zogster

Hey dudes,

My 1987 951 has been giving pretty poor fuel economy lately - around 15mpg even when I'm taking it easy, in mixed but mostly urban driving.

So I thought I'd have the injectors cleaned as a first step in trying to improve matters. I have the injectors back in place now, but I'm just wondering if anyone can tell me, from the attached results, whether they were dirty enough to have been mostly responsible for the problem. (The only thing the pic misses is the stat for "injector imbalance": 0.53% after cleaning, 2.27% before).

Now, I know the obvious answer is "why not just put a few more miles on her and see what mileage you get", but I'm in the middle of fixing a couple of power steering issues and don't want to hit the road until they're done also. But while I'm tinkering I'd like to know if it's worth looking into any other possible causes of the poor economy. (It's a UK vehicle which does not, I think, have the O2 sensor often referred to in this context.)

I sent the injectors to injectortune.co.uk, who charged very little and sent 'em back within two days - thoroughly recommended.

zogster

Hmmm... don't know why the pic's gone sideways on me. I swear it was the right way up when I uploaded it.

luftpirate

zogster

Ta-daa!! Thanks Luft

944Ross

The real benefit from cleaning is likely the spray pattern, not just the volume at a specific pressure. The data in the charts indicates mild plugging, likely from the screen in the injectors, not tip fouling.

You surely have an O2 sensor.

Mark944na86

+1. That would be the first thing I'd try.

I was amazed when I replaced one on a Honda led to a 33% increase in mpg efficiency (no kidding: 17mpg -> 23mpg).

zogster

Thanks all - I'll just have to look a bit harder for the damn thing next time!

Just waiting for PS pump seals to arrive and then I'll be back under the car for a little more light tinkering...

FortyFourS2

I'm not sure that he has a Lambda sensor to be honest being a UK car. Best to ring up RPM and ask thm if the 80s 951s came with them. I know my S2 doesn't have a cat from the factory either (but UK cars from 1990 onwards did get a cat).

944Ross

I can't believe it, the O2 sensor appears to be US-only even on turbos?! I looked it up in the FSM, and right next to the O2 sensor on the wiring diagram, it says "US Only".

zogster

Ah... so on the bright side, I don't have to feel so bad about not finding it before, plus it's one less thing to check.

On the down side, I guess the remaining likely causes of gas-guzzling are less easily rectified than replacing the O2 sensor.

Mark944na86

Well, my S2 is definitely not an US car, and it definitely has an O2 sensor!

Check your exhaust pipe near the front just after the connection to the exhaust flanges.

944Ross

His car is an 87 951, that's what I looked up. I'm sure by S2 days, emissions regs had tightened enough worldwide that O2 sensors were used.

zogster

I believe all S2s, regardless of market, had catalytic converters, which mine does not, so I think "no O2 sensors for this UK model" sounds right. In any case I'm definitely under the car again tomorrow (bit too windy today) so I can check for sure.

zogster

So... it actually took me a bit longer than I'd planned to finish fixing (rather than bodging) the power steering, but my baby's back on the road in proper working order again.

And I can report that:
• I definitely have no O2 sensor - where I think it would be fitted there's some kind of brass delete plug/bolt/thing-that-fills-a-hole. Looks factory rather than a previous owner mod, so far as I can tell the difference.
• After the injector cleaning (and with a new fuel filter) I'm getting around 17mpg, though that's almost all been city driving - plenty of traffic, speed bumps, etc.

So I think my mileage is better, but I really need a decent road trip to get a proper idea. And if things still look poor after a few motorway miles, then I should check out the AFM?

[and btw, power steering... pffft. I don't mind getting cold, wet and greasy to fix something that I need, but a power sapping luxury like that... ]

Luis de Prat

I would leave the AFM alone for now and try replacing the fuel filter and the fuel pressure regulator, first.

When I replaced these on my old 83, the fuel economy improved significantly. Keep in mind that the FPR fails in 'open' mode, meaning it's designed to let the engine run richer as it goes bad over time. Recently replaced both on my S2 and 951 as well.

Good luck with it.