1999 T/A random engine stalling woes

**springgroveTA** · 03-26-2015, 03:52 AM

I have a 99 T/A that has some possible fuel delivery issues that happen every once in a while. I am the 3rd owner of this car and it is just shy of 100k miles. It is bone stock, nothing was ever modified on the car. Other than battery change, brakes, etc. it has most of it's original parts. It is a non-WS6 car.

My problem has happened to me twice now. The first time I was driving back from a nice warm Spring time cruise with my wife. The car was driving fine then all of a sudden when I went to accelerate, the car sputtered, bucked and surged then just stalled/shut off. I was able to coast to the side of the road. I tried to get it started but it wouldn't stay running. The car would turn over, but wouldn't start. A couple times it stayed running until I put it in drive then it stalled. I had to have it towed home. I was pissed and let the car sit for a day before looking at it again. It fired right up the next day! I have a scan reader and checked to see if any codes registered. The only one I got was a P0508 (Idle Air Control Low) code. I found a small rubber elbow/vacuum hose by the Throttle body area that had a hole in it. I fixed that hose and also installed a new fuel filter just as a precaution.

The T/A ran fine after that. Fast forward a couple of months and it happened again. This time I was driving out to the Pontiac Nationals in Norwalk. I checked into my hotel then went to the track. Merging onto the highway, it sputtered and carried on as if it was going to stall/shut off again. Luckily, this time it didn't shut off. I was able to get to the track and the rest of the weekend, the drive home and after that it was fine (?).

Both times it happened it was very hot outside, or the engine bay would have been very hot. The first time it happened it was over 90 degrees and very humid. The second time I drove 7 hours, shut it off briefly, then drove to the track. The engine bay temp would have been very hot.

Any ideas as to what possibly is going bad? It has worked fine since, but I always worry as to when it's going to happen again. When it first happened I figured the fuel pump in the tank crapped out, but it seems when the car cooled down it was okay. One other note, at times when I start my car all the needles in every gauge peg and bounce to the right, then back down then up again, then finally settle out. Don't know if this would have anything to do with my problem.....Any help or ideas would be greatly appreciated!!

***SMWS6TA*** · 03-26-2015, 08:26 AM

Sounds like heat soak causing vapor lock. But before we get to that let's check some other common problems that also fit those issue.

Have you ever cleaned the MAF sensor? (Please tell me you are not using a K&N filter) Parts stores sell a can of cleaner specifically for MAF sensors. Disconnect the air duct and just spray the MAF sensor, let it air dry and repeat a few more times. DO NOT TOUCH.

Next - remove the air duct from the throttle body, look at the inside top where the IAC sits. Is it filled with junk. The PCV on these cars sucks. Lets too much oil blow by and can clog this up. Remove the TB and with carb cleaner and some q-tips you can clean it up.

It is possible the IAC sensor is starting to go.

Now to vapor lock, it should be an issue but it is possible. Make sure the fuel lines have the thermal tape wrap around them.

**springgroveTA** · 03-26-2015, 09:06 AM

Thanks, I did pull off the air duct & cleaned everything I could, MAF, IAC,PVC throttle body, etc. It wasn't too gummed up if I recall. I did all of that because of code & found that small 90 degree vacuum hose had a hole in it. I haven't had any more of those codes since so hopefully that part is okay.

Yeah, it reminds me of an old carburetor vapor lock issue. I will try to trace & double check the fuel lines. Make sure they are insulated properly. Thanks!

**springgroveTA** · 03-26-2015, 09:08 AM

Forgot to say I'm using an AC Delco air filter. Are you thinking the MAF or IAC could be causing my stall issues?

***SMWS6TA*** · 03-26-2015, 09:12 AM

If the MAF is dirty it can cause a lot of issues.

Same with the IAC. Look at the TB and see just how dirty it is. These are easy drive way issues to work on not needing any special tools.

**pajeff02** · 03-28-2015, 04:25 AM

Check the fuel pressure at the rail - you should have 58 psi. You can usually "rent" a gauge from most chain parts stores. The schrader valve is located at the front of the driver side fuel rail. Have you replaced the fuel filter lately?

Other than that, the items mentioned by Scott can all affect how your engine runs. Only other possibility would be something along the lines of a cam or crank position sensor on its way out. Generally, when they go bad the PCM will set the SES light and you can scan the code.

Let us know what you find.

**0rion** · 03-28-2015, 04:59 AM

Originally Posted by springgroveTA

Thanks, I did pull off the air duct & cleaned everything I could, MAF, IAC,PVC throttle body, etc. It wasn't too gummed up if I recall. I did all of that because of code & found that small 90 degree vacuum hose had a hole in it. I haven't had any more of those codes since so hopefully that part is okay.

Yeah, it reminds me of an old carburetor vapor lock issue. I will try to trace & double check the fuel lines. Make sure they are insulated properly. Thanks!

was this before or after the stalling issues? It could be a few things like Scott and Jeff pointed out. I'd be really curious to see what your fuel pressure is when it acts up. Wonder if that pump is weak and acting up when it gets hot? It's not if that fuel pump will fail but when.....all of GM's pumps are like that for the most part.

**springgroveTA** · 03-28-2015, 07:13 AM

Thanks for all the input. I will check the fuel pressure when I get a chance. The fuel filter was replaced early last year. I don't put a whole lot of miles on this car. Drive it to work on nice days, take it to car shows, etc. It happens so infrequently that hopefully I will find the problem.....I wish it would do it and not start .....sometimes, until something breaks officially, it's hard to diagnose it. I work on copier machines for a living and it is the same way. I am not sure if the "heat" issue has anything to do with it or it was just a coincidence. But I will keep this thread current if I find anything....

**RONS98TA** · 03-28-2015, 07:52 AM

With 100k on the clock, I would just replace the fuel pump. Just my opinion, but it really sounds like a fuel pump on its way out.

**jmgtrplyr1984** · 03-28-2015, 01:56 PM

I had this same issue on an 01 and it would start and idle in Neutral but as soon as you put in gear and give it throttle it chokes up and stalls. If you are not having the CEL come on then it will not be you MAF, IAC, or any other sensor.

The issue is your fuel pump.

**springgroveTA** · 06-29-2015, 03:54 AM

Just thought I would update my issue. I am 99.9% sure it was the fuel pump as many of you had suggested. On my way home from the Pypes show it almost stalled about a mile from my house (luckily!) and when I pulled it into the garage I could hear the pump "whirring" and "laboring".....it was very loud. Previously, I had never heard anything when it happened....So, my buddy has a lift at his garage and in went a new Fuel Pump on Saturday! We did it in just under 4 hours, taking our time and doing it right. I should be good to go for more cruising now! Thanks to all who took the time to respond to my post.