I have had this same simpletons it drove me craze it turned out to be that the catalytic converter had broke a pace off in side and found it's way down in to the muffler causing a restriction in the exhaust .i have also see maf. cause stall outs I give them the good old tap test and if it stall's replace it. if you cant keep it running long enough 4 that test UN plug it it Will run with out it .hope this help you fix your car .i have 5 of them but only one with a V6 like the body]the ease way to test the exhaust is to drop it just be four the cat. best to you .if this has been any help[ a that a boy ] would be nice but not need 4 me . im just here to lorn to spell . Have a Grate day and thank you 4 using fix ya.please let us know if we have helped and what did it so we can keep passing it on .
Very good answer I tend to concur , I'm a 30 yr Master Mech, from back when we were still Master Mechanics NOT Master Tech's , get it ? any how I believe your RIGHT.
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Hi.
If engine ir running ropugh when idling , the cause is often a faulty
idle air control valve, an air sensor, or a vacuum leak.
Check also the fuel tank cap, if this does not let air into the fuel tank, then you may experience problems, particularly when idling. Test the car without cap.
The IAC valve is fixed to the back the throttle
body by two torx screws. Disconnect the round shaped connector before
removing the screws.
Before replacing the valve ensure that there is no vacuum leaks. Big vacuum leak can be spotted because of the hissing sound
coming from the leak. To find small vacuum leak you will need an had
tool gauge placed between vacuum lines(eg.Actron Vacuum Gauge).
In
some case MAF and AIT sensor faults can also cause idling problem by
determining an incorrect amount of air to be used in the mixture. In
this case you often get a lean mixture code on the OBDII scanner.
If the failure is related to temperature, then the most likely cause is the IAT sensor
(intake air temperature sensor). MAP (mass air pressure) sensor, MAF
(mass airflow sensor) and engine gas recirculation system may also
concurr in causing the problem.
This sensors are in fact used to determine the quantity of air to be injected along with fuel in the cylinders.
The sensors are located in the air intake.
The
first step in diagnosis is doing an error code scanning. This is done
connecting an OBDII tool to check if there are error codes stored.
If
problem is the IAT or MAF, you usually get lean or rich mixture codes, along
with misfire ocurring when the engine is shutting down because the
incorrect mixture cause flooding or chocking.
Once you are sure that fuel circulation is fine, the most common cause for rough engine when idle is MAF, MAP, vacuum leaks and IAC valve problems.
Regards.
Ginko.
I cannot read your old conversation with other experts, and I did not mention simply a vacuum leak.
To resume: Do a scan code and replace MAF, test IAC valve.
After the negative feedback the question will be passed to a different expert.
Goodbye and good luck.
Ginko.
Also regarding vacuum:
Did you test the vacuum, or you are just guessing?
Not all vacuum leaks are hissing. You need to stick an hand gauge between vacuum lines and heat the vacuum lines with a blow torch while reading pressure. That is a common way to find leaks.
If problem is only when you idle, then EGR and solenoid is OK.
You read fuel pressure with the same pump. Fuel pressure giving troubles only at idle is strange.
Clean MAF before replacing it.
Scanning OBD codes as first step is essential, things are different if you get a lean or rich code then if you get a misfire code...
Goodbye.
Hi .
I noticed that you left negative feedback to any expert ansering you.
We spent time on your problem, and I will be grateful if you can change
the feedback unfairly given. The negative rating given only affect the experts helping you and does not affect eventual right to refund.
Goodbye.
Ginko.
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Ok so let me get this straight, you have fuel pressure(45 psi, good). Are both injectors pulsing? Just because the fuse is good doesn't mean the injectors are. The pass key will only stop ignition and will not have anything to do with driveability. Check the injectors and get back to me.
Hi! GOt MAF (mass air flow) sensor on your car? A faulty MAF has big contribution on engine performance. Might wanna look on that. Hope this helps and have a good one!
I suggest you start by replacing the fuel filter if you have not yet. Along with that I would check the fuel pressure regulator. Although this seems like a fuel issue, I recommend replacing the spark plugs and wires. This way you can check the plugs to see if they are fouled and a bad plug wire(s) can cause a very rough idle but as your rpm's increase the engine will smooth out. Also try disconnecting the vacuum line from the EGR valve. I am giving you all of these possibilities because it is very difficult to diagnose from a distance but please comment on this post with questions or more information and I will help you. We can narrow down the possibilities together.
I HAVE BLOCKED EGR VALVE. ON DIFFERENCE. ENGINE STARTS BARELY IDLE FOR MAYBE 10 SEC.
So the EGR is good. Have you cleaned out the butterflies in the throttle body? Use carb and choke cleaner and a toothbrush or soft brush. Are the injectors clean and the connections clean and secure?
MULTI-PORT INJECTION.
