01
Rough or shaky idle
At a stoplight the car feels like it is about to stall. Steering wheel buzzes, mirrors blur. One cylinder is dead weight on the others.
Engine misfire? Fix the cause, not the code.
Rough idle, loss of power, P0300 on the scanner. A misfire means one cylinder is not contributing, and the engine is dumping unburned fuel into the catalytic converter every second you drive. Bring it in before the cat goes too.
How a misfire actually feels.
If two or three of these match your car, it is a misfire until proven otherwise. The longer you drive on it, the more expensive the fix gets.
02
Loss of power on acceleration
Pedal hits the floor and the car hesitates, bucks, or feels asthmatic. A 4-cylinder down to 3 has lost a quarter of its power.
03
Check engine light flashing
Solid light is bad. Flashing light means active misfire damaging the catalytic converter right now. Drive directly to the shop or call for a tow.
04
Gas smell from the exhaust
Unburned fuel leaving through the tailpipe. You will smell raw gas, especially at idle. Cat is taking damage on every cold start.
05Diagnostic
Misfire code on the scanner
P0300 is a random misfire. P0301 through P0308 each point to a specific cylinder. The code narrows the search, it does not name the part.
06
Fuel economy dropping fast
MPG drops noticeably in a week. The good cylinders are working overtime to make up for the dead one, and the computer is dumping extra fuel.
We test before we replace.
Misfires are spark, fuel, or compression. We work the list in order and replace only what fails the test, not whatever the parts store has on the shelf.
Scan and pull live data
Read codes, check freeze-frame data, watch fuel trims and misfire counters in real time. The code tells us which cylinder, the data tells us why.
Test the ignition side first
Spark plugs come out, get inspected for fouling, oil, or gap problems. Coils get swapped cylinder-to-cylinder to see if the misfire follows the coil.
Check fuel delivery
Fuel pressure test, injector pulse check, and on direct-injection engines a balance test to see if any injector is weak. Carbon on intake valves is a known killer on GDI engines.
Compression and leak-down if needed
If spark and fuel are good, the cylinder is not sealing. Compression test plus a leak-down test tells us valves, rings, or head gasket. Honest answer either way.
Quote and repair
You get a clear breakdown of what failed and what it costs to fix before we touch a wrench. No surprise add-ons, no parts cannon.
Most misfires are ignition-side and finish same day. Compression-side repairs (valves, head gasket) get a real timeline once we know what is wrong.
Related engine problems.
If your check engine light is on, do not stop here. These pages cover the next-most-common engine issues we see at the shop.
01
Engine Overheating Repair
Temperature gauge climbing, steam under the hood, coolant on the driveway. Cooling system diagnosis and repair: thermostat, water pump, radiator, hoses.
02
Timing Chain Replacement
Rattle on cold start, P0008 or P0016 codes, check engine light. When the chain stretches, the timing slips, and the engine eats itself. Replace before failure.
03
Engine Diagnostics
Free check engine light scan. We read codes, pull freeze-frame data, and tell you what the codes actually mean before quoting any work.
04
All Engine Repair Service
Tune-ups, cooling system, head gasket, timing, full replacements. Start here for the full engine service overview.
Frequently asked.
Solid check engine light, short distance, slow speed: yes, get it to the shop. Flashing check engine light: no, you are destroying the catalytic converter on every revolution. Call for a tow or limp it the absolute minimum distance.
P0300 is a random or multiple-cylinder misfire. The computer cannot pin it to one cylinder, which usually points to a shared cause: fuel pressure, vacuum leak, timing, or several worn ignition components at once. P0301 through P0308 point to a specific cylinder number.
Depends on the cause. Spark plug job is on the lower end, ignition coil or injector is mid-range, and a valve or head gasket repair is a larger job. Call (336) 370-6710 for a quote after diagnosis. We will tell you the total before we start.
A few miles, no. Weeks of driving on it, yes. Unburned fuel washes oil off the cylinder walls, raw fuel hits the catalytic converter at 1,200 degrees and melts the substrate, and the unbalanced load wears the rest of the engine faster. Fix it the same week you notice it.
Most diagnoses take 30 to 60 minutes. If the cause is clear (fouled plug, bad coil), we can usually quote and repair the same visit. Compression-side problems need more bench time and a real timeline.
Yes, and it is the most common cause we see. Plugs wear out, get fouled with carbon or oil, or open up the gap from heat. On most cars the plugs should be inspected at 60,000 miles and replaced per the manufacturer interval (every 30,000 to 100,000 miles depending on the plug type).
Modern engines have one ignition coil per cylinder mounted directly on top of the spark plug, with no plug wires. When one coil fails you get a misfire on only that cylinder. We can swap a coil between cylinders to confirm before replacing the part.
Yes. A torn intake gasket, cracked vacuum hose, or leaking PCV line lets unmetered air into the engine and leans out one or more cylinders, causing a misfire. We smoke-test the intake system to find leaks the scanner cannot see.
Yes. Misfire diagnosis is the same fundamentals on every gas engine: spark, fuel, compression. We work on most domestic and import vehicles and use the correct scan tool for each platform.
Misfire on the scanner?
Bring it in this week. Honest diagnosis, no parts cannon, and a real quote before we touch a wrench.
1605 W Gate City Blvd
Greensboro, NC 27403
Mon–Fri · 9 AM – 6 PM
Sat · 9 AM – 3 PM
(336) 370-6710
Walk-ins welcome