Engine will not stay running

[Bill in Florida]

I bought a used 2004 Bonneville with low miles and recently have a problems with the engine not wanting to run after a couple minutes. It will start right up when I first get in the car, but will not start unless I pump the gas peddle after it warms up. Also after it warms up, I have to rev the engine as it will not idle after the engine warms up. It feels like it is starving for fuel. I borrow an engine code tool, but cleared the history thinking the engine malfunction light would come back on, but it did not come back on and I don't have any engine codes. This car ran great until I let my daughter barrow it and she does not know why the engine light came on while she was using it.
I changed the fuel filter and spark plugs with no change. I bought some MAP cleaner and used it on some of the sensors with no change.
No change in radiator water/ coolant level or discolor in the oil. The old plugs looked okay and I used the recommended plugs when I replaced them.

Does anyone have any ideas what I can do?
Thank you

I have not started the car in a couple days, so I went out and it started right up. Running real good and no engine malfunction lights on. All the gauges look good. I backed it down the drive way and back up. Engines still running good as I watch the water temperature gauge climb.Then after a few minutes it shuts off. I restarted it, but it will not idle and I have to rev the motor to keep it running. After a while it gets worst as I have to pump the gas pedal.

[michtom]

Possibly fuel related. Start with checking fuel pressure at the shrader valve on the fuel rail. First check with key on engine off, then check with engine running. Watch the gauge as it warms up to see if there is a pressure drop and the pressure after a restart.

[MKMike]

When you clear the codes, the check engine light doesn't necessarily come back on the next time you drive it.
Now that the check engine light has come on again, you can be sure there are some codes stored.
You can get the codes read for free at some places, like AutoZone--which also lends some tools and gauges for free.
I wouldn't take their word for what the problem is and have it repaired--- just have them write down or print out the codes for you--and then post them here.

I would also do as michtom suggested and check the fuel pressure.
Fuel pressure gauges aren't terribly expensive and you can probably borrow one for free.

To check fuel pressures, here's what you do:

(There is a valve, covered by a plastic cap on the metal fuel rail that feeds the fuel injectors, which you connect the gauge to.)
1.Turn OFF the ignition.
2.Turn OFF the air conditioning system.

Wrap a shop towel around the fuel pressure connection when connecting or disconnecting the gauge in order to reduce the risk of fire.
The towel will absorb any fuel leakage that occurs.

3.Thread the fitting on the pressure gauge hose onto the fuel pressure fitting.
4.Place the bleed hose of the fuel pressure gauge into an approved gasoline container .
5.Turn ON the ignition.
6.Bleed the air out of the fuel pressure gauge into an approved gasoline container.
7.Turn OFF the ignition for 10 seconds.
8.Turn ON the ignition.


Take the following 3 readings and write them down
A) Read fuel pressure Key On /engine OFF (KOEO) should be above 50
B)Key On /engine running (KOER ) mid to upper 40's is typical running fuel pressure
C)Key on/ engine running -- disconnect vacuum hose to fuel pressure regulator and then reconnect it
When you do this there should be approximately a 10 psi increase in fuel pressure until the vacuum hose is reconnected.
If pressure does not increase, you have a faulty FPR.
There should not be any gasoline in the FPR vacuum hose.

You also want to watch the fuel pressure with the Key off engine off and see if it rapidly drops or steadily drops.
It shouldn't do either.
If it does, this often causes hard starting due to there not being enough fuel/pressure in the fuel lines initially.
Causes are faulty fuel pump check valve or a leaky fuel pressure regulator.

Service manual lists normal fuel pressures as:
2001 - 2004 VIN 1 & K KOEO 53-59 psi
2001 - 2004 VIN 1 & K KOER 3-10 psi less than above

[Bill in Florida]

Possibly fuel related. Start with checking fuel pressure at the shrader valve on the fuel rail. First check with key on engine off, then check with engine running. Watch the gauge as it warms up to see if there is a pressure drop and the pressure after a restart.

Thank you for your reply and information. I will try this.

[Bill in Florida]

When you clear the codes, the check engine light doesn't necessarily come back on the next time you drive it.
Now that the check engine light has come on again, you can be sure there are some codes stored.
You can get the codes read for free at some places, like AutoZone--which also lends some tools and gauges for free.
I wouldn't take their word for what the problem is and have it repaired--- just have them write down or print out the codes for you--and then post them here.

I would also do as michtom suggested and check the fuel pressure.
Fuel pressure gauges aren't terribly expensive and you can probably borrow one for free.

To check fuel pressures, here's what you do:

(There is a valve, covered by a plastic cap on the metal fuel rail that feeds the fuel injectors, which you connect the gauge to.)
1.Turn OFF the ignition.
2.Turn OFF the air conditioning system.

