Mazda Protege Lean Fuel Mixture help

[JFace]

I need some help identifying a problem with my '99 Mazda Protege.

A few weeks ago my check engine light came on, indicating a Lean Fuel Mixture. I regularly run fuel treatments at every fill up, anything from MMO, to Lucas, to Red Line. I have reset the code, and it continues to pop back up. The idle speed is different now...whenever I come to a stop light, RPM's are much lower than normal, varying from 500 to 700 (750 is healthy for me). Often times it stalls out. It does not stall on start-up, however. It stalls only when I stop accelerating.

I just replaced the O2 sensors and Catalytic converter within the past six months. The car has 200,000 miles.

Any help would be appreciated. I'll provide more details the best I can if you need them. Thanks.

 

[javacontour]

Clean the MAF with electronic parts cleaner.

Stop with the additives until you get the code addressed.

IIRC, this is a P0171 or P0172, right? (going from memory so I reserve the right to be wrong)

ETA, you may also be able to use brake parts cleaner to clean the hot wire in the MAF

 

[bdcardinal]

Check the air intake boot from the air filter housing to the throttle body, very common for them to crack and leak.

 

[IndyIan]

+1 Also the behaviour might change when accelerating in reverse vs. forwards...

 

[mopar_monkey]

wifes volvo had the same issue this weekend, found a cracked vacume line, remember check the simple stuff first, a lot of people go worst case right off the bat, i was guilty of that this weekend, started thinking it was that maf going bad or the 02 sensors (which are $525 each for upstream has 2) but it ended up being a very easy/cheap fix.

 

[javacontour]

Yep, the intake tract leak,such as a bad vac hose or intake after the MAF is also a good thing to check.

 

[ottotheclown]

Yes Yes Yes my 99 had that code and that was what it was. Leak break always happens at the under part so you cannot find.. Now I am having code for EGR valve that baby has to be bought at the stealer and is over $200.
Originally Posted By: bdcardinal
Check the air intake boot from the air filter housing to the throttle body, very common for them to crack and leak.

 

[JFace]

Looks like the expertise on bobistheoilguy nailed it again. I checked out the intake boot, and sure enough, there's a crack 1/3 around the hose. I wouldn't have noticed it unless I knew to look there. I put some duct tape there as a temporary fix, and sure enough, it solved it. Now, to find a Mazda dealership and get the bad news of how much a replacement will cost...

 

[javacontour]

Why Mazda, hit up an auto recycler. The car has 200K miles.

 

[bdcardinal]

Originally Posted By: javacontour
Why Mazda, hit up an auto recycler. The car has 200K miles.


Odds are the one in the junkyard is cracked as well. We stock very few Mazda parts, just dont have the room, but usually have like 15 of those boots in stock in the 2 common part numbers. Guaranteed 3-4 sales a week of those, especially when the car wont pass smog.

 

[mechtech2]

Vacuum leaks from any lines, connections, or intake manifold are #1. The PCV system [the WHOLE thing] must be checked.
A dirty fuel filter or weak fuel pump may also be the problem.
Get the other stuff really right and tight first. Trace each thing carefully and fully.
I doubt this is an additive problem.