Weirdness with Quella: Attn Dennis!

[AZhitman]

Had 2 injectors and all underplenum hoses replaced a couple weeks ago. Soon after, I posted re: rough, loping idle when cold, which smoothed out once coolant reached operating temp. No noticeable loss of power.

She's back in the shop. Tech noted the entire R bank of injectors is throwing some strange COLD resistance readings: 23, 28, 18 and 22 (supposed to be approx 10).

They're still doing diagnostics, thinking a harness is bad.

Also, the tech is adding a "ground strap" from the MAF connector - Says they're doing quite a few of those on the 90-96 Q45's.

Any thoughts?

BTW, I'm getting 4 new rotors and new MetalMaster pads (ordered by Joe from Stillen) put on at the same time.

[DAEDALUS]

#2 injector is easy to reach. The 5 minute check would be to remove the harness from that injector and measure the injector's resistance directly. A bit of a pain, but #4 can be done the same way, just a little more trouble cause the plenum's right on top of it. But it can be done without removing the plenum, at least on a '90. I believe #8 can be done too, giving a pretty good idea if it's the harness, the injectors, or both.

New ground on the MAF is a good idea--can't hurt, might help.

[AZhitman]

Well, now the techs and svc advisor are saying, "It's an old Q - They all do that." I'm not buying it.

I've pushed them to check it out further - They don't know what's wrong. They say it's not the harness, but the svc advisor says it may be an injector that's bleeding down as the car cools... Beyond that he's got no idea.

Dennis, love to hear your thoughts on it.

[AZhitman]

p.s. The lead svc advisor says, "There's no need to do a ground strap on the MAF on a 95 Q - That problem was only on the 90-93."

It's irritating when these guys don't agree....

I expressed extreme displeasure with the SA's comment, "It's an old Q, they all do that."

[Q451990]

No doubt... I'd be ticked! They don't all do that. Sounds to me like a bad injector - more of a bounce at idle?

As far as the injector bleeding down - I had that problem with some remans I tried a long time ago. The main symptom was a hard start condition after it sat for an hour or two (hot soak). No idle problems, just a little bluish/black smoke and you had to turn the car over a long time before it started.

Replaced everything with OEM and it's been fine ever since.

Heath

[AZhitman]

Yeah, it's a really hard "lope" (or bounce) at cold idle. Like an old big block domestic car.

Goes away once warm, and smooths out real nice - No apparent power loss.

[Bayarea Q]

Hitman,

Just curious why your going with the metal max pads instead of OEM? I'm about to by the same from Joe, and I was plannnig on going OEM....

Good luck with that injector problem. Do you run BG44K before oil changes?

[AZhitman]

MM pads are actually cheaper, and IMO superior to the stockers. Hell on the rotors, but they're on their last "cut" anyway.

BG44K every 3K miles for the past 3 years, no matter what.

[Q451990]

Yeah, it's a really hard "lope" (or bounce) at cold idle.

That sounds like an injector failure for sure...or a dead miss caused by something. I assume they've tried a cold power balance test?

Heath

[Q45denver]

When was your last rail flush and plenum cleaning? Did problem develop suddenly. Is it worse when engine is cold?

[Q45tech]

A coil of wire [injector solenoid] should be within 1 ohm cold or hot as that would be an 8% change in resistance and copper has only 1%.

Use an amplified current probe and look at all the current waveforms [create a jumper for the injector fuse and loop the probe around it............you can see each pintle open and at what current.

[AZhitman]

Problem developed immediately after having 2 injectors and all underplenum hooses replaced.

Rails, plenum and TB are SPOTLESS. Shiny as new.

[Q451990]

I'd be concerned about a problem with one of the new injectors, maybe a pinched lower o-ring causing a bleed down? I think a cold power balance test will tell you a lot.

Heath

[Q45tech]

The problem is the automatic power balance test requires that the coolant be at or above 176F.You can cheat by using a manual override but the rpm are not fixed by ecu and things will changes as the coolant temp changes.

[AZhitman]

They swear up and down that it can't be a pinched o-ring. I looked at the old injector, and they showed me how they're installed, and I'm inclined to think that'd be a pretty slim chance (the way the injector is designed on the 94-96).

[DAEDALUS]

I thought the outer shell and o-rings were identical to the '90-'93, and pinched o-rings do happen. I could be wrong. The way to be sure is to do a pressure check on the fuel rail to see if it's leaking down after the fuel pump shuts off.

[AZhitman]

That's a good idea - I'm amazed the techs haven't done that already.

Grrrr.

[BIONICQ45]

p.s. The lead svc advisor says, "There's no need to do a ground strap on the MAF on a 95 Q - That problem was only on the 90-93."

It's irritating when these guys don't agree....

I expressed extreme displeasure with the SA's comment, "It's an old Q, they all do that."

Dear Catfish and vinegar sammit eater,

I took my Q in for some rough idle diagnosing and they recommended the ground strap for the MAF (94Q). It was free so I let them do it. It is hard to say if it cleared up the idle since the roughness was intermittant anyway. Shortly thereafter I got a MAF from Dr. Lee so I can't say if the new MAF cleared it up or the ground strap. Just my two cents.

[AZhitman]

Thanks, BQ!

Say Hi to 'Lizbeth and Lamont for me....

[NISTECH]

The thing here that is eye catching in their diagnosis is the resistance readings they took from the harness to the injectors. why so high? why are they not trying to find out why the resistance is out of spec. the fact it is variable with temp says to me there is corrosion or moisture in one or more of the connections. Q's arent my fortay but this just seems like the most logical problem if they have incorrect readings on those wires. Doing the current check as dennis said would be a realy good idea to determine if you have a wiring prob.

