when testing the MAF with a DVOM what exactly am i checking for? there are 3 wires to my MAF, a yellow one on the left, a black one witha white strip in the middle, and a red one on the right. Which one do I want to check? I tried myself and one of the wires read 4.53V at idle, and dropped down steadily to 4.0V when i increased teh throttle to about 2500 RPM. I didn't test the black wire witha white line in it, the other wire read 14V so im guessing that was the power feed.

 

that is not normal...ill discuss it with some guys at work 2moro and c what they say (and im horrible at remembering to come back on here so hopefully i dont forget)

 

ok so I just figured out my s-10 has the same MAF sensor, So I took the sensor off my s-10, cleaned it, and put it on my monte carlo. I started it up, the injectors were pretty loud, but they usually are when I first crank it. Then I ran a bit, it misfired alittle but then it started making it to 4k rpm, and the rev limiter, So I took it on the road and punched it, it worked fine, I drove down the road with the occasional hiccup but it climbed to 6k RPM then cruised at 8- mph fine. I turned around to come back, and punched it again, and then it started missing again and I'm right back where I started. I don't know if it was working good because the engine was really cold or what, It threw no dcodes and now I'm back to where I started, I'm so confused and disapointed with the false hope I was given.

any ideas?

 

THank you kweef, please let me know what this means and how I can fix it.

 

Ok I ran it a bit more and got the original symtoms again, except worse. I went about 4 miles to the gas station, when I pulled in, it died. I put 5 bucks in the tank then I was gonna ride softly to autozone since at lower rpms it seems to be fine, well not now. I pulled out of the gas station and it started bucking at around 1500 rpm, the tach would drop and jump all over the place. So I turned around and drove home. Even with my foot off the gas and cruising it would want to die, the tach would drop 500-600 rpm and I still couldn't get it to go over 2500 rpm, also when I pressed the gas sometimes it would seem to do nothing, Obviously this problem gets worse the more warmed up the car is, and first thing in the morning with dew on the car it managed to get to 6k rpm. I read somecodes and got a new freeze frame data from when i unplugged the MAF I think tho I may be wrong, heres the info it put out tho.

MAybe its an electrical wiring problem? I don't know.

p0102

Load 1.1%

2610 RPM

MAP sensor 37 KPA

Air Flow Rate 1.90 GR/sec

Throttle position 16.4%

Coolant temp 197 degrees.

Fuel trim same as above

Fuel system open.

If I goto I/M monitor it says OK or N/A or INC, no fails.

It threw p1676 again as well I guess I need to check that wiring as well.

Hope some of this helps, and someoen can figure out what -96.7% short term 3 fuel trim is.

 

I got another p1676 code so I'm really starting to think this has something to do with fuel tank vapors constantly flowing into the vehicle maybe?

I noticed my fuel trim hasn't changed in this code, I read that the PCM doesn't adjust anything untill the engine goes into closed loop? So why would my engine not meet closed loop requirements?

 

Check to make sure there is nothing blocking your air filter. With that Short Term Fuel Trim it sounds like either excessive fuel or a restriction. How was your cat tested by the way?

 

Trust me i've had this thing apart all the way up to the throttle body and it still acts the same, nothing is blocking my air short of the intake. I tested my cat by relieveing any chance of backpressure and running the car to see the same symptoms. I did this by opening a hole in the exhaust before the cat, once by pulling the o2 sensor and running it, and also by pulling the egr valve and running it, I get the same symptoms either way.

I noticed every code for the past 3 days hads had the exact same fuel trim information, that means my computer hasn't tried to adjust the fuel trim, possibly I'm not going into closed loop at all? why would this be?

 

OK i Just took it out on the road, and got a p0401 code, EGR FLOW INSUFFICIENT.

I got this error a few times before, so I used carb cleaner and cleaned the EGR vacuum out best I could, and got a new EGR valve. Not sure what else I can clean out of it to improve flow?

Freeze Frame data:

------------------------------------------------------------

Throttle Position - 0.3%

Engine RPM - 1136

Air Flow Rate - 4.67GR/sec

MAP Sensor - 30 KPA

Coolant Temp - 177 degrees F

Short term fuel trim 1 - 0%

Long Term Fuel Trim 1 - negative 13.3%

Short Term Fuel Trim 3 - 50%

Long Term Fuel Trim 3 - negative 45.2%

Vehicle speed - 45mph

Fuel System 1 - closed

------------------------------------------------------------

So It finally went into closed loop and tried to adjust, but it was still misfiring. Note I took this drive with the evap purge valve unplugged. I was trying to go through the OBD II GM driving cycle I read but i didn't have enough space

 

I don't think pulling the O2 and EGR are very good ways to relieve pressure. Once my fathers T-bird died out. We couldn't get it started. I even went and loosened the exhaust flange just before the cat, there was about a half inch gap and it still wouldn't start. We replaced the cat anyway and when we cut out the old one you could see it was plugged. After the new one was on it took a couple tries but it fired up and ran like a champ.

Do you have a vacuum gauge? If so hook it to manifold vacumm. You should be around 12"-15" of vacuum. Take the throttle and rev it up to 2000-25000rpm. The vacuum should go up to about 20" of vacuum. Somewhere around there. But keep it revved up, the vacuum should stay up. If it starts to fall then you know you have a restriction.