Performed Nissan Consult and Power Balance Test Today

[PopPop]

My Q still had the miss-fire off idle and sometimes during acceleration. Took it to Infiniti dealer after I tried all I could to no avail. Told dealer I wanted consult and power balance test done. I waited for 3 hours for them to tell me that they couldn't find anything wrong. He said that the Tech said it was the strongest running 1st gen. Qs he have ever driven. I told him that I always keep car as fine tuned as possible but, it still has a miss. He said Tech couldn't find anything. I said what did the consult and power balance test show. He said we couldn't do one because your 91 is to old. I flipped the F''K out . I told him that he needs another job if he thinks you can't P.B. and consult a 91 Q. I told him there better not be a charge for 3 hours of nothing. He said NO CHARGE! I left and went to a friend of mines who works at a Nissan Dealer and told the service lady I wanted my friend to work on my car and do an consult and P.B test on my car she said $98.00 I said OK. I went into the shop with him and we did a consult and P.B. Test and only things we could see was the O2 sensor was acting different from the other one on Bank 1. The readings were the same under load but, at Idle the one was off. We checked for vacuum leaks but found none. The coolant temp. sensor was running a little cool for the car being run constantly for about 40 minutes. It was around 165 degrees thought it should have been in the 180 degree mark. I replaced the coolant temp. sensor about a week ago so I was thinking Thermostat might be opening early but, that wouldn't cause miss. ALPHA & ALPHA 2 were at 100% and 102% respectfully. Timing was at 15 @ BDC the same when I checked with timing light. We seen nothing serious but, could hear and feel the miss. We finished up and he said I'm just going to put you down for an 1/2 hour labor $48.00. I saved a lot of money thanks to having my buddy at the dealer and went home and tore down the valve covers and found #1 & # 3 plugs were cracked up the sides of the plug. These were brand new Nissan NGK plugs only 2 months old now what would cause 2 brand new plugs to crack. I went back to dealer bought the new plugs and replaced them. Preliminary test seems ok so far no more miss.

[Flagship-Q]

Maybe from overtightening? Just a thought.

[3Q Jay]

i *think* the consult timing reading is always 15° BTDC--meaning the consult doesn't rally know the base timing, only what the ECU does to change from a constant 15 base.

how did you discern the crack on 1 and 3 insulator? if visual, are you sure it wasn't there all along from shipping damage? my guess would be damge during install--not insulting your wrenching, just seem to be quite sensitive on torquing. shame me if you must, but i never got quite to 14# on torque when i last installed on the g50. threads were starting to feel like they were relaxing ( i had put a dab of anti-seize) so i stopped before strip.

what were the p.b. drops?

[Q451990]

I would go ahead and replace the thermostat. The rubber seal breaks down in a few years and doesn't allow it to close completely. A cool-running Q won't warm up enough to go into "close loop" so your fuel economy will suffer, and you could damage your catalytic convertors. I would consider replacing the O2 sensors too... they get sluggish over time.

Did your knock sensors check out OK? I'm also very interested to hear your Power Balance numbers. Any major variance (more than 12RPM from one cylinder to the next) means it's probably time for a pressurized injector flush. It'll make a world of difference.

Heath

[PopPop]

Always important to torque spark plugs on aluminum heads because the last thing you want is to put an spark plug insert. I'm always careful with spark plugs but, I also thought of the damage thing prior to installation. I always check the electrode tip to make sure its properly gaped but, never really checked for damaged exteriors! P.B. drops were good on all cylinders and cracks were arcing style cracks. I don't have the print out so I can only give certain numbers off the top of my head. Your probably right about 15 BDC!

[PopPop]

Heath I already have Thermostat on my things to do list. If the loop wasn't closing I thought Consult would show that in number variances! I also remember racers installing a cooler temp. thermostat for more HP! I know for a fact that certain chip up grades call for also installing a cooler thermostat to increase performance output. Knock Sensors were good and O2's were in range. I ran temp. checks on both O2's and they were with-in specs. All the spark plugs were golden brown! Your right about cat's also! I tell people all the time when you let a problem go un-fixed for a long period of time. It will damage other components! Cylinder to cylinder variances were in range except #1 & #3 but, those were the two with the cracks. I keep up on the fuel system. Fuel pressure auround 34 psi and injectors were 12.9 to 13.0 on all eight around a week ago.

[Q451990]

If you can get your buddy to run a new power balance test with the plugs, I would recommend it. Even with good maintenence, it's nearly impossible to keep the injectors performing as new. My 60 - 70K mile injectors on Q1 had a substantial variance between injectors 1-6 vs. 7-8. Dennis (Q45Tech) mentioned this is common, but we're not sure why. Maybe proximity to the exhaust (pre-cats) cooks the impurities in those faster? I think I was seeing something like a 78RPM drop on most injectors and only a 40 or 50 RPM contribution from 7 and 8. A pressurized rail flush brought them all to an identical drop! Keep in mind that the Consult will give an "OK" verdict as long as the cylinder is reading almost any RPM drop during the test - so you have to know and interpret the actual numbers.