To check the harness when cold with the injector out of the loop disconnect your ecm and injector place a rigged up old brake light socket and 1156 bulb in place of the injector and at the ecm conector run a ground to the body from the pin for the ground of that injector. take a volt meter and do voltage drops between each point this will help isolate where your draw/resistance is in the circuit.

[AZhitman]

So the harness sounds like the most likely culprit in this scenario?

That's covered under warranty. However, I don't think the dealership will go to the extent of doing anything "out of the ordinary" as far as testing. They act like if they can't test it with Consult, they're stumped. Grrrrr.

[Q45tech]

We have a special homemade adapter which plugs into the harness output plug to ease the checking.How accurate is their ohmeter [bad/weak batteries?]With up to 1 ampere [ramp up] flowing in the injector this normally cleans the contacts but you have to look to make sure.

CA and Arizona gasoline just destroy the injectors.

[NISTECH]

So the harness sounds like the most likely culprit in this scenario?

That's covered under warranty. However, I don't think the dealership will go to the extent of doing anything "out of the ordinary" as far as testing. They act like if they can't test it with Consult, they're stumped. Grrrrr.

Actually the light bulb test I gave you is a very common recommendation from nissan/infiniti tech support in a situation like yours. If this hasn't been resolved yet ask them if they called techline for assistance yet.

[Q45tech]

The 90-93 and 94-96 Q and the 300zx TT injectors are/were the same [and there were injector connector corrosion problems on that unit].

The perfect test equipment would be an LCR analyers, which measure inductance [coil of wire] and resistance of the copper wire, and capacitance of the system [from coil to metal housing/pintle of injector].........a fuel injector has all 3 parameters.

Just measured my 3 brand new never used Q spares [12.06,12.11,12.18 ohms [1% variation] on 200 ohm scale of a very accurate [0.25%] multimeter at 72F].

Injectors should be within 1-2% resistance values [0.12-0.25 ohms].........the broad range [2 ohms----16%] in the FSM is to accomidiate less than accurate multimeters, operator error, and where the resistances are measured.......at the injector or at the harness or even at the ecu.

Most multimeters have at least a 1% accuracy with brand new batteries.......doubling that to 2% ..........would be +- 0.25 ohms plus the 0.12 ohm of the real injector variance says the readings should be 12.1 [+- 0.4]= 12.5 down to 11.7 ohms.

I believe many injectors have problems but the tech call them good based on too broad a range!

The ecu has a parameter that corrects for the time delay when current is appplied and the time the pintle takes to lift enough for fuel to flow ...................in the first 1.2 milliseconds only 1/3 of the expected fuel flows at 43.4 psi actually flows and that depends on fuel temperature as it's viscosity changes.

[NISTECH]

So the intial injector resistance greg posted is way out of spec and they should be focusing their diagnosis in that area? In other words trying to find the source of the high resistance?

Dennis what brand/model DVOM do you have?

[Q45tech]

I have 6, some Fluke 87,88, BK Precision Test Bench, and a Wavetek 87XT. All were over $150 and some $300+..........not your typical RadioShack $10-$30 but even cheap one have 1% tolerance on 200 ohm scale........find one with a 200 ohm scale is hard.

http://cgi.ebay.com/ws/eBayISA...25412

Flukes tend to be double priced

[Q45tech]

I have 6, some Fluke 87,88, BK Precision Test Bench, and a Wavetek 87XT. All were over $150 and some $300+..........not your typical RadioShack $10-$30 but even cheap one have 1% tolerance on 200 ohm scale........find one with a 200 ohm scale is hard.

Flukes tend to be double priced . vs say Wavetek or others sometimes real deals on ebay on bench type with batteries.....ugly, old fashion but accurate.........4 digits or more please...........called 9,999 or 10,000 counts.

[Q45tech]

Having a new fresh accurate battery in the multimeter is the key to accurate ohm reading.............as the battery must push its voltage thru the resistance [12 ohm] and the current flow is actually measured and converted to resistance.

Careful as 1 volts of [9volt battery] might be used on a low ohm scale [200 ohm] and the current [83 millamperes] may tax the small 9 volt battery and wear it out fast!!!!!!!!!!!

[AZhitman]

UPDATE:

Here's my latest Consult printout, they're now thinking it's a MAF sensor...

MONITOR - NO DTCCMPS-RPM(POS): 1000 rpmMAS AIRFL SE: 1.31vCOOLANT TEMP: 179FO2S1: 0.12vO2S1 (B2): 0.09vM/R F/C MNT: LEANM/R F/C MNT-R: LEANA/F ALPHA-R: 118%A/F ALPHA: 108%

Any thoughts from the Masters?

Doesn't do much for my confidence when i hear, "Hell, I don't know - Let's see if this helps."

[Q45tech]

CMPS-RPM(POS): 1000 rpmMAS AIRFL SE: 1.31v..........at what temperature and REAL barometric pressure [not altitude corrected as they give on TV].

Probably ok reading as 1.20v at 750RPM at 70F at 900' AMSL

Normal 2,000 rpm cruise is 2.00v.

MAF could be microphonic or have intermittent drop outs........unfortunately the Consult won't code if it passes the start up check and the signal is anywhere close to normal +- 25%........but the engine can throw fits.

Substitution is good it either solves the problem or not.

THE CAS is much the same without serious test equipment and lots of time spent on the road testing. With a scope look at the 360 pulses [plus auxillary 4] per rpm are they all the same height and rise time/shape.........rusty dirty interrupter wheel or sensor.

I know we are speaking of $1,000 worth of modules but you don't pay if it doesn't solve the problem..........luckily you can change both in an hour.