Slow 6, help please!


Well-Known Member
The car is a 1999 pontiac grand prix with a junk yard motor thrown in, I know the previous owner and the car will shut off on occasion, especially when the car turns left. Sometimes it starts back up, sometimes it wont. Not the alternator, or the battery. All the connections seem good and tight. And now the motor has a faint tick in the back center cylinder that comes and goes but then knocks under throttle. The girl Im helping keeps bringing it back to the previous owner but it doesnt have any problems when he drives it so Im trying to do what I can to help. Any help would be greatly appreciated. Thanks. :)

Slow 6

Well-Known Member
Any mods done to the car or is it stock?
Supercharged or non supercharged? 3.1 or 3.8?
What year is the junkyard block?
Have any codes come on at any point time before it started happening?

Some things to double check:
all vacuum lines.
Ask her if she is hearing the fuel pump priming when she goes to restart it. They are fairly loud she should be able to hear it. If it is the fuel pump there is an access panel in the trunk. Pull down the middle rear seat and unlock the panel to get trunk access. Pull the carpet back and you will see the fuel pump "door." It's literally about a 15-30 minute Job.

Has it happened to you when you have driven the car? Did you guys check for spark and fuel when you went to try and restart it?

some other possible causes:
Crankshaft position sensor or camshaft position sensor. Sometimes they will not throw a code especially crankshaft.
Faulty ground connection- check to make sure the ground is fully seated behind the coil packs.
Pull the plugs out of cylinder 4(rear middle) and 6(driver rear). Especially cylinder 6 cause it is right by the O2 sensor and it isn't uncommon for someone to snap the porcelain when they go to tighten the plugs.

When my car started to do this it ended up being the rear fuel pump relay by the gas tank(under the car on the passenger side). Pull the "box" apart and see if the connections are still good. They tend to wallow out over time and will intermittently cause the car to die. Especially when hitting a bump or taking a turn. After sometime the car will fire back up, but sometimes it won't.

Good luck and report back.
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Well-Known Member
Stock 3.8 block, non-s/c, heads are off something else. No clue on the year though.
No codes have come up other than ABS shit.
It died when I was just driving it down the road, it literally just shut off and would not restart until it sat for a minute on the charger.
I will double check the fuel pump and look for broken wired but I have not found anything out of the ordinary yet.
A few ppl online said maybe the fuel pump ballist resistor is bad but still unsure.

Slow 6

Well-Known Member
Did the pump prime when you went to restart it?

Dying while driving on a GP has notoriously been the CPS. What you are reading as far as the fuel pump resister is a possibility as well as they have been a widely known problem. Here's a good write up/article to see if its the problem:
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Well-Known Member
Found out the knock is the oil pump going bad.

And The only code I found was for wire failure in the computer


Pontiac Pilot
That will do it? Oil pump it and chase down the wire fault and you will probably have it.

The coil block fault in the 88 was intermittant, would run fine for days then just die and not start, then start again later and run fine. After much frustration and months of testing and fiddling, finaly discovered that their was a micro crack in the coil pack causing an intermittant fault. Friend had a Taurus with a similar problem that turned out to be a faulty wiring harness.