Hoping you guys could give me some advice on the caR.

Few months ago I was getting 550kms (340miles) to a tank of gas roughly. Had my timing belt and water pump replaced by Acura, now I'm getting half of that, about 280kms (175miles) to a tank.

Yes, I know that a more accurate way would be to get the exact gallons per mile instead of determining it on a "tank." It's bad no matter how you measure it.

Regardless of this, Im getting about half the mileage I use to be getting.

My oil level is fine, and there doesn't seem to be any excess burning going on.

I change my oil every 5000kms.

Have also changed:
stock spark plugs, fuel filter, cleaned air filter, distributor and rotor (oem). Up to date with my timing belt and water pump.

I don't want to blindly throw money at it to try and address this problem ie new O2 sensor, coil, ignitor, injectors...

Are there any tests I can do to isolate what's going on?

Any ideas? Injector stuck open? O2 sensor gone? How would I test those?

Thanks!

 

OEM ecu?
I have seen ECU's get stuck in open loop and quickly learn a fuel map that is super rich. Happened on my 2000R. i pulled power and let it sit for 20 minutes to kill the stored learned maps. It made it back the rest of the trip getting the 30mpg highway i was used to.
could be a stuck injector, only way to really test that is on a injector flow tester or pull them all and send em to get cleaned. RC does it for about 100$ for the set. better than new when they come back

 

Is your temp coming up while you drive? My thermostat was stuck open causing me to get bad gas mileage also. Car thought it was cold all the time.

 

Yes, I have the factory ecu.
Ill remove the negative terminal on my battery for 20mins and report back after a few tanks. Good suggestion!

Yes, my temp comes up to the normal range. I squeeze the upper rad hose and I can hear the thermostat move around as well.

 

I would drive it back to Acura and tell them they effed something up. See what they say. Perhaps a cam is off by a tooth or something.

 

Does it run normally? Perhaps the cam is a tooth off.

Are there any CELs? The stock ECU would diagnose many problems, such as O2 sensors and injectors.

 

I did bring it back and documented my mileage.
They re-checked everything, including valve lash, and everything was fine apparently.

It runs normally. Once and a while it takes an extra split second to start, but nothing out of the ordinary.

No CEL's showing on the dash.

 

check your tire pressure, also check and see if one of your caliper pistons aren't sticking causing the wheel not to rotate properly.

 

Ill check them again. The temperature is fluctuating a lot and they are probably low.
Car moves freely even with a slight grade, and there's no pulling to either side. Think the calipers are okay.

Good suggestions though.

 

If the temperature is fluctuating (dropping while coasting or cruising at highway speeds), the thermostat is bad and it will cause lower fuel economy.

I'd also check the ignition timing.

 

I meant that the air temperature is fluctuating a lot, which is probably messing with my tire pressures.
Water temp stays constant.

 

Check air pressure, and reset ecu.

2 tanks later, still same mileage.

O2 sensor? Injectors?

 

Ordered a new Primary O2 sensor and converting to OBD1. Picking up some newer injectors to swap in while I get mine cleaned and flowed.

Other suggestions?

 

have you checked fuel pressure? possible bad fuel pressure regulator(fpr)? vacuume(sp?) line connected to the fpr? and in good shape? it does sound odd that this happened right after having the tbelt done, could just be a coincidence or like others have said cam timing or ignition timing could be off...doubt it has anything to do with fuel consumption, but hows the pcv valve?

how many miles are on the caR? do you still have the original plug wires on it?

a quick look with a scan tool that has the ability to display live data will tell you how the O2's are doing, should be able to spot one thats "stuck" pretty quickly unless its not doing it all the time

 

Haven't checked the fuel pressure yet.
Seems like all the lines are in good shape.

It is strange that it happened right after, but its not like I brought it to a no name shop. Brought it to downtown Toronto Acura, and got them to re-check everything they did.

Has roughly 90,000miles on it. New spark plug wires.

Have a new O2 sensor on the way...Just don't want to keep throwing parts at it.

