Fuel Injection, MPG Diagnosis

01 Grand Am GT1 w/ 118,000

Have replaced/done the following

New Fuel Filter
New Plugs and Wires
New O2 sensor (the one on the headers directly behing engine, upper?)
Fuel INjector Cleaner in tank every 5,000 miles
Clean K&N filter every couple of oil changes

Lately my MPG have been getting worse and I want to find some input to what I should check into next to find the problem.

Could it be dirty injectors? How to check? Mass Air Flow Sensor?

Thanks

I dont know, any input would be greatly appreciated

I would use a Seafoam Motor Treatment. Put 1/2 in gas tank. Put 1/2 in the plenum (I usually remove the brake booster vacuum line and start the engine and slow pour the 1/2 Seafoam Motor Treatment. The engine will slow bogs down when it's sucking the seafoam motor treatment. Let it sit for 30 minutes or more. The longer it sits the better. I'd suggest doing this outside the house and at night because when you start the engine back, there would be a lot of smoke.

Also, I'd suggest using a catch can.

Unapproved link removed by Moderator

Hey Slade

Whats the plenum and what size seafoam bottle did you use?

Also, what is a catch can?

Is there anywhere online where I can see how to apply the seafoam?

Thanks

e3gordon, try a search you'll be surprised at what you find. ;)



Slade901 please STOP posting that link to fortunecity and I'm removing it from now on !!

Hey Slade

Whats the plenum and what size seafoam bottle did you use?

Also, what is a catch can?

Is there anywhere online where I can see how to apply the seafoam?

Thanks


Plenum is usually the top most metal part of the engine where the vacuum hoses are mainly connected to. The brake booster hose is connected there as well.

I use 1 pint of seafoam bottle which you can get at your local autoparts store. I put 1/2 on the gas tank. I get a funnel, start the engine, disconnect the vacuum hose on my brake booster, put the funnel on the booster vacuum hose and slowly pour the 1/2 seafoam. Reconnect the brake booster vacuum hose and turn off the engine. Allow the seafoam to soak for 30 minutes. I usually let it sit for hours and wait at night to start it again because there will be a lot of smoke for while when you start the vehicle and will the smoke will go away after a couple of minutes.

Well, my sample catch can link is not allowed here. :shakehead Even threatened me to disable my account :(

Anyway, search on the web for Catch can or Oil Catch Can.

Vehicles equipped with PCV valve allows blowby from the engine past the PCV valve and then into the intake. The problem with those blowby is composed of oil/water/fuel vapor. Back in the old days, people just connect a hose from where the pcv valve sits and let it drip the oil/water/fuel vapors. However, to protect the environment, the oil/water/fuel vapors must not be vented and so it was connected back to the intake to get it burned back. The consequences is that it lowers your fuel octane and your intake, valve, piston, spark plugs gets gunked up of carbon due to that that oil/water/fuel vapors being introduced back to your engine. This is where the catch can comes in. You place the catch can between the pcv valve and the intake via the vacuum hose.

I am not sure if some people know how much oil/fuel/water vapor gets sucked into the PCV valve and into the intake. It is probably due to the fact that they don't know what a Catch Can do and how much of those oil/fuel/water is trapped by the Catch Can.

Just search related to Catch Can and read what is the purpose of the PCV valve and you will realize the importance of the Catch Can.

If thiers a problem with the PCv system it will suck very small amounts of oil and vapors up and could get into the intake . Like I said the catch can is not the anwser to solve the real problem with faulty components.

Also when you put seafoam into the pcv it sucks it back into the purge valve, not into the intake. Just follow the pcv line, goes right behind the rear valve cover.
The brake vacum does vent into the intake, so does the vacum test port on the pass side rear intake.

When puting SeaFoam in the engine, I usually just use the brake booster hose to suck it out of the can (stick a smaller hose inside the brake booster vacuum hose so you can get it into the can). After about half the can has been sucked up, I submerge the hose in SeaFoam until the engine dies. That way you get as much to stay in the engine as possible.

Wow, Slade, you must really love that product. I counted 8 mentions of it in your last post alone :)

If the problem is oil/water/fuel vapors...
-Properly functioning, the PCV system will remove all liquid oil. Any vaporized oil burns as easily as gasoline (although most is seperated out.).
-How much water vapor do you think the engine sucks in on a humid summer day? Water actually cleans carbon deposits anyway.
-Fuel vapors don't hurt engines, and certainly don't cause deposits.

Here's a link to a site that makes a net that you install underneath your car to catch parts as they fall off. www.putanetunderyourcar.com (http://www.putanetunderyourcar.com)

With the brake booster hose you have to be carefull not to break that plastic part, or it'll leak and you brake will have issues. Works both ways though.

Here's a pic....
http://i28.photobucket.com/albums/c242/xeroinfinity/auto%20odds-ends/Vacumports.jpg

yello is the vacum test port and the red is where the brake booster connects.