Well... I've done it. The Q started leaking coolant under the plenum and I took it upon myself to remove and replace everything rubber under there. (Joe at Scottsdale will be hearing from me very soon!) I must have been crazy from the heat.

(1991 Q45a, 210k miles, original rubber under plenum)

Question: Since I've got them exposed now, I was wondering if I should remove the injectors and send them out for cleaning (~$15 each), or leave them in and have them cleaned on-car after everything is back together. If the valves look anything like the inside of the plenum, they must be covered with gack. On-car, off-car, or both? Suggestions?

(Replacing all top-side rubber, knock sensors & harness, O2, EGR, PCV, plugs, thermostat, water pump, fan and clutch, and radiator hoses. Did I miss anything?)

azskygod

My injectors have been in since Jan 1990 [235k], but for the last 6 years they get a can of BG44k every 90 days and a rail flush at least once per year.... as dictated by the power balance test after everything else has been cleaned.When the IAC duty cycle [% of extra air added to that which normally flows under the throttle body], when the reading gets above 20% the TB needs cleaning. The more miles the engine has the faster it gets dirty......not filthy like the first time but a squirt and wipe taking 2-3 minutes.

Another trick is to turn the AC on and off - the idle in drive should be exactly the same if everything is clean enough.

It really is important to change the fuel filter annually and to examine what drains out on a paper towel.There are two rubber lines in the fuel pump and 3 as the hard lines go onto the engine plus the underplenum ones. All these break down from the inside releasing bits of rubber into the system.

As to removing the injectors for cleaning it won't last any longer than a rail flush as the crud builds up quickly.The trick is to flush the rails at a 55 psi pressure [from the pressure bottle] vs normal idle 34 psi and WOT of 44 psi.

Be very very careful when you decide on taking the injectors out for cleaning. If they are too clogged, when you take them out the cleaning won't help. Also, putting them back in makes it worse. Example: just sent my 90 Q in for a tune-up. Mechanic took out and cleaned fuel injectors. Next day, picked up the car and the damn thing now takes 30 seconds to accelerate to 20 mph!!!! I have to replace all 8 fuel injectors now; at 1200 job. So be wary of this when deciding to take them out.

Q45TECH: What about replacing the rubber o-rings? I thought removal, cleaning and flow-testing would be a GOOD thing since everything else that was rubber under there is now hard as rock.

Cleaning off car and replacing o-rings seems better, but leaves the runners and valves untouched. Cleaning on car would clean everything, but possibly not as thorough. (I've heard horror stories about hydrolock after an injector replacement too.)

Looking for more advice/opinions... Thanks.

azskygod

Where would you have them cleaned? I'd agree that while you're in there it can't hurt to replace O-Rings. The only risk you're taking is that those things are very difficult to get out of the rails - I broke one or two (cracked tips, scarred tops, etc) trying to get them out - so if you can send the whole rail to the cleaners, that would be best...

Heath