Heath

[Q45tech]

"If the loop wasn't closing I thought Consult would show that in number variances! "

You can force the Consult test in Manual override or wait 5-10 minutes for the lockout [temp] to go away.

Consult I rounds to nearest 12-13 rpm.............75,87,100,112,125

Newer Consult II SHOWS ACTUAL RPM no rounding.

[PopPop]

The Consult was a brand new one because someone had just stole the old one around new years! I still wouldn't know if that would make it the II version just because it was new.

[Q45tech]

My point was if Nissan thinks +-6 RPM was immaterial so should you.

On early Consult it was impossible to tell whether an 87 reading was a rounded up 81 and a 75 reading was a rounded down 80.

A print out that shows 12 rpm variances could be ignored whereas a 25 rpm variance should NOT BE.

The Consult works by locking the ignition advance and injector fuel time along with the IAC duty cycle so nothing changes as athe injectors and spark are sequentially shut off except the rpm.

Since each cylinder provides 12.5% of the total torque [over 2 rpms] and supposedly creates the same drag [negative IMEP and friction] as it is shut off...........all that remains it the locked test rpm [BASE RPM REPORTED]which is a function of IAC bypass setting and TB cleanliness.

Some times a dead cyclinder will appear to gain rpm as not spraying and thus not compressing fuel that never burns is less loss/less work for the engine.

In tough case I do 3 -4 power balances: mormal in park, one in gear with AC on max lights on to load engine, and may tweek the IAC manually to change test base rpm.

Given the time I like to BG44k/rail flush the injectors, clean intake system..make everthing shiny to minmize the rpm variance.........it always makes the engine feel smoother and peppier in real world driving.

Medium low compression almost never shows up on power balance unless it is so bad as to cause a total misfire.

A misfire can show at idle rpm [650 in gear] and not be picked up during a regular test at 1100 rpm Base Test Rpm.

[PopPop]

Thanks for the info!

[mattd1979]

Q451990,

Here are the most recent power balance numbers to my Q that I pulled with the Consult II at work. Let me know what you think.

No.1 48rpmNo.2 56rpmNo.3 64rpmNo.4 70rpmNo.5 74rpmNo.6 78rpmNo.7 72rpmNo.8 78rpm

Coolant temp at 183 degreesCMPS-RPM(POS) 1124rpm

P.S. I also have bad knock sensors which I intend to replace this weekend.

[Q451990]

Q45Tech is the man to ask, but if it were me I would ohm injectors 1 & 2, and assuming they are in spec, go ahead and do an injector/rail flush. It should help bring things closer together...

Knock sensors will do a lot to help your performance too - since the car is in "bad gas" mode at all times when it doesn't get a signal from the knock sensors.

Heath

[PopPop]

Q451990,

Here are the most recent power balance numbers to my Q that I pulled with the Consult II at work. Let me know what you think.

No.1 48rpmNo.2 56rpmNo.3 64rpmNo.4 70rpmNo.5 74rpmNo.6 78rpmNo.7 72rpmNo.8 78rpm

Coolant temp at 183 degreesCMPS-RPM(POS) 1124rpm

P.S. I also have bad knock sensors which I intend to replace this weekend.

How far will the coolant temp. sensors temp. rise above the factory 170 Degree Thermostat? I know that Aluminum Heads do not like heat!

[Q45tech]

The oem factory thermostat is speced at 194F 100% open.IF THE TEMP rises to 195F the ecu starts decreasing ignition advance! To decrease power output................this can lead to thermal runaway once the ecu has reduced advance by 5 degrees: [195F>200F>205F>210F >215F]

The design temperature is supposed to be no less than 174F and not to exceed 194F.

People get confused at the above since the theromstat MUST BE Partially closed to regulate.

Themostats on Q fail from the rubber seal failing, allowing too much flow that the closing of thermostat cannot control.

Failure to reach 174F means the thermostat MUST BE REPLACED.

Many shops leave cars out overnight vs Nissan assumption that in the shop they will be started at 60F..........thus short Consult time lockout [10 minutes] which should actually require only 5 minutes to warm up a 60F coolant Q.

I would say half the Q I test won't warm up to 174F in winter.........they get close [meaning thermostat is worn] and still should be replaced.

Aged O2 take longer and longer to become sensitive and allow closed loop control to drop out fast as soon as the speed drops to idle.

AS new requires new parts frequently, some like thermostat every 30k and O2 every 60-100k.

OBVIOUSLY cylinders 1,2, and 3 need attention = BG 44k and or a BG Concentrate rail flush.

