Gusser

I have a 1997 E 420 with about 130 K miles on it. Last week the check engine light came on right after it started running rough. The errorr code was 300 and 307. I thought the driver's side front was cylinder 5 and the back eight. So I switched the 7 cylinder coil with the 5, and then got error code 305, 306, 307. So, to eliminate one possibility, I got spark plugs and installed new plugs on that side of the engine. I know, but I'm broke--really, really. With new plugs on the driver's side of the engine, I've still got error codes 305, 306, 307.
Could anyone help me with what could prossibly cause this behavior, and tell me what I would need to do to fix it?

If so this moneyless MBZ owner wouldl greatly appreciate it.

Thank you for the consideration.

ohlord

could be several things starting with a o2 sensor going south on you to a drivers side cat.
Sorry can't be of more budgetary assistance

plugs are like 2 bucks on that engine don't use platinum plugs cheap oe copper are what she requires

Gusser

I thank you for your quick response. If it were the right side cat, or the O2 sensor, wouldn't it give me a code specific to these malfunctions, or does the multiple misfirings indicate the same thing?

ohlord

begin with misfires as the efficiency of either starts to fall out of range.You can have a cat fail and death rattle(pebbles in a can sound) and not have a cel code.

Gusser

Thanks once more for your consideration and timely response. Please tell me, what do I do now?

Gusser

The error codes told me I had misfires on cylinders 5, 6, and 7. I swiched the coils on cylinders 5, 6, and 7, receptively with cylinders 1,2, and 3. Now I have misfires on cylinders 1, and 5. So I think I need a new coil for cylinder 1, but have no idea why cylinder 5 would still be misfiring. Would you have any ideas how to explain why cylinder 5 is misfiring when it has a new plug, and a working coil?

Any assistance or advice you could provide will be appreciated.

gold1997e420

I was wondering if you have found a solution to your problem

Gusser

Nope, I still haven't figured out what's going on. You remember, I have no money. I'm going to replace all the plugs while I'm at it, and I'm going to buy two new ignition coils and plug connectors. I'll put everything in, and see what happens. I was thinking partsgeek.com for the items, or would you have a better, less expensive source.

MBtech1098

Suppressors have caused a few issues on the M119, also be sure the engine harness is not brittle and the insulation cracking off causing the wiring to short out(although 97 should have the updated harness). Kepp in mind there are many other things that can cause misfires(though less common).

gold1997e420

im gonna work on mine this week end i have the same problem. i ran it low on gas and i put a aditive in the transmition. 3 blocks down the street the car started missing and check engine light came on. i have code 305. im going to try to figure it out.

Gusser

Yeah well, let me know. I can use all the help I can get.