szjalo

I just cleaned the MAF with some professional MAF cleaner. after air dry for few minutes, I set it back and started the car.

when the A/C, lights are all on, the car idle at 800rpm-750rmp. but it was slightly unstable and jumped between 1000rmp-660rmp, tho- mostly on 800-750.

Because before I clean the MAF, it also idles at 750 or so but a little more stable than now. do you think this this normal??

THX a lot

szjalo

plus it's an auto

jasonrxeight

what did you use?
drive it for a while allow the computer to relearn.

szjalo

CRC mass air flow sensor cleaner

after I cleaned it I probably just drove for 3 miles and filled the gas tank. is this enough for computer to relean?

jasonrxeight

no. at least 50-100 miles at different speed and different load.
also need go through a couple of on/off cycles.

laythor

ecu has to relearn trims. half dozen drive cycles then report back.

04Green

iTrader: (1)

Or, even better, do the ECU rest dance. There is a procedure here someplace. Something like turn on the car, pump brake pedal 20 times really fast, one of the gauges move. Then you start over from scratch. Nothing to un-learn, should speed up the process.

szjalo

Worst hwy MPG after cleaning MAF??


Alrite, here I came back again. After clean the MAF, I've run 60 miles, with a mixture of hwy and local(speed from 0 - 70mph). then I thought the ECU already relearned, b/c the idle started to be constant.

Then, today I ran a long trip with a full tank of gas. after back, I noticed the worst highway MPG so far. I've driven 270 miles (95% hwy), with 12.8 gallon consumption. the MPG is about 21. The first half of the trip was worst, with the consumption of half a tank (estimated MPG=17-18). on the way back, MPG was slightly better.

To compare with, the last time of hwy long trip(only 3 weeks before clean the MAF) was 245 miles with only 10 gallons (MPG=24.5). the other previous hwy mpgs are around 24.


so, would anyone suggest that the ECU relearn takes longer than 60 miles? or a not-yet-relearned ECU and MAF would make the car run tougher? or is there other reason that make today's MPG worse than the previous ones.


BTW: on the first half I drove a little harder, barely used cruise cntl, few hard steps on the gas, speed up to 95 mi. on the way back, mostly with cruise cntl on 70-75 mph. However I have no idea whether this can make such a big difference?

Thanks every one in advance!

jasonrxeight

how much difference was the temperature and what kind of tire pressure you running?

RX8Soldier

iTrader: (24)

how many times since you've cleaned the MAF have you started your car, bought it up to full operating temp, then shut down and allowed to cool for a few hours (approx 100 degrees), then start back up?
Cause that is ONE full drive cycle. Do this about 5 times and your fuel trims should have relearned.

Or, like jasonrceight suggested

szjalo

Donnu the exact number, but apparently I had more than 5 full drive cycles after cleaned MAF

RX8Soldier

iTrader: (24)

"apparently" could be very far from "did"

Anyways, cleaning the MAF isn't always the key. Our MAF sensors are pretty weak. If you continue to get low mpg, you could purchase a new one from Mazmart for pretty cheap.

check your tire pressure, make sure the sensor is seated securely, and remember to redline your engine every now and then

szjalo

it's 108F today. and the last hwy trip was about 98-100F, I guess

I didnt check the tire pressure before leave, but the tire pressure light didn't come up all the way. I checked the pressure 2 weeks ago, and pumped then.

8 Maniac

iTrader: (1)

24 sounds high honestly. It's not unheard of, but you're doing very well if you're seeing 24 mpg. I'd say you need to see 3-4 tanks as comparison to tell if mileage has really changed significantly. There's too many variables that can change the way 1 tank averages out.

szjalo

I normally have decent hwy MPG, tho the local MPG really sucks. most are 15 or so, the best so far is 16.5. I guess I need better local driving habits. LOL

sh0gunshin

lol