13
votes
4answers
26k views

what is difference between DOHC and SOHC?

I want to know the SOHC and DOHC configurations. On what factors an engine manufacturer decides to go with SOHC or with DOHC, what should I choose? DOHC or SOHC?
13
votes
6answers
21k views

How to properly dispose of old fuel?

I have some old 2 stroke mixed gas I need to get rid of. This could also apply to old fuel removed from a sitting car or any vehicle for that matter. What is the proper way to dispose of this? Are ...
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 ...
13
votes
4answers
3k 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
1answer
793 views

What is a governor and what is it used for?

I was watching a classic car restoration program on YouTube in which they were working on a '50s Cadillac with an automatic transmission. The mechanic in the video diagnosed a transmission glitch as ...
13
votes
3answers
11k views

When car is standing still, I smell Diesel exhaust. Why?

In my 2003 Opel Vectra, the cabin air smells of Diesel exhaust while stopped at e.g. a red light. The exhaust smell goes away when driving, and it also doesn't come back if I turn the ventilation off ...
13
votes
4answers
7k views

Is it worth switching to full synthetic or blend oil in my older car/truck?

I have a older (enter vehicle here) that has 100k miles on it. Would I see any benefit switching to full synthetic or synthentic blend oil? Is it worth the extra cost in an older vehicle? For ...
13
votes
1answer
3k views

What is happening when a two-stroke engine is said to be “four-stroking”?

Many years ago, I was involved in a hobby of building and flying model aircraft. The aircraft used alcohol-fueled 2-stroke engines with glow plug ignitions. When these engines ran rich (and always at ...
13
votes
9answers
211k views

Steering wheel shakes at high speeds

the steering wheel sometimes shakes at high speeds around 70 miles per hour. It does not always happen. Some day when I am driving at 70, I feel no shakes. some day it shakes badly at the same speed. ...
13
votes
3answers
89k views

What iPhone/iPad app works best with ELM327 Bluetooth OBD-II reader?

I've found a number of apps for the iPhone/iPad that connect to ODB-II readers via WiFi, but unfortunately that means that it disables 3G and all the benefits of having a 3G device built into my dash. ...
13
votes
2answers
666 views

How To Get Organized Without a Garage Workspace?

People I've seen who have garages have it made. They have a clean, dry workspace with all of their tools within arms reach. In the most organized garages, a mixture of rolling Snap-on Roll Cab with ...
13
votes
1answer
8k views

Is this what is making my car sound like a racecar?

Recently, my car (2000 Mercury Grand Marquis) started sounding like a racecar: the engine became very loud. There's clearly something going wrong with the exhaust system. I'm trying to understand ...
13
votes
1answer
25k views

How can I repair cracks in leather seat?

The leather on the side of the driver's seat has some minor cracks. I am using conditioner to help prevent this in the other seats but these cracks already exist. Is there a product or patch of some ...
13
votes
5answers
21k views

2000 VW Golf heater won't blow hot air

My 2000 2.0L Golf GLS won't blow hot air at operating temperature, the air is only lukewarm at best. This started a few months ago inexplicably. The car isn't overheating or underheating, it reaches ...
13
votes
1answer
134 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
1answer
2k views

How do I find the correct pins in a CAN-BUS connector?

This question might be too technical for this forum, but I'll give it a go. I have a 2012 BMW R1200R motorcycle with CAN-BUS. I'd like to make an Arduino interface to the connector on the bike, but I ...
12
votes
11answers
48k views

Should I pull my wipers away from the windshield when parked during a winter storm?

When we are expecting snow storm and the vehicle is parked, do we pull out the wipers so they don’t touch the glass to avoid the freezing to the windshield? Or would that hurt the springs in the wiper ...
12
votes
9answers
15k views

How can I remove a seized brake disc?

I'm changing the rear brake discs and pads on my Ford Focus C-MAX. I've done one side which was fairly easy, but on the other side I can't get the disc off. There is nothing holding it on as far as I ...
12
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 ...
12
votes
9answers
11k views

Diesel vs Petrol motorcars. Pro's and cons?

I realize this may be a silly question to those of you on here who are proper petrol-heads and this may even be a repeat question, but I could not find anything on it on here, so here goes: What are ...
12
votes
5answers
54k views

What does the 'cc' mean on a motorcycle?

I'm relatively new to motorcycles, my flat mate taught me how to drive his two Royal Enfields around New Delhi, and for the past year and a half I've been taking care of them as they break down ;) ...
12
votes
4answers
1k views

Should I fill my tire?

I measured the PSI on my rear driver tire (using a gauge pin - push it into the needle and a stick pops out with a reading), and I got a reading of 22 PSI. My tires are supposed to be anywhere from ...
12
votes
4answers
6k views

Car crash: when does a car catch fire?

Which kind of crash does it need for a car to catch fire? I'm asking because I was discussing about an accident where a car crashed into a full-grown brown bear. Is it realistic under normal ...
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 ...
12
votes
4answers
1k views

Why do 5- and 6-speed transmissions typically need different gear ratios?

My 2013 Subauru WRX has a 5-speed manual, and I long for it to have a 6th gear when cruising on the highway. A friend has a 2012 Subaru STI with a 6-speed manual, and I noticed his car runs through ...
12
votes
2answers
685 views

What does under-square and over-square mean?

