no idea what to do, need help. trouble starting warm

[Nick98talon]

Scanned my car and came up with p0420, p0170, p0120, p0303. The problem going on is I can drive it from a cold start but anytime I try to start it within 45 mins of shutting it off after a drive it starts super rough and misfires and is trying to idle and almost stalling eventually resulting in it stalling out. Any time I let it sit for about an hour it starts up just fine. I replaced the fuel pressure regulator and erased the codes hoping it would throw me the codes back and I could see if it fixed anything, well, same problem and its not throwing any codes now. What should I try?

 

[Nutsbad10]

It will take a little driving for the ECU to run a complete scan and start throwing codes again. It could be a series of things; You're idle air control, throttle position sensor, it could be as simple as you have a loose cable on an o2 sensor. Anything that regulates fuel and air mixture could be causing this.

p0420 - telling you your catalyst is below efficiency. You could have a bad cat or o2 sensor. How many miles do you have?
p0170 - could be a vacuum leak or a faulty intake air temp sensor
p0120 - this is the reason I said your throttle position sensor could be bad/dirty. (sometimes the components of your throttle body need to be cleaned but care should be taken not to soak any portion of the electrical fittings with throttle body/carb cleaner)
p0303- thats a cylinder misfire

Some of these codes can cause others to be thrown off. Have you ever cleaned your throttle body? When was the last time you tuned this baby up? You may need a good cleaning and tune up. If your idle air control gets bad enough the car will just die or not start. Hope this information at least gives you somewhere to start and you didn't already know all this stuff.

 

[Nick98talon]

Ive only had the car for 4 months or so, and it was running perfect when i first got it. Also forgot to include under higher throttle it feels like its being held back once boost hits and if i go WOT in does a little popping noise once or twice, looked in my rear view and didnt see any black cloud or anything

 

[rtrocket59]

From the information you provided, it sounds like the TPS code is causing your other codes. Know how to use a DMM?

 

[hotrodssnova]

Dmm=digital multi meter.

 

[rtrocket59]

Yes sorry, so used to abbreviating that. But p0303, p0170, and p0420 are all "condition" codes. Meaning they are the result of another failure. P0120 is a TPS circuit failure code. Meaning the ecu saw a value on that circuit which was above/below a calibrated threshold.

As a Ford technician, we are trained to diagnose circuit failure codes are first, because they are the most likely cause of the failure. If this was my car, I'd be getting out a wiring diagram and testing the circuit with a digital multi meter.

 

[Nick98talon]

So its looking like a TPS could be causing all this? also, I appreciate the help so far guys

 

[rtrocket59]

So its looking like a TPS could be causing all this? also, I appreciate the help so far guys

Yes, can you buy a digital multi meter? Its possible that it may need to be adjusted, replaced, or you have a circuit issue (open/shorted wire).

 

[luv2rallye]

anytime I try to start it within 45 mins of shutting it off after a drive it starts super rough and misfires and is trying to idle and almost stalling eventually resulting in it stalling out. Any time I let it sit for about an hour it starts up just fine.

Sounds like the classic vapor lock problem with faulty fuel pressure solenoid. The fuel pressure solenoid is designed for just that...hot starts. At a certain temp it will activate and pull from the outside instead of from the intake mani under vacuum. It is the same as removing the vac line from the fpr. It raises the fuel pressure to avoid "vapor lock" in hot conditions. Easy enough to check, when giving you problems, shut off the car, remove the vac line from the fpr and see if that lets the car start as it should. If that works replace the fuel pressure solenoid (or check it's hoses for leaks).

 

[rtrocket59]

Sounds like the classic vapor lock problem with faulty fuel pressure solenoid. The fuel pressure solenoid is designed for just that...hot starts. At a certain temp it will activate and pull from the outside instead of from the intake mani under vacuum. It is the same as removing the vac line from the fpr. It raises the fuel pressure to avoid "vapor lock" in hot conditions. Easy enough to check, when giving you problems, shut off the car, remove the vac line from the fpr and see if that lets the car start as it should. If that works replace the fuel pressure solenoid (or check it's hoses for leaks).

Hmm I was unaware of this, definitely makes sense though. Say he has the solenoid deleted, could the TPS code be related to his concern?

 

[luv2rallye]

No.

 

[Nick98talon]

Thanks guys, ill check that out and let you know

 

[Nick98talon]

Been driving for multiple days after resetting CEL and still no codes. Also, I never got a P1105 code which is FPS, could it still be bad?

 

[inthemidst]

Check for vacuum leaks and fuel pressure and fuel filter.

 

[jon2manyrides]

Clogged cat would make it feel "neutered"

 

[Kendric Steed]

I'm along with @jon2manyrides, he beat me to it, but i was going to say if you can unbolt the exhaust at the bottom of the manifold / header and just drive but be careful not to set anything on fire. Basically you are trying to test if the catalytic converter is clogged. By unbolting the pipe you would let exhaust flow freely.

I have a 2002 S10 and I replaced a transmission because it would not shift pass second gear and the whole time it was the catalytic converter. I spend $1000 before I took it to the dealership and they told me it was the cat. The cat was so clogged the truck didn't have enough torque to shift into the next gear.

Moral to the story, the cat can make it seem like you don't have any power. If you don't have a turbo, I would unhook the exhaust and see what happens. For one, it does cost anything. Also sometimes you end up putting so much money in guessing parts it's best to pay the diagnosis at the "stealership" and come on here to get help on replacing the part.

 

[Nick98talon]

well I tried pulling the vac hose from the fpr to the fps and no luck. so everyone says check cat next? I really do appreciate all the help guys