2.4L turns over fine, then dies

My fuel pressure regulator went and had the same problems you describe.

 

Interesting...thanks.

Could you elaborate a little further? How did you narrow it down to the regulator as opposed the pump?

 

So it dies after being started and left to idle on its own when COLD correct ?

If you keep your foot on the throttle it will run normally correct ? or is it missing/stumbling ? If it sounds normal under throttle, keep the RPMs up till the engine comes to operating temp. Will it now stay running or once left to idle it stumbles then dies ?

Also, the blueish-white colored smoke will be normal for a time after running seafoam. You may want to strongly consider an oil change after running the stuff. Its also possible you may have fouled your plugs. Pull one and have a look. Also, as all the carbon and gunk is broken down from the seafoam, it goes through the entire exhaust system and out the back. This may also result in a clogged cat or clogged up o2 sensors which could be causing your current CEL condition.

Do you have access to a code reader ? I suppose once we figure the idle problem out, you could go to a local autoparts store and have them pull it for you.

Depending on the results from the "warm the engine up test", it may be the EGR or related EGR components, or the IACV ( which controls the idle for cold starts. Pretty much lets the motor idle at a higher RPM till normal op temp is reached, then it drops to normal idle )

 

My problems have taken a turn in a different direction. I finally pulled the CEL codes today -- there was just one: P0100.

P0100 is Mass Air Flow Circuit Malfunction. I'm following the P0100 troubleshooting process in the service manual.

Test 1: Unknown, I have no way to read the Mass Air Flow rate.
Test 2: Check source voltage. It's good, 12.3V.
Test 3: Check voltage between terminal VG of the ECM and ground. This result is bad. Should be 1.0-1.5 V and it's reading close to zero.
Test 4: Check continuity between MAF and ECM. 0.3 ohms between the MAF sensor pin and terminal VG in the ECM. This looks good.

The flowchart says I should replace the MAF sensor. Would the MAF sensor problems cause the fuel starvation?

Does this explain the fuel starvation or a separate problem?

 

The MAF sensor failure would deff explain the fuel starvation. Depending on the incoming air temp, the ECU applies more or less fuel. Bad reading or malfunctioning MAF = no fuel. Also, make sure you are following the inspection procedure correctly. As i recall, you will need to have the key in the ON position to get a reading from/to the ECM and the sensor.

Prob gonna want to swap that thing out if it still tests bad. Or see if a friend will let you barrow/swap for testing.

 

I figured the engine would still run (roughly) with a bad MAF. But the more I read up on this, the more I'm convinced I'm wrong.

My dad has been helping me test the MAF sensor. He's an electronics engineer. In fact, he tested the MAF sensor on his workbench with a 12V power supply and is seeing the same results. So I think MAF sensor failure is a safe bet, unless somebody thinks otherwise.

What's unfortunate is the price of a replacement. Although I can get a remanufactured MAF sensor for $222.87 through a friend, I'm really close to selling this truck and getting a new Tacoma Prerunner. The problem with going to a junkyard is the inability to test a MAF...unless they allowed me to bring a 12V battery and meter along. I have a feeling, too, that MAF sensors would be long gone.

Frustrating.

 

Here's an update:

I programmed my ScanGauge II to read MAF. With or without the MAF sensor connected, it reads a constant 0.57 at all times. When connected, it does not change in response to RPM's changing, just 0.57 all the time. On other cars I tested, the MAF reading bounces all over the place as you manipulate the gas pedal.

Another thing I noticed is with the MAF sensor disconnected the truck runs smoother. Still not normal...it's tough to get it started, but once it's running, there's a noticeable difference.

 

MAF sensors get really dirty and the dirt seems to bake on. If you look at it it should be clean and I think it looks like an amber color. I cleaned mine with spray electronic clean and softly scrubbed it with a Qtip. That fixed mine. Anyway just a thought. good luck!

 

The voltage reading should fluctuate with throttle ( as it pulls in more air past the MAF. ) I suppose you could attempt to clean it. Electronics cleaner sounds good as the only thing that would really be caked on there is dust/dirt.

Its quite possible it may be a combination of things.Attempt to recondition or find a working used or new MAF, and see if that corrects the issue first.

You would probably stand to benefit more by getting your truck running smoothly. then attempting to sell it private party as opposed to trading it in if a new truck is what you are really going for. Also, 200 bucks for a new sensor is much cheaper then financing another 20k + for 5 years or more and paying all the sales tax, fees, etc all over again.

Up to you ! good luck with whatever you choose to do. If the MAF replace/recondition doesn't work, post back so we can keep trying.

 

Yeah, cleaning the MAF did nothing unfortunately. I don't know anybody with a compatible MAF I could use for testing purposes. The fact it failed the service manual test procedure is conclusive enough I think.

I agree, $222 won't break the bank -- it's just annoying, that's all. Including new tires and shocks, I'll probably have to spend 25% of it's current value just to get it acceptable enough for sale.

Oh well, that's life.

 

Does this answer your question?

 

Happy news to report! New MAF sensor installed, truck runs beautifully. Sure enough, when I watched the MAF reading on the ScanGaugeII, it was all over the place like it should be. With the old, dead, MAF sensor, it was a constant 0.57 all the time.

Special thanks to 98tacoma27 and sirlight and dangerbird and everybody else who offered me advice. I really appreciate it.