G50 - Hesitation around 1500 rpm?

[chomer]

Just swapped out a fuel pump. Fuel controller looks good, but trying to figure out where the hesitation is coming from. Last night, I swapped out the fuel filter and air filter and the car feels much smoother.

For some reason, the car seems to hesitate for just a small breath at around 1300-1750 rpms. Once it gets past that, no problems. I had always attributed this to the fuel pump not pumping enough gas... but I'm trying to figure out if it's the injectors or the FPCU. I'm going to get myself another FPCU to make sure that's not the problem, but after reading Texasoil's thread, I'm not sure it's the FPCU. I just bought a VOM at Sears to try to diagnose the injectors, but why do injectors work better at 1500rpm?

[Q45tech]

How small is small? The Q being heavy and the engine being small in displacement for the weight and the engine tuned for high performance creates a weak spot below 2,000 rpm.

Since brand new always weird below 2,000 rpm vibrations and sluggishness...........these were addressed in 1993 by changing to 1st gear start.

But still show up in uphill low rpms in 4th gear with AC on?

Sparkplugs should be replaced every 4 years or 60k which ever is sooner.Timing should be adjusted periodically to 15 Deg BTDC every 60k when plugs are changed to somewhat compensate for chain stretch.

Sure it's not the knock sensors use Consult to verify!

[chomer]

Wow. Ok... lots to digest. Let me take a quick peak:

1) How small is small? It's like a stutter. Hit the gas, it G-G-Goos. It feels like I let go of the gas for a quick second and then mashed it again. Very subtle, and sometimes not very noticable.

2) I have yet to pull the TCU to check the part #. The car feels like it shifts too early too. It's a 94, but it looks like it shifts to the next gear the moment you mash the gas.

3) "But still show up in uphill low rpms in 4th gear with AC on?" - Eh? I'm confused. How's this test again?

4) Do I have to go to Infiniti for the OEM spark plugs? My order for a fuel pump took over 2 weeks to arrive. Also, since I live in FL where winter is 70 degrees, what's the right "temp" to run my plugs? The summers are BRUTAL!

5) Can I borrow a timing light from Autozone? I should loop it around plug wire #1 and shoot it at the crank pulley wheel, yes?

6) How to pull Consult codes without a Consult device? Buy one off of FleaBay?

[96Qowner]

Run a can of BG44K through it first.

[Q45tech]

No plug wires, coils on each plug.

2 weeks the southern warehouse is in Jacksonville .............order things from Scottsdale and save 20% even with freight -----2 days.

Agree BG44k first before you do anything else.

[elwesso]

It almost sounds like normal Q, its not a monster off the line.. but try what the others have suggested and buy you rparts from scottsdale, tell them wes sent you...

Theres a writeup on Q45.org how to check and adjust the timing.

in answer to your quesitons...

3. The point is if its due to the car being low on power at low RPMs it would come on under the worst case scenario.... uphill, around 40MPH wiht the AC on full blast.....

4. scottsdale has the set for like $65 + SH, which is the best price on the internet ive been able to find.

[maxnix]

Do I have to go to Infiniti for the OEM spark plugs? My order for a fuel pump took over 2 weeks to arrive. Also, since I live in FL where winter is 70 degrees, what's the right "temp" to run my plugs? The summers are BRUTAL!

How to pull Consult codes without a Consult device? Buy one off of FleaBay?

You need to call the guys and girl at http://www.infinitipartsusa.com as they can get it to you overnight much cheaper than your dealer can get it in two weeks.

You can try PFRG6 in your climate, but is it really the heat or just the humidity?

You can read codes off the ECU, but a Consult is so much easier and faster.

Got FSM and TSB?
Modified by maxnix at 5:51 AM 1/29/2007

[chomer]

Been busy...

2 weeks - That's from Joe. Eeek. I know he has a good rep here, so I'll give him another shot with some other parts. In a nutshell, it took over 2 weeks to get some basic stuff that was available in stock.

BG44k - Dunked it in on a full tank of premium. Drove on it for half a tank. Then filled back up to max.

PFRG6 - In the evenings, the temp gets to the low 60s, or even 50s in the deadest of winter. This year was mild, last year was tough in the 50s. Yes, welcome to S. FL. In the summer, it is humid *and* hot. It's 100 degrees swimming. The pools don't even need heaters. It's around 80+ degrees. Bath water.

Can I do a laptop Consult? Any results?

FSM - In the trunk with the car. Although reading that is tough. It's not very descriptive.

TSB???

I'm not looking for monster off the line. I'm comparing the smoothness against the 1UZ in our Lexus LS400 from 99. And although that's also not a monster, I'm expecting engine/acceleration smoothness. If you have your foot on the gas, there shouldn't be a stutter (not quite the same as a dead spot).

Interestingly, I've been watching the idle when it's stuttering, and it seems to hang out at 600 rpm, then dips for a second, comes back to 600rpm, then dips for a second.

I haven't gotten a 9V batter in my new VOM to test the injectors. How much do those cost?

And what about the MAF?

[96Qowner]

I'd disregard the MAF for now - doesn't really sound like classic MAF trouble.

Rule out injectors first by ohming them, then look at the intake path in general. You might consider a full BG intake flush if the injectors are all good, or pull it apart and clean it manually.

That 500-600 rpm hiccup sounds like intake/injectors.

There are other possibilities, when those are ruled out.

[chomer]

Thanks for all the help guys.

I just did my usual Sunday night diagnostics.

I ohm'ed all the injectors, and am glad to make the following report:

ALL INJECTORS OHM'ED IN AT 11.8 ohm's through the harness.

I used alligator clips between the positive probe to the positive battery terminal. Putting the negative probe onto the battery post yields a 0.6 ohm response. So far... so good. I used the negative probe to contact the pins on the connector through the harness, and every one of them stabilized at 11.8. I think one stabilized between 11.8 and 11.9, but that could just be a shaky hand.

Whew! One hurdle and expense spared. I already have the BG44k through once, just got the car oil changed today.

So what's next?

BTW, today at the oil change place, the guy mucked with the airbox while attempting to pull the oil filter. Now the car drives worst. It seems to "shudder" all the way up to 2100 rpms. Consistently. I'm wondering if the MAF connector (or even the MAF itself) is bad??? After all, the only thing that changed today is wiggling the airbox?

I'll post KS ohms in a few minutes

[chomer]

Just did the KS:

-289 on one of the X pins-289 on the other X pin

This is with the VOM set at 2000kOhms.

So... do I need to replace the KSs?

[maxnix]

BTW, today at the oil change place, the guy mucked with the airbox while attempting to pull the oil filter. Now the car drives worst. It seems to "shudder" all the way up to 2100 rpms. Consistently. I'm wondering if the MAF connector (or even the MAF itself) is bad??? After all, the only thing that changed today is wiggling the airbox?

Why one never takes ones car to these minimum wage sludge shops.

Oil filter is always changed from underneath after windage tray is completely removed so shocks, suspension and brakes can be checked. MAF connector gets abused from the top.

KS should be 550K ohms.

Sounds like plenum, TB, IAC and EGR valve ceaning is next on your agenda.
Modified by maxnix at 1:19 PM 5/10/2007

[bigal8627]

so what ever happened with the hesitation did it come back is it still there or did it get fixed?