Car was running great but when I pushed it to 5000 rpm the check engine light came on and car went into limp mode. After a day or so the check light was off and car ran fine during normal driving but as soon as I accelerated hard it returned to limp mode/check end light.
had tech replace plugs and swap out coil on #8 and still a problem. Car has 100k miles

 

You're dealing with recuring limp-mode above 5kR at 100k.Mi.

If you're going to keep this engine in one piece you're gona have to learn to take it easy with your horses before something bigger comes up.

I bet you're now dealing with unstable fuel pressure.... either tank pump/filter or fuel rail pump or sensor.

-1- Get your chassis fully scanned, not just ECU.

-2- Read both the fuel tank + rail pressures at idle and under load.


Forget about muscling your engine while it's unbalanced. It's high wear for not much power.

 

How did the spark plug from the affected cylinder look? Was it black or covered in oil?

If the spark plugs have already been replaced and the ignition coils have been swapped with a known good cylinder, there are three possible causes on these engines:
-Failed fuel injector (leaking into the cylinder)
-Damaged exhaust valve or valve seat (a leak-down test will be needed to confirm)
-Cylinder wall scoring (would require engine replacement)


Perform a borescope inspection of the affected cylinder and check the cylinder wall, it should be smooth with no visible marks.
If the wall looks fine, perform a leak-down test both when the engine is hot and cold to compare the results.
You can also check for a leaking injector by using a borescope to observe the injector tip. Crank the engine to build fuel pressure, then inspect immediately after, you have about a 1–2 minute window to check for leaks.

If you’re looking for OEM injectors, I sell them for a fraction of the dealer’s price.

 

Get the specific misfire code read. It's likely a bad fuel pump, clogged filter, or another failing coil.

 

thanks for your reply and help. Making arrangement today to have a repair shop with more/better scanning equipment. Hopefully it will narrow down the problem

 

[QUOTE=CaliBenzDriver;9221143]You're dealing with recuring limp-mode above 5kR at 100k.Mi.

If you're going to keep this engine in one piece you're gona have to learn to take it easy with your horses before something bigger comes up.

I bet you're now dealing with unstable fuel pressure.... either tank pump/filter or fuel rail pump or sensor.

-1- Get your chassis fully scanned, not just ECU.

-2- Read both the fuel tank + rail pressures at idle and under load.


Forget about muscling your engine while it's unbalanced. It's high wear for not much power.
[/QUOTE

 

thank you for replying.

 

The tech swapped parts and didn't tell you what the code was? Not even on the receipt? I'd have to assume it was a code for the #8 coil and nothing else.

I see you're new here, so is this car new to you as well? I was thinking you should invest in a scanner to read & clear codes yourself. Even if you don't use it this time, odds are you will need to do it again. I have several tools I'd suggest:
I bought the "Launch X431 Elite 2.0 Pro" last year and it's pretty cool. I paid ~$150 on Amazon but I think they're less now. Aliexpress is cheap too.

I also have a phone app "Torque Pro" and a cheapo OBD dongle from Amazon; Combined net is ~$12 so you can't go wrong. It is nowhere near as powerful as the Launch dealie, but its value is recording live data from multiple things to help you find issues. You can watch the data live as you drive, play it back later, or my favorite is put the data in an Excel chart. E.g. the fuel psi Cali mentioned, which you could record with RPM, power and whatever else.
Fyi I've ran out of fuel pressure several times but never had a code, limp mode or check eng light. It simply didn't like it until I let off the gas, then ran fine again. I also had a coil fail but it never went into limp mode. If I recall correctly it did give a code, but not until some time later when it got really bad.

Lastly, I also have BenzNinja, which is very cool. A lot more $ because you also have to buy some hardware + his service, but when you consider it could easily pay for itself if you can avoid going to the dealer once or twice. I'd also rather have his experience and advice over the dealer, or an indy mech. It's also excellent for people who know nothing about diagnostics because Mr Ninja does the troubleshooting for you. Basically you plug it into the car and let him remote into your laptop, then he does his thing using the same software the dealer does. I don't believe anyone regrets being a member, so the earlier you consider it, the more you save. My spiel sounds like I get a commission, but no, just first hand opinion from a member.

 

hi ,
yes I am new and yes I haven’t figured out how to reply. So I do appreciate all this information you supplied.
I did by this about 4 years ago with 66k miles and it now has 100k.
the tech replace the plugs and when the misfire was still there he swapped out the coil pack with another cylinder and the problem remained. Have it in a shop now with better test equipment. I’ll let you know how I make out. Thank you for your reply.