I'm a new member. Right before the big change, I posted a plea (and paid my 35 bucks) for help. That post seems to be lost in the shuffle now. So I'll try to relate again what happens to my 92Q (133,000) and what I've done.

About a month ago, I bought a new fuel pump (the old one was noisy) from Tom Novak at Infiniti of Lisle. After I installed it, everything was AOK for about fifty miles. Then the engine started dying. At idle and at cruising speed. Every 20 or 30 or 50 miles.

I installed 2 new fuel filters a few days apart. No help.

Before I bought the pump, Tom had me disassemble the fuel-pump controller and check for any discoloration. There was none. But, when the engine started dying, the controller seemed most likely to be the problem. I asked Tom if I could return a controller if it didn't help. I took his silence as meaning "Nope", and, I do fully understand why there is a policy of no return on electronic parts. Tom, then, very generously, offered to lend me his personal controller (a spare part for his previously-owned Q). Unfortunately, no help still. (Tom also supplied every part, perfectly, when I changed my timing-chain guides last year).

Could it have been a bad new pump? I bought another one. No help, again. (Now I have a spare)

During one of our conversations, Tom said that, at his dealership, they often find that the electrical connection between the battery cable and the frame is corroded. Mine was. (I found the perfect wire brush for the threads at a local gun shop) No help.

Each action I took worked for 10 or 20 or 30 miles. Then the car usually screwed up just as I was telling it how great it was doing and that everything was all fixed.

When it dies, I can get it going by pumping the gas. At speed - by pumping and trying to get it to shift down and rev up (and consequently charging at the slowing traffic) and at idling - by restarting and pumping and reving up until it will rev up to 3000 rpm (sometimes takes 2 or 3 minutes of restarting and pumping). Then everything's OK. For a while. I can also keep it running by loading the engine by riding the brakes.

The engine dying happens at random times except that I can count on its dying every day after work. The temp gauge is almost at normal (plenty of sunshine all day). It runs OK for a few minutes and then dies when I climb a small hill. Then I go through the revving-up procedure. Then AOK for 20 miles.

I never looked in the tank. I certainly intended to, but I think the spewing gas threw me off the first time. The second time (after I read the posts and left the gas cap off (no more spewing)), I just forgot to look. So, something in the tank might be the trouble; but, the sock on the end of the intake tube was perfectly clean when I took out the 1st replacement pump, just like the filters were clean.

That's everthing I know. I sure hope I've described enough clues so that someone smarter than me can figure out the problem.

Thanks, in advance, for any advice.

Bob

It sounds like a fuel feed problem, but without having test equipment on it, it's a bit hard to tell.

Check the terminals on the MAF sensor as well, just for good measure.

Hopefully Q45Tech or Professor Mike can help more.

Your temp gage is "almost" at normal?Meaning when you are having this problem it's a little off from normal?Or am I reading too much into your post?(Just trying to make sure the Gurus have all the info they need)

Fred...

could it be just pure coincidence that this started happening after the pump replacement? could it be failing fuel injectors? or maybe you're not getting enough spark in the ignition... could this be the sign of a failing altenator? just some ideas...

Thanks for your replies.

To palmerwmd: When I read through my post today, before I saw your reply, I knew that I was unclear about the temp gauge.

Here's what I meant: At 4pm, as soon as I start the car, the temp gauge is almost at the midway point.

Bob

Maybe biting the bullet and doing a consult will give you enough base data to proceed with a more precise analysis.

I agree with maxnix - Get that thing to a dealer, drop the $100-200 for some diagnostic work and a Consult, and go from there. Post the results here and we'll discuss how much is DIY and how you can do it for less$.

But there's no telling how much damage is being done while it's not running right.

In response to the problem, I know it cannot be the fuel injectors. That only affects the first 10-20 mph of the Q45. Then, everything is fine. Also, the fuel injectors, if bad, cause your car to idle very, very roughly. I know this because I am spending 1200 bucks to get all 8 fuel injectors replaced on Monday.

I would take it to a mechanic as well. Spend that 300 bucks for a tune-up and I'm sure they can tell you what is wrong.

I was discounting the possibility of this, but perhaps the new pump has enough increase in pressure that it dislodged some loose detritus in the fuel line.

Did you check the old filter for contamination after the fuel filter replacement?

Save the fuel in the filter, then let it drain from the inlet side into a glass jar and check for junk. May want to blow out in reverse flow with air to see if anything is captured.

The only problem with that is, that when the car is sluggish & we suspect the injectors being blocked, they will not clean out by flooring it, it will only block them further.

To me, it nearly sounds like the injectors are flooding the engine, & by giving it a boot full, it clears the engine until the next time.

Check the terminals on the Temp. sensor & maybe even replace it, as this is one of the inputs the computer looks at for the amount of fuel it needs. So, if it's reading as a cold engine, it may be putting too much fuel in :thinker or you may have a computer playing up, (bad connections etc) & I can tell you now, without being nasty in any way, a Mechanic won't come close to what a consult can tell you. (I am one & have been for over 21 years, & until I bought a $12,000 machine, I was in the dark to a lot of weird problems in vehicles as well)

Good luck

I had similar symptoms a few years ago, and it turned out to be the ground connection on the MAF. An easy way to check the MAF connection is to press firmly down (or pull gently up) on the connector with your thumb while the engine is running. Any change in idle (stumbling, white smoke or a stall) indicates a problem at the connector.

