Hey all,

I've recently (couple of weeks ago) installed an led from the computer output of fuel mixture, to see what the hell is going on with my car (the intermittent bad running, it hasn't happend since i had the muffler changed for a pipe, but still). Now, the light flashes for *right* fuel mixture, it is solid red (red led) for rich and off for lean.... (i mounted the LED in the dash, so i can see it when i drive)....Now, at idle, with my foot on the brake, the light stays on, indicating rich....is this right? Does the extra vaccum pulled for the brakes make THAT much diff? when i take my foot off the brake the light flashes...

NOW, This is what worries me (i have an NA 88 "K" motor, i.e. stil weak conrods), when i floor it, no matter what speed, what gear, of for how long, the light stays completely OFF, even if i back off a bit, still off. This would indicate that whenever i accelerate, that it is running lean, which i don't think is right.....

Does anyone know why it does this? Could there be an induction leak? how about a faulty TPS? (i.e. not "clicking" the computer that i am at WOT?). It doesn't matter if i run 89 octane fuel or 98 octane fuel, it still does the same thing....Could this be a fuel injector prob? (I have a new pressure reg, so it isn't that, i hope!)...

If anyone could spread some light on this subject, it would be great....

Thanks all

Azza

P.s. My volvo is an NA, has a bit over 200,000 EASY km (cam still has a little bit of very faint crosshatching on it!), and it has a leaky distributor (i.e. it drips about 2 drops of oil overnight - could this cause a problem?)

Thanks again!

I also have an LED connected but it is under the hood. As I understand it the light indicates ideal mixture at idle and is not intended to indicate ideal mixture at other speeds. I have used it to tweak the mixture control which is on the air mass meter. (The black knob on throttle body is base idle adjustment).

At this time I do have a performance issue, poor acceleration at lower RPMs and my light cannot be made to flash. It stays off no matter where I set the mixture. I intend to check for false air leaks this week.

Have you adjusted the idle mixture?

I adjusted the idle mixture a while back (you mean the black screw under the intake, right?) so that the engine idled at approx 725rpm....but, for some reason, it started acting funny, so i readjusted it, only to find it would go past about 650-675rpm, before the screw became "loose", it didn't fall out, but it was prolly about to!! It refuses to idle higher than that without the IAC, so i just let the IAC do all the extra work....I don't get why it would have suddenly done this though....At traffic lights now, i can "feel" (through the gearstick, manual trans) that the car idles rougher for the first few seconds of each stop.....could this be contributing?

TIA - Azza

The black screw under thr throttle body is the idle spped adjustment. It sounds like you need to clean the throttle body if you couldn't get the edle speed any higher than 650 rpm. That is your problem, the base idle speed is too low. You need to go to the 700/900 FAQ and read on how to set the idle mixture, or go to the MVP site. Click below for the MVP site.

/// I like this idea.

There could be a slight leak in the valve in the booster. It should not allow outside air in until you release the pedal. I haven't been inside a Volvo booster. A slight leak might be normal, I don't know.

On flooring the gas lean might also be normal. Your o2 sensor might be on its way out.

Fuel mixture readouts use a second o2 sensor or in your case I think you are reading the computer output from the o2 sensor. (Right?) You are reading the oxygen in the exhaust manifold.

A leak in that new pipe connection could cause oxygen to get to the sensor even though the new pipe is down stream from the manifold. I found this hint on a site on o2 sensors. I didn't much believe it when I first read it either.