1998 V70 Timing belt, cylinder head work 330k miles!

[5rivers]

Well, after a short trip around the neighborhood, the code scanner tells me once again that the front O2 sensor is pending, hence problematic! But the good news is that code P0505 did not come up! So adjusting the throttle plate was beneficial. However, I did notice that after slowing down to turn left or right, that the idle would come down to 900 and then surge upwards to about 3000 rpm. If I punched the gas pedal, the idle came back down to 950 rpm. I am wondering if the throttle cable needs more tension. But, here's the problem, if I loosen it then with a quick hit to the gas pedal the cable is likely to come off its spool. If I tighten the cable, the idle goes up to 1300 or 1500 rpm and no amount of quick hits to the gas pedal will bring the idle back to 950. Any thoughts? Do I need a new throttle cable or is there some other way of increasing the cable tension without increasing the idle rpm?
I will drive for 17 minutes under 60 mph, then idle for 5 minutes and see what happens. Should I be erasing the pending code before I start? If so, do I need to drive the 50 miles first, let the engine cool down a bit then start the drive cycle over? If the CEL comes on, should I start the drive cycle over? OR make note of the monitors that are still red, so I can continue to search for what is preventing the monitors from turning green?
Appreciate any and all thoughts/suggestions!

[abscate]

Leave the pending code, keep driving. I suspect the OXS sensor fault I still holding up the monitors going ready.

[5rivers]

Here's the latest!
Took a few long drives along the 401 that runs between Montreal and Toronto. After 50 miles or so, the O2 Sensor code (P0130) came up again, plus code P0301. This last code is a misfire in cylinder 1 and I have since switched spark plugs between cylinder 1 and 2. The idle is still high, but not as high as it was, ranging between 3000 and 4000 rpm's! When it idles high now it might hit the 2200 rpm mark, then when I push in the clutch to shift gears, the idle goes back down to 950.
Should I be replacing all the spark plugs?
Any suggestions on what I could do next? Clean out the fuel injectors?
All the spark plug wires look fine and I have extracted them at the plug connection and reconnected them. How would you determine if a spark plug wire is faulty?
Am looking at easy fixes right now. I hate the thought of having to remove everything attached to the cylinder head, again! I sort of understand how a misfire would result in a higher idle. The car has definitely used more fuel recently.
Appreciate all your suggestions!

[5rivers]

I forgot to mention, I had an O2 sensor that I had cleaned a while back (it was not in the car very long), and had it installed a few days ago. Did take another long drive (50 miles +) and P0130 came back along with P0301. The code for the sensor did mention "circuit". The most recent long drive resulted in code P0131 (O2 sensor circuit low voltage bank 1 sensor 1) plus the code P0301. What is the difference between codes 130 and 131?

[scot850]

Your variable throttle/idle could be the cable itself. They stick with age and sometimes the wire can fray causing it to stick. Best suggestion is to swap with a new one. Buying used is a huge lottery for the effort required to swap it out. Can't think of anything that would cause the high RPM's other than maybe an air-leak somewhere, but the fact that the RPM 's can drop to normal sounds to me more like a sticking throttle plate or throttle cable.

So for those like me late to the party, what have you swapped in the ignition system?

1) Plugs - No, but how many km and how old are they?
2) Spark plug cables - When last changed and what brand are they?
3) When were the distributor cap and rotor arm last swapped and are they Bosch parts from a good vendor (many copy pars out there)
4) P-130 (O2 sensor signal error/malfunction) - You mention the replacement of the O2 sensor. On a 98 do they use Denso or Bosch sensors? I know on the 99 and 00 years on the non-turbos they use Denso brand.
5) When was the MAF last cleaned and or replaced? Again brand and source (again copy parts out there) - Have you tried disconnecting the MAF to see what happens?

Neil.

[5rivers]

Hi Neil, thanks for your reply!
The plugs are relatively new - installed new when I put the cylinder head back on (the second time).
Same with the plug cables (Volvo brand).
Same with the cap and rotor - all Bosch.
The O2 sensor was Bosch, double checked the numbers on line - OEM.
The MAF, again, was replaced and cleaned same time as everything else above. It's OEM.
Since replacing those parts and then getting the car to start (and run), I drove the vehicle for just a short bit (a few months if that) then it sat again for a while (almost a year). Am now trying to get up to snuff so it will pass inspection. Then it will be my daily driver, once again.
I believe it was in 2014 when I repaired the cylinder head, then it sat for a while, then got it running again and drove it about 200 miles before taking it off the road again. By then I knew it would not pass inspection. So for the past year or so, I've been slowly repairing/replacing things on the car. The last headache was the IAC valve.
I think I need to order a new throttle cable.
I will run the car and disconnect the MAF to see what happens and post results.

[5rivers]

Hi again!
I started the car and then disconnected the MAF, nothing changed in how the motor was running. Once I reconnected the MAF, the motor almost stalled out, but then stayed running. I will clean the MAF and do the test over again to see what happens. But, on this first test, I would think the MAF is bad. Is this correct?

[cn90]

- I have a brand-new MAF from my 1998 V70 (installed for only 1 week).
- PM if you are interested. Bosch Genuine MAF.

[abscate]

Hi again!
I started the car and then disconnected the MAF, nothing changed in how the motor was running. Once I reconnected the MAF, the motor almost stalled out, but then stayed running. I will clean the MAF and do the test over again to see what happens. But, on this first test, I would think the MAF is bad. Is this correct?

No, you don’t learn about the MAF this way. It’s also considered bad practice to disconnect stuff while electrically hot, although we have never seen damage specific to Volvo’s on these Fora

Your Volvo can run in three different modes:

Best....it measures air flow at the MAF, determines amount of fuel to inject, then adjusts this fuel amount att about 20times per second using the amount of oxygen detected by the OXS sensor as a guide...this is called “closed loop”

If for some reason the OXS isn’t working, it doesn’t make the fine adjustment and just uses the MAF value for air...open loop

If it doesn’t find the MAF reading plausible, it ignores it And just maps fuel by rpm.this tends to run rich.

( And 1999 on get a fourth mode called limp mode, where the throttle opens to about 2000 rpm and limps you home , because we are sexy Italians)

That glitch you get when you disconnect a MAF on a running car is the system jumping from one to another, again, not generally considered good practice and of limited diagnostic value

[5rivers]

Okay, here's what I've done so far:
I figured out why the idle was so high - whenever I pushed the clutch in to change gears, the throttle cable was getting stuck on the felt covering on the inside of the engine hood! Cleaned that section off, now the cable is not getting stuck! Who would have thought?!!
That took care of the IAC valve code.
As for the P0301 code, I took out the spark plug from cylinder 1, cleaned it up and reinstalled it. Did that to all the other spark plugs as well. Did a resistance check on the plug wires - I don't think this is good!
Had the multi-meter set at 20K ohms:
Cylinder 1: 4.72 ohm's (longest wire)
cylinder 2: 4.25
cylinder 3: 3.46
cylinder 4: 2.94
cylinder 5: 2.42 (shortest wire)

I think the readings should be a bit higher, but appreciate your feedback on this!

There were no cracks on the inside of the distributor cap, but the outer shell (black in color that goes over the cap with the plug connections) did have a crack next to one the bolts holding the cap to the head (must have tighten the bolt too much). Would this cause any difference in spark loss? Still trying to figure out the cause of the O2 sensor DTC.
Appreciate your insight!