[RESOLVED] Car Bucking

[97SpydermanGST]

Hi I have a GS-T Spyder, and yesterday it started to lose power and buck real bad under boost. So today I did a boost leak test and found 2, which I fixed. So I figured this was the problem, but it wasn't. It def. accelerates better but is still bucking. The CEL is on for a 02 sensor. Also when I did the boost leak test it bleeds off rather quickly, and you can hear it but I can find it at all. Sound like it is inside the engine or something. Do you think that a valve is bent or anything? And do you think a front 02 sensor would cause the bucking. Thanks alot - Matt Car has a 190 lph fuel pump, Boost gauge, 14b.

 

[xxShaneOmac]

Replace the front O2

they start to go bad and cannot read a correct AFR and then send the wrong values and your car cannot run without a correct AFR

 

[kenamond]

Sounds like boost leaks. The front O2 sensor has nothing to do with wide-open throttle performance, but you should still listen to what the CEL is telling you and replace it. I got mine for $50 from oxygensensors.com. The O2 harness runs from the O2 sensor, over the exhaust manifold heat shield, and plugs in under the thermostat housing. It's hard to see what you're doing, but it's just a male/female plug bolted to a bracket bolted to the head. Get an O2 sensor socket to get the old one out.

Here is a wiki page I put together on boost leak testing.

Use your eyes first to see if couplers have blown loose, vaccuum lines are gone, BISS has popped out, etc.. Then use your ears to listen for hissing during the test. Then use a spray-bottle with a super-soapy mix of water and dishsoap and spray everything. Bubbles will form for smaller leaks, but huge leaks will just pop the bubbles. Check the PCV valve. Do the test on a warmed-up motor so that the piston rings will have expanded; otherwise ring blowby appears as a boost leak. You can monitor the amount of air making it through either the PCV valve, ring blowby, valve stem seals, or blown turbo compressor seal via air leaking out of the VC breather line on the passenger end of the valve cover or from the oil fill hole (with cap removed). If all is well, you should be able to pressurize to 20psi and leak down 1psi every few seconds once you stop adding air. You need an aftermarket boost gauge to do this; the stock gauge calculates a guess at boost pressure which requires the engine to be running...and it lacks numbers on the dial.

Good luck!

 

[97SpydermanGST]

Ok so I found a couple more boost leaks, Biss screw and boost controller was leaking. I fixed all of those up and the boost is holding fine now, losing about 1 pound per second or so. I took it out for a drive and it is still bucking, but is now drivable. I removed the boost controller and it is still boosting to about 15 psi where it then bucks. I noticed that the air filter is completly broken off of the maf. So I ordered an adapter off of ebay. Do you guys think that this could be causing the bucking problem. Thanks for the responses already. -Matt

 

[97SpydermanGST]

Anyone?

 

[siceclipse]

spark plugs and wires.

My car was misfiring like a mofo and i replaced the coil pack and the igniter like a dumbass before checking/replacing the plugs.

 

[97SpydermanGST]

I had just replaced the plugs about a month ago....but I pulled them to look at them and they are nasty looking. They are all black, so I am now thinking that the 02 sensor has my car running really rich and ruining my plugs. Does this sound plausable? Or could it be the air filter adapter broke off and there was not air filter? iIchecked turbo and it is good and MAF is clean. I was not able to get parts today as I got home late from work.


EDIT: It is now that anytime it is in boost that it doesn't run right at all, and boost leaks are all fixed.

 

[97SpydermanGST]

O2 sensor and spark plugs to care of it. Thanks for the help!

 

[sirspoolalot]

if you have a bad front O2 Sensor, would it cause the car to not start???