PontiacBonnevilleClub.com

Greetings,

I bought my first car a couple days ago, and she's a 1999 Pontiac Bonneville SE that runs very smoothly.

Unfortunately, after pulling out of the gas station from her first fill-up the vehicle starts to stall and die (turns off) when idling. It's happened a couple of dozen times so far, and I would like it resolved. If the vehicle (sometimes) drops below ~500-600 RPM it will turn itself off, if the gas peddle is not pushed in response. If done quick enough, I can save the car from turning off but the engine makes a discomforting grunt.

The first time I filled the car up with gas, I used 85 octane fuel because I was unaware the K engine requires 87+. After riding off the tank of 85 octane fuel, I filled her up with 89 octane. It's certainly gotten better, but the issue still persists when slowing down to lower speeds. The Check Engine light also turns on when the vehicle stalls or would have stalled and died.

I've read that other people have had similar issues, though in my case the car starts right back up if you put it into park and turn the key. I do not have to wait 30 - 40min like most people reported. I've also read that it can be one of many things, like the mass air flow sensor, fuel filter, O2 sensor, etc. I unfortunately do not have the money to throw around at every part until the issue is fixed, so I'd appreciate some guidance. I've also been informed that a cheap start is a fuel injector cleaner. Also, can ethanol in the fuel have an affect on this issue?

I also read that I can read PCM codes to figure out what issues are present, but I can't seem to find an article related to my '99 SE model. Where can I find the connector, and the code values? Is this a safe operation? If I take the car to a mechanic, how much would they charge for a professional diagnosis?

-robodude666

Howdy folks,

I found out that AutoZone does free code scans so I went down earlier. The scanner reported only one code: P0102, which represents a low voltage on the MAF according to the code chart.

I'm going to attempt to disconnect the sensor as recommended by other individuals. If that resolves the issue, or makes the issue less prominent then I will figure out a way to buy a new MAF ($130 part!) and replace it.

Cheers,
-robodude666

While brand new is the best route, if you can't afford that price check out junkyards for used MAF sensors. Much cheaper.

Yup.

In the morning, when there's some light, I'll pop the hood open and look under the engine cover at the MAF sensor. I'll try disconnecting the sensor and running the car without it to see if it helps. If it does, I'll clean the sensor with MAF cleaner. If that doesn't help, I'll see if I can find one cheap at a junk or salvage yard. If not, I'll consider buying a cheap $30-50 one from eBay. They all include a 30-day refund/replacement non-DoA warranty. It'll certainly be cheaper than buying it for $130 from the local AutoZone or O'Reilly Auto Parts.

If anyone happens to have a spare fully working MAF sensor from a '99 Pontiac Bonneville SE, send me a PM .

-robodude666

also might check the FPR for a Diaphragm leak

http://www.youtube.com/watch?v=AKtR_yF7bi8

I'll take a look at the FPR when under the hood later today.

If I disconnect the 3-pin cable going to the MAF sensor, what changes should I expect to see -- besides the stalling/dying going away (allegedly)? If it regulates the fuel mass entering the engine, then how will the car receive the proper amount of fuel without it?

-robodude666

Howdy,

Sorry for double posting, but I've got an update on the MAF sensor.

I disconnected it before going on a ~60 mile drive. The engine feels happier, as it no longer jerks around ~30mph and ~40-50mph. Fuel economy has dropped a ton though. Driving ~60 miles (50mph most of the time) consumed about a quarter tank of gas. That yields about ~13 mpg, down from the previous ~35 mpg I had when driving 150 miles from Boise to Twin Falls (75mph most of the time).

Now... Unfortunately, the problem still persists but much rarer. The car stalled and died twice again. Once when slowing down from 50 mph to make a turn, and another time when driving 10 mph through a bumpy parking lot.

I'm suspecting there may be another issue with the vehicle besides (possibly?) the MAF sensor. I will let the engine cool down, as I do not feel comfortable working with it while it's warm, and will take a look at the FPR diaphragm for a leak, as well as trying to see if the MAF sensor actually is malfunctioning. I've read that tapping it with a screw driver would cause the RPMs to change if the internal electronics are damaged.

-robodude666

looking back at your post about problems starting after you filled it up - I would give it a can of "Seafoam" you might have gotton some bad gas and still have moisture in the tank.

