1998 S70 Stumble and Misfire Off Idle

NickD · Post by **NickD** » 17 Aug 2009, 07:35

I have a 1998 S70 (non-turbo) that's been great up until last week. I parked the car for a few months and then it was hard-starting when I got back to it. It cranked over fine, but would not light off (sometimes it seemed to want to start just as I stopped cranking it).

I pulled the air filter and found a mouse nest, cleared it out and it started, but once it was warmed up it developed an off-idle stumble and misfire.
I cleaned the MAF sensor and put it back together and it started right up, but then developed the same stumble and misfire when warm.

The check engine light is either on or flashing. I don't have an reader so I haven't pulled any codes, though I suspect they will say "misfire".

I came back to it cold the next day and it started right up, ran fine for about 5 minutes, and then developed the same stumble and misfire when warm.

I pulled a few plugs and they looked fine (though worn), the wires all look fine (though they are getting old too).

I'm starting to suspect the fuel injectors are partially plugged from sitting so long, but before I start pulling the fuel system apart I figured I'd post this to see if anyone else has had the same issues and there is an easier fix.

Thanks in advance for your help.

Nick

FCPEURO · Post by **FCPEURO** » 17 Aug 2009, 08:58

Nick,

I would run some SeaFoam through the fuel system and through a vacuum line. Just don't put it in your oil. See if that helps.

If it does not help, then I would look more into the fuel system like a clogged fuel filter or something along those lines. But start with the SeaFoam first.

NickD · Post by **NickD** » 18 Aug 2009, 07:41

Well I found someone with an OBDII reader and pulled the codes: 0172, 0302, 0303, 0303, 0302, 0300, 0303 (some repeats).

The 0172 is "system too rich, bank 1", the rest are misfire codes (general, cyln2, cyln3).

Does this sound more like a cap, rotor, wire, plug issue, or could these still be caused by an issue with the fuel system?

Nick

FCPEURO · Post by **FCPEURO** » 18 Aug 2009, 08:34

Sounds like a cap, rotor, wire and plugs issue. I would change them out and clear all the codes.

NickD · Post by **NickD** » 18 Aug 2009, 08:38

I starting to think the same thing.

I was leaning toward fuel system because the car sat for a while and I figured some water got into the system. But I guess it's just as likely that something went bad in the ignition system as well. Either way, the car needs a full tune up so that's where I'll start.

Thanks for your help.

Nick

NickD · Post by **NickD** » 20 Aug 2009, 11:23

Well a full tune-up fixed the problem (plugs, wires, cap, rotor, air filter). The cap and rotor were streaked with black so I suspect they were the main cause. I just cleared all of the codes and I'm good to go.

Thanks to everyone for helping me out with this problem.