86 740 gle poor milage 12mpg

any suggsetions this is emptying my pockets i have checked for vacumm leaks and none heard or seen any other things?

Reply to
pepe256
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have similar problem with 87 740gle. it starts to cut out like it is starving for gas or has dirt in injectors then runs fine for a while then does it all over again any suggestions to help out is appericiated

Reply to
badboywithbadtoyz

mine was doing that when i was hitting around 55mph then i had the lines cleaned and a fuel filter replaced and that fixed it for me

Reply to
pepe256

_____ If in addition to very high fuel consumption the tail pipe is very black, and smells of fuel, then you should check the oxygen sensor. If it has failed, the ECU will have been running the engine on a rich mixture, causing fuel consumption to almost double. Measure the sensor output voltage as a double check. Generic sensors are available. Is yours a 1-wire or 2-wire type of sensor ? Probably a 3-wire one. If you need details about generic sensors, please email me off-line at c.o.n.t.r.e.x AT s.h.a.w..c.a . You need to be concerned about the cat converter as well because it can plug eventually when the sensor is not working properly.

/ JCH

Reply to
jch

it doesnt really put out black smoke i changed the muffler a week ago and been running it and doesnt really look black so if that isnt the problem any other suggestions

Reply to
pepe256

A long shot but easy to try - our 85 765T ran very rich at high throttle, and with the turbo we could see black smoke as we tried to get it to boost. After driving on the highway the plugs were sooted up. It turned out to be a bad connection at the cylinder head temperature sensor, located under about the #3 intake manifold branch. It isn't visible, but if you stick your hand under there you can feel it. Try pulling the connector off (typical spring latch, just like the injectors) and pushing it back on. Then clean all the goo off your forearm.

Mike

Reply to
Michael Pardee

Are you leaking? Is someone stealing your gas? The fuel is going somewhere, if it's not smoking check the catalytic converter, is it glowing after a drive? If so things to check would be the coolant temperature sensor that connects to the ECU and the AMM, either one can cause it to run rich. If it's running fine and the cat isn't excessively hot then I would suspect a leak or theft.

Reply to
James Sweet

I do not believe that i am leaking and there is no one stealing my gas and im not smoking so i dont know im not smelling any leaking gas under the hood so could it be a temp sensor or what u were saying?

Reply to
pepe256

mine does it when first starting engine. then after running it at higher speeds it idles down where it should. could it be the mass air flow sensor?

Reply to
badboywithbadtoyz

replaced filter but still having same problem any other sugestions? also found clogged catylatic convertor put hole in front of it and seems to help some

Reply to
badboywithbadtoyz

12 mpg means that it is getting about half what it should, which means that it is burning twice the fuel it should. This means that WAY too much fuel is in the cylinders, and you can guarantee that it is washing lubrication off the rings. Get this taken care of ASAP.

A certified shop can place a bypass pipe in place of the convertor for testing purposes. Or you could drop the convertor and start it to see if it runs better- that is, assuming that it is running bad now beyond the bad fuel mileage.

Replacement convertors are available for about $125 on eBay.

BUT- if the car THINKS it is cold and not warming up it could be enriching the mixture. Other things could cause that as well I would think.

If you followed my diatribe on the AMM problem you can see that it isn't always easy to find out what is wrong. Low spark voltage, bad AMM, bad IAC valve, carbon tracking in the distributor cap, bad ignition wires, bad coil, bad electronic ignition ground points, bad fuel pressure regulator... get the idea? Who knows what it could be? it took me two weeks to figure out that it was the AMM and only because I got another one and tried it.

And one last factor that folks sometimes forget... does the car have a locking gas cap? Remember the story of the guy who was bragging about the mileage he was getting in his new VW, and the mileage slowly went up each week to about 48mpg becasue his friends were putting gas in his car each day? Later he was getting 12mpg when they started taking the gas OUT!

__ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"

Reply to
Randy G.

I had the cat in our 85 765T replaced for less than $150 US parts and labor maybe ten years ago. It was at an independent shop in Phoenix a friend recommended.

Isn't there an enormous amount of noise coming from that hole?

Mike

Reply to
Michael Pardee

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