What am I missing?

[GTwolf]

So today a new problem popped up. I started driving this morning, car is fine, then about fifteen minutes later I hit the brakes to stop at a stop light. The rpms dip down to about 300, I hear a very loud grinding noise, then jumped back up to about 2000 and the car lurched forward, almost smacking the car in front of me. Now almost every time I hit the brakes the car stalls out on me and I have to pull over and try to get it to crank over. Sometimes it turns back on right away, sometimes I have to keep cranking it. Also the revs sound a little different when I'm driving. Almost whiney, but not supercharger whiney, like my girlfriend's ecotec whiney. I hooked up the scanner, and the only off thing I noticed was vacuum pressure kept dipping down to 9 and shooting back up to 21 or so, so obvious vacuum leak right? Well I covered that whole damn engine in brake cleaner multiple times, including shooting some straight at the IC to check the seal, and can't find a thing. Also after that first time in the morning my SES light popped on for low MAF circuit, which doesn't make any sense because it's a fairly new LQ4. The scanner said certain engine conditions can cause the maf to throw a code when it's not actually faulty though. Is this true? Any ideas what's wrong with this thing now? Anybody wanna buy a grand prix? It's supercharged....

Click to read more...

 

[10sec]

Doesn't matter how new it is, those things are hit or miss. If it's running like that, i'll put money says the maf is taking a shit or the wiring is jacked up.

 

[GTwolf]

Doesn't matter how new it is, those things are hit or miss. If it's running like that, i'll put money says the maf is taking a shit or the wiring is jacked up.

Would that make the vacuum pressure drop?

 

[10sec]

Crazy idle makes the vac drop, that's the IAC opening and closing attempting to keep the car running.

 

[Turbocharged400sbc]

if ve was tuned then unplugging the maf would result in it running perfectly, if not then it'll take it a bit but it will learn trims with maf unplugged

 

[10sec]

You and the effin VE tune

 

[Turbocharged400sbc]

im thorough, sue me

 

[02BlueGT]

im thorough, sue me

Except when it comes to responding to calls/texts :gtfo2:

 

[Handsome Jesus]

X2

VE tune doesn't help my car stay running even with the maf plugged in

 

[m_dogg]

I got a spare working LQ4 - case of beer and it's yours

 

[GTwolf]

I got a spare working LQ4 - case of beer and it's yours

Deal. Lukes? Got a brand preference? You don't always trade mass air flow sensors for booze, but when you do, you prefer dos equis?

 

[m_dogg]

^Im sorry good sir - I don't have a working vehicle at the moment so you'd have to stop by my place and pick it up. Btw, regular Becks (not lite) is my beer of choice.

 

[GTwolf]

Fine with me, I'll check it out tomorrow and shoot you a PM.

 

[m_dogg]

:likes:

 

[TommyGloves]

Except when it comes to responding to calls/texts :gtfo2:

James always responds to me.

 

[GTwolf]

So I unhooked the MAF for awhile and drove it around town, no change. I looked up the code it threw and it said if the throttle is open past a certain position with the engine at 300 rpms or less (which has happened multiple times since this started) it can throw the code without the MAF being bad. Still think I should try swapping out the maf or could it be something else?

 

[GTwolf]

Bump, car is still being a pos.

 

[GTwolf]

Just broke out the scanner again. P0102 - MAF circuit low input, P0135 - 02 Sensor heater circuit bank 1 sensor 1 (also almost brand new - makes no sense), and P1676 which I have to google because the scanner doesn't know what it is.

 

[SaturdaysGS]

Possible bad/blown fuse?

 

[10sec]

Touche, i remember james telling someone they had a bad fuse, and it was bad.

Where did you get the o2 sensor? Unless it's a GM one, they usually don't work very well and will throw codes all the time. Especially with a cam.

The other code looks to be Evap related (did a quick search, didn't read, but saw evap) that could be another cause of shitty idle. Did you put it back on? Some cars run better without it. Neither one of my cars had one.

 

[10sec]

Also, my blue car with the ST5 would never idle right, the IAC kept trying to fix the idle and it actually ended up making it worse (i didn't have any error codes though) so i set it to idle at 950rpm, and unplugged the IAC. From then on out, it idled just fine. Just had a little stumble when the a/c was on.

 

[Turbocharged400sbc]

http://www.thechicagogarage.com/forum/showthread.php?t=50484&highlight=fuse+maf

 

[SaturdaysGS]

Damn I was doubting myself too but I did remember that thread!

 

[02BlueGT]

Just an fyi, my car did exactly the same thing when my maf went out.... It acted the same when it was unplugged too cause my VE was not tuned

 

[Turbocharged400sbc]