Q: Rough idle, missing, almost dies when in gear, shaking violently when driving in low speeds

asked by on September 29, 2016

Husband did tune up. Plugs, egr valve, cops, fuel filter, etc. Noticed a misfire right away. Had codes pulled, cop 2 was misfiring so replaced it again. But now it has continued to get worse. Found a hose that was rotted, replaced it. He's cleaned throttle body, MAF sensor, injectors. We've literally tried EVERYTHING!! Any suggestion on what we might be missing?

My car has 139000 miles.
My car has an automatic transmission.

Car idle is rough Inspection $94.99 - $114.99 Get a Quote

Hi, thanks for writing in. I’d be happy to provide my insight. I recommend you have the engine checked for vacuum leaks, or and check if carbon is clogging the EGR valve. If you still cannot find the reason the engine is running bad, then my advice is to have a mechanic come out and diagnose the problem for you. I have seen carbon breaking loose and holding valves open, and also I’ve also seen coils for the plugs not firing or shorting out, causing misfires. Try moving the coil in the misfiring cylinder to a firing cylinder to see if misfire moves with the coil. If so, replace the bad coil and coil boot.

If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

How do you use the SYNC® system hands-free feature?
SYNC® is Ford’s on-board computer system. It’s designed to offer a wide range of functionality, from navigation to hands-free calling. Here’s how the steering wheel controls works: Press the Talk button. You should hear a chime/tone. The word “Listening” will...
What should I know about the Power Steering system?
Like all other modern cars, your Fusion has a Power Steering system that assists with turning the steering wheel. However, depending on the engine in your car, you’ll have one of two possible systems. 2.5-Liter and 3.0 Liter Engines: If...
How do I check the engine coolant?
Coolant is just as vital for engine operation as oil. While it’s running, your engine creates a lot of heat. If left unchecked, that heat would eventually destroy the engine itself. Coolant is used to remove heat from the engine...
Jeep won't shift from second to third
The information provided for your Jeep Grand Cherokee is limited so it is difficult to point you in the right direction. However the symptoms lead me to believe that your vehicle may have put itself in “limp mode”, meaning that...
Groaning noise in SUV front end
Hello. There are several components that could be causing this problem. The power steering pump, serpentine belt tensioner, serpentine belt pulley, or water pump could be going bad. It is also possible that the compressor clutch is faulty. I would...
My car only overheats when ac is on?
If you have overheating only when you have the A/C on then you most likely have a bad fan clutch (https://www.yourmechanic.com/services/fan-clutch-replacement). The fan clutch should lock up when the added heat from the A/C is added from the condenser to...
Leaking coolant no signs of leak anywhere 2006 Scion tC
Hi - this problem sounds a bit more challenging as you have done all the logical things - well done! Remaining possibilities include coolant leaking into the exhaust (cracked cylinder head) which would give you white smoke with a sweet...
Idle problems
If the throttle body is leaking vacuum on the throttle shaft then it should be replaced. If you are just getting a noise of sucking air through the throttle plates then it can be caused by carbon build up on...
2015 mirage 51000 miles sputters and hesitates on acceleration from stop. problem stops at about 30-40mph starts fine. no stalls
Among the possibilities are faults in the throttle position sensor (https://www.yourmechanic.com/services/throttle-position-sensor-replacement), mass airflow sensor (https://www.yourmechanic.com/services/mass-airflow-sensor-replacement), vacuum leaks, a clogged fuel filter, defective EGR valve or control circuit, and worn out spark plugs and wires. A mechanic would simply investigate these...

Related articles

The Best Used Cars to Buy for Senior Citizens
Everyone Everyone needs a way to get around. You need to get groceries, get to doctors’ appointments, visit with family and more. However, senior citizens have very different needs when it comes to buying a used car than other demographics....
Symptoms of a Bad or Failing Ball Joint (Front)
Common signs include clunking noises and excessive vibration from the front, and you may start steering to the right or left unintentionally.
The 5 Safest Used Cars You Can Buy For Under $20,000
The Subaru Legacy, Honda Accord, Ford Fusion, Chevy Volt, and the Volvo XC60 are five of the overall safest used cars you can buy for under $20,000.