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1993 Maxima rough idle excessive fuel consumption
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tyrex
Novice
Apr 23, 2014, 3:32 AM
Post #1 of 8
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1993 Maxima rough idle excessive fuel consumption
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Greetings, I need some help.
I have a 1993 Maxima,3.0,DOHC,224,000 miles
My daughter drove to work and the car was running fine,when she left work and started the car it was running rough/misfiring/strong smell of gas in the exhaust/wouldn`t idle kept stalling.
Here`s what I`ve done with it so far:
Replaced worn spark plugs
Replaced filthy fuel filter
Replaced all 6 of the cracked coil packs
Replaced the leaking valve cover gaskets
Changed the oil and filter
Replaced PCV valve
Replaced the oil saturated air filter
OHM`s tested the fuel injectors (all were between 11-12 OHMS)
All of those helped but they haven`t fixed the real problem.The car still idles real rough at about 400-500 RPM`s, I can still smell gas in the exhaust,still getting really poor gas mileage.
I took it on a 40 mile test drive and burned half a tank of gas.I figure it has an 18 gallon tank so 9 gallons to go 40 miles is about 4 miles per gallon.
I currently have the intake plenum removed so I could check the fuel injectors.All the O rings look good and the filters aren`t dirty of clogged.
I unbolted the fuel rail and raised it up so I could see if any fuel was leaking from the injectors when the key was turned,no fuel was leaking but fuel was shooting out of the lower plenum where it leads to the intake valves of the back 3 cylinders.The only way fuel could be forced up the plenum from the intake valve is if the intake valve is open while the piston is moving up.Right?
Obviously the intake valves shouldn`t be open when the piston is moving up.
My worst fear is that the timing chain for the cam on the back 3 cylinders may have broken.
Any suggestions?
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 23, 2014, 3:47 AM
Post #2 of 8
(1761 views)
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Re: 1993 Maxima rough idle excessive fuel consumption
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The only place fuel can come from is the injectors or the incoming fuel line.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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tyrex
Novice
Apr 23, 2014, 4:24 AM
Post #3 of 8
(1757 views)
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Re: 1993 Maxima rough idle excessive fuel consumption
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Thanks for replying,
Here`s the strange part.
I`ve had the battery disconnected for about a week,I had to disconnect it because something was draining the battery after 3-4 days of sitting the battery was so drained i couldn`t crank the engine.when I removed the first injector to inspect it there was no fuel or pressure in the fuel rail.
I had the injector in the house with me overnight and when I went back out the next morning there was gas all over the top of the engine.The lower intake plenum, next to the removed injector,was full of gas.The fuel rail had gas in it and the injector hole was full of gas.
I know the fuel pump didn`t run overnight because the battery was still disconnected after 5 days.
I put the injector back in and connected the battery and When I cranked the engine a few times,all the gas that was in the lower plenum hole shot out and hit my buddy who was standing in front of the car.
I thought that if I cranked the engine all that gas would go down into the cylinder so I was surprised that it shot up and out of the intake plenum.
The air should only be going one way through that plenum,down into the engine not coming up and out of the engine back into that plenum?
it gets even stranger, my wife swears that when she has been out in the yard that she has intermittently heard "noises" coming from the back of the car.I told her that the only thing in the back of the car that could be making "noises" is the fuel pump in the gas tank, but that can`t be intermittently running because the battery is disconnected.
She said it`s a humming/buzzing/rumbling sound coming from the back of the car that lasts for about 10 seconds and then stops.
ETA:
Now that I think about it there couldn`t have been gas or pressure in the fuel rail when I lifted it to check for leaking injectors because After I bolted the fuel rail back in place I disconnected the battery and removed one of the injectors and there was no gas in the injector or in the fuel rail, but after about a min or two gas started slowly filling up the hole where I had just removed the injector from.
I put the injector back in real quick to stop gas from spilling all over the top of the engine.
Thats twice that there was no pressure or gas in the rail both times it only started filling with gas after I removed one of the injectors.
(This post was edited by tyrex on Apr 23, 2014, 5:06 AM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Apr 23, 2014, 5:10 AM
Post #4 of 8
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Re: 1993 Maxima rough idle excessive fuel consumption
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Wouldn't be at all surprised if that engine got hydrolocked and bent a rod or two. Those side feed injectors o rings can destroy a motor if you don't know what is going on and what to look for.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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tyrex
Novice
Apr 23, 2014, 5:57 AM
Post #5 of 8
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Re: 1993 Maxima rough idle excessive fuel consumption
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no, I`m pretty sure it`s nothing like that.
