Hey!

So ive been having a problem recently with my 99 v6 and idle. I was having issues with the engine running rough and blew a couple MAF codes so i replaced the MAF sensor. Seemed to run fine after, but when i parked and went into a shop when i came back out it would not idle after start. I have to keep the revs above 1000 to keep it idling.

After a full inspection of my engine and sensors, i noticed i forgot to reconnect the O2 sensor. So i cleaned it up and plugged it back in. At that time i also disconnected the battery and turned on the key. Left the battery disconnected for 24 hours to be safe.

Idled the car for about 20 min, turned the key off, and it started back up fine. So i thought okay, maybe this will be okay.

Finally drove the car again today to the store and found the same problem that it wouldn't idle after being warmed up then turned off.

Anyone have any suggestions? Its not currently blowing any codes with this problem. MAF codes haven't come up after i changed it out.

Thanks!

 

Without being at the car we can only guess. Hearing and seeing make a world of difference in cases like this. But things for you to look at would be fuel pressure, make sure it is up to snuff, I cant remember the exact specs but engine running it is supposed to be 45+ lbs at the rail.

Also you could have a bad MAF even tho it is new. The computer checks the resistance of the sensor elements and if they are in spec it calls it good. If the MAF elements dont get to the right temp or maybe they are the wrong elements then the computer will not get the right readings to keep the engine running. You did leave the screen alone in your MAF I hope? If not there is a major issue. That screen has a MINIMAL restriction to air flow and it's purpose is to not only keep big objects out of the MAF (but your aircleaner should be doing that anyway) but to make a "wind tunnel" for the air crossing the sensor elements. The air must pass over the sensor evenly for best results. Removing the screen creates turbulence and this could interfere with the elements ability to read airflow as the air will not pass over the element in a uniform manner.

Since this happens when the engine is warm try next time it does this to unplug the MAF and see if it will run. I know the CEL will come on as the computer will not be able to read the MAF but it should put the computer in open loop mode and run off a pre-programed map that ignores the MAF and a few other sensors. Make sure you only unplug the MAF and leave the servo plugged in. Also make sure the AIT is plugged in and installed in the air cleaner, this little guy does alot more than people think


Massey

 

Yeah the situation is not cut and dry for sure. I started noticing some electrical issues yesterday such as the lights dimming and the interior fans slowing at idle and picking back up when I give it any throttle. It blew a code yesterday so I'm interested to see what is is. Were having some -23c weather here today, so I don't think she will be going anywhere anyway.

I've heard that about Mags. I didn't touch the screen at all but I did blow a little bit of sensor cleaner on it to make sure it wasn't too gummed up. I inspected the AIT last time and it looks alright. No codes from it or MAF since I replaced the MAF but, I guess I'll see what this new code is.

Thanks for your recommendations. I'll have to do a bit more fiddling and hopefully get done more of an idea of what's going on.

 

If you are dropping in RPMs below the normal idle range then the power dropping off is normal. It is somewhere around 600-700 RPMs and the alternator stops out putting power. The problem is the low RPMs not the charging system.

 

My RPM seem to stay right around 1000 in idle at start up when its cold.

I checked out my codes today I have P0172 and P0175. So i suppose im running rich in both banks. I don't believe these two came up after having to keep the revs high after it was warm. Its not directly a MAF code, but its related isn't it? So either my new MAF is also bad, or i never had a bad MAF technically and its always been something else perhaps? (My first code when this trouble all started was P0068)

Also my OBDII was showing my fuel system status as "Open loop due to insufficient temperature" WITH the MAF plugged in.

This poor thing was overheated pretty badly before i got it a few years ago, so i've been dealing with everlasting small issues. This one id say is the most troublesome since it wont run sometimes, haha.

 

If the MAF is not reading properly the computer will not be able to get the mixture right which would pop the too rich codes. I would take the new MAF back and get another one. To me all signs point to the MAF.

About the fuel system in Open loop due to unsufficient temp, that could be a couple of things. First off is there a T-stat in the car? Your computer knows how long it should take to get to operating temp, it also knows what operating temp is. What alot of people dont know is that a Thermostat is not there to determine engine temp but to help regulate engine temp by allowing or restricting coolant flow. Some engines will overheat with the T-stat removed because the coolant does not stay in the radiator long enough to bleed off the excess heat, other engines will not get hot enough because the radiator cools too well. Check or simply replace the T-stat with a new 195° unit, your temp gauge should read in the area of 210° on this engine, that is normal. Also you may want to check the engine coolant temp sensor. This little guy tells the computer what the engine temp is and that information is what pulls the computer out of open loop and puts it in closed loop. The computer will try to go to closed loop even if the temp is not right after a given amount of time, but if it cannot get the fuel mixture correct then it pops back to open loop and sets a code. It sounds complex, and it is but it is not hard. Liberty usually has the flowcharts for the codes and if you ask him he may have the ones you need for this problem to assist you in getting this fixed.

Also for those who will suggest to you that your IAC can be the problem here... it cant... you dont have one. You dont have one because your throttle is servo controlled and since the throttle plate can be moved by the computer it does not need the IAC to help with the idle mixture.

So go and warranty this MAF and get another one, and check out the T-stat to make sure it is working or simply replace with a new one. Also make sure to purge the air from the engine really well or you will have a slew of other issues.

Massey

 

Alright, will do. My MAF is from Standard, i hope i don't have too much of an issue dealing with their warranty.

Thanks again. Have a great weekend.

 

Standard, which means you either got it from NAPA or Autozone. Standard does not make the same quality of parts that they used to. I prefer Neihoff and BWD (same company actually). Their stuff does cost a little more but the quality IMHO is much better.

Simply let the guy at the parts counter know that once this MAF was installed the car would not run hot and the computer was popping mixture codes that it was not doing before with the old MAF.

Massey