bad mass airflow sensor?

[boostoutlaw]

I have a 1995 eclipse gst, when i start up the car it idles at around 3000rpm and stays there, when i unplug the maf sensor the idle goes back to normal but as soon as i plug it back in the idle goes back to 3000, any idea what could be wrong?

 

[92AWDHX40]

is there a a code.

 

[boostoutlaw]

No code at all, starting to get real confusing.

 

[boostoutlaw]

I was told it could be the maf sensor but i wanted to check here first before i went and spend the money on anything since you guys might have had similer problem before.

 

[pauleyman]

Youre likely seeing a symptom and guessing at the root cause. Blindly replacing parts is not a solution.
Is the throttle physically closed?
Did you check throttle cable?
Idle position switch working?
Throttle position working?
Any leaks?
Any codes?
Did you actually check or assume because light isnt lit?
Coolant temp?
Isc and biss set correctly?

 

[boostoutlaw]

Exactly thats why im asking, im use to older cars with carbs,

No leaks
Throttle is closed
Throttle position is working
No codes
Yes i actually checked, not that stupid.
Coolant temp is right where it should be, checked everything and all is good.

 

[pauleyman]

Car shouldnt idle above 1500. Idle position switch is not right. Might be part of throttle position on a 2g. You'll have to look that one up, biss and isc need to be checked. How did you check for air leaks?

 

[boostoutlaw]

Ill check the isc and biss again just to make sure im not over looking anything. And i took it to a shop and they used a smoke machine.

 

[asexton6969]

So you have performed a boost leak test? You have properly set your BISS screw? You used a scan tool to read throttle position at closed and full open positions? Verified the coolant temp sensor is accurate? Checked idle count and requested idle speed?

Doubt the mass air flow is bad, do the hard work and diagnose the car. Don't just LOOK at it, go the extra mile and perform any necessary testing.

 

[boostoutlaw]

So you have performed a boost leak test? You have properly set your BISS screw? You used a scan tool to read throttle position at closed and full open positions? Verified the coolant temp sensor is accurate? Checked idle count and requested idle speed?

Doubt the mass air flow is bad, do the hard work and diagnose the car. Don't just LOOK at it, go the extra mile and perform any necessary testing.

I did test everything, nothing came up, i dont just stand over my car and say hmm everything looks just fine" no i actually go and get things tested. No one can find anything that points to the problem, thats why i came here.

 

[asexton6969]

A smoke machine will not pressurize the system enough to find boost leaks. You need to build a boost leak tester and test the system to what you are running for boost and then some.

 

[boostoutlaw]

So you mean to tell me, a shop that actually installs turbos and has done machanic work for years and also specailizes in imports wouldnt know how to check for boost leaks?

 

[pauleyman]

It would be a good idea to test the isc. Only way you should idle high is air is getting in somewhere. If it were a bad leak car would run bad. If its through the normal idle controls then air is still read and idle increases. Most likely candidates are throttle itself, biss and isc.
And if this shop was just a normal mechanic shop then no, they probably do not know how to proply check for leaks on a boosted car. What has been done to the car lately? Did this just happen out of the blue?

 

[asexton6969]

I'm here to help not beat you down. You didn't give information on what kind of shop is doing the work. Smoke testing (EVAP Testing) is using less than 1 PSI to introduce smoke to identify intake leaks. Boost leak testing will pressurize to 15,20,25,30 PSI depending on your setup and what you are running. Is the car driving normally other than the ridiculously high idle?

 

[patrick ellsworth]

I would think its the ISC or TPS
Testing these things is pretty easy if you have a multi meter
ISC TEST-

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Tps should be .9 closed 5.0 ohms WOT
MAF- this is exactly what my manual says

Backprobe terminal 4 of the connector with the positive probe of the voltmeter and connect the negative to the ground. Turn the key to on but do not start the engine if the voltemeter does not read around 12v. If so check the circuit back to the MFI relay and fusible link.

Backprobe terminal 3, it should read 4.8-5.2v with the key on. If not check the circuit to the ECU.

Backprobe terminal 5 with an ohmmeter and measure the resistance. It should be less than 2 ohms. If not, check the circuit from terminal 5 back to ground.

If none of the above work, the MAS or ECU is dead. Replace it.

 

[Colt4G63 also]

I can't see how it could idle at 3000 while the closed throttle switch is activated. The ECU would cut fuel and the engine would start surging. Something isn't adding up.