If you can, remove one of the spark plugs to see if it is fouled or dirty.
Sorry about that. When I read 2.8L I thought of my old truck and was picturing it's engine. Is the intake leaking at all or showing signs of leaking/
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Here's some from from my experience. Pull the negative cable for 30 minutes. - Also Try removing the fuel filter completely. If you have moisture of any kind in the fuel your filter is very sensitive to water and can shut down because of moisture. ALSO - while you're at it - take down the VIN # - and call the Dealer asking about RECALLS can save you a lot of money over the years. Also ask about Service Bulletins. SB's are not paid for by the dealer but they can many times give you a heads up concerning problems like this one. RECALLS are good for the life of the car in many cases so please do this and get back to me here on the forum.
Thanks
Gary 
HAVE ALREADY TAKEN FUEL SAMPLE . OK. HAVE TALKED TO DEALER . NO UP DATES OR RECALLS. TO OLD. FOUND NO TSB IN MY MITCHELLS ON LINE. ANY MORE SUGGESTIONS,WILL ONLY IDLE FOR ABOUT 30 TO 45 SEC. BEFORE CUTTING OFF. THANKS.
Hi,
I am referring to what happens to a fuel filter when moisture enters the equation.
Please try by passing the fuel filter. Also - check to be 100% sure that is enough fuel pressure. I think you may have experienced a poor replacement fuel pump. Some GM vehicles will only work with certain fuel pumps as I have experienced. Seen the time when a GM car would work for a little while with the car - then after about 20 miles quit. Did this twice before we ordered from a GM dealer and bam - that one worked great and no more problems. I had forgotten about that incident until now. Sad as it is - you can check with GM mechanics and they will tell you how that can happen. So if all else fails - put a factory replacement fuel pump in the vehicle.
Best of it.
Gary
REPLACED GM PUMP AND RELAT AND STRAINER AND FUEL FILTER 0N12/09/09.HAS ONLY DRIVEN 457 MILES SINCE THEN. DUE TO SNOW THIS WINTER AND ITS A WEEKEND TOY. ITS GARAGED.HAVE A SOLID 45 LBS. PRESSURE. WHEN PINCH OFF RETURN LINE IT GOES TO 80 PLUS AND STILL BARELY IDLES AND QUITS.
OK - gocha - You should pull the plugs - I think you have or had a problem with the plugs do to either too much heat or too much fuel. I would pull one bank of plugs looking for one that is fouled.
Let me know how that goes.
Also just for reference - new doesn't mean good working order sadly - these parts are many times manufactured in China - unless it came from a dealer - I say either bad pump - bad fuel pressure regulator or even a partially hidden bad fusible link can do this. I have a 91 Mustang and I feel for you because I been there done that and had to go to craigs list and ask for a local expert to come fix it - he did - rewired a lot of stuff I had already paid to have done because of time constraints and he fixed it right for 100.00 - no more problems. I hope you get this corrected soon and I want to be a part of it. But if you rather another person help - - please just reject my help and you will get a new FixYa person.
Thanks for choosing Fixya.
ok - with this I am out - the problem is a bad fuel pump wrong one or just bad - must be a GM with the exact same replacement number - fixed to the VIN # - Been there - Done that - Got the faded T-Shirt -
Best of it - -
Gary
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Thanks for contacting Fix Ya. I have two thoughts given all the work you have done and running good up til now. When was the last time you purchased gas? Wonder about bad gas of water in gas Could put a can of heat in tank regardless just in case. Other thought, did you take fuel pressure check with engine running and watch what happens to pressure when at idle and when you rev the engine? Did you change fuel filters lately? An after thought, wonder if your fuel pressure regulator is working. You may have tried all of this but when it runs good when you are spraying 2+2 we have to know it is starving for fuel. Let me know how you come out with this. Darrell S
REPLACED FUEL FILTER WHEN NEW FUEL PUMP INSTALLED. HAVE 45 LBS. OF PRESSURE WHILE ENGINE IS STUMBLING & RUNNING LEAN.WHEN I PINCH OFF PRESS. REGILATOR RETURN LINE , PRESS. GOES TO 85 LBS. STILL HAS ROUGH IDLE & QUITS IN VERY SHORT TIME. FUEL O.K. CAR HAD BEEN DRIVEN 15 MILES BEFORE QUITTING.
Another check. Disconnect the fuel line and check the volume of gas the pump is producing. Interesting to know if the pump is quitting. You know your engine is acting like it is starving shortly after starting because it is either not getting any fuel or the pump is letting up. Not unusual to get a faulty pump either.Maybe the injector is quitting? This has central injection doesn't it. I have not worked on the older stuff for some time trying to remember. Good luck these issues are frustrating.
FUEL DELIVERY IS OVER 1 PINT IN 10SEC. ALSO THIS IS MULTI PORT INJECTION. MAP & TPS SENSORS TEST O.K. WITH MY OTC.
