mazda 3 Front Passenger window motor receives signal to go down, but not up

If you look at the picture below you will see that I took the plastic panel off my door, and separated the motor from the regulator. After I disconnected the motor that I thought was bad, I connected ...

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