 

I would check fuel pressure and see if you can plug in with a scan tool and see the live data before you buy any more parts...then again I suppose since you already bought the 02 sensor you could just change it and see what happens, but I dont blame you for not wanting to throw parts at it and hope something works

 

Picking up a fuel pressure gauge, and bringing it back to Acura to double check everything (timing, timing belt, and belt tightness).

What am I checking for fuel pressure? That is at 50psi only? Doesn't drop very quickly after the engine is turned off (leaking injector?)

If this is okay, do I check my compression and do a leak down test?
A clogged cat would have a big performance reduction wouldn't it?

Vacuum lines leaking would cause problems?

 

This might be related, it might not. This last weekend I went to an Autox. It was 110 miles round trip. I went through nearly a half tank of gas on that trip. That didnt seem right to me so I started investigating. Everything looked/sounded good until I got to the gas cap. When I took the cap off I could hear plastic rattling around inside of it. I couldnt see anything broke, just hear it.

I replaced the cap and retook the same trip, last night. This time it only took 1/3 tank of gas. Problem appears to be solved.

 

Not ruling anything out, every suggestion helps.

I swapped out my injectors, installed a fuel pressure gauge, and dropping my stock injectors off to get cleaned and flowed today. If that doesn't help, Im all out of ideas.

 

what I meant by checking the fpr vacumme line was to make sure it was connected and not ripped or torn and leaking, any vacumme leak is going to cause problems, i just asked about the fpr specifically because your having fuel consumption issues and because its in the same area as the tbelt (well kinda) and could have been disconnected or ripped during the course of the tbelt job...also I thought the spec for fuel pressure was around 38-44 at idle, that may be for other B series and not for an R so I could be wrong, I was just thinking that maybe the fpr had gone out on you and was running at a slightly higher pressure than normal, which would cause excessive fuel consumption, but it sounds like thats pretty close to in spec

im wondering what the short term and long term fuel trims are in the obd2 computer, thats what I meant by looking at the live data with a scan tool...see if an ECT sensor or IAT sensor are way out of whack or if an o2 is stuck lean, which would make the fuel trims way out of spec, which would probably kick a CEL, but I've seen stranger things happen and not throw a CEL

did you ever go to the obd1 ecu? anything change ?

 

is your air filter clean? is your compression up to spec? also, having a fuel filter that is restricted will cause you to keep the gas pedal down a little harder just to feed it fuel. swap out primary and secondary fuel filters. if you don't want to, its best since tthey have to be changed sooner or later.

also..a clogged catylatic converter will cause some problem's.

 

I hate to ask something that might sound stupid, but here goes...

You didn't by any chance change wheels and tires (winter->summer) did you? Could it be that the tire diameters are way different, and that revs per mile were much faster (smaller diam) with the previous set and slower (larger diam) now? If so you could have had a falsely optimistic view of mileage previously and a falsely pessimistic view now.

I don't see how it could make this much difference unless the diameters are so different as to be completely obvious.

 

Fuel pressure is sitting steady at 42psi, and all the vacuum lines seem fine.

Still on the stock computer. Want to diagnose it a bit further before swapping out the ecu. Im sure Acura will want the stock ecu in as well to check everything again. Bringing it in Thursday morning to re-check everything.

Air filter was just cleaned out but ill take a look at the mugen intake again.
Im going to get a compression and leak down test while Im at Acura Thursday.
I recently swapped out the fuel filter in the engine bay, which other one are you talking about? The sock on the fuel pump?

A clogged cat I always thought would give me a horrible drive, and would really hesitate while driving. Im not getting that currently.

How do I check for a clogged cat?

Didn't change my tires until 2 weeks ago to RE-11's in 205-50-15's. The big drop in mileage was with the same tires and rims.

Good ideas though.

Getting the injectors back tomorrow. Asked for the before and after results, flow, and spray pattern. Seemed like they were very familiar with this.

 

My guess would be O2 sensor. It might just be coincidence that it went bad just after you got your car serviced....

But on the other note, 550km from one tank if really high for me. I "only" get 450 from normal driving....

 

I was getting over 630 in my gsr...

Main problem is that it dropped in half all of a sudden.

Got the injectors back. They were all fine...