im new to the sight.ive got an 02protege 5 with engine light on.ive taken it to the shop and had diagnostic ran.mechanic said it was prob bad MAF sensor b/c of close circuit readings.So...got new MAF,and now seems to run worse.The vehicle runs fine while driving,but rpms drop and start to sputter a few sec after coming to a stop.Sometimes even stalls out.Anyone have any ideas on this?

 

Welcome to the forums!! If you could fill out your signature (use mine for example) with all your vehicles details it would help us out tremendously! So what car do you have (engine, trans etc)? It sounds like you have a vacuum leak somewhere, start by checking all your intake piping especially the flex tube from the MAF to the throttle body since it got worse after changing it, the tube might be cracked, next if there are no cracks VERY CAREFULLY spray starter fluid around the intake manifold and various vacuum lines while the engine is running, if you hit a bad gasket or vac line the idle will rise with the added fuel.

 

Its an 02 protege5 automatic trans.When i had it in the shop the mechanic checked for vaccum leaks and said he found none.He did however mention i should replace the intake.Its some cheap POS short ram that was on the vehicle when i bought it.I dont really want to go back to the factory box though.I would like to add new headers/exhaust later on.The drop in rpms comes and goes with every drive.Sometimes barely noticable.But only noticable when stopped.Coming to a stop too fast seems to cause it to be worse.

 

Factory boxes are almost always (were talking 90%) better than aftermarket intakes on a stock engine, even one with exhaust mods you would be better with a factory box. Whats your idle RPM? Do you have the codes that the ECU is throwing? Here are a couple decent videos on intake mods &

 

Some air intakes are crap. If the diameter is much bigger than stock diameter a cel will follow. In this case you need an air straightener. AEM used to have one. Can't find it. I found a couple pics of what one looks like. It inserts in to existing piping and starightenes air flow as well as making diameter narrower. MAF sensors on corners are not the best spot either.
Another disadvantage with a SRI is heat soak. It sucks in all hot air from behind the rad, losing performance. There is a solution. You need to find a bit longer SRI (like i have for my 6) and isolate it from hot air all the way up to the hood, making sure it can get at cold air, without water splashing up at it!

 

I'm not impressed with those videos. They are using cheap **** intakes and they did not properly seal the filter from the engine like i did on my car. They put a "cover on it" --- don't know how sealed it was @ side. If you don't properly seal it hot air will be pushed over from the fan behind the rad. There must also be a proper airflow for cold air to get in there. On my car there is a spot beside rad and in front of wheel which allows this---this is important as well----you may have to add holes to fog light area. Their outside fan was too far away as well for the test, when headlight was removed as hot air still pushed over from rad. When they did put it outside there were gains, but they could have had more gains if the tube was shorter. That long tube sticking way out in front of the car was ridiculous and it still gained some.
The outside temp was 15 yet the filter was seeing 24-26 when it was under the hood, yet it was seeing 15 when outside with gains!-----what does that tell you! That means colder air increases power.
The intake MUST BE SEALED FROM ENGINE and get air from outside. BOTH must be done for proper gains!
Sure on a small engine you may see only 2-5% gain, but it's a GAIN! It does take innovative thinking to do it properly, short SRI's suck hot air without it, and long CAI's suck water: you need to find something in the middle (like mine).
PIC below shows where air comes in from front and back

Before i installed my baffle, my SRI was not very good, it kept heat soaking and was lagging, since the baffle close to Zoom Zoom

 

HERE is a great video on ideas about how cold air works and how to make a custom box.

 

try coils, plugs , and wires. mine calmed right down then p0421 cat code came up but runs strong

 

In this case you need an air straightener. AEM used to have one. Can't find it. I found a couple pics of what one looks like. It inserts in to existing piping and starightenes air flow as well as making diameter narrower.

 

What did we learn form this thread... there are MYTHs and even some seemingly good information is not exactly the results others doing the same testing have resulted in? Look carefully at the DYNO...
In the case of a devise that "starightens" the air intake flow.... ok well some can believe anything! The description in the part makes some of use ..... and then LOL