Intermittent Idle Problem

[Jesda]

So, I cleaned the TB, replaced the air filter, cleaned MAF (twice), cleaned CAS connector, cleaned TPS connector, ran injector cleaner at 1/2 tank... everything's running much smoother overall but I'm still getting idle problems.

Once in a while, and only when the engine is warmed up, I'll come to a stop light and the idle will start to fluctuate and sometimes the car will die. If I restart the Q its as if nothing happened. When the idle fluctuates, I sometimes get a strong fuel smell.

Also, on the interstate with cruise on at 60mph it feels like it sometimes gets "stuck" then "frees" itself, like the car is lightly choking on something for a moment?

Is it time to replace the fuel filter? I'm completely out of ideas. I can't duplicate the problem at all -- its entirely random to me. Happens on hot days and cool days. High or low humidity. Just now I left the Q idling in the driveway for 90 minutes while I made and ate dinner. I came out and it was fine.

-Jesda

[elwesso]

When was the lsat time fuel filter was replced??

$10 for an OEM you cant go wrong!

[Jesda]

March 03, 20k ago. I guess its due. Hell, even if it doesnt fix the problem I suppose its worth doing as PM.

[elwesso]

Seeing how my Q does this same thing, ONLY when restarting from a hot soak, I think it HAS to be electrical...

[metaverse3]

hmm..check your grounding points...especially the one for the MAF sensor.. The last time I checked this problem, it was on an Altima with a faulty fuel pressure regulator.. Might help with a fuel pressure gauge hooked up to the rail and drive for a while..

[Jesda]

Hmmm, Im starting to think electrical too. Since when it does happen, letting off the brake and turning off the fan helps a slight bit, like somehow reducing the electrical load helps.

That used alternator that was installed by the last owner in 2001 is getting suspcious.

[elwesso]

Used alternator..... Cheap battery...

NOW We're getting somewhere!!!!!!

[Jesda]

Found this thread... http://nissaninfiniticlub.net/...tuate

Looks like I'll start with replacing the battery. Alternator will follow (its overdue).

-Jesda

[squeefoo]

I accidentally ran my battery down to zip the other day. I drove it last night and remembered the ECM has to relearn, after strange OD shifts, loopy idle events, ETC. If your alt.has bad diodes AC will go through the system and cause strange things too (for the ECM). Test for AC with a multimeter at the batt. I forget what the tolerance is... can't be much, don't know if it's in the FSM or whether it has been addressed here at all (oh Q45Tech!). I'll try to find something out tomorrow. Hope this helps.

[Jesda]

Went out just now to clean the battery terminals. Sprayed some electrical cleaner, wiped. Reinstalled the terminals.

Started the Q... nothing. A very faint ding ding sound and the air bag light was very slightly on. Went out, wiggled the cables at terminals a bit, and I was able to start.

The plot thickens...

-Jesda

[squeefoo]

http://www.allpar.com/eek/alternators.html

You might find this interesting...I'll look tomorrow to find AC tolerances in my library.Yeah I know it's from a ******** website I hope I don't create any germ vectors here! :grin

[Q45tech]

Under 100 millivolts of AC ripple [140mv =-40 db down] ..... 70 mv = -46 db ~~ 1/2% ripple.

Different brands of batteries will have differnt abilities to supress ripple [act as a capacitor].

Really need an oscilloscope to view the condition of the 3 phases.........those cheapo alternator tester often show good when it is bad!

[HeavyDuty]

I, too, would check/clean/replace battery cables, replace the fuel filter & check for a weak ground at the MAF.

[redmanfx]

I had an issue similar Jesda and I had to replace the terminal leads to the battery. They didn't look to bad to me, but when changed the problem was gone. They are about $1.50 If I remember correctly. Not saying this is your problem but it has an eerie simularity to it. I'll be interested to find the cause of your problems.

red

[pito11213]

I would say since the car cut off while you were at a stop that it is related to the maf in some way. I would also try the fuel filter as recommended just because.

By the way I read you epinion review and enjoyed it. Nice plug for nico.

Did you try that throttle position sensor out?

You could get the voltage checked out to see if it is within spec

[Altiman94]

don't just start replacing parts for no reason. have your alternator and battery tested. Dont go wasting money on things that you dont need. Check injectors for leaks if you are smelling fuel, fuel pressure regulator for good flow, and also the fuel pump for proper flow.

[Jesda]

All of these things are overdue for replacement. I'll get the fuel system items checked, however. Its been a hot summer and the fuel tank hasnt always been full enough to cool the pump.

A big indicator of an electrical problem, is that as I'm cruising on the highway, turning off cruise and AC resolves the hiccuping problem.

[elwesso]

That sort of screams alternator to me... Its possible its running at full capacity maybe just to supply enough voltage!!!