Guest ekvh Posted March 18, 2008 Share Posted March 18, 2008 Should my O2 sensor readings continue to fluxuate rapidly? In the diagnostic mode, mine runs from 0.0 to around 0.80 and then back every second or two. Does anyone know if this is normal? I am trying to figure where my poor gas mileage is from. I get no codes to help me. I only get around 20 on the highway. I haven't changed plugs and wires yet and I'm guessing that's the next recommendation. I would like to get best the "maybe I'll get lucky" stage of being a mechanic and just guessing at what the causes are.Thanks in advance for any advice. Link to comment Share on other sites More sharing options...
Guest mongeonman Posted March 18, 2008 Share Posted March 18, 2008 I looked in the service manual and it is suppose to run from .1 to .9 so yours is OK.Does the tranny shift to fourth gear on highway?Is the idle ok?I would change plugs and wires first. Link to comment Share on other sites More sharing options...
Ronnie Posted March 18, 2008 Share Posted March 18, 2008 <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ekvh</div><div class="ubbcode-body">I only get around 20 on the highway. I haven't changed plugs and wires yet and I'm guessing that's the next recommendation. I would like to get best the "maybe I'll get lucky" stage of being a mechanic and just guessing at what the causes are.Thanks in advance for any advice. </div></div>Get the car up to normal operating temperature and take it out on section of road where you can get it up to cruising speed. Look at the diagnostic screen and see if the TCC light is on indicating the Torque converter is locked and look to see if the 4th gear indicator light is on.If the TCC is not locked or you are not in 4th gear it could help explain the poor mileage. If those two items are OK, I would suspect the Catalytic converter or exhaust of being restricted some where. If the exhaust is restricted, you should notice a loss of power and the car will usually run hotter than normal after driving for a long period. Link to comment Share on other sites More sharing options...
Guest ekvh Posted March 18, 2008 Share Posted March 18, 2008 The TCC is locking up and in 4th gear. I pulled the boots off the coils and noticed the #1 cylinder's was very rusty and corroded. I was hoping that was it, but alas, I cleaned it and it is still poor. It does have a skip when it idles. It is not consistent, so maybe I just have a bad plug or wire. Thanks anyways. Link to comment Share on other sites More sharing options...
Jim NotreDame IN Posted March 18, 2008 Share Posted March 18, 2008 other things that commonly cause poor mileage besides the o2 sensor are the egr system / pcv system. if either of these are ducting abnormal amounts of exhaust or smog into your intake, you will have decreased mileage. simple things like an old clogged air filter can do this as well. keep your tires up to inflation spec and use the correct weight of motor oil. that's all i know of besides just keeping things running properly. lemme know what else you find out may need attention, i'll take all the mileage i can get. Link to comment Share on other sites More sharing options...
Jim NotreDame IN Posted March 18, 2008 Share Posted March 18, 2008 rough idles are caused by a vacuum leak as well, check out all the vac circuits, they can affect almost everything else in some way.do maf (mass airflow) sensors ever go bad or cause poor mileage? Link to comment Share on other sites More sharing options...
D-a-n-i-e-l Posted March 19, 2008 Share Posted March 19, 2008 do you have a cat on the car? and do a tune up. Link to comment Share on other sites More sharing options...
Guest ekvh Posted March 19, 2008 Share Posted March 19, 2008 Your post asks if I have a cat on the car. Did you mean CRT? I do have both a CRT and a cat converter. Yesterday I swapped the plugs and found the wires to about shot. Some were crumbling away inside the boots. I will get a new set today and see if that helps. The old plugs were fusion I think. Four pronged. I wonder how well they behave. They appeared to be okay color wise. I am at 145000 and I suppose I should do a timing chain replace soon. I wish I knew if the previous owner had done it or not. I lost the motor on an 86 Olds that way. It looks like that shouldn't be too big of job for a backyard mechanic like me.As an American, I am grateful for guys like you who serve our country. Link to comment Share on other sites More sharing options...
Richard S Posted March 19, 2008 Share Posted March 19, 2008 The 4 prong were usually Bosch 4s. Not a bad plug, though I prefer Autolite Xtreme, which can be had from rockauto.com for about $4.50 minus the rebate from Autolite. I would take a good look on ebay for wires. The stock were 7mm. 8s are now common, and I have used both 9 and 10mm which is overkill unless you are on the track, but they really don't cost more than a set from the local parts store. You do have to modify the wire looms a bit, but that's not much of a problem. I do not agree that the chain needs to be replaced at 145k. These motors can go 300k without that kind of work. The serpentine belt is quite another matter. Link to comment Share on other sites More sharing options...
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