I am hoping someone out there can shed some light on this-

I have a 1998 s70 2.4 non-turbo with 130K.

Symptoms:
15-16MPG
very potent exhaust fumes smelling of raw gasoline
occasional hard start (having to step on gas and turn over alot)
occasional stall at stop light
occasional "bump" in idle (idles about 900 or so then suddenly drops to 700 and then up to 1000 and back to 900)
loss of power
check engine light

Getting stored codes:
P0130 O2 SENSOR BANK 1 SENSOR 1
P0131 O2 SENSOR BANK 1 SENSOR 1 VOLTAGE LOW
PO172 SYSTEM TO RICH

Occasional pending codes:
P0410 Secondary air system

Live Data shows:
CL_Fault
O2 B1 S1 Voltage usually about .3 .4 on startup then fluctuates between .1 and .2v. Seems low to me (probably because of the rich mixture)
O2 B1 S2 (rear) VOLTAGE ALWAYS 0V!


I have tried all this:
Replaced worn vac lines and did full PCV system overhaul
Smoke test no leaks found
Multiple new and used Bosch oem MAFs tried
New Bosch oem front HO2S
New Bosch oem rear HO2S
New coolant temp sensor
Swapped ECUs with another 98 motronic

Things I have noticed / checked:
Tried swapping o2 plugs - rear still reads 0v on live data.
Traced o2 sensor wires all the way to ECU pins no issues
drilled hole infront of Cat checked pressure less than 1 psi
checked compression all cyls. running about 190-195 seems alot higher than other cars I have checked.
Checked pressure at fuel rail ~42psi
Checked each injector individually energized while still on rail - streams seem even and fuel atomized well.
ohmed out Throttle position sensor back at ECU pins, found 960 ohms at idle, up to 2500 full throttle. Seems right. One thing i have noticed is after shutting engine off I can hear a high frequency noise coming from the TPS sensor for about a minute- then hear a relay click off and the noise goes away...



Other things done to car:
Airbox thermostat flap removed hot air inlet plugged
Cap rotor plugs and wires all replaced about 3k before having problems (about 8k ago)
cap rotor and wires non-oem
Plugs are Bosch FR7DP gapped to about .029-.030 I just checked each today and they are each equally very black with carbon. Electrodes seem a little worn - but I am not sure this would cause such a rich burn.
New Airfilter

I am considering replacing the NEW bosch front o2 sensor in case it was defective - but I dont want to lose anymore $$ on this freaking thing.
Also considering replacing the TPS sensor as I am running out of things to replace.

I am about to the end of my rope as my wife can't handle me spending all my time and our money on this thing. She is trying to get me to sell it but I will feel so defeated if after all this I still can't get it figured out.

I am new to this forum so feel free to criticize my posting if I am not doing it correctly.

I have faith that you guys will have some ideas for me.

 

Definitely don't sell it, it has to be some sort of relay that's shorted out something with the fuel system. You said you replaced the O2 sensors? Is it possible that they are the wrong type? this is a long shot, but how is the quality of the air tube and the MAF sensor? If the ECU is replaced and working correctly, it seems that there is a problem with how air is mechanically getting into the engine or the fuel delivery. Maybe the fuel pump is acting up? Good luck with it and I hope you figure it out soon!

 

So today after tearing the whole car apart i found the aftermarket distributor rotor had a small crack in the plastic near the tip so I replaced it, along with set of bosch wires, and platinum 4 plugs. Still no luck.

The front o2 sensor was showing about .150v and ranging from 0-.3v.

The rear still had 0v showing.

I learned online that the lower the voltage the leaner the o2 sensor thinks the car is. So why is it running rich? From what I could tell the sensor was putting out too low a voltage and the computer was trying to compensate and add more fuel.

So I replaced the front o2 (had already recently replaced with oem bosch) and found the voltage ranged from .2 - .9v and the engine appearing to run much smoother and so far (50mi) no codes yet! I am hoping this is the end-all, but I am still wondering 2 things:

Why does the rear o2 still show 0v?
Why does the live data FUELSYS1 CL-FAULT appear?

Does this mean I still have a problem?

ps. don't assume new parts work. I just wasted some of my life (and money finding this out)

 

Your old front O2 sensor was indicating lean so the ECM was trying to compensate. Your new front sensor sounds like it is now working. Where did you get those sensors? These cars don't like anything but real OEM O2 sensors; not OEM-like replacements.

I didn't see it on your parts list so I'll ask; is engine is getting up to proper operating temp? If not, bad thermostat will also cause engine to run rich.

Here's pretty good link on O2 sensors:
OXYGEN SENSORS

Assuming FUELSYS1 CL-FAULT means it's never getting into ClosedLoop Mode; probably because of bad rear O2 sensor. Let us know what you find.

 

Thankyou GDOG for the input. Also, that link on the O2 sensors is the best explanation I have seen. I learned alot from it. The old O2 sensor was a factory oem numbered bosch, installed about 7-8 months ago. Not sure why it went bad.

Now I have about 1000 mi on the car with the new front o2 sensor and it is running smooth.

EXCEPT- last weekend I took a trip over the mountains with it and the cam position sensor went out! I spent hours in a parking lot troubleshooting it, determining my CPS was bad and nobody for 100mi had a new one. So had to get a lift home and drive out and fix it after work. About 3 hr drive. Put in new CPS sensor started right up.

THEN-
Over the last week it has been having some issue with the starter- when I turn it over about 50% of the time it wont start instead it stops turning over and sounds like the starter motor is disengaged from the ring gear and makes the sound - ssssssshshshshhshshhsh, then 'pop'. Not sure whats going on but everyday getting worse- I have to try about 10 times before it engages all the way enough to turn over to start.

What could this be? Ring gear tooth chipped? starter motor bendix bad? solenoid?

I am literally about to mentally lose it because of this car and was hoping to get out from under it, but now how am I going to sell it if I can't even start the darn thing?

Appreciate any input here thanks alot!

 

Wow, sorry for your string of bad luck. Well if your lucky the starter issue would be fixed by a new solenoid and/or bendix but i would just replace the whole starter with a rebuilt one. But once you have the starter out, manually rotate the flywheel (take off access cover from underneath) and inspect the flywheel teeth. Chances are you'll find spots where the teeth are ground away almost half their width. If so, you need a flywheel too, and you know what that means (trans R&R).

These are really nice cars once you get the maintenance items up to snuff, and that takes working on them and spending $$ on parts at a minimum. I was at IPD today for their Garage Sale and Open House; got sway bars for the S70 and other stuff. I just really enjoy driving both my volvos! Once you get them dialed in they are very fun to drive IMO.

 

So I pulled the starter out today, and after taking the starter apart, found a lot of gunky dirt in the helix gear- that pushes the gear into the ring gear- so I pulled it apart and cleaned, re-installed and now I have no problems.


Note grime on helix gear



Starter taken apart


I was worried about some of the chipping on the ring gear- but after cleaning inside of starter I don't have the problem anymore.

 

That grime looks like ground up metal to me, but hard to tell from those pics. If that's the worst spot on your flywheel ring gear, then you're probably OK there.

 

my 1998 volvo s70 is running rich on bank one. what to do to fix the problem.