New owner question, P0171 and hesitation

[ibexlatham]

I bought a 2000 SE 5spd in January and its been relatively problem free so far... despite putting 28,000 miles on it from the day I bought it. The only problem is its thrown a few codes so far, some my fault, but others random.

All I've done to it so far is a Injen CAI. Within about a month from that it threw Bank 1 too lean code, cleared it, a few weeks later same code, cleared it, then a few days later threw Bank 2 too lean code. I own a cheap scan tool, so clearing codes isnt a problem. I realize that those codes point to a bad MAF and plan on changing that once I can.

But, after throwing and clearing the bank 2 too lean code it developed severe hesitation under heavy load within a few miles. light acceleration isnt much of a problem, but heavy acceleration isnt possible, but its not throwing any codes. I've let it run in the driveway for awhile, took it on several drives giving it full throttle whenever possible, but no code. I even unplugged the MAF and an O2 sensor just to set codes to see how quick they set.

I realize P0171 points most likely to the MAF, but wouldnt such severe hesitation caused by a bad MAF cause a code pretty quickly? How about an exhaust leak, it sounds like there is one, but not one that would cause any problems like this? How long do the fuel pumps last on these, I've got 109,000 miles now and no service history. I doubt the exhaust leak or the fuel pump, but I cant figure out why its not throwing a code.

Also, if I replace the MAF, do I need the ECU reprogrammed like the service info says? I'm sick of driving my parents Mazda 6 so I want to fix this ASAP

Thanks for the help,James

[vonbrutus]

I just recently brought my 2001 20th anniv. in to the shop for the same code 00171 - bank 1 lean. So I had the mechanic replace the two upstream O2 sensors. He also cleared the codes when he did this.

Now two days later - SES light is back on and the car is hesitating when cold and at low speeds. It also tends to top out at 4500 RPM which is the most troubling thing.

Considering MAF replacement soon as many people are directing me that way. Unfortunately they are a pricey part to buy.

Good luck - and if you find a fix let me know as i will do the same.

Cheers,

MVB

[MaXimaSE]

You can try cleaning the MAF with some Electronics Part Cleaner from Autozone, made by the companiy CRC or whatever.. about $3.50 for a spray can of it.. I would reccomend removing the whole MAF from the car so your holding it in your hand.. spray the electronics cleaner about 2 inches away from the sensor. Be sure to spray from both sides and then let it air dry for about 20 minutes.. then reinstall the sensor and try again.. If this don't work then It is really shot ...

[Mike G]

Going through the same thing on my '01 I30. The problem is that the TSB for the P0171 points to about 6 items that could be an issue. They of course range from the variuos sensors to leaks in the intake flow or EGR problems. I am to the point of wondering where to toss money first....

--Mike

[Mike G]

Update 10/31/07 -- No leaks in the intake area, no exhaust gas leaks, front O2 sensor acting fine, the next big ticket was the MAF (last item is fuel system check). The MAF was tested and was flowing 50 grams/second. Of course the unit should flow around 100 grams/second so it was replaced (no reprograming was needed). Codes were cleared and BG44k added to the full tank of gas. Car runs like a champ but after 20 minutes of driving the SES/CEL light is back on, however, seems to be free of the cold start hesitation and warm knock

More to come... --Mike

[ibexlatham]

I went ahead and changed my MAF, I had the cold start hesitation also it would "stumble" leaving the parking lot at work while in second gear.

I got a reman MAF from Pepboys but it has a 5 prong connector and the old one is 4 prong... I used it anyway because I needed it, the car runs like a champ now. No more hesitation and it seems to have more power then I remember...

I suspected the MAF and not the other things mostly because of the severity of the hesitation and the fact it was all of the time (not just cold) I also had an increase in gas milage recently and using the scan tool the fuel trims were 33~34% and according to this board they should be around 0~1%.

I swapped it, cleared the codes and no problems... for a while at least.

Driving down the highway it threw P0138 and P0139, slow response from 02 sensor, Voltage too high 02 sensor.

But, the hesitation is gone and the fuel trim is back where it should be so I think its just coincidence or a few problems all at the same time

[vonbrutus]

A link I found that may shed some light.http://en.allexperts.com/q/Nis...K.htm

I am considering going to the transmission shop for a scan to see if there anything amiss there before I commit to the MAF fix.Just doing due diligence before spending mucho dinero.

Cheers,

VB

[Mike G]

Update 11/1/07

Parts to fix - $150Labor to diag and replace - $170 Small shop owner obsessed with your problem - Priceless

Stopped back by the shop with my new CEL/SES situation. We pulled the codes and found an 0140 and 0160, after cat O2 high voltage. Assuming it was a learning curve for the new amount of fuel, we cleared out the codes and took her for a nice trip down the highway. Now at 6 key-cycles the light has not re-initiated iteslf. I will not jinx myself yet...

--Mike