What does Seafoam do? I bought a bottle of fuel injector cleaner, but haven't used any yet as it needs to be applied on a full gas tank. Would that kind of stuff help? If I don't have Seafoam at a local store, is there another product that might help?

Okay dokey. Problem still persists, and it's stressing me out.

I put a 16oz bottle of Seafoam into the gas tank after filling it up with 87 Octane fuel. Checked the FPR and no diagram leak was present - I let the car idle for 15 minutes while monitoring the port; no fuel came out. The car still stalls and dies with the MAF unplugged.

I drove today 12 miles in the city, with the MAF connected because otherwise my MPG drops below 10, and the car stalled and died at least 10 times. In addition to it happening when idling at a stop sign or traffic light, it also died when slowing down to make a left turn (in the ongoing lane!), as well as right after putting the car into reverse to back out of a parking spot.

My mom loaned me the money to buy my first car, and it's really starting to stress me out that it's having these issues which were not present during several road tests at the dealership. While I'm certain using lower-octane or ethanol fuel may upset the car, I'm certain it's not the cause of the issue. I'd be glad to take the car to a mechanic and tell them to "fix it!" but I cannot afford that right now. I found a MAF sense on eBay for $60 w/ a 60-day non-DoA return policy, but I'm not willing to buy it right now as there may be another issue. The AutoZone mechanic reported only a P0102 error code from a code scan.

The car runs pretty constantly with the oil pressure around 40, battery between 13 and 14v, and the engine temperature between 150 to 200f.

How can I test the O2 sensor, and where is it located? Is there anything else I can do to test the FPR? Some people reported this issue being fixed by replacing the Fuel Pump. Where is that, and how difficult is it to text, and replace? Same for the fuel filter.

-robodude666

robodude666 wrote:Okay dokey. Problem still persists, and it's stressing me out.

I put a 16oz bottle of Seafoam into the gas tank after filling it up with 87 Octane fuel. Checked the FPR and no diagram leak was present - I let the car idle for 15 minutes while monitoring the port; no fuel came out. The car still stalls and dies with the MAF unplugged.

I drove today 12 miles in the city, with the MAF connected because otherwise my MPG drops below 10, and the car stalled and died at least 10 times. In addition to it happening when idling at a stop sign or traffic light, it also died when slowing down to make a left turn (in the ongoing lane!), as well as right after putting the car into reverse to back out of a parking spot.

My mom loaned me the money to buy my first car, and it's really starting to stress me out that it's having these issues which were not present during several road tests at the dealership. While I'm certain using lower-octane or ethanol fuel may upset the car, I'm certain it's not the cause of the issue. I'd be glad to take the car to a mechanic and tell them to "fix it!" but I cannot afford that right now. I found a MAF sense on eBay for $60 w/ a 60-day non-DoA return policy, but I'm not willing to buy it right now as there may be another issue. The AutoZone mechanic reported only a P0102 error code from a code scan.

The car runs pretty constantly with the oil pressure around 40, battery between 13 and 14v, and the engine temperature between 150 to 200f.

How can I test the O2 sensor, and where is it located? Is there anything else I can do to test the FPR? Some people reported this issue being fixed by replacing the Fuel Pump. Where is that, and how difficult is it to text, and replace? Same for the fuel filter.

-robodude666

Not sure if your 99 has an IAC valve, but if it does, I would be removing and cleaning (if not replacing) that to start with. Also (probably FIRST) check your throttle plate, and clean the crap out of that. Dirty throttle plates and bores can cause all kinds of idle issues.

Don’t stress yet

All you have done to the MAF was to unplug it and sounds like it ran somewhat better but worse plugged in. you should try cleaning it first before your replace it. Get a can of “MAF” only cleaner take it out and spray the two little wires carefully and put it back in.

Follow renchjeep’s suggestion and clean the IAC ( should next to the MAF) and check the IAC plug pins for corrosion

Fuel filter should be located on the frame in front of the right rear wheel – make sure you bleed off the fuel pressure with the Schrader valve before you try to change it and have a drip pan ready.

to check the fuel system you need to find a fuel pressure tester - should be 40-45psi at idle

Does that appear accurate for a '99 Bonneville? Or is this more accurate:



Unrelated, yet somewhat related, would you recommend the haynes or chilton repair manual for the 1999 Pontiac Bonneville SE? They may help with locating parts, and diagnosing them.

