2002 Starting and Stalling Issue

[Reynard]

I've tried to search the forums for a thread similar to my issue but haven't found one that deals directly. My apologies if I've missed it and have posted a repeat thread.

Got a 2002 GT with the NA 3.8 and 150,000 miles. The car has pretty much sat for the past 6 months, driven very sparingly. If it's been sitting for a while (like over night or longer) it will start no problem. If I turn the car off for a shorter period, it will crank but not fire. It will start only if I pump the gas as I'm turning the ignition.

In addition, on occasions it has died while at idle or coasting to a stoplight. After it dies it will fire back up no problem.

Fuel problem perhaps?

The "Service Engine Soon" light has been on for about a month before it started acting up. I had the codes checked at AutoZone and it came up with P0442 and P0128.

Any help or suggestions would be greatly appreciated.

Thanks!

[82Stang]

Hello, the p0128 is a coolant related code, not up to tmp. Likely the T-stat, should have oem 195 T-stat. If a colder T-stat was used previously, that would set the CEL. If not T-stat, then coolant temp sensor and last possibly a coolant mixture that is set too cold for the colder climates, i.e. coolant set to -50 below F, -20 is fine. The p0442 is a small evap leak and that can mean many different things. First and easiest, is a new gas cap. Also check all vac hoses under hood, check fuel filler neck for cracks, rust through, broken vent tube etc. When in doubt and if inspection isn't needed anytime soon, clear the codes and see what comes back. You can clear the codes with a scan tool or unhook bat cables, pos and neg, and touch them together for a minute, or just unhook neg cable for 5 mins or remove the bat fuse.

[Tech II]

Stang has explained the codes....

As for the stall, hard start:

Check IAC operation, and clean pintle of IAC and throttle bore/plate.......

Check vac line to fuel pressure regulator for fuel....

When car won't start, try disconnecting the MAF sensor and then try to start again....

[82Stang]

Originally Posted by Tech II

Stang has explained the codes....

As for the stall, hard start:

Check IAC operation, and clean pintle of IAC and throttle bore/plate.......

Check vac line to fuel pressure regulator for fuel....

When car won't start, try disconnecting the MAF sensor and then try to start again....

Very good additional advice from Tech II for you Reynard. Vacuum leaks can happen at the IAC pintle too. The vac line to FPR(fuel pressure regulator), while running disconnect hose and wait. Sometimes I've had to wait 2 to 3 minutes and then it started spitting fuel out the FPR = bad. And disconnecting MAF(mass air flow), is a very good old school tried and true method to check MAF operation. If car runs better w/o MAF plugged in = bad MAF.

[Reynard]

Originally Posted by Tech II

Stang has explained the codes....

As for the stall, hard start:

Check IAC operation, and clean pintle of IAC and throttle bore/plate.......

Check vac line to fuel pressure regulator for fuel....

When car won't start, try disconnecting the MAF sensor and then try to start again....

Originally Posted by 82Stang

Very good additional advice from Tech II for you Reynard. Vacuum leaks can happen at the IAC pintle too. The vac line to FPR(fuel pressure regulator), while running disconnect hose and wait. Sometimes I've had to wait 2 to 3 minutes and then it started spitting fuel out the FPR = bad. And disconnecting MAF(mass air flow), is a very good old school tried and true method to check MAF operation. If car runs better w/o MAF plugged in = bad MAF.

Thank you both, Stang and Tech II!

Got called into work, but when I get a chance I'll definitely try this out.

[FISH96]

from 825stang

Hello, the p0128 is a coolant related code, not up to tmp. Likely the T-stat, should have oem 195 T-stat. If a colder T-stat was used previously, that would set the CEL. If not T-stat, then coolant temp sensor and last possibly a coolant mixture that is set too cold for the colder climates, i.e. coolant set to -50 below F, -20 is fine.

so cars above the artic circle set the code because of the coolant mixture is a ratio for -40 or greater. your logic seems faulty.
correct me if I am incorrect.

