HELP HELP HELP...'92 Q45 Fuel Consumption

[werepe]

PLEASE SOMEONE HELP ME...I'm about to go bankrupt. My car is burning fuel extensively. I went thru half tank in only 80 miles. I filled up my tank and drove literally about 80 miles and the tank was already at half mark. The car bas been bad on gas for a while so I try to only drive on weekends for weekend fun. Now my primary to/fro car has broken down and I had to revert back to the Q and I'm crying for help. I've used 85 dollars worth of gas in 4 days with little mileage. PLEASE HELP.I've changed the injectors to 2nd Gen injectors, fuel pump has about 17k miles on it, spark plugs have about 10k miles. Please help me...I'm desperate for help. My bank account is about to dive into the RED if I don't find a solution soonest.I'm in the DC, Maryland, VA (DMV) area.THANK YOU!

[Q45tech]

Unfortunately MODIFIED Q engines ["I've changed the injectors to 2nd Gen injectors"] come under the category of "So Sorry" better luck next time American. Gasoline consumption is a multiple of inj open time in ms, fuel pressure, and rpm..................of course inj o ring leaks are a special condition

Without HARD ACCURATE DATA impossible to diagnose precisely.

[RustyBucket]

What steps have you taken to troubleshoot and diagnose?

Dow does it coast? Does it feel like a brake could be dragging?Does the exhaust smell like it's running rich? How does the engine idle and run? Have you checked your MAF?

I had higher fuel consumption a while back that I tracked down to a bad MAF. The car was also running rich and not idling right. The only other time I've noticed high fuel mileage was when we got a blizzard and I was driving around in deep fresh snow and ended up getting stuck several times. Spinning the wheels and idling for long periods of time while you dig eats up gas. 60Lb of bricks in the trunk to aid winter traction also doesn't help mileage any.

Driving style can also have big effect on fuel consumption.

[werepe]

Thank you RustyBucket for the input. It definitely smells like gas when it's running...especially the first 5-8 minutes. You can smell the gas very well. It does seldom hesitate sometime but just for a few seconds while taking off from rest. It cruises on the highway fine but consumes a lot of fuel.thanks.

[werepe]

Mr. Q45tech, please don't blame me for changing the injectors to the 2nd gen ones. I got fed up of changing the old ones almost every 4 months since i was putting used ones rather news (too expensive to afford). I read somehwere on here that the 2nd gen ones were more durable so i ventured into replacing mine. Was that a bad idea? Can that be the culprit of my problem? It wasn't burning this much gas before until recently.

[Q45tech]

You read here that some allege that 2nd gen are more reliable however as I've pointed out [many times] we see as many 2nd gen failures as 1st gen.

My brand new 1st gen on odd bank have now lasted 22 months since installed. Quite a bit better than 12 month warranty promise. {if they fail tomorrow the cost will have been $34/month}.

In fact zero replacement 1st gen oem injectors have failed since we started replacing them in March 2008 when GA went to E10 gasoline.

You and rest of US CHOSE to use E10, you could have filled up at airports or removed the ethanol chemically prior to using in Q45.

So far I've gotten 8 months on my used 1st gen rail on even bank.

[qship96]

You read here that some allege that 2nd gen are more reliable however as I've pointed out [many times] we see as many 2nd gen failures as 1st gen.

My brand new 1st gen on odd bank have now lasted 22 months since installed. Quite a bit better than 12 month warranty promise. {if they fail tomorrow the cost will have been $34/month}.

In fact zero replacement 1st gen oem injectors have failed since we started replacing them in March 2008 when GA went to E10 gasoline.

You and rest of US CHOSE to use E10, you could have filled up at airports or removed the ethanol chemically prior to using in Q45.

So far I've gotten 8 months on my used 1st gen rail on even bank.

Considering the replacement injectors have all survived this long, it makes one wonder whether the entire "ethanol" problem is due to old heat cycled damaged plastic injector bodies.....just like the knock sensors. nissan failed to effectivly control under-plenum heat buildup and/or did not spec plastic that could take the heat cycling long term. Sure sounds like an engineering issue to me.

[goody90q45]

PLEASE SOMEONE HELP ME...

I can't quote Q45T*ch since his writings are copyright protected but the probable answer to your problem is in bold in his first response. The chances are good that you have a leaking lower injector o-ring coupled with a possible loose fuel hose connection under the plenum. You could even have another injector going bad.

Start with a fuel pressure leak down test by teeing into the fuel inlet hose past the filter. Turn the ignition to the ON position and listen for the fuel pump to pressure up the fuel system. Turn the key off and see if the pressure holds at at least 35psi. If it drops off quickly you have a leak. Fuel hose leaks are pretty easy to spot in the dark with a flashlight for the first few minutes while the engine is still cold. The dripping may stop once the engine warms. Start at the rear under the plenum on the passenger side.

How's your engine oil look/smell (of gas)? Might as well ohm test the injectors while the hood's open. Good luck.

[Q45tech]

Take a few hours to metally visualize the fuel flow.For example at 60 mph [2000rpm] that's 8 injectors squirting every 2 revs or each injector squirts 1,000 times in a minute.

In 1 hour [steady speed hour] the injectors combined squirt 2.4 gallons or 307 ounces.

Hopefully you will see the importancae of 1.8 msec vs 50% more which is roughly what you are alleging is the consumption.

The O2 sensors can signal the ecu to only enrichen the system by 20% max.The MAF has an extraordinary wider range, as does the coolant temp sensor and TPS.

[Infinitiguy19]

It might be what the above posters said or see this: zerothread?id=382897.

Were all the parts OEM?

Do you have anymore info on this problem?

Quote » Q45Tech7171 One thing to look for would be an air or vacuum leak that is getting into the air intake system after the MAF sensor. When thecar is warm, the ECU does not enrich the fuel mixture. If air is getting into the system that is not measured by the MAF sensor in theintake, the extra air leans out the mixture. This usually results in poor warm start and idle.Check to see if there is a loose or cracked vacuum hose or clamp. One way mechanics check for vacuum leaks is to spray a little gas(butane or methane or ?) in various spots and see if the idle RPM goes up and it smoothes out. If so, that indicates that the gas got intothe intake system, and that air is sneaking in through that spot.Have you recently disassembled the intake system or vacuum tubes? If so I would check there first - maybe you forgot to tighten aclamp or replace a vacuum hose. Make sure all vacuum hoses are connected, since this is an easy way to create an air leak in thesystem. See Q45tech's response to recent inquiry about cold start problems. I don't know if crank angle sensors would show up only inwarm start or not. A bad coolant temperature sensor might. I do think it is a good clue when the problem is only when warm andsuspect that something is making the mixture too lean. I had exactly those symptoms once when I forgot to reconnect a small vacuumconnection. sensor/speedometer [1] panel driver assembly or speedometer[/quote]Modified by Paul Wall at 11:37 PM 3/18/2010
Modified by Paul Wall at 11:38 PM 3/18/2010