When I took on that 40 mile test drive,once it got above 25-30 mph it ran smooth and quite,had plenty of power.
There should have been 43 psi of pressure in the fuel rail when the car was turned off and sitting, but there was none.Both times that I removed the injector there was little to no gas in the injector well and zero pressure.
When I removed the injector gas should have been squirting out all over.
The other thing that puzzles me is why the check engine light doesn`t come on? There must be no fault codes, which I assume means that whatever is causing the problem isn`t something that is monitored by the ECU.
I think I`m going to concentrate my efforts on checking the fuel system and emissions components.
I`ll find the problem eventually I`m just not going to throw money at the car by buying parts it doesn`t need.So, far everything that I have replaced needed to be replaced.
I`m in no hurry,my daughter bought another car
(VW Passat) and gave me this old thing, she doesn`t want to be bothered with spending anymore money on a 21 year old car 
I`ve been tinkering with it for about a month.so far all the parts that I`ve replaced have only cost $97 total, I got em on E-Bay cheap 
ETA: One other thing I failed to mention is when the car is idling I used my hand to pull the throttle open about half way and when I released it the car continued to maintain a steady,even, smooth high rev for about 4-5 seconds (while the throttle was closed) before it went back down to low idle rev`s and started sputtering and idling rough again.
so, I thought obviously the TPS is bad but when I tried to check it with an OHM meter I got really bizzare readings.
The reading should be 14 OHMs, I believe, but when I set the digital meter on 200ohms I didnt get any reading, so I raised it to 20,000ohms and I got a reading of 2357.1
I`ll try checking it again when I figure out what I`m doing wrong.
(This post was edited by tyrex on Apr 23, 2014, 6:21 AM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Apr 23, 2014, 12:13 PM
Post #6 of 8
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Re: 1993 Maxima rough idle excessive fuel consumption
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The only other place fuel could be leaking into the engine is from the fuel pressure regulator. If the diaphragm is ruptured, the fuel will leak into the manifold via the vacuum hose attached to the regulator.
You have to be absolutely sure your injectors are not leaking when you put it all back together. The bottom O ring inside the injector bowl is the only thing keeping raw fuel from filling up the cylinder(s) and cause hydrolocking. Many 3.0L have met there demise because of that.
When ever I do injectors on those I always use new o rings and then verify the injectors are not leaking before cranking the engine.
You can do this by watching fuel pressure at the rail with your gauge. Pressure shouldn't bleed down. Or you can remove the rail and visually see they are not leaking from the bottom.
Ohm checking a injector coils is fine, but the best way is current ramping them. Coils may fail when they get hot. Of course, ohm checking doesn't tell you the mechanical condition of the injector(s). You may have a sticking injector or one that isn't spraying correctly.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2014, 12:20 PM)
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tyrex
Novice
Apr 23, 2014, 2:00 PM
Post #7 of 8
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Re: 1993 Maxima rough idle excessive fuel consumption
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Thanks for replying.
ok, so the first thing I`ll do is find out why there`s no pressure in the fuel rail and fix that then I`ll pull the rail up again to make %100 sure that none of the injectors are leaking,replace the ones that might be leaking, then replace the lower O rings on all the injectors.
The whole purpose of taking the intake manifold off was to make sure there wasn`t any problems with the injectors so I want to do it right and make sure everything is ok.Idon`t want to go through the expense and time of buying new gaskets and putting it back on unless I`m sure they are working correctly.
Putting it back together without knowing if they are working correctly would defeat the whole purpose of taking it off,and I don`t want that big question mark hanging over my head (are they working correctly or aren`t they?).
Thanks again for replying.
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Discretesignals
Ultimate Carjunky
/ Moderator
Apr 23, 2014, 2:45 PM
Post #8 of 8
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Re: 1993 Maxima rough idle excessive fuel consumption
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Really the only way of knowing if the injectors themselves are functioning properly electrically and mechanically is to send them off and have them flow tested if you want peace of mind and don't want to go ripping the intake off again.
Flow testing them can let you know if they have good spray patterns and they are putting out the correct volume of fuel. 10% or more of a difference in volume can cause misfiring. That same company can also refurbish and clean them if they are good candidates for that.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 23, 2014, 2:46 PM)
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