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

Post by **utilityaudio** » 18 Jan 2019, 07:33

Hi folks.

as the title says, I have a '98 S70 with 93K miles, on Wednesday everything was great.
yesterday it started rough, so I put it back in park and let it warm up a little until it smoothed out.
stalled at the stop sign around the corner from my house, started back up, got it restarted and kept going (work and my mechanic are the same direction).

made it to the highway without much drama, about half way it started having intermittent engine shuddering and it felt like something was sucking power away from the engine. once I got off the highway, the shuddering got worse, and while driving to my mechanic, I stalled a bunch of times (more than 50% of the times I came to a complete stop at lights or signs).

I tried to use my Bluetooth OBD reader, but it didn't pull any codes.

how bad is this going to be?

Thanks

Post by **E Showell** » 18 Jan 2019, 10:26

Could be lots of stuff. What's the current status of ignition components? Plugs, rotor, cap, wires? How old is the fuel pump relay? Original to the car? If so, I'd think about changing if for peace of mind even if it isn't producing the current problem. How are the electrical grounds in the engine bay? How old is the battery? What's it's condition?

Unfortunately, engine shuddering and loss of power sound suspiciously like burnt valve symptoms, but a burned valve will usually produce a CEL. Can you run a compression test on the cylinders? Do you drive the car in a spirited fashion on occasion or is it mostly short trips at lower speeds?

What grade of gas have you been running (please don't say regular)?

Post by **utilityaudio** » 18 Jan 2019, 11:15

Since July the tires, battery, heater core, oil change and a tune up have been done. I'd have to look at my receipts to see if cap and rotor are part of my normal tuneup, but if not they're a max of 3 years old as I know I had them done when I had my timing belt done. Don't know the age of fuel pump and relay.
I do run regular grade gas, most driving is 50/50 highway and city, highway is typically traffic speed up to 7~10 over the posted limits, since july that's included 8-10k miles of trips back and forth between MD and OH cruising at about 75-80mph.

Post by **E Showell** » 18 Jan 2019, 11:30

Search for the thread on here about burned valves. Lots of folks running regular have ended up with valve issues (causation not demonstrated to any degree of statistical significance). And you know what they say -- correlation is not causation, but . . .

Post by **misha** » 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!

Post by **BEJinFbk** » 18 Jan 2019, 16:24

Pretty near all of these suggestions should throw codes.
I’d start with a “2nd opinion” from another OBDll reader.

Post by **utilityaudio** » 18 Jan 2019, 16:48

BEJinFbk wrote: ↑18 Jan 2019, 16:24 Pretty near all of these suggestions should throw codes.
I’d start with a “2nd opinion” from another OBDll reader.

Yes, I've never been super pleased with my Bluetooth scanner and have been leaning towards getting a better device, but I don't know where to start. Seems like 98's are in kind of a grey area between using generic OBDll codes and more customized VIDA/DICE codes that started apparently with '99s and later? (this is according to what I've been told by members of a local Facebook Volvo group).

Post by **BEJinFbk** » 18 Jan 2019, 19:56

Basic engine/emission related codes are generic.
For now, most auto parts stores will happily come
out and scan your vehicle right in their lot.

WhatAmIDoing · Post by **WhatAmIDoing** » 18 Jan 2019, 22:09

My primary suspicions would be fuel pump relay, vacuum leak, MAF, in that order. First and last are pretty easy to test in just a few minutes.

Also, a burnt valve should cause a constant missfire which should cause a flashing CEL. Even running on 4 of 5 cylinders, engine should not be struggling to run.

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

Yes...these engines runs pretty good on 4 cylinders.