98 S70 non turbo loss of power

45DegreesPDX · Post by **45DegreesPDX** » 04 Mar 2018, 01:54

Alright, so I've replaced the plugs, wires, cap and rotor and I'm still experiencing the same issue. I took a video to kind of help describe the symptoms. Sometimes when I start the car up and run it, it seems to idle just fine, yet it runs rich. Other times it'll bog around the 300-600 rpm range or not even start at all. Here's the link to the video: Part 1:

Part 2:

45DegreesPDX · Post by **45DegreesPDX** » 04 Mar 2018, 01:55

Alright, so I've replaced the plugs, wires, cap and rotor and I'm still experiencing the same issue. I took a video to kind of help describe the symptoms. Sometimes when I start the car up and run it, it seems to idle just fine, yet it runs rich. Other times it'll bog around the 300-600 rpm range or not even start at all. Here's the link to the video: Part 1:

Part 2:

Post by **wizechatmgr** » 04 Mar 2018, 05:31

It sounds like it is missing. Try unplugging the fuel injectors one at a time and see if you can figure out which cylinder. If you haven't already done a compression test, I'd do that first.

45DegreesPDX · Post by **45DegreesPDX** » 04 Mar 2018, 20:04

Alright so I did a little research and tried to do a hard ECU reset. This cleared the check engine light and had the car idling good for a little, until it started rough again. While it was running rough though I decided to unplug the MAF and that immediately got the idle stable again and threw the check engine light. I'll try cleaning it and see if that helps. I'm on a tight budget so I can only do so much with the tools I have so I want to be sure to check everything. Will let you guys know what happens.

Post by **wizechatmgr** » 04 Mar 2018, 20:55

You might get lucky and be able to source a good one from a junk yard - though at the moment, that's probably easier said than done.

Post by **erikv11** » 05 Mar 2018, 11:37

Every MAF I've ever picked up from the junkyard has worked just fine.

45DegreesPDX · Post by **45DegreesPDX** » 28 Mar 2018, 20:45

Alright, I've been pretty busy but I have an update. I've since cleaned the MAF and that didn't seem to fix the problem. I was able to pick up one of those bluetooth OBDII readers so I could get a little more information on what was going on. I did another ECU reset, and I've run it a couple times, same symptoms but no this time no check engine light has come on since. The info I got from the reader was "Closed loop, using 1 O2 sensor (feedback fault)" I was able to get a voltage reading on O2 Sensor 1 Bank 1, but nothing for O2 Sensor 1 Bank 2. I'm guessing this is the culprit. Is this the rear O2 sensor and is it difficult to replace?

WhatAmIDoing · Post by **WhatAmIDoing** » 28 Mar 2018, 23:13

You do not have a bank 2 sensor(s). You have O2 sensor 1 (before cat) bank 1 and O2 sensor 2 (after cat) bank 1. Only cars with split exhaust like on a V6 or V8 would have bank 2 O2 sensors. A malfunctioning O2 sensor after the cat would not cause rough running or reduced power. The sensor before the cat is used to adjust fuel trim, so a malfunction where the sensor reads wonky but within spec could cause rough running and reduced power. You could try unplugging the upstream O2 sensor and see if power improves, but I doubt it is the O2 sensor.

Post by **abscate** » 29 Mar 2018, 04:46

erikv11 wrote: ↑05 Mar 2018, 11:37 Every MAF I've ever picked up from the junkyard has worked just fine.

NSFW? Oh wait, misread, carry on.

Post by **erikv11** » 29 Mar 2018, 08:06

I agree, I would try other things before the O2 sensors. Also note that cleaning the MAF almost never does anything, unless it is visibly dirty beforehand.

Unplug the MAF with the car off, then start it up. If the problem goes away, bad MAF is the problem. Don't unplug/re-plug the MAF while the car is running.

Another free test is the one suggested by wizechatmgr, about the injectors. These you can unplug while the car is running, one at a time, see what that does to the idle.

If it's the MAF (likely) and you can't easily get to the junkyard, I have used ones and I would ship one to you for cheap, PM me.

98 S70 non turbo loss of power

Re: 98 S70 non turbo loss of power