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2008 Pontiac Grand Prix hard start

A few months ago my 2008 Gran Prix stopped running in the middle of the road. It turned out to be a cracked ignition coil. My local mechanic replaced all three coils. Shortly after that the car began cranking hard upon starting. The first start of the day is always fine but subsequent starts will often give me slow/hard cranks before starting. This happens about 1 out of every 10 starts. I replaced the battery even though it tested out just fine. I then changed the starter and it still does the same thing. Any ideas on what is causing the hard start? I’m afraid its going to leave me stranded one of these times. Thanks, perplexed.

I doubt the coil problem had anything to do with your current issues.

Stop changing perfectly good parts hoping to fix the car. Diagnose the problem, fix the problem.

I will assume - you don’t say - the check engine light is not on. What do you call a “hard crank”? Cranks slowly but it still fires? Cranks slowly then faster then fires? OR cranks fast but take a long time to fire?

And you say this is only after the first start of the day? So can we say it is heat related?

Get out your volt-ohm meter. Check for proper ground from the battery to the engine block. Check this cold and later in the day when the engine is hot. Are the values the same? They should be.

Yes, the check engine light is on but my mechanic said its an emissions issue that is not affecting the starting problem.

When I say “hard start” I mean it initially turns over for a split second, then hesitates a split second, then fully starts. If I’m out running errands and start the car 5 times it only happens 1 time out of the 5 starts. Sometimes it doesn’t happen at all.

I appreciate your response!

Replace this.

https://www.rockauto.com/en/moreinfo.php?pk=539028&cc=1440276&jsn=398&jsn=398

Tester

Good idea above. When you hear a starter motor’s cranking speed change , faster/slower/faster before it catches and runs, and the problem isn’t the starter motor (b/c you already replaced it), the next thing I think of is a bad connection somewhere along the path from the battery + to the starter motor, then from the starter motor case to the engine to the chassis and back to battery -. Pay particular attention to the point where the battery negative wire connects to the chassis. Maybe all you need to do is remove it, clean the area of corrosion and rust, and re-connect.

If you want to go all-scientist like, you could measure the voltage at the starter, probing from the terminal to the starter case during cranking. If that voltage is lower at times when it doesn’t crank robustly, you’ve found a very good clue.

Thanks, I’ll replace that and see what happens.

Thanks, I’ll give that a try!