1998 S70 Rough Engine, especially idle. Losing Power

[jersey240]

1998 S70, 107k miles

The engine has been acting weird recently—
- Got home from a 7 hour drive, and after getting off the highway, at the first red light, engine felt like it was losing power for a second and then came back to life.
- That kind of behavior has repeated some over the past few days, but not consistently. Just sometimes, after driving at highway speed, the first red light leads to some sputtering.
- Last Friday, started up after not driving for about an hour (engine was cold prior to that, though), and idled for a few minutes while checking texts. Which I shouldn't have done, but probably useful that I saw the following stuff happen: After a bit, the engine dropped to about 700 rpm, then revved to around 1100, stabilized for a second, dropped closer to 600, then revved, and was starting to cycle again when I hit the gas to try and break the pattern. Temporarily okay, then started to get weird again. Shut off the car. Started back up and just drove, seemed okay.

Then a _bunch_ of stuff, all today—
- This morning, got onto the highway, never got past 25-30 mph for the first leg of the trip. And while sitting in traffic, the engine did the same sputtering thing. So now it even happens without hitting highway speed.
- Also, occasionally felt like it was starting to lose power even while driving around 55 mph (!), if only for a second here and there. But enough to make me nervous.
- Tonight, getting on the highway, felt like I got maybe half the power I expected when trying to reach 65 on an uphill entrance ramp. Worked out okay this time, but not normal.
- Engine also felt noticeably rougher the whole ride home. Not really horrible, but definitely not the way it usually sounds. Including rougher on the local roads, at the end of the trip.
- Finally, after all this weird behavior, got a CEL late this evening. Heading to Advance Auto Parts tomorrow to check the codes.

Pretty new to this, by the way, but that's probably already clear from how I'm writing. I've tackled a few projects over the past few years (timing belt, front struts), but it takes me a _long_ time to research and even longer to do it.

This older post and another I just found sound like possible leads for my problem, but I'm not too familiar with O2 sensors, IAC valve, and other parts people mention. I'll research those more tomorrow—briefly wondered if the problem might be related to either some physical obstruction related to air, or possibly fuel, but really don't know how this stuff works or if that even makes sense.

Does anybody have a rough idea of what I should look for? Or other links I should read up on. Once I know what this problem is maybe called, definitely easier to search for better results than just plugging in "losing power" into the search.

Thank you for any ideas!

[rmmagow]

First thing I would check is fuel pressure. You can bypass a failing fuel pump relay, easy to do, search here. Second thing I would then check is the spark plugs, wires, cap and rotor if they have not been touched in a long time. In that case, put in all new proper parts. Get the code, P030x is misfire code and point to plugs, wires etc issue. Come back after these things are checked for next steps.

[phils94850]

how long has it been since tuned up ? If it does need a tune up use only OEM parts, these cars don't like aftermarket.

[abscate]

You can't eyeball fix these engines. Get the codes read and make sure you get the actual code

P-1234 and not just (EVAP CODE)

Only 84k miles, right? Probably a bad vacuum hose somewhere.

[850 LPT]

All of the above, plus the possibility of a bad MAF maybe?

[jblackburn]

All of the above, plus the possibility of a bad MAF maybe?

^^^Sounds like this.

But get back to us with the codes

[jersey240]

Thank you for the feedback and the great leads, everybody!

I stopped by Advance Auto Parts on the way to work, and they no longer check CELs…. After work, when I was ready to swing by Auto Zone and try again, the CEL had disappeared. ?

If it comes back, I'll go back to Auto Zone, since they said over the phone that they do still check codes. Hopefully, they'll pull the actual code numbers, so I can give you all the proper answers. In the meantime, looking into an OBD II reader for myself. I remember seeing a review Matt himself posted a few years ago, probably go with that one.

I'll have some time over the weekend to check things out, which will include:
- fuel pump relay bypass
- condition of spark plug wires, cap, rotor
(Haynes says to check condition every 3 years / 30,000 miles. Any rule of
thumb for just replacing them, even if they still look okay?
- MAF—think I've read you can disconnect this without major problems, it'll
just run rich. So I'll double check that info and give that a shot
- vacuum hoses

Hm, my signature line is ancient and needs editing. The car is 107k now, think it's in the original message body but sorry for the confusion! I did plugs, wires, cap, and rotor 3 years ago, and just a week ago realized I'm overdue for plugs—despite starting to learn how to do this stuff, I was clearly not paying attention to maintenance intervals… should have replaced the plugs 6-12 months ago, when I hit 30,000 miles on the current ones.

Thanks for the heads up—got OEM tune up parts from FCP last time, and will do so again this time.

Thanks again! Will keep you posted.

[erikv11]

Regarding tune up parts: if the wires were OEM (Bougicord) and the cap and rotor too (OEM is Bosch for those) then they are fine, should not need replacing. I agree likely time for new plugs.

[jersey240]

Thanks for the confirmation that the Bougicord wires and Bosch cap and rotor should still be okay.

Yesterday, crawling on the highway during rush hour, I had to keep one foot on the brake and the other on the gas to try and prevent it from stalling. Finally I pulled over, let it die, and couldn't re-start. Unplugged MAF, got it running again, and thankfully got to my second job on time. Thanks to whoever posted that tip in the past! (Probably a ton of MVS members, but still, thanks.)

So I still have to check out the other leads you guys mentioned, but it looks like the MAF must be bad.

Is it okay to drive until about next Wed, when I figure I should have a new Bosch MAF in from FCP? I have 40 miles round trip on the highway both tonight and tomorrow, and again Monday and Tuesday… just read some on this thread and it sounds like I might be pushing my luck to wait that long. If it's a major safety issue, then I will just go spend the extra $100+ to get a blue box MAF from the dealership.

As for engine codes, no time between jobs yesterday, but I expect to be at an AutoZone tonight or tomorrow morning. More info soon.

Thanks again!

[E Showell]

Depending where you are in Jersey, I've got a code reader and would be happy to read the codes for you.