When building an engine, the terms over-square and under-square come up. What do these terms mean? How do they apply to engine building? Which is better for what purpose? Can you give examples ...
12
votes
4answers
872 views

Is there a benefit to belt driven motorcycles?

What are the pros and cons of belt driven motorcycles compared to chain driven bikes?
12
votes
5answers
505 views

How exactly does running fuel-lean increase the temperature of ignition?

I learned in this question that running an engine fuel-lean will increase the temperature of ignition, among other things such as causing problems with the catalytic converter. I have no idea how or ...
12
votes
5answers
280 views

How do I remove a broken drill bit from metal?

I was building a mount for my custom bobber. My 1/4" carbide drill bit broke off into 3/4" plate of steel. How do I remove it?
12
votes
5answers
20k views

How difficult is it to rebuild a transmission?

I have a 1984 Toyota Supra that is now exclusively a track car. The last round out we let some less experienced drivers take the wheel and they basically destroyed the transmission. Nothing but 4th ...
12
votes
2answers
5k views

What happens to a car when it hasn't been driven for 12 years?

I'm hoping that I'll soon be the owner of 2l turbo charged, 4wd hatchback that's been sat in a garage, undriven for over a decade. Trouble is that I won't be able to give it a full inspection until I ...
12
votes
3answers
136 views

What is regenerative braking and why don't we use it?

I know that many electric cars use regenerative braking to enable the car to become more efficient by converting what would otherwise be lost heat energy in to a more useful, reusable form of energy. ...
12
votes
4answers
76k views

How important is a fuel cap?

I lost my fuel cap a couple months ago and haven't bothered finding a replacement. I haven't noticed any issues with it, but I'm wondering whether it's causing any damage or reducing gas mileage or ...
12
votes
2answers
62 views

What is an A/R ratio?

I heard the term A/R ratio today while watching a video about turbochargers. What does the term A/R ratio mean? Does it just apply to turbos? If not, what else does it apply to? How is it computed? ...
12
votes
2answers
215 views

Why do Harley Davidson engines suffer from such poor performance?

The modern Harley Davidson engine has very poor power output. Even when highly modified a 130HP engine can cost tens of thousands of US Dollars. Here are specs on one of the modern engines. ...
12
votes
5answers
29k views

How to test for defective glow plugs?

On a diesel engine, how can I know which glow plugs are defective, and can I change these only?
12
votes
3answers
5k views

Is it harmful to drive at high rpms

Does driving at high RPMs (3000-3500) in a manual transmission car cause any extra wear and tear to any mechanical parts? It obviously hurts gas mileage, but does it hurt anything else?
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
2answers
2k 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 ...
12
votes
5answers
65k views

Is it possible to harm your car by giving someone a boost?

This post explains why it's a potential hazard to clip to the negative post on the dead battery when giving a boost. But I've also been told that I could damage the electronics in my own car if I give ...
12
votes
2answers
273 views

'00 Honda CBR929RR - Unknown issue, help!

Sorry for the ambiguity here.. I'm not sure what the issue is with my bike. I have a bunch of symptoms and my hypothesis is that it's a cascading failure and I'm just seeing a bunch of effects down ...
12
votes
2answers
470 views

Brake flush vs. Replacing the brake fluid

Is a brake flush the exact same thing as replacing the brake fluid? Or is there a difference?
12
votes
2answers
4k views

How to test a clutch

I have just bought a second hand car, and I have the feeling that the clutch is worn out. How can I do a quick clutch sanity check?
12
votes
2answers
223 views

Does waiting until the gas cap become faulty cause any damage?

The description for a fuel tank cap says: You can prevent unnecessary service costs by replacing the gas cap on modern vehicles before they go bad and the check engine light appears. Is this ...
12
votes
3answers
9k views

Why (almost) all dirt bikes have single cylinder engine?

Every dirt bike i know has a single cylinder engine. I myself ride a Yamaha XT660Z which has a huge 660 cc cylinder. What are the characteristics of those engines? what are the benefits of such ...
12
votes
3answers
742 views

Afraid to crank engine - how can I tell if my cylinders are flooded with water?

Backdrop We had really heavy rains here today. I was in my '99 M5, idling in traffic when I noticed the brake pedal feel became really notchy. When I let go of the brakes the pedal would not travel ...
12
votes
3answers
954 views

What to know before buying and OBD-II reader

I read the features to look for in an OBD-II reader, but I am curious if getting one is the right move. I'm just planning to get a cheap one, which is proving to be interesting shopping local. What I ...
12
votes
2answers
293 views

What factors affect the maximum air pressure that should be put in a vehicle's tires?

For just about every car, there's at least two different "maximum tire pressure" ratings. The vehicle manufacturer's rating. This is usually found on a sticker attached to the driver's door. The ...
12
votes
1answer
3k views

how to optimize fuel consumption by changing the rear differential ratio?

Is it possible to improve the fuel consumption (decrease it) in my van by changing the rear differential ratio? I would like to optimize it for low-speed driving about 40 km/h (25 mph). Is it true ...
12
votes
4answers
45k views

What would be the most likely cause of engine sputter?

Most of the time my 2001 Honda Civic sounds like this... Vrooooooom. But some times when I start driving it sounds like this... Vrooom putt pa putt pa putt pa vrooooom. When it's in the "putt pa ...

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