How long can the Q45 go with Bad Injectors

[tegva]

1994 Q45 with 195K miles starting running very rough yesterday. I checked the injectors, #3 was 14.9 and #7 is open, the rest ohm between 11.7-11.9. Will I do any damage to the engine running this car? Obviously I want to replace the injectors as soon as I can but want to wait until I am near an infiniti technican.

[Q451990]

1994 Q45 with 195K miles starting running very rough yesterday. I checked the injectors, #3 was 14.9 and #7 is open, the rest ohm between 11.7-11.9. Will I do any damage to the engine running this car? Obviously I want to replace the injectors as soon as I can but want to wait until I am near an infiniti technican.

That's a good question... I can't wait to see some input from Q45Tech and the others. My guess is that your rough running is from #7, since it's reading open. Mine has no noticeable roughness with one at 25ohms and another at 250 - but I have gotten the "injector death bounce" (dead miss) a couple of times intermittently. My assumption is that the injectors work to some extent until they read totally open.

I guess my concern is that the ECU can only adjust the injector pulse width (open time) per bank - so it can't individually adjust cylinders to account for a dead other cylinder or malfunctioning injector. So if you have one injector underperforming, the ECU will try to adjust the pulse width wider for the whole bank, and you'll still get a rich condition on three cylinders and a lean condition on the other.

If you had two or three dead cylinders on one bank, I would be concerned that the ECU might flood the other one trying to compensate - but I don't know. All of this is just a WAG (wild a$$ guess) on my part. Like I said I will be very interested to get some more answers on this - specifically on how long one can run the car with a dead miss without doing engine damage.. Heath

[snobrder]

I would like to know this aswell because I am running on dead injectors aswell

[Jesda]

Its harmless, but it's a HUGE WASTE of gas because fuel economy suffers terribly.

[elwesso]

as long as its not dumping fuel you should be OK..

[Q45tech]

Actually steady state cruise should see a small improvement in MPG since only one bank is affected. Assumming only 1 injector is dead.

Acceleration is impaired but I drove 85 miles on 7 injectors at 60 mph ac on.

After all the modern cylinder shutoff engines cruise as a 4 cylinder.

City use with constant acceleration is a more serious stress.

Everyone should practice by discoing # 1 or # 2 injector harness and see how you like it in advance of the failure.

[Q45denver]

I the past my car would run real rough and smoke a lot if only one or two bad injectors.

[mxr662]

Maybe a switch could be wired in the shut off 2 or four injectors to save gas cruising on the highway.

[Haitian_King]

Maybe a switch could be wired in the shut off 2 or four injectors to save gas cruising on the highway.

Wouldn't you be able to do with with a CONSULT or the Nissan Datascan program?

Wait. That might be a little more cumbersome than a simple switch. I think that it would be the easiest way to go because (this could be due to my lack of electrical engineering experience) it seems to me that although the purpose and activation of the switch would be simple, the installation and wiring would be the "hard" part?

I'm thinking that the switch would have to run to the ECU and be connected to the part of the ECU that would control injector flow/cylinder management?

Or, an idea that just struck me is to have a modified ECU with a "fuel-saver" program that would run the Q on 4-6 cylinders (is that possible to do the 4?) and be activated much like the Stage II program by a simple 3 position rotary switch?

I hope some of these ideas are valid and not just implausible nonsense. I feel a bit smarter with these ideas, but I'd feel like quite the buffoon if it was all just retarded babble.

[Q451990]

The problem is setting up the firing order so that you have the 4 or 6 cylinders you're going to continue to use firing in sequence. If you simply cut fuel to the cylinders you don't want, you get the dead miss feel out of that cylinder. So it would have to be done with the ECU, and automatically tied to demand through some sort of reading from the TPS or TCU I would think.

I'm sure there are more considerations than this... but that's what I can think of.

Heath

[Q45tech]

Cylinder cut engines must have a mechanical method to hold the intake closed otherwise you waste energy compressing and pumping the air in and out of cylinder.

After combustion the hot mixture is forced out by heat expansion when the exhaust valve open, with zero combustion the air is 800F colder and must be pushed out by piston and rings [this takes added HP from the other cylinders].

The above is why a dead cylinder [no fuel] doesn't reduce gasoline consumpion by 12.5%..................4-5% at best is the result.

[mxr662]

Cylinder cut engines must have a mechanical method to hold the intake closed otherwise you waste energy compressing and pumping the air in and out of cylinder.

OK

All the other kids has the visible V8. My father was rather forward thinking and I had the visible rotary engine.

[jimbyjimb]

OK

All the other kids has the visible V8. My father was rather forward thinking and I had the visible rotary engine.

FREAK!

Totally kidding.