Acceleration problem after spark plug change

what kine of plugs did they use, and did they check the gap?

what kine of mechanic doesn't stand behind their work?

 

It sounds like some issue related to the spark plug wiring - spark plugs (shouldn't be as you've eliminated this option), spark plug wires, or ignition coil. I think the most likely cause is the spark plug wires as it was running fine prior to changing the spark plugs, which would require unplugging the spark plug wires and moving the wires (which could have caused a break in the wires/connectors). On most cars, these should be replaced at about the same interval as the spark plugs: about every 100k. On my 2004 Ford Focus I had similar problems and replacing the spark plug wires cured the problem.

It might also be worth disconnecting and reconnecting the battery on the car to reset the ECU. If your old plugs had a really large gap, the computer may have adjusted the timing to compensate and now with the correct gap you're getting misfiring.

If you use a code reader, is there an error code showing?

 

Have you double-checked the connection of the of the ignition coils to the plugs, and the wiring harness connections to the ignition coils?

Was anything else changed or pushed around while you changed the plugs? If so , also check those. For example , have you rechecked all the surrounding connections to things like the mass airflow sensor?

 

Has the car actually died? I would look at cleaning the throttle body and do a reset of your 12v battery by disconnecting for a few seconds.

 

Prior to the spark plug change, did you have an acceleration problem?
Did the problem occur immediately after the change, or did the car operate OK for a while before the problem started?
Have you purchased fuel since the spark plug change, and did the problem start after the refueling?
How long have you owned the car, and were the spark plugs changed at 120K miles (which is the normal service interval)?
What is the brand and spark plug type that was installed? Do not think that all spark plugs are alike. If the correct NGK or Denso iridium spark plugs were not installed, that may be causing your problem.
Is the check engine light, or any other warning light, on?

 

Is the Check Engine light on?

 

1. Is it a correct assumption that these problems presented immediately after the plug change?
2. What type of plugs were used?
3. Were any other components replaced?
4. Are there any codes? Do you see any indicator lights on the dash signifying there is a problem?

Since someone else did this work for you, I believe they should be willing to diagnose and fix the problem. All of the suggestions you're seeing are good, but they require your effort, when I would assume it was an error on the party of the mechanic that resulted in this problem. Their problem, their effort is how I typically think.

My best guess is that the plugs are either the wrong ones, incorrectly gapped, or the harness was damaged. But it should be on your mechanic to figure that out. Good luck!

 

So what made you decide to do this plug change if the car was running fine? Unless someone showed you proof the plugs were old and affecting the car, I wouldn't be messing with them.

From what you're describing it actually sounds like a problem with your HV battery, but that would produce a warning light.

 

Well.....that's something new. Maybe you have an emissions problem...like a bad MAF sensor, bad A/F sensor. Read the codes to the car......

 

Agree with others, best course of action is to have the codes read. It will be hard to diagnose without this. Many auto shops/stores will do this for free. Once you have the code(s) you can google it and see what the problem really is.

 

The very first thing your mechanic should have done is read the code(s). Without doing that, it's like trying work blindfolded. If he doesn't have the equipment to check them, he has no business being in business. You can get the codes read for free at most auto parts stores (Advance Auto, Pep Boys, O'Rielly)

 

CEL/MIL being on totally changes the game, as others have noted.

1. Was the light on before the spark plug change?
   
2. Did you get the codes pulled? You can have the mechanic who did the work pull the codes, or an auto parts store will do it for free. Those codes should enlighten you as to the cause of your actual problem.

Once we know the codes, we can more accurately recommend the correct course of action.

My money is on a damaged harness. Anyone wanna take me up on that?

 

Maybe the mechanic got careless when removing the air filter housing, didn't disconnect the maf sensor and pulled up, stripping the maf sensor wires from it's holder

You should check the wiring to the maf