MAF

[corvette66]

I have idle problems, amongst many others. Everyone has told me that if I unplug the Mass air flow and the car runs better, the MAF is probably bad. Well here is what my car is doing. It idles at about 1,100, I unplug the MAF and the car dies for just a second, then it kicks back up and runs about 2,000 RPM steady. So is that what happens when its bad, or is it good? the car is still running smooth just faster. ???????

Now my idle problem is when the car is cold. It takes a few minutes before the car will run at a steady idle. usually I have to hold the gas for a while to get it warmed up. Otherwise it will stall. But after about 3 minutes, she idles somewhat smooth at about 1,100-1,300 RPM

Then today I ran into another problem, when I stomp on it, it picks up fast but after about 2 seconds she dies completely and i have to let off the gas and wait till the motor catches up with the car. hmmmmmmmm?????

MAF maybe

 

[Vettefan87]

Any codes? I would replace the power and burnoff relays first before you go buying a 180 or so dollar sensor. The relays are right behind the batter. When I changed mine I think they were like 17 bucks for the both of them. Hope this helps.


Justin

 

[taegdh]

By all means, check your codes first.

I've seen EGR cause similar symptoms. You might try cleaning the MAF screens and the Throttle Body if you have no codes. But be careful.

Check all the vacuum hoses, a little dawn for dishes in water painted on each. If it calms and smooths, you've found your culprit. 18 and 19 year old rubber tends to get brittle and pin holes develop that only act up under vacuum or pressure, but aren't plain to the naked eye.

 

[corvette66]

well i used to get MAF codes. but i no longer get them. i also used to get egr codes, also no longer get them. and i have not done anything to it since. I disconnected the battery a few weeks ago, and have not gott'n the idiot light yet. I tried mess'n with the vacuum lines, but even if i disconnect them while its running, nothing happens, only if i disconnect the lines coming out of the plenum will it die.

Do I have to remove the battery to get to the burn off relays? Is there a way to check them, or do i just have to replace them.

 

[Vettefan87]

Is your SES light working? When you turn the key to the on position does it come on? If it does come off and you unplug the maf and you dont throw a code, then I dont know what to do.


Justin

 

[nyernga]

Removing the battery depends on how large your hands are. A good throttle body cleaning may be in order as well. If you remove the rubber air intake tube, look inside the TB for buildup. The other thing I'd check is the IAC valve. It's possible that it's gummed up. Be forewarned though that if you remove it for cleaning, don't lose the "pintle" inside.


Len

 

[unleadedbrew]

Removing the battery depends on how large your hands are. A good throttle body cleaning may be in order as well. If you remove the rubber air intake tube, look inside the TB for buildup. The other thing I'd check is the IAC valve. It's possible that it's gummed up. Be forewarned though that if you remove it for cleaning, don't lose the "pintle" inside.


Len

So, it's possible to just clean the IAC or better to get a new one? I'm sure a new one is always better, but the approximate cost?

My idle is also going south.

Gordon

 

[corvette66]

Justin: When I turn the ignition to ON, the light comes on. But it never comes on while the motor is running. So I assume its working.

Len: I tried cleaning the IAC in my pontiac before, but it didn't work, the little pintle thing it screws out, and you can clean the shaft and what etc. Is that what I should do? Also when I stick it in I could close the pintle all the way shut. and fire the car up, if the pintle never moves, then I know it's bad right? the pintle should move when the car is fired up correct?

Gordon: Join the club

 

[corvette66]

Well i found the relays. you say a burnoff relay and a power relay. Whats the power relay do?

Can't find my MAP sensor, it must have went on vacation, cause it's not there. Can't find it in my Parts/Illustration Catalog either.

Also a new problem today, my tachometer only works when I drive it, when it idles the tach says 0, and the speedometer was also acting funky.


I need a new car

 

[nyernga]

Well i found the relays. you say a burnoff relay and a power relay. Whats the power relay do?

Can't find my MAP sensor, it must have went on vacation, cause it's not there. Can't find it in my Parts/Illustration Catalog either.

Also a new problem today, my tachometer only works when I drive it, when it idles the tach says 0, and the speedometer was also acting funky.


I need a new car

The power relay does just what is sounds like. Provides power to the MAF for normal operation. The burn-off relay allows 12 to the MAF after shutdown to burn off any contaminents on the sensor wire.
The pintle is controlled by the ECM and yes, it should move.
The tach problem could be a bad filter. Of cocurse I'm working off an 88 GM service manual.

Len

 

[corvette66]

I didn't know the relays were for the MAF. It all makes sense now. thanx LEN.

I'll replace them, and let yins know whats up. thanx

 

[redc4corvette]

The map is under the plenum at the front under the throttle body.

You can see it from the drivers side.There is a black vaccume pre fab hose going to it.

 

[corvette66]

Red C4 Corvette:

isn't that the unit that is attached to the thermostat housing with the same bolt? says in my manual that that sensor is some EGR thing, but if thats also the MAP sensor, super!!!! I thought my MAP sensor took a hike, cause I coiuldn't find any other sensors.


dano

 

[redc4corvette]

I have an 86 coupe and the black square like thing right at the front of the intake would be the map sensor with a single vacumm hose on it it's near the thermostat. I can look at mine again to be :CRASH :CRASH .