vacuum leak or fuel system?Long

richie · 05-27-2001, 09:03 PM

My car for the past 8 months doesn't have the same grunt as it used to most of the time.Sometimes the car will have very show throttle response and not a whole lot of go and a few seconds later the car will have very quick throttle response and will haul a#s.I have do a full major tune-up.Plugs,wires,distributor cap and rotor,throttle position sensor,fuel filter,upper intake vacuum lines.I also ran one of the fuel injector cleaners that your car runs on.I cleaned the throttle body,egr and mass air meter.Yesterday I replaced the old o2 sensors.I ran a compression test and leak down test and the engine is tight.Does anybody have a clue on the the problem is?

jimberg · 05-27-2001, 09:18 PM

If you didn't reset your computer, reset it. That would be a good first step.

Disconnect negative cable from battery for 15 minutes. Reconnect, start, let idle for 10 minutes (all accesseries off), turn of, start, let idle for 10 minutes (all accesseries on). See how it runs then.

If you've already done this, let us know.

------------------
351W 89 Mustang GT Convertible

richie · 05-27-2001, 10:00 PM

I disconncect the batterey yesterday while replacing the 02 sensors.Why would I need the reset the computer?

jimberg · 05-27-2001, 11:41 PM

If you disconnected the battery, you reset the computer. It's also a good idea to do the idle procedures. Resetting disposes of the adjustment table data and allows your computer to relearn from scratch. When you make so many changes at once, the computer will be using obsolete data when your engine is running. It will take a while to adjust. Resetting and then just driving the car tends to cause all sorts of problems like surging idles, hesitation, etc.

------------------
351W 89 Mustang GT Convertible

richie · 05-28-2001, 10:52 AM

I didn't change everthing at once,but over the course of many months.I always think my stang is running good then all of the sudden the car will run a lot stronger for a very short amount of time.A example is yesterday on the freeway at 70 I barely touched the gas and the car accelerated up to 80 plus two to three times as fast as usual.Then I slowed back down to 70 and got on the gas and there wasn't nearly as much power this time.My car jerks sometimes slightly when accelerating.

SlowStang2 · 05-28-2001, 08:40 PM

My car jerked around like you described. To correct this problem, I had some1 look through my computer for problems. One problem was timing. The jerking disappeared. Try retarding it, or advance it. Worth a shot if you havent tried yet.

richie · 05-28-2001, 09:42 PM

I got a vacuum gauge today and hooked it up to my upper intake and then all other vacuum line and the psi was around 17 on all the lines.When the engine was idling I could hear a hissing sound coming from the right side of the intake.I used my sethescope and found no leaks.Then I sprayed come carb cleaner around the intake gasket and intake bolts and around the fuel injectors.The idle didn't change at all.The hissing sound comes and goes,it's not constant.A couple months ago I checked for codes and got a egr postion sensor code 34 if I can remember.I disconnect the egr vacuum line and plugged it and the other line.Then drove the car and it ran real strong on the freeway.

05-27-2001, 09:03 PM	#1
richie Registered Member Join Date: Apr 2001 Posts: 47	vacuum leak or fuel system?Long My car for the past 8 months doesn't have the same grunt as it used to most of the time.Sometimes the car will have very show throttle response and not a whole lot of go and a few seconds later the car will have very quick throttle response and will haul a#s.I have do a full major tune-up.Plugs,wires,distributor cap and rotor,throttle position sensor,fuel filter,upper intake vacuum lines.I also ran one of the fuel injector cleaners that your car runs on.I cleaned the throttle body,egr and mass air meter.Yesterday I replaced the old o2 sensors.I ran a compression test and leak down test and the engine is tight.Does anybody have a clue on the the problem is?

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05-27-2001, 09:18 PM	#2
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	If you didn't reset your computer, reset it. That would be a good first step. Disconnect negative cable from battery for 15 minutes. Reconnect, start, let idle for 10 minutes (all accesseries off), turn of, start, let idle for 10 minutes (all accesseries on). See how it runs then. If you've already done this, let us know. ------------------ 351W 89 Mustang GT Convertible

05-27-2001, 10:00 PM	#3
richie Registered Member Join Date: Apr 2001 Posts: 47	I disconncect the batterey yesterday while replacing the 02 sensors.Why would I need the reset the computer?

05-27-2001, 11:41 PM	#4
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	If you disconnected the battery, you reset the computer. It's also a good idea to do the idle procedures. Resetting disposes of the adjustment table data and allows your computer to relearn from scratch. When you make so many changes at once, the computer will be using obsolete data when your engine is running. It will take a while to adjust. Resetting and then just driving the car tends to cause all sorts of problems like surging idles, hesitation, etc. ------------------ 351W 89 Mustang GT Convertible

05-28-2001, 10:52 AM	#5
richie Registered Member Join Date: Apr 2001 Posts: 47	I didn't change everthing at once,but over the course of many months.I always think my stang is running good then all of the sudden the car will run a lot stronger for a very short amount of time.A example is yesterday on the freeway at 70 I barely touched the gas and the car accelerated up to 80 plus two to three times as fast as usual.Then I slowed back down to 70 and got on the gas and there wasn't nearly as much power this time.My car jerks sometimes slightly when accelerating.

05-28-2001, 08:40 PM	#6
SlowStang2 Registered Member Join Date: May 2001 Location: Stuart, FL, US Posts: 147	My car jerked around like you described. To correct this problem, I had some1 look through my computer for problems. One problem was timing. The jerking disappeared. Try retarding it, or advance it. Worth a shot if you havent tried yet.

05-28-2001, 09:42 PM	#7
richie Registered Member Join Date: Apr 2001 Posts: 47	I got a vacuum gauge today and hooked it up to my upper intake and then all other vacuum line and the psi was around 17 on all the lines.When the engine was idling I could hear a hissing sound coming from the right side of the intake.I used my sethescope and found no leaks.Then I sprayed come carb cleaner around the intake gasket and intake bolts and around the fuel injectors.The idle didn't change at all.The hissing sound comes and goes,it's not constant.A couple months ago I checked for codes and got a egr postion sensor code 34 if I can remember.I disconnect the egr vacuum line and plugged it and the other line.Then drove the car and it ran real strong on the freeway.