Engine under load causes car to shudder
 

My car has 46k miles and started to shudder or studder when I accelerated to quickly. My car in neutral will rev up like normal, but when under load my car will shudder. If I accelerate slowly my car will go to whatever rpm , but if i mash on it or just a lil bit it shudders at 2-3 k rpm or higer. I took it to a mechanic and he thought it might be the intake manifold gasket , he said it was fine. They did a compression check and all turned out ok. I'm not sure whats wrong ,but help will be appreciated.

Try adding some ground wires and see if that fixes it.

It's sounds like an electrical problem, check your coils and wires and plugs...

Also check your fuel filter...You should change it if it hasn't been done recently.

Also dont take it to your mechanic anymore if they check compression because your car is bucking :roll:

When was the last time you changed your plugs? If they foul out you can get some bucking and hesitations, I know its happenign to me right now cuz my car is running on the rich side.

If you did change your plugs and put the plug wires on incorrectly the same thing will happen. I accidently plugged my ignition coil harness in wrong, and it would be okay on smoothe soft acceleration, but buck like mad if I gave it gas.

thats what I can think of off the top of my head. It would be beneficial to you if you posted your mods too :)

A blow intake manifold gasket would result in a high idle, whats your idle?

and low vaccum, Whats your vaccum readings... ( Im assuming you have a boost guage )

Do you have a CEL?

Could be in limp too.. Try resetting the ECU.

Take off neg battery cable and stand on the brake pedal for 30 seconds. Reconnect cable and start car. See if that's it.

if im not mistaken, limp mode wont let you go past 3k period, and he mentioned that everything was line when he was dealing with light throttle.

Hmmm... Not sure. Last time I was in limp I could revv all the way up... But if I was making boost at all it would crap out.. But who knows, my car is a freak.

perhaps im wrong then. I cant remember the last time I was in limp mode :)

Thanks for the replys. My mods right now are stock, before I took it to the mechanic I only had dual intake so i put the stock airbox on. They checked my intake gasket and said it was ok. who knows ....sigh....
but all help is appreciated

A bad coil, or a bad spark-plug or spark-plug wire can cause this, because the voltage needed to fire is higher under heavy throttle.

well this is an old topic but..... My car is now running perfect ! my sparkplugs are replaced,fuel filter, and intake gaskets. I reset the ECU and now the car is running better than before . Thanks alot for all the help.