850r failing emissions miserably (HC and CO) Topic is solved

[BlackBart]

Great explanations! I learn things here on MVS.

[scot850]

I do have a question on fuel pressure being too high. What would cause this? A bad FPR (fuel pressure relief) valve?

Another fuel related issue to watch for at this age is fuel injectors that are worn/dirty/leaking or failed injector seals.

Neil.

[JayPea44]

Fantastic information thanks a bunch Roger. I’ll check the fuel pressure like you say.

The regulator hose was heavily worn and splitting so I replaced that. Also, I have replaced all wires and plugs rotor and cap, the old plugs were filthy.

Like I say. I have an o2 sensor on the way, and if that doesn’t fix it and it turns out to be pressure or a corroded connection to from the sensor (could be as the car has been sitting) then I’ll have a nice spare for when my o2 sensor finally does give up.

Thanks again for the info. Really valuable stuff.

[JayPea44]

I do have a question on fuel pressure being too high. What would cause this? A bad FPR (fuel pressure relief) valve?

Another fuel related issue to watch for at this age is fuel injectors that are worn/dirty/leaking or failed injector seals.

Neil.

I do have a new set of injector seals waiting to go on. The old injectors do look a little grimey, but I’m reluctant to think they have failed.

[scot850]

Maybe some new seals, injector filters (the ones that sit in the top of the injector) and some fuel system cleaner and every bit helps.

Maybe it just needs some fresh gas and a good old Italian tune up on the highway?

Neil.

[JayPea44]

Definitely needs fresh gas and fuel system cleaner. Previous owner had been running it on 85… so I’ll fill it up with 87 or 91 and bung a bottle of Techron in there.

And yes an Italian tune up haha!

[scot850]

Put 91 in there if you want to keep your engine long term and don't want to burn valves.

Neil.

[JayPea44]

Belated update for prosperity - I finally got my new upstream o2 sensor installed after a cold snap here in Denver. Was a fairly easy job, was able to get it all done from underneath the car, plug and all.

Took it for a drive and checked the Fuel trims:

LTFT -1.6 (started at +1.6) (before the change was 21.9!!!)
STFT variable between + and -3 (the highest I saw for a split second was -10). (Before the change was either 0 or 21, no in between)

STFT also seems to behave as it should, constantly fluctuating around as the driving conditions change. LTFT is where it should be. I also filled it 3/4 full with 91 and some techron. It seems to drive much better and feels smoother.

I'd say the o2 Sensor was likely my biggest issue, we'll see if it passes the test or not when I take it later this month.

[scot850]

Give it a good hard drive and 'tune it' with the right foot to try and clear all the line, muffler system, cat, and anything else that may benefit. Get the Techron and fresh gas running and it will be a better car. Good enough to pass, I don't know but you must be close.

Glad to hear the O2 sensor seems to have made such an improvement, and all the rest you have done will also have incrementally improved the combustion.

Good Luck and let us know how you get on.

Thanks for the update.

Neil.

[JayPea44]

Cheers. It definitely feels so much better. But will it pass? I feel like if it fails this time it’ll be by a whisker.

I’ll be sure to update. Thanks all.