Wrap a shop towel around the fuel pressure connection when connecting or disconnecting the gauge in order to reduce the risk of fire.
The towel will absorb any fuel leakage that occurs.

3.Thread the fitting on the pressure gauge hose onto the fuel pressure fitting.
4.Place the bleed hose of the fuel pressure gauge into an approved gasoline container .
5.Turn ON the ignition.
6.Bleed the air out of the fuel pressure gauge into an approved gasoline container.
7.Turn OFF the ignition for 10 seconds.
8.Turn ON the ignition.


Take the following 3 readings and write them down
A) Read fuel pressure Key On /engine OFF (KOEO) should be above 50
B)Key On /engine running (KOER ) mid to upper 40's is typical running fuel pressure
C)Key on/ engine running -- disconnect vacuum hose to fuel pressure regulator and then reconnect it
When you do this there should be approximately a 10 psi increase in fuel pressure until the vacuum hose is reconnected.
If pressure does not increase, you have a faulty FPR.
There should not be any gasoline in the FPR vacuum hose.

You also want to watch the fuel pressure with the Key off engine off and see if it rapidly drops or steadily drops.
It shouldn't do either.
If it does, this often causes hard starting due to there not being enough fuel/pressure in the fuel lines initially.
Causes are faulty fuel pump check valve or a leaky fuel pressure regulator.

Service manual lists normal fuel pressures as:
2001 - 2004 VIN 1 & K KOEO 53-59 psi
2001 - 2004 VIN 1 & K KOER 3-10 psi less than above

Thank you for this information and making it easy for me to understand. I will go to Auto Zone and borrow this tool. OEM/Fuel pump diagnostic kit Price: $150.00 as listed on the Auto Zone web site. I can barrow it for free with a deposit. This is a learning process for me and hopefully I can get my Bonneville back on the road. It still does not have an engine malfunction light since I cleared it.

[Bill in Florida]

I borrowed a fuel pressure test kit at AutoZone. Everything looked good.
I pulled off the the electrical terminal plug on the Idle Air Control (IAC) Valve and the motor stated working fine. I tried using a spray cleaner and it does no good.
I ordered a new one from RockAuto for $ 22.36 with shipping. When I looked on the AutoZone site, there were a lot of choices, but none of the pictures looked the same and cost a lot more, $55 for the cheapest. I have had good luck with RockAuto with past orders.
I hope this fixes my problem and I appreciate all the information that everyone has provided me. Not being a mechanic makes it hard for me to diagnose problems. I may still have a problem and will know more when I change out the Idle Air Control (IAC) Valve.
I am also still trying to learn how to use this site. It is a valuable tool for everyone.
Thank everyone for all the help that has been sent to me.

[MKMike]

Not being a mechanic makes it hard for me to diagnose problems.

With today's electronics, it isn't easy for mechanics to diagnose things either.

Hopefully, it was just a sticking IAC valve.
What happens when it sticks open is that it makes the fuel mixture too lean--hence the lousy idle and stalling.

Of course there are at least a half dozen other things that could do that, as well....
One frequent offender is the MAF sensor.
When it goes bad or gets too dirty, it wreaks havoc on the air/fuel mixture.
If you want to clean the MAF be sure to only use a designated MAF sensor cleaner.
Other cleaners leave a residue that makes it work poorly.
Some have had success with rubbing alcohol, as detailed here http://www.pontiacbonnevilleclub.com/fo ... c1661.html

Let us know how it works out.

[Bill in Florida]

Thanks for the additional information. When I took the IAC out, I tried to push it in and pull it out. I also sprayed cleaner on it. The inter spring did not do anything and it took a lot of force to move it.
I did buy MAF sensor cleaner at AutoZone and used it on the MAF sensor.

[Mad_Coachman]

You will not be able to move the IAC by pressing it. When I replaced mine there were instructions in the box for setting how far the pintle goes in. It is adjusted by screwing it in or out and should be checked with a metric ruler.

[DCJREDLINE]

Any update on your IAC replacement?

[Bill in Florida]

I received the new IAC this evening in the mail & installed it. I drove it around the block and decided to wash it as it ran good. After I wash it, I was going to filled up the gas tank and the vehicle started acting the same as before. It got dark, so I will look at it tomorrow. Maybe I have to reset something. I may purchase the MAF sensor to see if that fixes it afterwards. I already cleaned it with MAF sensor cleaner.

