[E&A's T/A]

Ok first the info it's a 94 trans am with long tubes, tb bypass, and msd coil and opti that have around 2k miles on them the plugs and wires have around 4-5k on them. Now on to the problem it has seemed to me that it has been idling just a little rough for aa while now but always smooth off idle but just recently it has been stumbling off idle and staying rough to around 2k then smooths out and it does this intermitently also when it starts doing it the idle starts dropping slowly almost like it slowly flooding. So i scanned the car with my snap on scannner and really didnt see anything that stood out other than the MAP sensor is showing around 10 inHg at idle which my mityvac is showing 20 inHg at idle. I checked KOEO and the MAP sensor is showing the same as Baro at 29 which is correct for this area. So is my MAP sensor failing in range and would that cause my stumble? Also i am getting BLMs at 117 and 112 if that helps and O2s appear to be responding quickly. I really cant afford to throw parts at this and I'm not going to so good input is much needed. Thanks in advance. Also no codes.

 

[steveo]

30-35KPA @ the map sensor (which is around 10-12" i think) is supposed to be within spec for these engines.

remove your map sensor and inspect the seal just for fun, but fyi, i have a new map sensor and seal, and mine reads way under a proper mechanical vacuum gauge too. i think it's by design.

check for simple vacuum leaks regardless, you do have a mightyvac, so its easy

 

[E&A's T/A]

Well dang I wanted to hear hell yea thats your problem replace the Map sensor and you'll be good. I checked the vacuum about a year ago with the same gauge and got the same reading as i did today. Just guessing but i would think it would be lower if I had a leak but i may check for one anyway. Couldnt hurt right? Any thoughts out there on why the BLMs are so low? Could be just from having the long tubes without a basic tune?

 

[steveo]

trims like 117/112 are totally normal for full exhaust/intake and no tune, i'd think.. but there could be going something on there.

 

[steveo]

i was untuned with a mild cam and headers and some vacuum leaks, and my trims were hitting 155-160. it still went like a scalded rat.

 

[E&A's T/A]

Well maybe I just got some crappy gas. I'll dump some fuel treatment in it and see how it acts thats about all I know to do at this point. Thanks for the input Steveo.

 

[steveo]

definitely could be

seafoam it and change the fuel filter just for kicks too