ECU Code 45 (Injector Leak) and Consult Readings

[goody90q45]

The CEL has come on a couple of times on the 90Q and the stored ECU code has been 45- Injector leak. I learned early on that white smoke is the code for an injector leak and code 45 shows more of an inbalance in the air/fuel mixing and monitoring downstream.

I took both Q's out for a spin this morning and monitored the engine on Nissan Data Scan. Both oxygen sensorsa re working fine and have <15k miles on them. Here's the results:

..............................90Q................94QIdle......................750rpm...........700rpmCoolant temp.......179*F.............179*FThrottle Voltage...0.50................0.48Injector cycle........2.00................2.50 (not sure what this is)Duty Cycle............1.20................1.50 (not sure about this one either)A/F Base...............96...................100IAC.......................38.......................8

The PO had complained about the occasional CEL and took it to his mechanic who appears to have fiddled with the IAC valve to maintain idle rather than clean intake components. Under the right conditions (hard acceleration?) could this be the cause of the ECU code? This Q passed smog with flying colors about a month ago. Since I don't know what's gone on maintenance-wise for the past couple of years it looks like I'll be cleaning at least the IAC, TB and EGR as soon as gaskets arrive. What do you all think?

[slybydesignq45t]

I don't know the answer to your question. I just wanted to say whats up. As you know my current Q is totaled, but I have placed 3 calls to purchase another Q in my price range. One of the Q's I am currently looking at is in LA, the other two are locals. I will let you know if I get my hands on one. All three have way lower miles then my current one, and I am just going to use parts from my wreck. So I got my fingers crossed. OK, happy Holidays Goody94q45. I will keep you posted.

[jltibbs]

Not sure exactly what's up, but I can tell you one thing from experience with my Q. I got my Q from Keith (Rex) and he explained that when driving around town the CEL would never come on. Once on the interstate, it will come on shortly thereafter, he told me. So when I got back home with it, I tested it out. Sure enough, I could drive around town all day and never see the CEL. But, if I got on the interstate, before I got from my town to the next, the CEL would be on. So, one day I take it to my mechanic that has a Consult. He plugs in and get the 'leaking fuel injector' code. I tell him that I can't afford a new injector and that the Q seems to be running fine. As he laughs, he pops the hood, reaches towards my MAF, grabs the plug, and wiggles it. While he is doing so you can hear the engine bog and stutter. I'm obviously confused. He turns back to his toolbox and grabs a connector in a package and throws it to me. He said that the MAF plug was updated and that mine was never replaced, thus it was my problem. I replaced the plug and my light has not come back on since. Maybe you could look into this.

[Q45tech]

The injector leak code [on California ecu] is a GUESS by ecu after it has tried the normal injector time adjustments and O2 still reads rich. It is not applicable to idle since even a brand new O2 may not be hot enough to stay in the operating range.

Usual proceedure is to replace O2 [make sure OEM versions] after you have tested [isolated] fuel rail from return line..................the isolated rail and injectors must be leaking if the pressure drops.

The ecu assumes a +- 20% fuel trim is/could be normal depending on air temp and MAF reading density due to barometric variances [3% per 1000'].

So it gets out of control in Denver if temp exceeds 90F or cruising at a cool 8,000'.

The MAF voltage is necessary to even attempt to correlate all the others you provided.

A 1.1>1.2 MAF at 700 rpm idle might only increase to 1.7 volts at 2,100 rpm 63 mph cruise....................since the air flow per second has tripled due to rpm. The injector open time will go up a little since idling is < 10 HP while cruising might be 25.

A good education to view parameters at idle with and without ac, lights, steering assist, etc etc...............then do the same at 60 mph on a very level road.

[NJ 666]

Not sure exactly what's up, but I can tell you one thing from experience with my Q. I got my Q from Keith (Rex) and he explained that when driving around town the CEL would never come on. Once on the interstate, it will come on shortly thereafter, he told me. So when I got back home with it, I tested it out. Sure enough, I could drive around town all day and never see the CEL. But, if I got on the interstate, before I got from my town to the next, the CEL would be on. So, one day I take it to my mechanic that has a Consult. He plugs in and get the 'leaking fuel injector' code. I tell him that I can't afford a new injector and that the Q seems to be running fine. As he laughs, he pops the hood, reaches towards my MAF, grabs the plug, and wiggles it. While he is doing so you can hear the engine bog and stutter. I'm obviously confused. He turns back to his toolbox and grabs a connector in a package and throws it to me. He said that the MAF plug was updated and that mine was never replaced, thus it was my problem. I replaced the plug and my light has not come back on since. Maybe you could look into this.

What he said..check out ITB95-020. Seen it a few times before. And always look at alpha readings. It tells you how the computer is evaluating the input info.

[Q451990]

I suspect the IAC opening as displayed with Consult (or a laptop software package) is the target that the ECU is calling for, not what's actually happening... much like the timing advance. So it's probably not taking in to account the setting of the adjustment screw.

So that would lead you to believe that the ECU on your '90 is seeing something from an input somewhere telling it to hold the valve open more than the one on your '94. The first guess would be the temp. sensor, but I don't think that's the case given the readings you posted. Any chance you had the A/C set to Auto on the '90 and to Econ on the '94?