[MKMike]

Did you happen to take note of the codes that had set after the check engine light had come on?
The MAF is a frequent offender but the far cheaper oxygen sensor is also a possibility. A cleaning won't help the MAF if its electronics have gone bad.
You can check the connectors and make sure there's no corrosion.
Many have isolated the MAF as the problem by unplugging it and seeing how the car runs. If it runs well, then you know the MAF is sending bad info to the ECM and needs to be replaced.
Since you haven't mentioned changing the air filter or the PCV , I'd suggest changing those inexpensive parts before spending big bucks on a MAF sensor.

[Bill in Florida]

Thanks for the advice. I did not take notes on the codes and now the check engine light does not come on.
When the car was running bad, I unplug IAC and it would run good, that is why I thought it was the IAC.
I was going to disconnect one of the battery leads and then reconnect it in hopes of resetting anything. Then I was going to take it for a ride over 40 mph for a few minutes to see if that helps.
The air filter looks good. I will also try unplugging the MAF sensor. I will also look at the other parts you mentioned.
The problem seems to appear after the engine warms up.
Thanks for the information.

[MKMike]

Any progress?
There's no shame if you get frustrated and choose to have a reliable shop diagnose and repair it.
Posting what fixes an issue helps other people.

Since your fuel pressure is good, I'd suspect the MAF sensor has gone bad.
Sometimes you can tap on it and get it to act up. Other times unplugging a faulty MAF can result in the car running better.
You don't want to leave it unplugged and forget about it, since it will hurt your gas mileage, reduce power and the car won't pass emissions testing.
You can check the connector for corrosion.

Once in a while, someone gets a tank of bad gas that makes the car run poorly, so that's also a possibility.
If you always go to the same gas station and never had an issue, then that is unlikely

Any leaking vacuum hose(s) will cause the engine to run too lean, since the computer uses the MAF to calculate how much fuel to supply--and vacuum leaks introduce air into the engine after the MAF.
As they age, the hoses become brittle and crack or even fall off.
A stuck PCV valve will have the same effect.
It should freely rattle when you shake it and it must have 3 things with it: a large o ring, a small o ring and a spring.
If any 1 of these is missing, it will cause problems.
The PCV is rather hidden. It is at the belt end of the intake manifold, underneath the MAP sensor.
This picture may help you find it in your car http://www.rockauto.com/en/moreinfo.php ... 84&jsn=234

[Bill in Florida]

I disconnected a battery lead and then reconnected it after a couple minutes. I took it for a ride to get the speed over 40 mph for a few minutes hoping it would reset something. As I was headed back home, the motor died and would not restart. I try restarting it on the side of the road and I had to pump it to keep it running. It got worst, so I called AAA for a tow truck. I also smelled gas but saw no gas leaks, probably from pumping the gas to keep it running.
The MAP sensor has not arrived yet.
The idea of bad gas is something I should think of since the last tank of gas was when I let my daughter use it when I was out of town. She told me she got the gas at a circle K.
I also changed PCV today and it did not make a difference. The old PCV did rattle okay. It did have both o rings and a spring.
I looked for leaking hoses. I may have over looked one as I am not that familiar with this car yet.
Thank you for the additional advise.

[MKMike]

Disconnecting the battery to reset things wasn't a bad idea.
You mention that the MAP sensor hasn't arrived yet.
I hope you meant MAF sensor.
The car has both; MAF on the throttle body. MAP on top of the PCV

Did you try unplugging the MAF and seeing if it will run?

If you do flood the engine, press the accelerator to the floor and hold it there while cranking.
It's a "clear flood" mode that stops the injectors from adding more fuel temporarily.

[96 SSEi]

Hi, I agree with mike, I too had similar problems and it was MAF. unplug it and see the difference

[Bill in Florida]

I changed the MAF sensor today and did not correct the problem. I still have no check engine lights. It only seems to run bad after it warms up.
I also disconnected the grd. lead on the battery and reconnected it after replacing it.

[dougtoth]

Have you looked at the ICM?(ignition control module)
My 2001 Bonneville SLE would run great until it warmed up.
Then it would die and not restart until it cooled down.(no lights came on)
I replaced the fuel pump,fuel pump regulator,fuel pump relay and the gas filter.
After all of that it still would die and not restart until it cooled down.
I thought it was a fuel problem but it turned out to be a spark problem.(ICM)
It was really frustrating because without warning the car would just die.
Don't know if this is your problem but thought I would just mention it.
Good Luck.

[96 SSEi]

I changed the MAF sensor today and did not correct the problem. I still have no check engine lights. It only seems to run bad after it warms up.
I also disconnected the grd. lead on the battery and reconnected it after replacing it.

I think I posted on wrong issue somewhere else.....sorry

changing the MAF sensor is useless if the connector or wires are rotten....please unplug and see if it helps