hey guys...my tl is getting bad gas mileage....timing belt..water pump..spark plugs and air filter were done about 2 months ago....and also both upstream o2 sensors...i have no cel on...i was wondering if it could be the imrc valve or something like that...i was reading some forums and it was just a thought...any help would be great

 

What is your MPG and is this city, highway, or both?

 

Yes posting mpg would help. Valve adjust is needed at 105k. It should have been done as the timing belt & spark plugs.

 

Valve adjustment is only needed if the valve train is noisy, otherwise no adjustment necessary. Actually, any time the valve train is noisy, it's time for an adjustment.

 

im only getting just about 200 miles with a full tank....i filled up my tank last night...i frove 18 miles n the needle moved...at idle, the cluster shows 8 miles per gallon...while driving it shoes 13 miles per gallon...my valves are not noisy at all...what i noticed is that after like 3500 or 3800 rpm...my engine sounds loud and im losing power...

 

also i have my stock rims on....

 

How many miles do you have on the car? assuming you have over 100k due to the service....
you might want to clean your throttle body and run some seafoam.

 

What about your PCV valve and the fuel filter? A clogged PCV valve and/or a dirty fuel filter can cause poor gas mileage, poor idle and performance loss.

Also if you check for vacuum leaks.

 

What was the reason for replacing both O2 sensors? I remember a couple of years ago I got a CEL on my Dodge P/U. Well to make a long story short I replaced the O2 sensor and it cleared the CEL but my MPG went to shit, I'd say close to half of what it was before so I replaced it again and this time with an OEM and my MPGs went back to normal and CEL stayed cleared.

 

i have 125k on it....i allready did the seafoam....no luck...i used the vaccum line that is connected to the purge solenoid...the pcv valve was also done about 2 months ago....i was thinking that it might be the fuel filter but wouldnt my car like really run like shit cause the gas isnt getting to the motor?...i always use 93 and twice a month use the lucas fuel system cleaner....as for why i changed the two upstream 02 sensors was because like a month ago, i got a cel "p0171"...which is bank one too lean...i brought it to the dealer and was told that the rear 02 sensor was bad so i just changed both....the cel never returned....but im still getting bad mileage and loss of power

 

I'm assuming problem turned on after the sensors were replaced and since replacing the O2 sensors takes about 15 minutes. I would rule them out first. So if you still have the old sensor that came from bank two, I would put that one in bank 1 first then run it for awhile and see if that has any affect. If not then move it to bank 2.

 

Mine has dipped down to 13mpg with pure city driving. It's on the low side but entirely possible with nothing wrong with the car. Your average mph would be a good indicator to tell if there's something wrong with the car or if it's the driving conditions.

FWIW, a dirty TB won't affect mileage nor will a bad PCV valve. Intake valves get noisier because the clearances get looser over time. Exhaust valves generally get tighter and don't make noise until it's too late.

 

Thanks.

 

why? because the ECU controls the A/F ratio?

 

If it's dirty it just won't let as much air in for the same % opening. Since AF ratio always stays constant, a dirty TB is the same as giving it less throttle.

 

therefore, you mash on the gas, giving less miles to the gallon?

 

No, you give it more throttle just to equal the airflow of a clean TB. Same amount of air equals same amount of fuel. The accelerator pedal position is irrelevent, only airflow matters.

 

gotcha. so whats the point of cleaning a dirty tb?
ive noticed when i clean tb's of various diff cars, acceleration is smoother and idle is smoother.

sorry if im not following, had a couple of drinks.

 

That's a great question lol.

It can effect idle on DBW cars that don't use an IAC. When it's mostly closed, the extra buildup can choke off airflow and/or make it erratic. Once it's partially opened, there is no difference.

Don't worry about the drinks, I've had half a bottle of Nyquill lol. I'm probably worse off than you.

 

so what are the chances that it might be the fuel filter?....there is no way of checking huh?

 

if the timing was off by one or two teeth...would that cause me the bad gas mileage n power loss....

 

If timing was off by 1 or 2 teeth, your car would sound like a tractor. The motor would rattle, etc etc.
Yes really, even 1 single tooth and is very very noticeable

 

Totally agreed. I almost posted but everytime I say this, someone tells me about how their car ran perfect when it was 2 teeth off lol.

My friend's 944 Porsche was off by one tooth and with the pedal to the floor in neutral it took about 10 seconds to hit 6,000rpm. 6-7,000 it made ok power lol.

Something I'm guilty of and I should not admit was timing an engine with a hangover and bending valves being only one notch off.

 

Wow damn, it actually bent the valves at one notch!

I accidentally missed one tooth doing the timing on the TL, at night..but didn't hit valves. Sure enough, it was noticeable to a deaf person. Only one tooth on one head. 3 Teeth, the car won't start. I found out accidentally, when the car wouldn't start after it had jumped 3-4 teeth lol..don't ask how

 

allright....so then i can take that out the picture...now what about our 3 cats....i had my girl rev the car at a steady idle(4000) so i can see if any of the cats get red....im not getting a egg smell....but do you guys think that its possible for one of the cats to be clogged?...or do you think it can be one of the secondary o2 sensors have gone bad?....

 

just an update...i swapped out the imrc valve and that didnt do no good....i was also thinking....what if my iat or map sensor went bad but isnt showing no cel....is that possible?

 

Let's re-examine the P0171 incident. If that was the only code, then your dealer did not make a correct diagnosis. According the the SM, there is no call to replace either the O2 or A/F sensors for a lone P0171 code. I have to assume your dealer detected a secondary code besides the P0171??

 

We still don' t know your average mph or what type of driving you do. There may be nothing wrong with your car.

 

Bad front or rear cat (bank 2 or bank 1, respectively) or bad A/F or bad O2 sensors should throw a CEL and code/s.

Bad (inefficient, non-functioning) 3rd CAT won't give a code (no A/F or O2 sensors). And I doubt it would affect mileage...

Clogged CAT (any) should reduce power noticeably.

 

My average mph is about 50 mph....my job is about 6 miles from my house and thats 5 days a week...

 

I dont beat on my car..i never even hit vtec....last time was maybe like 3 months ago

 

im still on the stock clutch...i have 125k....maybe its time to replace the clutch...could that give me bad gas mileage n power loss....its not slipping or anything

 

^ no.

 

I have a feeling there's nothing wrong with your car.

 

he said he drives 6 miles to work.Sounds like city driving to me.

does this 6 miles include stop signs and traffic lights?

 

^^^driving 6 miles to work doesn't indicate something wrong with the car lol..

OP, What kinda plugs did you use?

 

I don't know but I think something sounds off here....is it just me?

 

yes, because he hasnt given us full details.
incomplete snippets here and there.

 

50mph would be very hard to average even if 5 of it was freeway. By the time you hit the freeway, go through some surface streets, and park it's not likely your mph is going to be at 50mph. Is this an estimate or off the MID? The reading off the MID will tell the story. Don't reset it, the longer the average the better. If the actual average is down in the low 20s, your mpg is somewhat normal. At an average of 19mph, my average was 13mpg.

You're making this extra hard. Let's find out if the car has an actual problem before we go troubleshooting.

 

i used to get 320 miles with a full tank...now im only getting about 205 with a full tank....same type of driving as always...i would deff think there is something wrong....