Air Intake & Filter

At the intake tract between the measuring point and the throttle. Splits form in the corrugated sections of intake hoses and are frequently on the underside where they close up when the engine is off and open under vibration, which is why a visual check can miss them. Flex each hose by hand with the engine running and listen for the idle to change. Check the crankcase ventilation pipe at the same time, since a split there produces exactly the same symptom.

Follow the service schedule and shorten it if the environment is dusty, since intervals are set for average conditions rather than gravel tracks and building sites. A visual check tells you a great deal: hold the element up to a light and look at how much passes through. Resist the temptation to blow it out with compressed air, which drives dust through the media and enlarges the pores, leaving a filter that looks clean and filters worse than the one you removed.

Almost always just the element. The assembly is the plastic housing, its mounting and often the ducting, and it is ordered when the housing has cracked, a mounting has broken or the sealing lip no longer holds the lid down. If your car is simply due a service, the element is the part. The listings distinguish between the two, so read the description before ordering rather than assuming the picture shows what you need.

Directly, rarely. Indirectly, it causes trouble. Unmetered air makes the mixture lean, and while the control unit compensates, a large leak can push it past its authority and produce misfires, poor idle and a lean fault code. The greater risk is that a split forming before the filter would let unfiltered air in, which does cause wear. Fix a split hose promptly, and check that the clamp at each end is holding, since a slipped clamp mimics a split.

It is a tuned chamber that cancels a particular intake frequency, and removing it makes the engine noticeably louder in the cabin without adding meaningful power on a standard engine. On some designs it also affects the flow characteristics the fuelling map was calibrated against. If your resonator has cracked, replace it rather than blanking it off, and remember that the extra noise is not a performance indicator. It is listed here as its own part.

This is one of the less expensive categories on the site. Filter elements, clamps, connectors and brackets sit at the bottom of the range, hoses and resonators are modest, and complete air filter assemblies cost the most here without approaching the price of a mechanical component. The live minimum and maximum are shown in the band at the top of this page. Given how often a cheap split hose causes an expensive looking fault, this is a good category to check first.

On a standard engine the gain is very small and the risks are real. Oiled cotton filters can pass more dust than a paper element and, if over oiled, contaminate the air mass sensor, which produces exactly the fuelling problems you were not looking for. Manufacturers size the intake so that the filter is not the restriction at standard power. If your aim is a healthy engine rather than a louder one, the factory element is the better purchase.

Use the fuel trim data as a guide, since a leak shows as positive long term trim that is worst at idle and reduces as engine load rises. Then locate it physically: a smoke test at a workshop fills the tract with vapour and shows the leak in minutes, and at home you can flex each hose and connector while watching live trim values. Avoid spraying flammable aerosols around a hot engine, which is the traditional method and a poor idea.

Because it feeds into the intake and any fault in it behaves like an intake fault. The pipe returns blowby gases from the crankcase to be burnt, so a split lets unmetered air in and upsets idle, while a blocked or collapsed pipe raises crankcase pressure and pushes oil past the seals. Both problems are cured by a cheap part and both are frequently misdiagnosed as something more serious. Inspect it whenever the intake or an oil leak is under investigation.

Only where the number agrees. Duct shapes follow the packaging of the specific engine bay, diameters follow the throttle and the measuring point, and mounting tabs follow brackets welded or moulded to particular positions. A hose that is close will sit under tension and split at the same place within a year. Read the number moulded into the old part where legible, match it, and use the quote form where the reference brings back nothing.

The spring band type do, and they are cheap enough that there is no argument. A steel band spring clamp holds its tension through heat cycles by design, and once it has been opened and closed a few times it loses some of that, which shows up later as a slow leak at the joint. Worm drive clips can be reused if undamaged. Order a few clamps with any hose so the joint is properly sealed.

Yes, and this is one of the categories where it happens least often. Filter elements are stocked references and usually show a figure straight away. Moulded intake hoses, resonators and crankcase ventilation pipes are the ones that occasionally appear without pricing, because each is shaped for a single engine variant and moves in small quantities. Send the reference through the quote form and a figure comes back against that exact moulding. If the old hose split at a clamp, ask for the clamp and the connector as well, because reusing a tired band clamp reproduces the leak within weeks.