94 Q45 stalls

My 94 Q45 has developed a stalling problem at idle. When cold, it idles fine. When it warms up, it will stall when first started. When the engine is restarted, it tries to stall but recovers with an unstable idle for about 15 seconds and then it is stable. Engine runs beautifully otherwise.

Any thoughts for first step troubleshooting?

My 94 Q45 has developed a stalling problem at idle. When cold, it idles fine. When it warms up, it will stall when first started. When the engine is restarted, it tries to stall but recovers with an unstable idle for about 15 seconds and then it is stable. Engine runs beautifully otherwise.

Any thoughts for first step troubleshooting?
IAC valve cleaning? Any maintenance history for intake and fuel system?

Could be a solder joint on the FPCU if your fuel pump is noisy and therefore drawing too much power.

I took the car to the dealer. They cleaned the IAC valve, changed a leaking # 3 injector and adjusted the timing of the engine. It was smooth for a couple of days. The engine no longer stalls which is good. However, it still shakes when it idles. I replaced the champion spark plugs with NGKS but the engine still shakes. I sprayed carburetor cleaner into the MAF and cleaned the butterfly valve during the spark plug change. However, the engine is still shaking and misfiring during idle. Any further suggestions appreciated. I still remember when the engine idle was so smooth you could not tell the engine was running unless you looked at the tach.

First have them check the fuel pressure vs. rpm and report the results. If not 43 psi at WOT, then suspect the FP and maybe FPCU. Dealer will insist on replacing both for warrranty. But FPCU may be fine.
Have them run a power balance test at 1200 rpm and log it. If there is not a Senior Infiniti Technician (one who was trained on the G50 in 1989 at its introduction), you may be SOL.

Report back the results.

You did well to change back to the NGK pfrg as recommended by the FSM.

Where are you located? May have a better solution for service.

The fuel pump was replaced a couple of years ago......hive of bees in the trunk. I'll have it checked out again. I did notice one thing when changing the plugs....

last time I had this problem, it was the number 3 cylinder. That cylinder had oil around the spark plug when I changed the plugs (installing the champions) before. Replacing the coil on the cylinder solved this problem (very smooth idle) . When I changed the plugs this time (putting in NGKs) I noticed the number 3 was dry but the number 5 had a small amount of oil around the outside cavity of the plug. I've ordered a new coil for the # 5 cylinder to see if there is a low power issue with it. Will change it as soon as it comes in.

I live in Atlanta now. I lived in Connecticut until May of this year. I am finding most dealers no longer want to work on the vintage Qs unless there is a technician on staff that has the patience for the old cars. I get the feeling they would rather not mess with it. Any suggestions for service would be appreciated.

I live in Atlanta now.
Boo on the Champions. You're lucky your engine didn't eat the electrodes and self destruct. Really.

You have the best shop for the G50 in the world. Call Ty at T-3 in Smyrna on South Cobb. If you meet a guy with an old 1990 Q45 that runs like a tiger on steroids, that is Dennis Evans who posts as Q45tech on NICO. Listen to everything he has to say, and if he offers a ride in his car, buy the gas for him.

Tell Ty someone from NICO sent you, and you will be treated correctly. If possible, let Byron analyze your car.

Please report back. Hope you have some cash saved because at the minimum, you need a valve cover gasket job. If you go that far, might as well do all the under plenum hoses and KS and its harness, EGR valve, TB and clean the plenum to save on repeated labor. Read at www.nicoclub.com in the Infiniti Oline Mechanic Forum if you want to attempt to do it yourself, but have T-3 do the diagnosis first so you can budget and triage unless your rich aunt just died.

Get your parts from Joe Tesensky (tell him Brian from Austin sent you) and pay only $5 shipping this month only (special for NICO members).

www.infinitipartsusa.com

The whole under plenum hoses, KS and its harness and VC gaskets will cost you $400 at least. Get the heavy stuff like the upper links now while shipping special is on.

Generally speaking, VH45DE coilpacks do not fail, so you may have wasted money. Hope you saved them.

Brian

email me if you have any questions.