riofrio

What involves cleaning the fuel injectors? Why is it advised to send them to the shop instead of doing it ourselves?

Also, is there a way to test the oxygen sensor? I suppose I could just buy a new one being that they're so cheap.... but that's not my philosophy.

84 GSL-SE by the way.

eddierotary

iTrader: (7)

well is much better insurance of buy one that testing it, remember your car have close to 20 years and probably never replaced the O2 sensor. and i dont know what really is involed on cleaning injectors but i thing they take them apart and clean them up and then flow test them so is flowing the right amount.

LongDuck

I had my 84SE injectors cleaned by a local speedshop late last year and it made a world of difference in throttle response, total power output, and most of all - fuel economy.

The shop put them on a test rig that squirts fuel injector cleaner chemicals through the injector to get rid of any carbon fouling that may be present. They then check flow rates of the injectors, side-by-side to ensure that they flow within 5% of each other which provides better performance and fuel economy, and then leak test them. The final step is adjustment of the spray pattern to get a good looking 'spray' instead of streams of fuel - better atomization of the fuel to the air helps with better ignition of the AF mix and better throttle response and power.

Out of the 5 injectors that I sent off to them (was collecting them in my garage), they had 2 that were 'best' and usable. Out of the other 3, they found that 2 had cracked barrels causing leaks at the bodies, and 1 was non-responsive. I might add that 2 of these were 'factory' rebuilt Cobra-brand rebuilds from BAP, and were low quality ($90 each, however).

The 2 that I got back to install were Factory Mazda fuel injectors with unknown mileage on them. When I go to replace these in the future, I will go with Factory parts, but they are getting harder to find. They are orange-top, low-impedence, 680cc nominal flow injectors, and you only need 2, obviously.

The benefit to using a shop for this is that they have the test rig already built, and can supply you with a 'spec-sheet' for the injector flow at specific fuel pressures. While interesting, this helps you to see that they're within spec and will perform as you expect them to. HTH,

riofrio

What's a good way to tell whether or not m injectors need cleaning?

LongDuck

Some indications that your fuel injectors may be stuck/leaking/etc.:

1) rough idle - usually noticed early on, since as soon as you step on it, the flow increases.

2) 'surging' engine speed under highway cruising - could also be TPS setting, but can be the injectors not in-phase, in other words, one injector is pumping more out than the other, resulting in one chamber developing more power than the other, resulting in surging power

3) fuel leaks from the injector bodies - not good, means you need new injectors and may need yours for core return.

4) Unusually high or unusually low mpg - no kidding, if a bad injector isn't flowing fuel, you're not burning it. If you notice your fuel mileage jumps up 2-3mpg or more, along with the other symptoms, may be worth pulling them. Conversely, if the mileage drops 2-3mpg, you may have an injector stuck open and leaking pressure down - rich mixture = black smoke.

5) Get a mechanics 'stethescope' and put the probe down on the injector top (the orange plastic part) and listen, you'll hear a clicking sound and idle that increases with engine speed - that is the solenoid firing. Both injectors should click evenly and sound about as loud. If one is silent - that's your bad one.

Generally, the symptoms that you see with failing fuel injectors are about the same as you'd see with a carb that needs to be tuned up and/or cleaned. Injectors are pretty easy to change, they're just expensive for the quality that you need to keep your SE running well. Lucky for us, there are only 2 to worry about.

My Infiniti Q45 has 8 that seem to hate oxygenated fuels...

eddierotary

iTrader: (7)

good info long duck, but one more recomandation from manufactures is that you should get them clean your injectors at 75K miles, less on a rotary because of the high temps of the engine. that my .02 cents

riofrio

Any good recommendation as to where to send them? Price? Contact Info? How long will they take?

Hmmm.... where's the 02 sensor and how do I get it out? The Haynes manual seems to say nothing about it.

too many questions, i'm sorry!

LongDuck

Look in your local phonebook under 'speed shops' or 'Automotive' and you should be able to find someone who lists Fuel Injector Service as one of their sales points.

On the O2 sensor, it is located only on SE's (obviously) on the exhaust manifold, just above the #1 Pre-monolithic converter. You'll need a special wrench to remove this because of the location, but it's easy to do - be sure to put new anti-sieze on the replacement, else you'll never be able to remove it. HTH,