Auto Repair
Fuel, Air & Induction Repair
Lean codes, rough running and poor economy usually come down to what the engine is being fed and what it is being told about it. Both are testable.
What you might be noticing
If any of this sounds familiar, it is worth having looked at.
- Lean or rich codes, or a check engine light after fuelling
- Hesitation, stumble or loss of power under load
- Rough idle that smooths out when driving
- Noticeably worse fuel economy
- Whistle or hiss from the engine bay
- Hard starting, hot or cold
Fuel delivery, injection, intake leaks and forced induction produce overlapping symptoms. Fuel trims tell us whether the engine is compensating and in which direction, and smoke testing finds the unmetered air behind a lot of it.
On direct-injection and turbocharged engines there are additional failure patterns worth checking specifically, including intake deposits and boost-side leaks that only appear under load.
How we approach it
- 01
Read fuel trims and live data
Which direction the engine is compensating, and at what load.
- 02
Smoke test the intake
Unmetered air is behind a large share of lean and rough-running complaints.
- 03
Test fuel delivery under load
Pressure and volume, at the conditions where the fault appears.
- 04
Check boost-side integrity
On turbocharged engines, leaks that only open up under pressure.
Pricing
We quote this work once we have seen the vehicle. The same job can differ a lot between model years and conditions, and we would rather give you a real number than a low one we have to walk back at the counter. Call and we will tell you what diagnosis costs and what the realistic range looks like.
Every repair backed by our 24 month / 24,000 mile warranty
Prices are pre-tax and cover the work described. Anything we find that changes the job gets discussed with you before it happens.
Common questions
What does a lean code actually mean?
That the engine is being told it needs more fuel than expected for the air it is getting. That is usually unmetered air entering the intake, but it can also be fuel delivery or a sensor reporting incorrectly. Fuel trims and a smoke test separate them.
Will a fuel additive fix a rough idle?
Occasionally, on a mild deposit problem. It will not fix a vacuum leak, a failed injector or an ignition fault, and it is not a substitute for finding out which of those you have.
Why is my fuel economy suddenly worse?
A meaningful, sudden drop usually has a cause worth finding — a sensor, a thermostat stuck open, dragging brakes or an intake leak. It is often a cheap repair that pays for itself.
What is carbon build-up and does my engine get it?
Direct-injected engines can accumulate deposits on the intake valves because fuel no longer washes over them. Whether yours is affected depends on the engine and how it has been driven. It is inspectable rather than assumed.
I hear a whistle from the engine bay under acceleration. Is that the turbo?
It can be, but a whistle or hiss is just as often a boost-side leak — a hose, a clamp or an intercooler connection. Those only open up under pressure, which is why we test under load rather than at idle.
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East Bridgewater, MA
Black Oval Automotive530 Spring St Ste# 3East Bridgewater, MA 02333Hours Mon–Fri, 9:00 AM – 4:00 PM
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