Gas mileage decrease after injector cleaning... (1 Viewer)

[ThirdShore]

I recently allowed the dealership to do the fuel injector cleaning, along with a few other maintenance items (oil change, rotate tires, alignment, new air filter, new front brakes) on my '06 with 75k miles.

Since I picked it up, I've noticed a 2 MPG drop in highway mileage, and about a 1-1.5 MPG drop in mixed/city mileage. The idle also seems to be a bit rougher than it was prior. At the 70k visit they cleaned the throttle body, and I noticed an increase in MPG, which I immediately negated by adding new tires.

Ideas? Is there something that could have been messed up or clogged during the service, or is this something that will be normal for a few tanks after the injector cleaning?

 

[1loudLX]

Obviously they're injecting more fuel now. How far have you driven? one tank? two? ten?

 

[ThirdShore]

Obviously they're injecting more fuel now. How far have you driven? one tank? two? ten?

I've been through about 2.5 tanks of gas.

 

[e9999]

I doubt it has something to do with cleaner injectors. Unless the performance is also much better and you enjoyed a peppier truck which in turn would explain the mpg loss. The roughness is probably another telling sign that there is something not right.

Likely that they messed something up while doing the work.

 

[ThirdShore]

I'm not very knowledgeable when it comes to auto mechanics, but I was wondering if it's possible some of the gunk that was cleansed from the injector, or wherever else the cleaning covers, could have broken away and clogged something else, like an embolism.

It also crossed my mind that something else could have gotten tweaked while they were under the hood leading to the new symptoms, but wouldn't have any idea where to begin.

 

[jwagner]

what exactly did they do for the cleaning? just add a bottle of stuff to the fuel tank? or something more invasive?
-i would think everything done sould improve mileage if anything, either something is amiss or the ecu needs more time to adjust.

 

[ThirdShore]

Not sure, they said they hook it up to a machine to do the cleaning, I didn't get any more info than that, since they do everything through a service advisor it's difficult to get any kind of detail out of them.

 

[2001LC]

... I've noticed a 2 MPG drop in highway mileage, and about a 1-1.5 MPG drop in mixed/city mileage. The idle also seems to be a bit rougher than it was prior. ....

Sound like a vacuum leak, easily fixed. Take it back and they should be able fix it while you wait.

 

[NMuzj100]

ECU resetting after a power disconnect can result in a little rough running until it reprograms.

A lot of times the mechanics add a fuel tank cleaner to the tank in addition to the injector cleaning. It could effect performance.

Did your area just go to winter blend ethanol fuel?

 

[staggrlee]

If they use a machine (do you know if it "Goes Ping" too?) then they probably do them off-car and immerse them in solvent, then cycle them in combination with ultrasonic cleaning. Sometimes an injector can just fail (or start to) once they leave the home they've been accustomed to.

Take it back to the dealer and ask them to test the injectors pulse width and duty cycle. One of them is probably now out of spec.

 

[jwagner]

would be interesting to see what they did. how much did they charge you for the cleaning?
-reason i ask is ive had my race car injectors ultra soniced and it was $35 per injector... thats a pretty standard price for that not including the removal. they also give you a print out of all the flow rates/resistances. also replace the pintles, screens, o-rings, and gromets. they would tell you if they were bad and cant imagine the dealer reinstalling an out of spec injector. im really not sure that very many places have the setup for this. that said if they didnt charge you $200+ for that id be willing to bet all they did was add a bottle of injector cleaner to your tank and probably charged like $69 bucks for it. if thats the case id run my tank almost empty and refill a few times and see if that doesnt help.

 

[scottm]

How long would it take for the computer to re-compute the length of time it needs to open the injectors after they're cleaned? Maybe pull the battery cable to reset the ECU and force it to calculate them from scratch?

 

[ThirdShore]

would be interesting to see what they did. how much did they charge you for the cleaning?
-reason i ask is ive had my race car injectors ultra soniced and it was $35 per injector... thats a pretty standard price for that not including the removal. they also give you a print out of all the flow rates/resistances. also replace the pintles, screens, o-rings, and gromets. they would tell you if they were bad and cant imagine the dealer reinstalling an out of spec injector. im really not sure that very many places have the setup for this. that said if they didnt charge you $200+ for that id be willing to bet all they did was add a bottle of injector cleaner to your tank and probably charged like $69 bucks for it. if thats the case id run my tank almost empty and refill a few times and see if that doesnt help.

I think it was around $118 for the injector cleaning. I'm bringing it back in today, we'll see what they say. I would hope that they would do more than just pour injector cleaner in the tank for that cost.

 

[spressomon]

FWIW the 100-Series, at least based upon my experiences with my '99, ECU takes considerable time to adjust to any related changes. It took several tankfulls...like 1,000 miles-ish IIRC...for the MPG to come back up after I replaced both O2 upstream sensors (OEM O2 sensors too).

Ditto for the DT headers. I'm just now, after close to a couple thousand miles post install, getting better MPG than prior to the DT header install.

And yes I've disconnected the battery for minimum 30-minutes for each of the above to no real difference.

It just seems to take it time to adjust to changes...

 

[OregonLC]

It just seems to take it time to adjust to changes...

It gets worse the older you get! Just ask my wife.

 

[ThirdShore]

Got it checked out....they said everything seems fine, no leaks, and everything is connected properly. Hopefully it just takes a few more tanks to work itself out.

 

[jwagner]

did you find out what the injector service really was?

-i know in some smaller cars it usually takes atleast a tank or two to adjust. no idea about the cruiser.....at some point i just started doing the maintanance and not paying attention to the mileage...its never great.
-how come they can make trucks with larger displacement, more power, and better fuel mileage now? seems like we should be able to "update the drivers" in the ecu

 

[ThirdShore]

did you find out what the injector service really was?

-i know in some smaller cars it usually takes atleast a tank or two to adjust. no idea about the cruiser.....at some point i just started doing the maintanance and not paying attention to the mileage...its never great.
-how come they can make trucks with larger displacement, more power, and better fuel mileage now? seems like we should be able to "update the drivers" in the ecu

Never found out exactly what was done. They did let the same tech evaluate it that had done the work, I kinda wish they would've gotten another head involved too, but oh well.

I've been through about 4 tanks of gas, and about 1000 miles or so with no signs of improvement. If it doesn't improve in the next 1000 miles, I might take it in to another Toyota dealership to see what they say. Any other ideas?

 

[NMuzj100]

Any other ideas?

Maybe they were clogged up and not letting enough fuel through. Now that they're cleaned it uses more fuel!

A better running machine will not always use less fuel.

 

[nomembername]

ASNU – fuel injector diagnostic, testing, servicing and cleaning

This is pretty much the 'gold standard' of shop-owned fuel injector testing and cleaning machines... most likely to be the type used by your shop.