Engine light, poor gas mileage

[joebroni99]

Ive been having some issues with my 92 xlt. First the engine light has been coming on intermittent. I keep getting a bunch of different codes from 565 118 117 and on and on. They change though depending the day i run the tests. Wasnt that big of a deal until two weeks ago my mpg got cut by a third. im averaging 10 mpg. engine idles fine has lots of power. New plugs wires air filter fuel filter and new synthetic oil. All the codes keep pointing to sensors but they just keep changing every day. I didnt want to just start ripping all the sensors out and replacing them until one fixes the problem and costs me alot of money. Any help or suggestions would be greatly appreciated.

Joe C.

 

[boggs1227]

codes 117-118 are for the engine air intake temp sensor....this sensor screws into the upper intake manifold ( should be near the vac tree area )

codes 565 is for the " canister purge solinoid ciricut failure " ...this is for your intake system ...un-used fuel fumes get piped back into the gas tank through this solinoid then to a evap canister ( some people call it the charcoal canister ) then finally back to the gas tank .

to get to this sensor requires a little more time to get to because you can't see it because it's under the fuel rail and injectors ...i dought very seriuosly that you can get it out with out takeing the upper intake off ...not like the other thats easy to see and replace .while your at it you may want to see if you fuel pressure regulater is bad to ...real simple to see if it's gone south ....be carefull to pull the plastic vac line off the fpr and if you see gas or it's wet at all then it's bad .

 

[joebroni99]

So do you know if any of these sensors would contribute to a large drop in fuel efficiency? Im down about 70% of wat i was getting. Averaging 17 to 19 mpg down to 10 mpg.

 

[Maniak]

A bad FPR (fuel pressure regulator) can do that.. There have been a few vehicles that were getting bad gas mileage becuase of the FPR. Usually the diaphram rips and allows fuel into the vacuum line which draws it into the intake. Also, when that happens the fuel pressure as seen by the injectors goes way up (i.e. 60 psi).

Its an easy check if you have an fuel pressure gauge that can read EFI fuel pressures. ($20 tool).

As stated before though, if you pull off the vacuum line from the FPR and find gas in the line you know the FPR is bad then.

~Mark

 

[MrShorty]

KOEO and/or CM codes? SOP is to start with the KOEO codes.

KOEO 565 probably wouldn't effect gas mileage like that. My experience with this one is it either takes a full open or short to ground in the CANP solenoid circuit to trigger it. Shouldn't be too hard to track down with a voltmeter and a wiring diagram, especially if it's a KOEO code (I've only ever seen this as a KOEO code).

ECT is a simple thermistor and can be checked pretty easily with a voltmeter/ohmmeter and a wiring diagram. There have been a few posts with a table of temperature vs. resistance posted.

 

[joebroni99]

Ok did some work. I found that the vacuum line to the fpr was disconnected. And for the low gas mieage i may have found the cause. It appears transmission fluid is going into the intake. Thier is trans fluid coming from a vacuum line connected from the trans to the upper intake. Ive never seen this problem before. Does anybody have some advice for that?

 

[Maniak]

Thats a blow transmission vacuum modulator. There are a bunch of threads on that.. Other being a little difficult to get to, its a somewhat easy fix..

Until that is fixed it will shift funny and as you get trans fluid into the vacuum T you will find hoses are going to get soft and fall off.

~Mark

 

[joebroni99]

Ok changed the trans modular valve. Took apart all the vacuum lines and cleaned them out as well as the sensors. Took apart the upper and lower intake and cleaned the trans fluid out. Changed the oil again and now the engine is running real smooth. Reset the computer and no error codes are posting. Thanks for all your help with this issue.

Joe C.

 

[joebroni99]

ok got more problems. i didnt know if i should continue on this thread or start a new one. well i replaced the trans modular valve, and i added some trans fluid because i had disconnected the cooler lines. i have alot more fluid in it now than should be. i plan on draining it out after i get home from work today. heres the problem: my trans is now slipping out of gear. It is happening in all gears, and it happens wen its cold and hot. Could it be caused by having too much fluid, or is it from the new modular valve? or did i finally kill my trans from running it low on fluid so many times?

 

[boggs1227]

only thing i can say on this is that too much is not good .i'm not going to comment on the internal slippage problem.when i put to much fluid in mine i used a big 2 oz syrnge and a long skinny plastic tubeing.you have to make sure the diameter is small enough to get it past a certain spot down in the filler tube (i imagine the area i'm talking about is just right past the tube where it joins the pan ..maybe 1/4 inch hole to aim for) but once i got it down inside the pan i just pulled it out slowlly ....the syrnge wont let you pull the fluid up fast kinda slow going .

you can use a fluid pump but the first one bought at advance auto ( orange plunger type) did not really do all that hot so then it tried the syrnge and that worked perfectlly .you can get them at "tractor supply company " or any vet will have such items .

 

[joebroni99]

uh oh. I think i found out the problem. Well im not one for reading the complete directions. apparently the small metal shaft that fell out of the old modulator is important and needs to go into the new modulator when installing it. i hope the piece of metal is still in the road where i left it thinkin it was just a broken piece from the old one.