94 Infiniti Q45 mystery missing

[Avery123]

My 94 Infiniti Q45 began missing last summer. No. 1 Mechanic replaced 1 engine coil. Ran great for six weeks. Then started missing. He replaced 2nd engine coil. Ran great for six weeks. Missing. New Mechanic, No. 2, replaced harness wire and No. 5 O ring. Ran great for 6 weeks. Missing again. No. 3 Mechanic pulls 2 codes: bad no. 7 injector and bad knock sensor. No. 2 mechanic replaces both and clears computer but says it is throwing the same codes again: bad injector and broken knock sensor. So, now he says the problem is a bad computer. So--3 mechanics and 900 dollars later--everyone has thrown spaghetti at the wall and I've still got a car that shakes like it's missing, shakes badly accelerating up hill, and yet--no one can say what's wrong with it. Very frustrating--and very expensive.

[maxnix]

You probably would be best served by taking your car to T-3 in Atlanta or Keith Van Meter in Mantua, NJ.

Obviously these guys have no familiarity with the VH45DE and were just guessing.

No mention of fuel line pressure, filter maintenance intervals, nor other intake path and fuel system maintenance. BG44K? Tier 1 Premium always? Mileage?

Welcome to NICO!

[alexander]

I am curious what all the repairs to date have cost you.Were these repairs done at an infiniti dealership?My 96 Q doesn't miss like yours just very sluggish at times, most of the time.Knock sencor code popped during a test drive and would be a $1800 fix.Took the car a different Infiniti dealership and they said KS code could show when it is something other going on, lose wiring etc.He told me to stop future repairs unless I had a s...t load of money to spend on the Q. I have already pluggged 8 grand this year on the car.So good luck.

[Q45tech]

Labor and parts inflation and higher cost in SF, CA make your $8k look just like my $6k in 1998 in ATL at 150,000 miles. During 1999 I spent $7100 and that was the peak year. I decided to limit my subsequent years to a max of $3,000.After a few year by 2002 the only way I could stay in budget was to buy GOOD wrecks [$500] and strip newish parts........[alternator, starter, evap, condenser, fans, AC compressor, dash instruments, switches etc.]

Since 2002 80% of labor has been done on weekends at a $40 per hour discount rate.

I've gotten the M&R costs down below $2,000 per year.

Some things you cannot skim on: Tires, batteries, brakes, bulbs, shocks, and rubber bushings which you must buy new.

Again by planning and luck my only flat bed tow or jump was in 2002.

[Infinitiguy19]

Do you have any service history on the vehicle, I sugest calling your local Infiniti Dealer and getting it, If they don't have it then get a Carfax report and see where the car has been then call the dealer it was sold from for the service history. That said now for recomendations:

I would sugest chaging all the spark plugs, read these articles:

http://www.q45.org/roughidle.html

http://www.q45.org/maf.html,

http://www.q45.org/sparkplugs.html

http://www.q45.org/tbclean.html

http://www.q45.org/ohminjectors.html

Then search around if doing all the above does not help, Or seek professional attention for you and your car because you will have gone nuts after not finding the problem.

But I know it will.

Good luck and Welcome to NICO

[Denver90Q]

Nine times out of ten the fuel injectors are usually the culprits especially in states that use ethanol to oxygenate fuel. If one fails the other 7 usually follow shortly.

On a related matter does anyone know what the ohm readings (infinity?) are for injectors that fail open? The local infiniti dealer claims that usually the injectors fail open and that this can result in hydrolocking the engine.