Mine would stall randomly at idle and while driving, and restarting required lots of pedal pumping just to maintain an idle. If I could get the engine to rev above 2-3k the smoke would clear and the idle would smooth out. Performance was erratic. The problem first appeared after an oil change at a local car wash (Danny's). They removed the oil filter from the top and had to disconnect the MAF to get to it. The black ground wire had come loose inside the connector and was intermittent.

It's a long shot, but it's an easy check. Good luck!

azskygod

Suggest you install a fuel gauge that you can view while driving and see if you lose pressure while the problem is occurring. This should eliminate the fuel pump question. Then you can move on to the next check.

Thanks to all of you for your insight.

Prof Mike - your logical procedure of eliminating the fuel pump as the culprit seemed to me to be the right thing to do.

But, since I don't own a fuel pressure gauge, I decided to try to eliminate another possible source of trouble, that MF connector.

Even though I had wiggled it right in the beginning; it took 3 more sessions of fooling with it to get it to work right.

After reading azskygod's post, with its detailed description of my problem, I wiggled up and down as he suggested. It seemed to help a little. Next, contact cleaner from the electronics store. Didn't help (or hurt), but the next time I noticed that the contacts looked more corroded.

The 3rd and final time, I removed the AFM and cleaned its contacts, and the contacts in the wire-side connector, with needle files and then reassembled the connector with a toothpick-tip-full of dielectric grease on each contact.

That did it.

Again, thanks to everybody; this forum proved its value to me as a viable and valuable source of knowledge.

Bob

P.S. I hope that childish "Mom's car" crap will go away soon.

It's weird, but I just had to do that on my Q the other day, again! Mine just started to idle erratic & accelerate poorly etc, & I hadn't touched a thing.I cleaned mine the way you did & presto, the car flew again.

The ecu is very sensitive to MAF voltage errors because most of the time [non WOT] the air flow is so low. There might be only 0.2-0.8 volt difference between idle and 60 mph cruise [2000 rpm].Remember the voltage range is 1.1-4.4 volts .The ecu compares the MAF voltage to a computed norm and goes into fail safe if outside the range [the temp and air pressure are the external variables and they might be +- 5% from 20F to 120F and 0 to -15% in Denver vs sealevel.........so the guessimate and MAF reading MUST be within 20% [to compensate for a Hurricane in a high altitude] vs the rpm and throttle position sensor //gear vs speed in mph.

Say you leave Atlanta [1000' & 30F]and drive to Miami [80F] ....+3% for altitude and minus 4.5% for temperature netting a minus 1.5% so the idle MAF reading might change by 0.02 volts lower in Miami, at night when the temp drops to 60F the readings would be the same as colder Atlanta.Going from Atlanta to 5,000 foot mountain in NC/TN might lower the MAF by -15% and then raise by 1.5% for colder temp on mountain = 13.5% [1.2 drops to 1.038 volts]

20% of 1.2 volts is +- 0.24 volt variance.The manual says idle 1.0-1.4 volts and 2000 rpm 1.4-1.8 volts, ac off in neutral engine warm.

If the MAF fails while in drive the ecu will attempt to use the guessimate to run the engine but this is not always successful.

Doesn't take much corrosion to add enough resistance to throw these numbers off.

So the numbers you would normally see is 1.0-1.8 [750-2000 rpm], the 4-4.44 volt range is only delivered above 5500 rpm.

Same with the engine coolant temp sensor it normally reads 300-330 ohms at 176F.....extra resistance will make the ecu THINK the engine is colder and still needs extra fuel [super rich] to warm up faster.

Corrosion on the CAS may cause the ecu to loose track of EXACTLY where the pistions are [there are 360 pulses per cam rpm and once every 90 degrees as a backup just in case.......wierd things can happen to exact plug firing when the primary has a signal drop out [looses 5,10,30,50 pulses]especially one that comes and goes. Goes in and out of failsafe!

Glad its fixed!

Just another suggestion to those it doesnt work for. Idle Air Control Valve can cause some of these same problems. Another thing that does go bad rarely, but at times, is the Cold Start Valve. Just to add.

This time it's really fixed

It really wasn't fixed by cleaning and and greasing the contacts. Next I cut off the female connector and soldered the wires to the Air Flow Meter. That also worked great - for a few days.

Next, I replaced the temp sensor. That worked for a couple of days.

Next, I give up

I take the car to Jerry Tucker at All Import Service in San Diego. His technician Steve finds some hoses not hooked up (not the problem), a cracked hose, and (while driving with the Consult) a bad Air Flow Meter.

Fixed - hasn't missed a beat for 10 days.

Bob

RJ:

We are really glad everything worked out ok.

Now go do some Lexus hunting.

Fred...

I used to say the MAF never go bad but this year we have had to replace maybe 5 units - all were over 10 years old, so they do have a finite life.