I have a trick which shows if a rail flush will help: Use non biting pliers to close off fuel return rubber line in repeated but very short [ a second closed then wait 3 and repeat 10-15 times to raise rail pressure from 34psi to 60-70 psi to force trash thru the injector screens ----- fleck off carbon/deposits from injector tip..............does power balance ratios change? It should get temporarily better.

Usually helps without doing much fuel pump damage [pump has it's own blow off high pressure valve]. Afterall the pressure rises to 43.4 psi under acceleration.

[PopPop]

The oem factory thermostat is speced at 194F 100% open.IF THE TEMP rises to 195F the ecu starts decreasing ignition advance! To decrease power output................this can lead to thermal runaway once the ecu has reduced advance by 5 degrees: [195F>200F>205F>210F >215F]

The design temperature is supposed to be no less than 174F and not to exceed 194F.

People get confused at the above since the theromstat MUST BE Partially closed to regulate. QTech so whats the purpose of putting 77 degrees celsius on the bottom of the thermostat which is around 170 degrees fahrenheit if its not the actual temp please explain!

Themostats on Q fail from the rubber seal failing, allowing too much flow that the closing of thermostat cannot control.

Failure to reach 174F means the thermostat MUST BE REPLACED.

Many shops leave cars out overnight vs Nissan assumption that in the shop they will be started at 60F..........thus short Consult time lockout [10 minutes] which should actually require only 5 minutes to warm up a 60F coolant Q.

I would say half the Q I test won't warm up to 174F in winter.........they get close [meaning thermostat is worn] and still should be replaced.

Aged O2 take longer and longer to become sensitive and allow closed loop control to drop out fast as soon as the speed drops to idle.

AS new requires new parts frequently, some like thermostat every 30k and O2 every 60-100k.

OBVIOUSLY cylinders 1,2, and 3 need attention = BG 44k and or a BG Concentrate rail flush.

I have a trick which shows if a rail flush will help: Use non biting pliers to close off fuel return rubber line in repeated but very short [ a second closed then wait 3 and repeat 10-15 times to raise rail pressure from 34psi to 60-70 psi to force trash thru the injector screens ----- fleck off carbon/deposits from injector tip..............does power balance ratios change? It should get temporarily better.

Usually helps without doing much fuel pump damage [pump has it's own blow off high pressure valve]. Afterall the pressure rises to 43.4 psi under acceleration.

rp

[mattd1979]

I just pulled the intake off last night and found a rats next along with the knock sensor harness chewed completely through where it branches off and goes to the passenger side knock sensor. It looks to me like the harness is going to be $170 along with all of the other little hoses that I am going to have to buy(not including the already payed for hoses that came with the under plenum kit from Infiniti of Scottsdale.)

Matt

[Q45tech]

While you are there, remove and examine Knock sensors with a magnifying glass for the start of tiny cracks in plastic.

[mattd1979]

I am going to replace the knock sensors with the harness. I was originally going to replace the knock sensors to begin with until I found the harness had been chewed through.

[99q45t_vl]

Looks like the Florida rats like the Qs

[Q45tech]

Usually more of a problem with Lexus----rat's nest

[mattd1979]

Ok here are the results from checking the ohms on the injectors. the number 1 injector is at 17.4 ohms while the rest range between 12.0 and 12.3 ohms.

Matt

[Q45tech]

17.4 is that at the injector or thru the connector and harness?

[mattd1979]

That reading is at the injector after unplugging and putting the negative probe on one terminal and the postive on the other terminal.

[99q45t_vl]

Replace the injector while you are there.

[mattd1979]

What could have caused the ohms to be higher on just that one injector?

[99q45t_vl]

Corrosion from bad gas, among all of the reasons.

[mattd1979]

Ok. I am in the middle of installing my knock sensors and I just wanted to know if anybody has heard if the torque effect would change the reading of the knock sensor. Like if it is tightened to much would it make it to sensitive. The reason I ask is becuase I have two different types of torque wrenches in which one takes more twist to get the same reading as the other. I have one torque wrench which is a clicker and the other uses a needle that runs the length of the torque bar with a gauge mounted near the hand grip and as the bar flexes the needle moves. That is the one that takes more effort to get the same reading. I just want to know which one I should trust. I know I read some where that the tighter the knock sensor is, the more sensitive it becomes but I don't know where I read it.

[goody90q45]

Since the knock sensor is sensing vibration (knock) the torque is very important. I read the same posts as you recently and I seem to remember Q45Tech writing in with a good explanation. I do recall that if they are overtorqued the sensor won't react to the correct range of vibration.

I personally trust the click type torque wrench vs. the fan dial but I am not sure how you could tell that either you own was giving you a correct reading. There must be a way to check (calibrate) them at home. I am fortunate that I can borrow calibrated torque wrenches from work when I need one.

[Q451990]

I seem to recall someone saying that Sears will calibrate them if you happen to have a Craftsman wrench... I haven't confirmed this though...

Heath