10 Reasons Why Engines Lose Power Over Time

Why Do Engines Lose Horsepower As They Get Older?

There are four things a gasoline engine requires to generate power and almost any engine problem will come down to something relating to one of these four factors. 1. Air 2. Fuel 3. Compression 4. Spark

Dirty Air Filter
A clogged air filter makes the engine work harder to pull in air, and can restrict the maximum amount of air let in. Less air means less power.

Exhaust Restrictions
The engine will have to work harder to push out exhaust gases, limiting power. Catalytic converters can clog up on engines with an improper air/fuel mixture or as a result of fuel additives reacting within. Mufflers can also fail internally, and alterations of the internal piping can result in an airflow restriction.

Fuel Injectors
Deposits can build up on the injectors over time from heat soak or poor fuel. Small restrictions can cause the O2 sensors to read a lean mixture, and so more fuel will be added to compensate. This can result in a rich mixture for the cylinders without injector problems, or even misfiring if the injector isn’t capable of injecting enough fuel.

Fuel Pumps
Overtime the fuel pump can wear out, but it might not necessarily fail catastrophically. While it may still be able to supply fuel at lower pressures, it may begin to struggle to provide fuel at higher pressures or for longer durations.

Worn Piston Rings
One of the major things that can happen over time is the piston rings will wear down, and this will allow for blow-by. Some of the high pressure air and fuel mixture combusting will pass by the pistons and travel along the cylinder walls into the crank case. This is pressure that should be pressing the piston down, so power is lost. It also means less compression as some of the air can escape as the piston travels upward on the intake stroke.

Carbon Deposits On Intake Valves/Valve Seats
If carbon deposits build up on the valves or valve seats, this can prevent the valves from closing properly. If an intake valve cannot fully close, it will allow air to escape during the compression stroke, effectively lowering the compression ratio.

Carbon Deposits On The Piston
If deposits build on the piston or cylinder walls, these deposits can create hot spots. These hot spots can result in engine knock if conditions allow for it. If the engine is capable, it will retard the ignition timing to reduce the likelihood of knock. By retarding the ignition timing, power is lost.

Fouled Spark Plugs
Spark plugs can build deposits with time. Inconsistent spark plug firing means you’re likely to misfire. Maintaining clean plugs ensures that the spark part of the equation doesn’t result in a loss of power.

Reference Article (EE on Car Throttle)

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[GAS.M]

10 reasons, 5 mins, 2reasons per min, 1reason every 30secs, excellent video...quick and to the point. 👍🏻

[boyotm]

You’re helping me so much to learn about the mechanics of cars rather than just blindly adding mods. Keep up the amazing work and I can’t wait to see your future!

[frisbee]

My 3.4L V6 GM engine is more powerful today than it was back in 04.  I changed out to Mobil 1 soon as I got it home. Been using it ever since.  Changed out OE air filter to K&N. Changed out restrictive exhaust to dual exhaust with 1/2" larger pipes.  Changed out to new OE plug wires.  Bosch Iridium spark plugs. Change out AT fluid at 60000. Maintain the car all the time myself so I know the work is done correctly with the right fluids and oil. Changed to all LED lights, including dash light. Added performance tires and wheels which lets the vehicle roll easier (reduces road friction). Stuff like that.

[Titan]

Camshaft wear. I had an engine that was low on power. It ran just fine, quiet, smooth, started OK. It was the lowest power version fitted to this car so I thought it was normal. i decided to pep it up a bit with a performance cam, cylinder heads and headers. When i removed the cam it was so badly worn some valves must have been barely opening. Just replacing the cam with a new standard one would have given a substantial power increase. Once put back together the power increase with the performance parts was incredible!

[HudsonStronck]

I just keep modding it... doesn't loose power over time, just increases the potential breakdowns

[MichaelRodriguez-vlby]

I just saw you on a GMC commercial and I wanted to comment and say congratulations but comments were disabled on that video so I came here, congratulations on all your progress! It's so cool to see how far you've made it.

[BMWEHQ]

Those bad plugs look great compared to the ones I pulled from my 328i a few months ago! They were so bad!

[MrMusicweekly]

This has been your most short and to the point video I have yet to see, I like it.

[alighanadian]

dirty fuel filter sometimes makes your fuel pump work harder so you might wanna check that too.
besides this pressure on fuel pump may cause damage so replacing it might be a good idea

[OFFICIAL_VIDEO_AWARDS]

I've got 600, 000kms from a Land cruiser all original still running like new when I sold it. As well as getting hundreds of thousands of kilometers from other cars.

My tips:
1) don't use the oil your manufacturer recommends, use synthetic oil according to your climate grade. For example, Toyota put 5w-30 in engines in Australia where it gets to over 40c and the engine starts burning the oil. I use 15w-50

2) Change your fuel filter annually and if you have a diesel with mechanical injection pumps, use a good quality fuel stabilising additive that conditions seals and rings while removing contaminants and algae.

3) Don't forget gearbox oil changes, and if you have a 4WD, transfer and diff oils too. Don't forget to grease all grease points in the drive line and suspension.

4) Flush out your radiator properly, I mean removing hoses, flushing the heater core, making sure no hoses crunch with rust when squeezed and use coolant that feels slippery and silky between your fingers.

[leslynnlewis]

Can you work on. my S600? You really elucidate car mechanics! I learned a lot!

[heensworth]

Although you are right about ring gap increasing over time it is the wear on cylinder crosshatching that adds the most noticeable blow-by which is why a hone is essential for an engine build; with a worn cylinder wall there would be very minimal compression

[briant]

friend of our converted his truck to propane and we did a tear down of his engine and it looked bran new, another thing we hav noticed our engines once getting around 36k miles is when we noticed a increase in fuel mileage, people dont like to maintain or do mantaince until they have a problem this is key to follow up on follow thur with proper maintence and you will be fine, again my friend came down from canada we had same trucks but he gets almost 3x the fuel milage we get, the tech, is there and yes after he was here for 8 months the dealer said he had a recall on his fuel system, ha, he said he wasnt changing anything, and he didnt,

[xLoBx]

i had idle problems with my car, it was idling around 600rpm. after adjusting the spark plug gaps, at first start rpm went up around 2k and slowly fell down to perfect. its incredible how little things can cause big power losses.

[jamesatkinson]

Quite a comprehensive description there, and suggests many inexpensive solutions to maintaining power, much of which is manufacturer's recommended maintenance intervals...

[kalabash]

How about a fuel filter? I would think a clogged fuel filter would restrict fuel, especially under heavy loads.

[flagmichael]

An important detail about "knock" (detonation).... Detonation comes from either of two sources; ignition or pre-ignition. All vehicles sold in the USA since 1996 must have OBDII, which effectively demands monitored knock sensors. If the detonation is the result of ignition, retarding the spark (the system kicks it back a *lot*) controls it. If you hear pinging, it means you have pre-ignition caused by hot spots. Ignition timing does not control pre-ignition.

[jaimeandrealmeida]

this is by far the best car channel on youtube. thanks for everything!

[HAL-dmeh]

Man, my 98 Expedition just turned 240, 000 and has none of these problems (that make it noticeable), save probably a need to adjust the throttle cable and I did replace the fuel pump (it was wearing out, FIXED). All fluids/filters get changed so that's not an issue. The thing runs, rides and drives like brand spankin new. If anything ever impressed me about it, this just did!

[jakub.anderwald]

Some of these things can be easily fixed (e.g. replacing a single cheap part), some not. It would be great if you could have a video explaining what to do to diagnose and fix each of those possible issues.