ballerchris510

I am trying to troubleshoot my buddys 1992 maxima vg30e it is running really rough has a bad missfire at idle and clears up alittle when reved above 2500 rpm, also lots of black smoke coming out of exhaust. I disconnected the maf and it idled much better and no black smoke with maf unpluged what would cause this? No cel light, could it be the injectors or maybe the ecu? The ecu was replaced like 10 years ago. Already tried replacing maf with a new one and ran the same. what could cause this it is running rich alot of black smoke? All help is appreciated Thanks

ballerchris510

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ac max 92

iTrader: (13)

Could be running lean. Not enough fuel. The injectors are notorious on the 3rd gens especially seeing it's a 24 yr old car. Try taking a multi meter and check the resistance on the injectors. Each injector should be 10-14 ohm though there is one under the left side of the upper intake manifold under the bend that you wont be able to test without taking off the intake manifold but for starters try checking all the others if they are out of spec. change the ones needed or for piece of mind being you'd have the upper intake off change em all. There is a member in the classifieds that has a used set with the rail up for sale but personally i'd go all new if your going to do the job. That is ofcoarse if that's your problem. Try pulling the spark plugs aswell to see what the signs are for which cylinders are causing the problem. Running better when pulling the maf harness sounds pretty strange to me though.

ballerchris510

Thanks for the response I thought it could be an injector how can I go about checking them un plug connector and connect volt meter directly to injector? Car running on or off?

Tiniform

You are checking resistance across the injector pins with car off. Unplug the connector from the each injector, set your meter to ohms, and read across the injector pins - should read between 10 - 14 ohms. Tons of postings on here on how to do it.

ballerchris510

Thanks for the help i appreciate it i will try that later and post the results.

JSutter

iTrader: (46)

How do the spark plugs look? How does the distributor cap and rotor look?

ballerchris510

Plugs look ok some carbon build up not to bad rotor and cap still look good.

ballerchris510

Checked a few injectors a few showed 13.5 and one showed 23.5 ohms. It looks like a pita to change the injectors, what i still cant figure out is why the car idles almost perfect with maf unplugged only thing is with maf unplugged car wont rev past 2k rpm's. I have been starting the car like that for a few days without a problem.

ac max 92

iTrader: (13)

The car may start with it unplugged but won't run properly. Does seem strange it would idle well unplugged though the ecu would probably be advancing or retarding the timing to compensate for the mixture being you have an injector or more out of spec. As for your injectors like i previously mentioned change the ones that are out of spec. or change them all for piece of mind and not have to worry about them again for years to come being you'll already have the intake off. It can be a bit of a pita if you havent done it before. You'll need to get yourself some intake manifold gaskets too and put new gaskets when your ready to clean up and put everything back together. Just take some pics. so you remeber where all the vacume lines go back and make sure all the injectors are seated properly in the rail with no pinched o rings etc. or you may find yourself taking everything apart again. Probably wouldn't hurt to change the pcv valve aswell for what they're worth though it's a simple one and only takes about 5 minutes but that can be done anytime without removing the intake. Do a search and you should be able to find a write up somewhere on changing the injectors and ofcoarse if your stuck you can post back and get some help.