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View Full Version : Thumping when booster is at 5 psi



stonehouse
09-20-2009, 02:48 PM
95 SC 5 speed 3.8 liter - had it a month, trying to get it right to sell it.

When we accelerate and it goes up to 5 psi on the boost side of the gauge the engine thumps until it goes back to other side. It had a code 214 and the cam sensor was replaced but it didn't fix the thumping.

Had 87 gas in it for at least half a tank. I refilled with 93 and fuel cleaner but it didn't go away.

Any help would be greatly appreciated.

Tim Groth
09-20-2009, 02:56 PM
95 SC 5 speed 3.8 liter - had it a month, trying to get it right to sell it.

When we accelerate and it goes up to 5 psi on the boost side of the gauge the engine thumps until it goes back to other side. It had a code 214 and the cam sensor was replaced but it didn't fix the thumping.

Had 87 gas in it for at least half a tank. I refilled with 93 and fuel cleaner but it didn't go away.

Any help would be greatly appreciated.

Not really sure what you mean by thump...sounds like you may be discribing a miss.

-Tim

stonehouse
09-20-2009, 02:59 PM
The thumping is like a hesitation.

It may be missing but after it goes back to the other side of the vacuum gage it sounds and feels like it is running fine again.

Tim Groth
09-20-2009, 03:09 PM
The thumping is like a hesitation.

It may be missing but after it goes back to the other side of the vacuum gage it sounds and feels like it is running fine again.

Sounds like bad plugs and wires to me. These cars will run fine with bad plugs and wires without boost. Usually anything 5 lbs or higher and it will be very noticable.

I'd get some Autolite 103s gapped at .38 and some good wires and you'll be good to go.

Where in NC you located?

-Tim

stonehouse
09-20-2009, 03:11 PM
Thanks for your suggestion.

I have looked under the hood and there is No Way I want to change the plugs at home...there are so many things on top of the engine it scares me!

We stay 'tween Raleigh and Fayetteville in the middle of the state.

stonehouse
09-20-2009, 03:59 PM
Just went for a spin... when you push past the 5 psi, it stays on the boost side and smooths right out.

Mercutio
09-20-2009, 04:38 PM
I agree on the plugs and wires. Take a look at the wires to make sure they're not contacting the headers/manifolds and burning out. The middle driver's side one tends to do that on my car.

stonehouse
09-27-2009, 03:12 PM
We have put 100 miles on the car since the cam position sensor change with 96 octane gas and the thumping is gone. There is still some missing/hesitation but it is better than it was by a long stretch. Scheduled for a spark plug and wires change next week.

89XR7TD
09-27-2009, 11:30 PM
I think you mean 94, and you said you scheduled like taking it to a shop to do it:rolleyes:

They usually F things up but goodluck with it:)

I did all my spark plugs from the bottom of the motor and didn't take anything off but did take some skin off my hands:D

Tom

stonehouse
09-30-2009, 08:18 PM
Ok, we decided to follow 89's idea and change the plugs from the bottom.

The 3 on the drivers side were ok but the 3 on the passenger side are not coming out that way. Only a couple inches between plugs and wall. It looks like the a/c has to come off on the top, heater lines, etc, just to make some room. Any advice would be appreciated.

GOOD NEWS: the stutter is gone! We magically got the plug that was acting up. I know the other 3 gotta get changed too but I am happy the car feels happy. I thought she was fast before...wow! Actually, I won't go over 90 but she gets there fast and smooth.

Kurt K
09-30-2009, 09:16 PM
You definitely do not need to take off the AC or heater hoses to change the passenger side plugs. Remove the air intake tube and possibly MAF (I have to remove mine, but I'm not stock so I don't remember if it's in the way). I use a 3/8" ratchet that's the size of a 1/4" ratchet with a spark plug socket (I use a 1" extension for some of the plugs). I have headers, so you may need a different extension or maybe a swivel.

stonehouse
09-30-2009, 09:51 PM
Thanks Kurt. We will try it with a smaller handled ratchet or a swivel.

rzibilske77
09-30-2009, 10:03 PM
i reach all of the plugs from the top, removal of the intake is all thats needed to be removed. I dont use a swivel, just the 3/8 ratchet and a extension.....basically what Kurt said.