99 GA hestiates or misses on full throttle

[roadgrime]

well my 99 grand am seems to hesitate or miss if you mash down on the gas doing around 40 mph. so far i have taken it in to a local shop as well as the dealer and they say they cant findanything wrong. last time i did it the check engine light came on and i took it back to the dealer and they said no code was stored... any ideas what i need to be checking etc?

[roadgrime]

just as a followup i can make it do it in N or P as well but its more noticable when i go to pass some one and from a stop sign into ttraffic etc.

[Ridenour]

Check / maybe replace your wires. Make sure they're all seated really firmly on your plugs.

After I got my set of MSD 8 mm wires, I had similar symptoms, and it turned out a few of them weren't seated all the way.

[roadgrime]

the coil packs have been replaced and all of that now looks good.

[Forkliftguy]

Check your fuel pump, sounds like it's headed for the junkyard in the sky. Most fuel pumps that are toast will develope enough pressure for regualr driving but once the engine demands high flow from it, it will not be able to build enough pressure causing the engine to stumble at high rev (like what you explained in park/neutral and under heavy load like passing cars).



Marc

[roadgrime]

is there a way to test it? or do i need to take it into the shop?

[BNaylor]

Originally Posted by roadgrime

is there a way to test it? or do i need to take it into the shop?

I'd replace the fuel filter first before checking into the fuel pump. Try the spark plugs and wires as others suggested but if that doesn't work, try disconnecting the MAF sensor (Mass Airflow) to troubleshoot. You appear to have classic symptoms of a dirty or defective MAF sensor which is a miss/hesitation at WOT and could occur as soon as around 4000 rpm. The MAF is located at the input of the throttle body and has a standard GM electrical quick disconnect.

The ECM/PCM computer may or may not give a DTC error code and many times the SES light will not illuminate when the sensor starts to act up. At least you can rule it out. Good luck!

'97 GP GTP/'01 Regal GS/'02 Alero GL2

[Forkliftguy]

If you're talking sprk plug wires, you must have a 6 cyl engine. If this is the case you can easily check fuel pressure from the schraeder valve on the fuel rail with a fuel pressure gauge. It'll just screw right on. The 4cyl is a little more complicated where you have to disconnect fuel lines and insert a fuel pressure gauge in line with the system.

[Car_whore]

It could also be that when you floor it at 40mph.. thats when it down shifts and there is a bit of a hesitation, beacuse it doesnt know wether to stay in that gear or down shift.
HTH

[Ridenour]

^ ^ Yeh good point. It seems like I remember reading about how lots of late model Grand Am owners notice their car dogging it at 40 MPH when at WOT. And I think this is true with most GA's, as it does it in mine as well. I think it's just where the revs were at / where they end up that causes the lag at WOT when you hit 40 in GA's. Might be something bigger in your case though.

[Hoags]

Hey Guys, Heres a twist, I'm getting a hesitation in my 5speed manual when I shift out of 3rd and 4th, the damn thing sputters and coughs and spits until the RPM start coming up. What does everyone think, It's been going on for a while I've replaced all the ignition parts already. There have been some great ideas on the preceeding posts so I' going to check out a few of them.