hcole05

Hello all,

I have been trying to diagnose my vehicle as it has been experiencing some engine misfires. In February my CEL came on and flashed but then just stayed steady. Since it flashed I took it to the shop and the code read that coil # 3, got that coil replaced and the corresponding spark plug.

Lately, my acceleration hasn't been very good and occasional misfires. This morning the CEL came on flashing for about 2 seconds while driving at slow highway speeds (45-50 mph) and then went off as soon as I accelerated a bit (I was in traffic and couldn't afford to stop without causing a wreck)

I did some self diagnostic and wanted to check the front three ignition coils (2,4 and 6), they are all good. However, I noticed that one of these orange plugs was just hanging there unplugged (the bottom one in the picture). What are these plugs and could it be causing the issue? I see an empty space where it appears it should go, should I plug it back in?

(Note: this picture is from google, it is not my car but its the same plugs)



Thank you for your help!

salimshah

I can tell the image is of my engine ,,, my unique bridge to hold the harness. But that does not matter. You would have found it here in CL

Are you talking about the brown plugs ,,, if so, they modulate vacuum. Very unlikely that they will cause misfire. They may trigger some CEL

Welcome to CL

Salim

hcole05

Thanks! Yes, the orange/brown and the blue plugs. Yes, your picture showed up in my google image search as I forgot to take a picture.

I'm thinking (hoping) the misfire might be the spark plugs, as I'm not sure when the last time they were changed (I inherited the car), but without a CEL code, I'm not sure. And I have no idea how to reach the back ignition coils to check those.

Thank you for the information about the plugs, I'm not sure why it would have been unplugged but I plugged it back in

salimshah

Lexmex posted a DIY on spark plugs. 110K is the service interval. Make sure you buy OEM (others may work but do your homework).

Salim

hcole05

UPDATE: So I finally got a CEL going off to help me diagnose. It is giving me P0304 and P0300, as I understand this is to replace ignition coil #4. A couple of questions:

Should I be concerned that Coil #3 failed in Feb and Coil #4 has now failed? It is a 99

The mechanic shop wants $140 for the parts, I think I can find a better deal online but I have read it needs to be OEM....I see Denso Ignition coils everywhere when I search OEM....is that correct?

Am I doing a disservice or causing any issues by just replacing coil #4 and all the spark plugs? I was considering replacing all the coils but at $140 a pop....that is very expensive if not necessary.

salimshah

I would suggest that you replace what ever is broken. There is not too much of extra effort that you save by preemptive change.

I replaced one coil 100k miles ago. I could have replaced other 5

Salim