Bucking
 

Ok.. here is the problem. My niece has a 1998 or 99 saturn ls1. bought from another owner who had someone install a used engine in it. No I know it's an older engine because when I went to start to get the plug wires, they handed me ones for the the ones that go over top of cover and not on the side of the engine.

Any ways, I think it's ike a 95 at least that's what I say hen i get parts for it and they fit perfectly.

Car runs and drives fine for about 15 minutes or so or atleast untill it gets warmed up. Once warm though it starts to buck like it's getting gas then not getting gas, and so on ... stomp it to the floor and it stops bucking but doesn't get going fast... almost like it's just getting enough gas to keep it running smoothly. She had an issue not long ago, where a spark plug wire ( hence the new plug wires) fell on top of the exhasut manifold and burned through to the core and was arching on the exhaust manifold, and also she had a coil pack that was burnt though on the side and that got replaced also.

Now I have check the fuel pressure and its a steady 55psi at test port. if I bip the throttle if acts like it's getting to much and and wants to die but then sucks it up and revs. It still continued to have 55psi the wole time.

Any suggestions, she really needs this car back.:confused:

Uh,huh -- sounds classic. Here's a little test; go to the driver's side of the engine. Underneath the air duct, you will see a two wire sensor screwed into the engine, below where the top radiator hose is located. Disconnect the wiring, and use an ohmmeter to measure the value (in ohms) of that sensor, and report it here on the thread .....

sounds like you think it's the coolant temp sensor.

ok. I pulled the sensor and got a new one, first one was just a temp sensor... car fans came on and stayed on... and set a ses light..
Called staore and went back and got right one. installed it and let engine warm up. No change.
Just pulled battery cables to reset CPU and the old part had 2.96 ohms of resistance across the pins.

ECTS was my first inclination as well. 55 psi sounds kinda high...the normal range for S car engines is about 38-44 psi (key on, engine off) and 31-36 psi (engine running).

Suspect fuel pressure regulator may have failed.

Pull vacuum line from fuel pressure regulator. If you can smell significant fuel through the vacuum port (or fuel comes flowing out the port, it's bad....

ok that's what i thought to begin with but figured since it was a cheap part why not right? anyways. I looked up the part on advanced autoparts. the pic shows a round PRV i followed both fuel lines, one goes directly to the fuel rail.. nothing inbetween it and the rail, the other goes to a little black box under the backside of the intake manifold.

Is the little black box the regulator? If not where is it located?
Also could it be the EGR? I have heard this will case the same problem.

Thanks,
G

Indeed, a sticking EGR can cause similar symptoms, with gyrating RPMs, especially on accel and decel where the pintle should be opening or closing but is not moving freely due to carbon buildup. Usually you get RPM gyrations and a bunch of stalling followed by no start conditions for a few minutes -- then it starts up like nothing ever happened.....

Wouldn't hurt to pull EGR and clean the carbon deposits out with carb/choke cleaner --especially if you've been burning considerable oil and have never cleaned it -- just don't damage the pintle. It should move freely when you're done cleaning.

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But the fuel pressure seems pretty high for an S car engine and would basically lead to a flood of fuel at the cylinders......
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The fuel line leading right to the rail is the return line.
The black box you refer to (behind and below the intake) has the incoming fuel line going onto it. It contains a spring loaded diaphragm which is under severe pressure--so be careful when you remove the fastener/clip holding it in place.

I actually replaced my fuel pressure regulator with the fuel rail removed from the vehicle (as I was replacing injectors on a 95 SC2) and had a "sweet" time getting that damn clip back on -- so be prepared for some fun.

Make sure the replacement part is the right one BEFORE you pop the clip off the original.

Keep us posted.

ok first of all the line that runs to the fuel injector rail ( on top intake manifold, towards front of the car) has the pressure running to it. There is no fuel pressure regulator on that line. I know I pulled it apart. It has one long thin odd shaped piece of metal that runs almost the whole length of the tube inside, one piece of plastic with several spines on it inside, and the fuel inlet connector. the line that runs to the black box underneith ( near firewall under intake manifold) is the non-pressure line that connects to the canister purge solinoid valve.

Now I did pull it off and I am going to replace it because the manul says it cold cause the problems I am experiencing. I was wondering if anyone has replced this with similar problems and knows that it works?

My bad....my mind was lost in 1st gen S cars (note my reference to my 95) when describing the above.. they had an inline fuel pressure regulator accessible in about the location you described...(not quite)

Indeed that looks like a canister purge solenoid....never had the pleasure of messing with one.....