I have an intermittant high idle issue and need to spend some time with the FSM to see what inputs the ECU uses to set the IAC value...

Heath

[NJ 666]

Your readings don't look that crazy. I would think that if the IAC were at fault you would also have some idle issues. Like was stated earlier, as carbon builds up on the throttle plate the ECM will compensate to keep the proper idle RPM. That's why the IAC counts might be a little high. I've only seen this code pop up a few times and it was always a MAF or connector issue.

The code doesn't seem to have accurate logic. I've seen a few Qs with wet ECMs and shorted drivers that hold the injectors on and it didn't set this code. Just my $.02

[Q45tech]

The code is only available in the SPECIAL CALIFORNIA MODEL ECU not in any other state [49 state model].

[goody90q45]

I've only seen this code pop up a few times and it was always a MAF or connector issue.

Most everyone is leaning toward the MAF or connector being the culprit so yesterday I took a closer look at it. Even though I had cleaned, lubed and tightened pins only a few weeks ago the connector was still a bit loose even with the retainer clip installed. In fact, I was able to pull the connector off the MAF with the metal clip still attached.

The connector has been replaced some years ago and the wiring may have been shortened rather than splicing in new wires. It looks like the connector could possibly be pulling loose under hard acceleration or even a hard bump (pothole?). I'll take a look at it again today and probably swap in my backup MAF which has intact tabs to hold the connector. TB and IAC cleaning are also on the list.

Thanks for all your responses.

The code is only available in the SPECIAL CALIFORNIA MODEL ECU not in any other state [49 state model].

A lifelong NorCal resident, originally purchased in Pleasanton.

I don't know the answer to your question. I just wanted to say whats up. As you know my current Q is totaled.....

Sorry to hear about your Q Sly. It doesn't take much to end up with a salvaged title and even a minor crumpled rear quarter panel is the death knoll for most any older car. Good luck in your search for a replacement. Take your time (you are) and wait for the right one. I see lots of 97-99 Q's for sale in LA/SD if you're ready to move up and only have to deal with coil and shock issues.

[Infinitiguy19]

I find it weird that the ECU would throw a "Injecotor Leak" code when the MAF is bad.

But check this out: http://www.q45.org/gallery2/d/...+.pdf

Perform all the test to see whats wrong.

[NJ 666]

I think the "rough" logic is if everything is within a "reasonably" parameter and the o2 sensor is still rich it assumes a leaking injector. If driveabilty problems were logical we could all fix cars.

[Q45tech]

Hopefully one can see in their mind that a single cylinder total misfire would only make the average of 4 [what O2 sees] only ~25% richer.Instead of reading 14.7 as normal, a full single cylinder misfire would drag the AF down to 11.25............................less than the 10.5 AF WOT acceleration might be.

As to the MAF accuracy only the low flow idle to cruise air flow is important. The range from 1.1 to 2.0 volts................any amount higher probably means the accelerator is WOT and rpms are above cruise 60 mph.

Not to say in 1st gear WOT above 30 mph you can reach 4.4 volts at 45 mph But you are accelerating.

All of these diagnosis require some time at steady cruise speed to zero in on a best guess.

AS a California only solution they could afford to smoke some weed Fuzzy Logic in programmer slang language.

http://www.topcoder.com/tc?mod...ities

For those with Science/CS Degrees look at page 4 of pdf below good vs bad maf: The 137 pages of slides show how to crete an intelligent agent for diagnosis, fuzzy logic, and wavelet theory for segment diagnosis.http://www.engin.umd.umich.edu...2.pdf

[Zekdafied]

This sounds like a similar issue to what is going on with my '98 Q45 as well. I noticed slight misfire at Idle and a few times the car would die out at immediate stops. I turned the idle up a tiny bit and it has helped,but there is still that "hiccup" at idle.

Eventually the Engine Service Soon light came on RIGHT as the misfiring was getting worse. It was like a switch came on and made the car run like crap. I noticed the misfire in all cruising and idle. I scanned the code and it read a Cylinder 6 misfire. I left the car parked for a day while I gathered spark plugs and some info on the subject. I start the car a day later without touching anything and the engine light stayed off.

I did spark plugs and still have a misfire at idle. I just changed cyl. 6 and 2 coils and am waiting to see what happens.

What can I do next? The MAF like stated , 02 sensor, injectors? I'm still unsure as to what exactly is causing this.

[Infinitiguy19]

Most likely the coils as they seem to go bad all the time on second gen Q's.

And adjusting the IAC AKA AAC only fixes the symtoms not the problem.

[NJ 666]

Look in the airbox under the filter. It is very common for dirt/debris to get in there during filter changes and cause weird MAF readings. Even a tiny piece of leaf or plastic stuck to the screen can cause all sorts of "hiccups"

[Zekdafied]

I checked the air box a week ago and cleaned it out and have a new filter installed. I think I'm going to try and get some injector cleaner today or tomorrow and see how that helps. I was thinking of putting some 94 octane in the tank as well but have mixed feeling about that.

Thanks for the suggestions everyone.

[silkysmoothyjud]

If not maf then its the injectors PERIOD THE END!! Might as well replace them all while your there, keep the old ones for spares as they go out a LOT...about to deal with mine for the FIFTH and final time...All OEM cept 1 and 2....which can be replaced without plenum removal...