'98 S70, 93k miles, intermittent Rough running and stalling Topic is solved

Post by **erikv11** » 19 Jan 2019, 07:37

Check the MAF, it's free and easy to do and a good possibility.

Doesn't sound at all like a burnt valve. Vacuum leak also fits, have the lines ever been replaced or are they 20 years old?

Sommerfeldt · Post by **Sommerfeldt** » 19 Jan 2019, 10:48

It’s also worth checking the fuel pump relay (as someone suggested) and fuel pump. Low pressure or unevenly operating pump will cause your symptoms, and probably not set a code that will stay until you get a readout.

- S

Post by **bmdubya1198** » 19 Jan 2019, 15:02

I wouldn't think it's a burnt valve, you'd definitely have a CEL and codes present. Plus, as it's been said already, these cars run fairly well on 4 cylinders. My cousin's S70 T5 even ran pretty well on 3 cylinders after we connected two of the coils backwards!

I'd say check the cam sensor and crank sensors, but I would recommend testing the MAF sensor as described first. I'd also try swapping the fuel pump relay or jumping it. It seems those will slowly fail in some cases, while other times they just go out and that's it.

magna224 · Post by **magna224** » 21 Jan 2019, 03:06

bmdubya1198 wrote: 19 Jan 2019, 15:02
I'd say check the cam sensor and crank sensors

I thought when cam sensors fail it causes a no start?

1998v70xcbill · Post by **1998v70xcbill** » 21 Jan 2019, 05:00

check the coil.
fuel pump is usually ,no start
valves would not be intermittent. cam and crank you would think throw codes.

Post by **erikv11** » 21 Jan 2019, 08:16

Cam and crank sensors are no-start, yes. Sometimes with a code, more often without because they get checked at startup and if the car won't start ...

Fuel pump relay is likely, pump relay and fuel pump problems can be no-start or they can be flaky, either way.

Post by **bmdubya1198** » 21 Jan 2019, 08:22

magna224 wrote: 21 Jan 2019, 03:06 I thought when cam sensors fail it causes a no start?

Not always. When my crank sensor went out, it was having these weird "hiccups" when I would start accelerating from a stop, almost cutting out. It was a little scary at times!
Eventually I got a multi-cylinder misfire code and a crank sensor code. Now this was the crank sensor, not the cam sensor, but to my understanding they present very similar symptoms.

1998v70xcbill wrote: 21 Jan 2019, 05:00 cam and crank you would think throw codes.

Usually, but not always. I've had a bad/failing cam sensor without a code. Put in a newer used one and I haven't had any issues since. My car was having small little stutters here and there. Similar to, but not quite as severe as the situation I explained above when my crank sensor failed.

Post by **utilityaudio** » 25 Jan 2019, 07:54

misha wrote: 18 Jan 2019, 13:57 Disconnect Maf connector,start the car and test drive it.If problem disappears...Maf is bad.
Other than that...could be a HUGE vacuum leak or FPR failure.
But,let's go one step at a time...cheapest things first!

*Ding Ding Ding* we have a winner.
Mechanic finally got to my car, MAF was bad, didn't throw any codes.

also replaced the fuel filter for good measure. I'm relieved it's fixed, just wish it hadn't taken so long for them to work through their backlog.

going to try to sort through maintenance receipts from the PO, to look for Fuel Pump, relay, and Vacuum lines... if I don't find them I'll put them on my list of things to save up to replace.

Thank you to everyone who posted.

Post by **misha** » 25 Jan 2019, 08:08

Keep the old Maf,just in case....because connector can also make problems.
I hope that you used oem Bosch maf #0 280 217 107 since aftermarket ones will not last....if work at all.

Post by **utilityaudio** » 25 Jan 2019, 08:29

I'll ask.