Rough idle MAF?

[Damicci]

1994 Q45 194K Miles maintenance history unknown. Previous owner bought from an old couple.

SO driving home last week Monday, car wouldn't accelerate. Got home and car died in front of house. Let it sit after fiddling with things here and there.(Redid the ground to the maf as the wiring was exposed and only about 4 strands were actually still connected. CHecked everything over saw AAC plug was not firmly plugged in.) After about 2 hours of checking this and that, car started up and ran fine. Today get 80% home and car starts acting up again doesn't accelerate. get to parking car dies. after sitting for maybe 15 minutes start it idles rough. unplug maf idles rough dies. plug in maf won't turn over. unplug maf again idles then dies. Get home and go to check temp sensor unplug it and car starts up. drive home get to house and dies again. Temp sensor unplugged the whole way.

Tried checking Ohm on temp sensor and couldn't get a good reading. (****ty meter)checked maf and on position got about .2- .17 voltage. started up car but due to rough idle couldn't get a good solid reading.

fuel line pressure seems fine didn't check but the feed hose is building pressure. fuel pump is whirring like normal no abnormal sounds. this just randomly started after giving the car some throttle last week. other than that the car has driven fine. And will probably drive fine for a few more days until it acts up again.

Any thoughts? I will be checking the coolant temp sensor with a real meter later on today.
Modified by Damicci at 3:24 PM 6/17/2008

[Damicci]

The ECT shows .38 kOhms at Idle and car in on position Temp gauge shows car at operating temperature.

MAf was about 1.17 VDC and rose when opening the throttle. seems to be working fine as well.

No CEL either.

But now like I mention the cars runs fine (since sitting for about 2 hours.)

Another

Will try cleaning maf while I am at it.

[goody90q45]

.....fuel line pressure seems fine didn't check but the feed hose is building pressure. fuel pump is whirring like normal no abnormal sounds. this just randomly started after giving the car some throttle last week.....

It's pretty hot in Tuscon, ecpecially for a feeble FPCU tucked its entire life underneath the scorching hot rear deck. If you're not hearing any abnormal fuel pump noise (beehive in your trunk), and have no CEL or ECU codes, then I'm guessing bad solder joints in the FPCU. Have you looked at the FPCU connector to see if there's any burning or melting?

[maxnix]

1994 Q45 194K Miles maintenance history unknown.

What, you haven't done any? Never obtained Infiniti dealer performed service history? First thing to do is change out all fluids and filters for a baseline. Then inspect and start replacing obviously bad components.

Probably not MAF wire element unless air filter are non OEM or abused by lack of changing.

[Damicci]

I know I know

I admit my ignorance, and that's all I can do.

I am scheduled a transmission flush for this week. I have a borrowed vehicle I will be using for a while until i either decide to part out the car and scrap the chassis or find out what are the problems and fix them. The car ran great and now a year later here I am.

[Q45tech]

"The car ran great and now a year later here I am."

What happens when you don't spend the $2500 per year or do equivalent self repairs.

Bad things pile up and hit you all at once in the gonads.

Luckily we all now spend $3500 per year on gasoline so the required mainteances look smaller.

[Damicci]

I spent time doing oil changes, replacing belts valve cover gaskets and spark plugs but didn't know about the fpcu and other such things.

[Q45tech]

Funny I've been discussing FPCU on Net since 2000 and dealers have been replacing FPCU since < 1993..................on 300zx, J30, and Q45.

ASk any Nissan technican how many dozen they have replaced personally because of owner abuse of pump.

[maxnix]

Q45tech does have a point. Spending 30 minutes every evening reading the previoius posts where the rich original discussion of these failure phenomena offersa more profound explanation. With a little study, even the most desk bound newb can know more than most junior Infiniti Techs in a couiple of weeks when it comes to the G50 in particular.

[Damicci]

Hey I am not blaming anyone but myself.

I wasn't sure what exactly bees in the tank sounded like sothat's why I mentioned in the beginning post about not hearing anything strange. I am used to S13 Fuel pumps being obnoxiously loud. whalbro in particular.

Anyway, Looks like the pump is bad. And the ohm reading was 1.12 at times then if i wiggled the connector would drop to as low as 4-6. But ripped all the trunk stuff out and took a second listen to the pump and there were bees in my gas tank. It was very loud and sounded pretty bad.

The FPCU connector visually looks ok no burning smells or anything. I guess Should still consider replacing it. Car started fine and i was able to move it in front of the garage to being inspection.

I am sure I need a new fuel pump at this point though.

Don't get me wrong, I appreciate all the help you guys provide. I suck when it comes to car trouble shooting but am mechanically inclined to do the needed repairs. Hell I did diagnose and replace my brake booster.

Thanks again for all the help any any other suggestions.
Modified by Damicci at 10:29 PM 6/16/2008

[maxnix]

Yeah, the brake booster was a real first time anomaly.

The solder can melt and solidfy when cooler, so don't ocunt your self out of the woods yet. Do replace FP before driving again if possible. Get a new O ring also. Great write up in this forum.

[Damicci]

Thanks I read about inspecting the FPCU so I will try to repair myself. I am pretty handy with a soldering gun "earn my keep"

I will call Joe and order a pump tomorrow. Thanks again.

[Damicci]

Just talked to Joe, amazingly nice guy. got pump ordered with new O-ring and filter.

Tank is fairly full so I can't tell if the bottom is dirty, i can see metal and no debris though.

I opened up the FPCU and it looks fine. The solder points #4 and maybe #8 (directly beneath #4) looked to have a little damage around the solder points, but on the terminal the board looks to have bubbled but not burned. ????

Anyway Thanks for the help.

[fixer]

ohm injectors when engine the problem is present, dont wait till it cools, if engine is idling rough could it be a dead cylinder because of the injector?