2000 Taurus dies at idle after warmed up

[routerman]

I have a 2000 Taurus with 108K on it and it started stalling at idle when sitting at stoplights. It's a 3.0 24V DOHC and I've cleaned the throttle body and what I think is the IAC maybe on top of the intake not far from the throttle body. I disconnected the power connector to that module as well and the stalling didn't change at all so I'm wondering if it's that module but here's more details. After I cleaned the throttle body I sat in park with it warmed up idling and when it wanted to die I would tap accelerator and it would jump to about 1500RPM for about 8 seconds and then drop back to 800-900RPM. It would stay there for 15 to 25 sec and then drop to 600 and try to die and if I hit the accelerator it would jump back up to 1500 and I could pretty much do that over and over and it was pretty consistent. Would die if I didn't tap pedal to keep it going and it had P0172 code in bank 2. I had a bunch of others that were caused when I cleaned the TB so I've cleared the codes and will watch for new ones but figured I'd ask if this sounds like anything specific with the pattern I see. Thanks

[sheila]

I was going to suggest you check the pcv hose buried down in front of the intake (po171/174-both banks lean), but po172 is: system too rich bank#1 (firewall). Might try cleaning the maf sensor and check injectors.

[Breeves002]

^
+1 with sheila

It could be a stuck open injector or even possibly more than one. Way to test is watch the fuel pressure after you turn the car off. If it drops you have a stuck open injector.

[routerman]

I may have gotten the code wrong because it said too lean so maybe it was a 174. How can I check the fuel pressure and where is the MAF sensor located? I'd assume for the fuel pressure I can't check it measuring voltage and need to be in the fuel line path?

[Breeves002]

If it was too lean it could be p0171 or p0174 or both. Where it is matters. If it's p0174 then it means it is the front of the motor that is running lean vs p0171 means the rear of the motor (back 3 cylinders) are running lean.

There is an easier way to check fuel pressure. First way is using a scan tool that supports it, second way is buying a cheap fuel pressure gauge and plugging it into the Schrader valve on the fuel rail. Looks like the cap that goes on your tires. It's on the passenger side of the motor near the top on a silver 'rail'. Should be around 40psi.

[routerman]

I have the Innova 3160 but don't think it does the fuel pressure. I know where the valve is you mentioned and may just pick up a gauge to check it. I never thought it could be an injector since it runs smooth the rest of the time. This all started when the PCV hose elbow went bad and I had to replace it. I assume it was just a vacuum leak and I know I've gotten codes indicating lean in both bank 1 and bank 2 which I thought would go away with the PCV fix. Figured it was just pulling in air since the hose was disconected from PCV. It didn't bother me as much since I drive with 2 feet but kids don't so they're complaining about the stalling so gotta fix it..lol

[Jeff K]

If you have a 174 and no 171 (current or pending), or vise versa, the problem is NOT fuel pressure related, nor is in MAF related. You most likely have a vac leak effecting the lean bank. Intake gaskets are well known vac leak points on the 24V DOHC.

Gen 4 with the returnless fuel system eliminated the schraeder valve for mechanically measuring fuel pressure. To measure it you would have to splice a "T" into the line or use a scan tool to measure pressure via the electronic pressure/temp sensor on the rail.

[Breeves002]

Jeff couldn't it be fuel pressure related in theory? Kind of like it will start to misfire on one cylinder and not be a random miss if the pressure is only slightly too low. If he could look at the trims, it's possible the other bank is running lean, but not enough to set codes.

Anyways Jeff is right. It's probably a vac leak that only effects the bank that's running lean.

[routerman]

My daughter drove it and said the check engine light is on again so I went and got the codes. Turns out it has both the P0174 system too lean bank 2 and P0171 bank 1. She said it still dies but didn't do it as much but I suspect that could just be because of the colder weather since I haven't done anything to it. I do have freeze frame data and it shows fuel pressure at 110 but I know that was when it set the code. I have STFT and LTFT numbers as well if those would help any or you think it's vacuum leak and I need to focus on that?

[Breeves002]

Please post the STFT and LTFT numbers!

Probably is a vacuum leak if both codes are present. However the fuel trims behavior will help diagnose. If they are high at idle, then go to normal (+-5%) when you rev the engine, it is likely a vacuum leak.