The Throttle Plate is located inside of the Throttle Body, which is connected to a black house?

Can I use MAF cleaner on the IAC valve, or does it require an IAC cleaner? What do I clean the throttle plate with? Can the car run without an IAC Valve installed, like the MAF, to test whether or not it's a defective part?

EDIT:

Up and early in the morning, I opened up the hood of the car. Disconnected the MAF sensor so I wouldn't forget. Before turning the car on, I disconnected the hose to the FPR and sniffed it. It did smell like fuel, which I didn't notice before when I examined it. After reconnecting the hose, and turning the car on, I checked for a leak. No fuel came out of the spout, though it did smell like fuel.

I then drove to AutoZone with the MAF sensor disconnected. The car stalled and died twice when slowing down on a red light. I borrowed a set of security torx screwdrivers to remove the MAF sensor, and cleaned it with MAF Cleaner that I got for $8 (the CRC 05110 stuff). Right after turning the car on, the RPM gauge bounced to 1000 RPM, below 500 and then jumped back to 1500. It kept bouncing around until it settled between 800 and 1000 RPM. I then drove home with the MAF sensor reconnected without any issues. After arriving home, I turned the car off and turned it back on. The RPM gauge bounced around a bit. If I switch to Drive before the gauge settles down at 800-1000 RPM, the engine stalls and car dies. However, if I switch to drive after it settles the car idles fine in drive. I also noticed there is a very small hesitation when starting the car.

-robodude666

Use “throttle body cleaner” on the IAC and plate

Symptoms sound like a bad FPR and you smelled gas in the vacuum line – replace the FPR. make sure the engine is not hot and bleed off the fuel pressure before you replace it

Is there a benefit to getting a fuel pressure regulator with a built in gauge? They're on eBay for cheaper than what a replacement FPR without one? Also, is there a difference between the generic $20-30 ones vs the $55 replacement AutoZone recommends?

Also, how does one bleed the fuel pressure? I've looked at some other threads here and didn't see people saying they bled their fuel pressure beforehand.

-robodude666

I would not trust a generic FPR with a gauge for $30 – I would get one that I know fits at the parts store and pay the $55 - change it now - and get a 1yr warranty and could return it. But that’s me

To bleed the fuel pressure there is a Schrader valve on the fuel rail – has a cap on it and looks like a tire valve stem but a little bigger. Just cover with a rag and push the valve stem in to catch the gas. BYW you need snap ring pliers to change the FPR

Looking over eBay, even the $40 ones don't have a warranty. I'll just get the AutoZone one for $55+tax which comes with a 1 year warranty.

Is it crucial to bleed the fuel pressure? I've watched How-To guides on YouTube that don't mention it.

-robodude666

it's crucial to me to cover and CONTROL the spraying fuel - better safe than sorry

Alrighty, I'll make sure to do that! Thanks again for all your help.

In case anyone knows nothing about cars like myself, and got to this thread while trying to figure out how to bleed fuel pressure or locate the schrader valve or fuel rail, this post has a good photo guide:

http://www.grandprixforums.net/fuel-lin ... l#post7652

Skip down a bit to the "relieving fuel pressure" section.

Once the fuel pressure is bled out, and the FPR is replaced, will the pressure build itself back up once the car is started again? Also, is this schrader valve where one would connect a fuel pressure gauge to check the pressure? Low, or dropping pressure, would indicate a failing fuel pump or clogged fuel filter? I notice my car has issue starting up after dying while going up hill. Is this an okay fuel pressure gauge for testing pressure?

Also, do I have to replace just the FPR or do I also need to replace other components related to it? See below:



Part 2 is the FPR. Parts 3, 4, 5, and 6 are the o-ring seals and filters. May I use the existing ones or do they need to be replaced? Or are they included with the new FPR?

This is the FPR that AutoZone recommends for a '99 Pontiac Bonneville SE.

-robodude666

what comes in the fpr box should be all you need - use the new snap ring . wire brush around the old snap ring before you take it out so no crud falls in the fuel rail. cycle the ignition it will pressure up – check for leaks
hope it cures the problem

Yes that is where you test the fuel pressure – but get a “GM” compatible tester - not that one