Check Engine Light On the Q

[SFBayQ45]

I know this is a very general question, but what does the Check Engine light warning indicate other than O2 sensors going bad? I'm sure there's a ton of other things related to it, so excuse me for lack of knowlege. It came on for about 5 minutes while I was driving to a local grocery store, but then it disappeared after I started the engine again as I returned from a 10-min shopping trip. Since then, it hasn't turned on again as I observed the indicator throughout my 60-mile drive this morning. Should I be concerned about taking this Q on a long-distant trip this weekend? Last time this light came on, I replaced both O2 sensors in the front less than a year ago. Any leads?

[Q45tech]

At most with a perfect O2 sensor the fuel trim range is 20%......a totally dead sensor [both] could reduce mpg by 20% but this is unlikely as even one working somewhat will be enough for ecu to guess within 10% error.

California cars have extra sensors [egr temperature to check egr flow], actives and tcs cars have more sensors.

By the fact that it doesn't come on immediately it means sensors are passing the open/short test.

I guess it [a trip] can't hurt much be sure to check all fluid levels [brake, transmission, coolant, ps, oil, winshield washer] before you go.

Have chain guides be replaced/updated? nothing to do with SES/MIL.

[911/Q45]

In CA, I'm betting on a fading injector.

[Alan]

When I had a check engine light everyone suggested I access the ecu and check the code. It's not too complicated, described in the service manual, possibly do an archive search. Or maybe one of the experts will post the procedure here. Be sure and check that washer fluid???!! At 130k plus CA miles we have done four injectors. We have had some sucess running Chevron gas to clear an injector code, and I thought all that advertising was bull.

Good luck , Alan

[elwesso]

I posted the procedure many a time...

Basically what you do is remove the ECU, take off the harness connector (to take the ECU out), reconnect it, and then turn the screw on the front.....

[SFBayQ45]

Thanks for the lead fellas...

I went to a shop that had a machine to read the error code, and sure enough it indicated a "leaking injector". I was advised to not drive the car on the extended long distance trip for safety reasons. The guys said that there's a potential of the engine catching on fire if there the right combination of heat and leaking injectors. Does that sound right? Since my "check engine light" hasn't come back for two days now, does that mean that the leak has temporarily stopped? Or is it constantly leaking at this point, and I should retire the car until I save up some greens to buy all 8 new injectors. Joe priced $142/each, however does anyone know where I can get new ones cheaper? When I get it fixed, what kind of other replacements should I make so that the work overlaps and the damage for labor incurs only once? One source told me I should have a tune-up done at the same time. What are your thoughts?

[maxnix]

Do a hose kit (all rubber under the plenum) and budget for knock sensors and harness. Might as well do a cooling system flush and thrmostat while you're there (how's the radiator?).

You may not need all eight, but with crappy CA gas, you may.

[Q45tech]

The California ecu reports an injector code WHEN one or more of the O2 sensor swings goes extra rich from the average of the other 3 [per bank].

Not the best way to guess at what's happening but it kinds works some times............off course if a plug misfired the cylinder or just created a weak burn the ecu would see the same thing a rich signal when others in the bank were leaner.

Deposits on the injector pintle can make it harder to open and close........sometimes this is all that is a problem.

You measure the injector resistances and check the fuel rail pressure [for leaks] with engine off. BEFORE changing injectors.If injectors ohm out ok a rail flush then BG44k every 90 days should delay the problem.

The Injector code is a great selling tool, when only plugs and a cleaning are required. ODB2 cars have more computer power and now just report a cylinder # misfire........could be plugs, coils, or injector.

BUT CALIFORNIA, ARIZONA, and NEVADA are special case where the presumption of bad injectors is more often correct.Ethanol states are now seeing this problem.

Spending $3,000 on injectors and plenum hoses and knock sensors, new plugs and general engine cleaning on a 1991 usually means the car gets retired as there are probably Another $3,000 - $5,000 of other issues.

[911/Q45]

On my 90 there is also an electrical failure injector code.

[texasoil]

A leaking injector code can often be cleared if you either run some good injector cleaner or have it done at a shop--and quit buying the cheap gas. It doesn't have the detergency needed to keep them clean.