Greetings,
I have a 1993 maxima that is getting horrible gas mileage and is idling rough and very low, in the 300-400 rpm range.

so far i`ve replaced all 6 of the cracked coil packs
the fuel filter
air filter
pcv valve
spark plugs
front valve cover gasket

as I said it gets really bad gas mileage ( 6-7 miles per gallon) and i can smell gas in the exhaust coming out of the tailpipe.
My next step is to replace or rebuild the fuel injectors but before i do that is there anything else i should check?

ETA: It`s a 6 cylinder DOHC engine.

 

Injectors would be your next step by the sounds of it. Test them for resistance with a multi meter. They should be between 10-14 ohm. Probably a bad O ring or pintle cap causing it to leak too much fuel into the cylinders causing your misfire ( bad idle) and the smell of your fuel out the tail pipe. Hopefully it hasn't yet caused damage to your cat or 02.

 

One important thing i should add is that the check engine light has NOT come on so i`m assuming that there are no codes to check, which makes me believe that all the sensors are working correctly.

I checked the front 3 injectors and they were all at 11.9 OHMS, i can`t get to the back 3 because they are under the intake manifold.

so, i guess the next step is to remove the intake manifold and replace the injectors,since i have to remove it anyway to check them i might as well just replace them and the knock sensor too.or, if they check ok maybe i can just replace the pintle caps,O rings and filters on them, that would be much cheaper.

 

CEL on 3rd gens arent really sensitive, they can run like ***** and not trigger it. OBDII is the 3 consecutive fails and trigger, the old systems not so much

any vacuum leaks?

 

Coolant temp sensor maybe? i.e. "It's running with the choke on."

 

This is actually worth checking out - my Engine Coolant Temp sensor failure caused numerous issues, and in my case, when it completely failed, prevented the car from starting at all. Prior to that, intermittently it would idle like absolute ***** and flood itself out if I didn't floor the pedal in time, and take several minutes of my giving it a bit of steady throttle to settle down into an idle of 1900 RPMs, then 1200, then 400, then 2500, then 1000, then start hunting for RPMS, then when it feels like it, idle normally for a bit before doing it all over again at random

ECT failures can cause all kinds of unpredictable wierdness with the engine, sometimes subtle, like the idle taking longer to drop to normal after warming up or bad fuel economy... or in my case, very blatant and erratic symptoms that were difficult to diagnose due to how random they were. It was quite literally the last thing on my list of possible causes of my symptoms, and it wasted a lot of time and money chasing a problem caused entirely by that little guy. Its pretty simple to test if you have a meat thermometer, a multimeter and a pot to boil water in.

Worst case scenario its not the cause and you're not out anything, but if your injectors check out and there are no obvious vacuum leaks, the ECTS is where I'd look next if nothing else stands out as an obvious cause.

 

I removed the intake manifold and checked the back injectors and they all checked out at 10.9 OHMS.
I removed one of the injectors and the first thing I noticed was that there was no pressure or fuel in the fuel rail so I`m pretty sure the O rings are leaking,i`m going to replace them next week and see how that works.

 

could also be a bad fuel pressure regulator or even a dying fuel pump. need to stick a pressure gauge on the fuel line and see what happens.

 

now I`m really confused, this morning i went out to remove the other injectors and when i opened the hood there was gas everywhere.
The hole where I had removed the first injector was full of gas,and the top of the engine was covered in gas.Keep in mind that the battery is disconnected so the fuel pump couldn`t run.
Yesterday there was no gas or fuel pressure in the fuel rail and today there is gas everywhere, where did all that fuel come from,what the heck is going on?
Pressure regulator?

 

Just curious.. was it warmer in the morning than when you had it open yesterday? If you have a fuel line to the tank open somewhere, it's possible that it's simply vapor/air expansion in the gas tank pushing fuel back down the lines.

 

It was about 50 degrees when i went out today yesterday when i was working on it it was about 70 degrees.
There was a lot of gas i would guess at least a half gallon or so all over the top of the engine and in the lower intake plenum.

My wife swears that she keeps hearing intermitent noise coming from the back of the car, I told her the only thing back there that would make noise is the fuel pump in the gas tank but it couldn`t be making noise because i disconnected the battery about 5 days ago. I had to disconnect it because something was draining the battery.
If i let it sit for 2 or 3 days without driving it the battery would go dead, no dashlights would go on, no starter selinoid clicking, nothing but as soon as I hooked jumper cables to it, it would start right up.

I lifted the fuel rail up today and turned the key to see if any fuel was leaking from the injectors.I let it sit for about 3 or 4 minutes with the key turned and no fuel came out of the injectors.
I then removed one of the injectors and there was no fuel in the fuel rail then after about a minute or so I saw the fuel start filling up the hole where the injector was so I put the injector back in real quick.
I turned the key off and disconnected the battery again before i took the injector out so i know the fuel pump wasn`t running when i took it out.

It has me baffled, when it`s running it gets way too much gas but when it`s not running with the key turned it doesn`t seem to get any gas to the fuel rail until I pull an injector out.
I replaced the fuel filter a few weeks ago and i`m 99% sure I put the hoses on the right way.The supply hose from the tank is going into the bottom of the filter and the hose from the top of the filter goes to the fuel rail.

I`m not going to do anything with the fuel injectors they seem ok I`m going to put it all back together next week when I get new gaskets.

 

stick a fuel pressure gauge in line just to see what's going on.

your fuel pump should never run when the ignition is off. it should only run when the ignition first turns on (for about 2-5 seconds to build pressure), then only when the engine is turning after that.

If you are hearing things from the car while the car is off, it could be a fuel pump relay or something causing issues. This could be the explanation for your battery drain too.

What's causing the fuel to puddle in the intake is something else.. you have a leak somewhere on the o-rings or something. second issue that needs to be checked out after you sort the first one.

 

Just an update to let y`all know what`s going on.

I replaced the O2 sensor, temp sensor,PCV valve, MAF, and a used TPS.
I put the manifold back on with a new gasket, replaced all the rotted or cracked hoses and started it up, it runs great now.
Idles smooth at 700 RPM with no missing, and there`s no more fuel odor coming from the exhaust.

I replaced all those parts at the same time so I don`t know if it was just one of them that wasn`t working or a combination of 2 or more of them.I am going to replace the fuel pressure regulator next month because it looks like the original part, it can`t have much life left in .I`m thinking I`ll get an after market adjustable regulator with a gauge on it.

I did notice a new problem though, a puddle of oil (about a coffee cup full) by the inside of the passenger front tire.
I have to go hunting for the leak now, I haven`t noticed any puddles before so maybe it`s not too serious, but oil leaks always seem to be serious.
The oil filter is right there on that side, I`ll check that first, then the oil pan gasket and finally the crank seal.