[SleepyHead98]

The code p0128, is coolant related. Check coolant level for sure. Its running dexcool, if it hasent been serviced, flushed, it sprobably acidic, need to get it out of the engine. The stalling issue, I also think its the IAC. Check vaccum leaks aswell, but IAC would be my first look. You can clean it, and even test it with a multimeter.

[Tech II]

P0128, more often than not, is caused by a bad thermostat.......

What happens is, the thermostat is opening too soon....

One way to check this, is with a scan tool(kind of tough watching the dash gauge), observing coolant data.....let the car warm up from a cold start....when it reaches 190-200F, take it out on the highway at 65 mph......that temp should only drop to 185-190F.......if it drops down to 160-170, it's the thermostat...

Put a new stat in, burp the system of air, clear code, and repeat the road test......doubt it drops below 190F......

What sets the code is this.......the PCM observes the coolant temp from a cold start.....then based on time, load, and speed, the coolant temp should reach 190F in a specified amount of time....if it takes too long, or doesn't achieve it, the code sets....by going down the highway, the wind going across that motor cools the engine temp below the 190F threshold, because the therm has opened too early.....with the car sitting still, that engine compartment raises the temp, even though the therm has opened early.........

[82Stang]

Originally Posted by FISH96

so cars above the artic circle set the code because of the coolant mixture is a ratio for -40 or greater. your logic seems faulty.
correct me if I am incorrect.

Faulty coolant mixture can cause this.

[Lukas111]

You need to clean the throttle body plates. For sure this is a problem with 04+ grand prix, assuming could be prob with previous models as well.

Symptoms should be something like this.
ON cold start, it will start and work, but will struggle at first.
Randomly car will start for a second and engine will stall immediately.
It will start if you push gas pedal a bit.

Your throttle body plates are dirty. Take throttle body off and clean nicely, dont clean while it is on the engine. It already worked out for one guy on the forum, search and you will find it.
worked for me as well.

[Reynard]

Here's an update:

For the temp codes, I replaced the thermostat. Had the code reset, so far so good.

As for the starting and stalling issue I cleaned the IAC and the MAF and even the connectors (used the proper chemicals for each). While this seemed to help at first, the issue has since remained.

Guess my next step would be to clean the throttle body as Lukas has suggested. While removing the TB doesn't seem very had it does look a little labor intensive with the placement of some of the bolts. My question is what is everyone's opinion on cleaning it while attached to the manifold still (providing i take all of the sensors out)?

Any tips or suggestions would be greatly appreciated.

Thanks!

[Lukas111]

Originally Posted by Reynard

Here's an update:

For the temp codes, I replaced the thermostat. Had the code reset, so far so good.

As for the starting and stalling issue I cleaned the IAC and the MAF and even the connectors (used the proper chemicals for each). While this seemed to help at first, the issue has since remained.

Guess my next step would be to clean the throttle body as Lukas has suggested. While removing the TB doesn't seem very had it does look a little labor intensive with the placement of some of the bolts. My question is what is everyone's opinion on cleaning it while attached to the manifold still (providing i take all of the sensors out)?

Any tips or suggestions would be greatly appreciated.

Thanks!

Throttle Body problem.
The way it works is when you start the car, engine seems to start but suddenly it shut off.
I highly suggest you to take throttle body off and clean it nice, also you don't get any cleaner inside the engine. That's easier and better way. Have only 4 10mm bolts and with 4-6 inch extension it is piece of cake. (My first throttle body I removed with regular 10mm wrench)
If you clean it attached you can get to much cleaner inside and potentially damage the engine.
Let it dry nicely before put back on, otherwise you are gonna have problem starting the car.

[Reynard]

Just wanted to give an update on the situation.

Finally had time to get around to it, but I followed all of the suggestions everyone gave.

Turned out to be a bad fuel pressure regulator. Took off the vac line and fuel instantly started spitting out.

Also took off the throttle body to clean it as Lukas suggested just for good measure. For 150,000 miles I was very surprised to that the TB was damn near spotlesss. Cleaned it and the IAC and MAF, too.

Other than some bruised pride in some how screwing up the reinstallation of the TPS, having her idle too high, and taking everything apart again, was an easy fix.

Thank you all for your help on this one!