Hate to say it but I am at a loss too from here at least. Thank for contacting me another tech will take this if just turn mine down. Good luck and againa thanks
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How is the fuel filter? Is the throttle body cleaned out? Do you have a service engine light that could indicated dirty or bad sensors?
new fuel filter,multiport,fuel ok. no service engine light.
found spark gas fouled even though it will run at higher rpms when i spray 2+2 in the throttle body. it idles very rough a stalls within 10 sec. it actually is rich at idle to foul plugs but takes 2+2 to make run faster like its lean at off idle rpms.please check previous questions and my answers. possible pressure regulator ? but does not see possible.
I would test fuel pressure regulator, o2 sensors, and camshaft position sensor if this has one.
If it runs with a good spray in throttle body, then there isn't getting enough fuel in the throttle body. I do see there is a new fuel pump and fuel pressure is 45 lbs. Is this a constant 45 lbs? If it varies, then regular may be bad. But if it is a constant 45 lbs, then pressure regular is good. The camshaft position sensor and o2 sensors also determine how much fuel is sprayed into the engine by means of lean/rich mixtures. Your car could be running way to lean and not getting enough fuel. Double check your vaccum lines, check the sensors with a meter, clean the throttle body out as good as you can, and make sure you fuel injector is getting a good pulse and is not leaking or plugged.
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Sounds like u may have a vacuum leak on the engine. follow the vacuum leak diagnosis below.
Vacuum Leak Diagnosis and Repair. [Inquiry]Anyone know of a good method of test for and locating vacuum leaks in the the air intake system?
· By Listening. [Response: Don Foster] Find or buy a 3' length of new fuel hose. Stick one end in your ear and snoop around the intake system with the other end listen for any pronounced hisssssssing. [Warren Bain] I was able to isolate a vacuum leak with a mechanic's stethoscope with the probe removed and only using the tubing to get very close to the gasket and follow the contour of the manifold. You can also modify the stethoscope for locating vacuum leaks by replacing the probe with a length of plastic hose or fuel line.
· Spraying With Liquid. Another trick, for small leaks such as loose intake manifolds or shrunken injector seals, is to spray them with carb cleaner. This will temporarily seal a leak and a rough idle will smooth out for 10-15 seconds: you will hear the change in idle rpm.
· Using Propane to Alter the Mixture. [Tip from Bruce Young] I use Propane to test for vacuum leaks It's as safe (or safer) and less messy than spraying carb cleaner or other flammables . Take the nozzle tip off a propane torch and replace it with some snug fitting rubber hose about 2 feet long. Practice with the valve to get a moderate gas flow (not a roaring blast). With the engine at a warm idle, open the gas valve and poke the end of the hose around each injector for a couple of seconds. If the seals leak, you should hear an RPM change when the propane gets sucked in and burned. Do the same around any other suspected areas, like hidden vacuum hose ends and the intake manifold gasket itself. To block the breeze from the fan, lay a piece of cardboard from the fan shroud to the engine.
· Using Smoke to Locate Vacuum Leaks. Filling the intake system with slightly pressurized smoke from a smoke generator will allow you to see leaks where the smoke emerges.
If u have no vacuum leaks then what engine control/fuel injection fault codes do u have?? what is the fuel pressure reading?? u have a lean fuel condition here from what u say, u may also have vacuum leaks on the bottom of the intake manifold, it is not as uncommon as u might think, does the burn more than 1 quart of oil every 500 miles? if so that can be a leaking intake gasket o n the bottom, If u have not run the codes on this here is how u do that using the check engine light to read them, code list is provided as well, go to the link.
http://check-engine-light-codes.blogspot...
ONCE AGAIN, ANY FAULT CODS?
WHAT IS THE FUEL PRESSURE?
YOU CAN ALSO CALL ME AT HOME IN USA UNTIL 5 PM PACIFIC TIME
925-459-0571 I HAVE 35 YEARS EXPERIENCE WITH THIS TYPE OF WORK, AM A MASTER TECH IN DRIVEABILTIY PROBLEMS
HAVE U CHECKED EVERYTHING I ASKED? I NEED THE FUEL PRESSURE AND WHETHER U HAVE CODES/
NO CODES. PRESSURE 45LBS & OVER 80 LBS. W/PINCHED RETURN.
this is a 3.1 liter not a 2.8, 2.8 was not used in this year, they look very simliar.
I believe u eithr have plugged fuel injectors or a defective MAP sensor, here is a picture of the map, it will make the engine run very lean if defective or vacuum hose is not connected or collasped.
ACDELCO Part # 2131545 {replaces 213-185 #12569240, 16137039, 16254719, 213356}
SENSOR,MAP
I PLUGED NEW MAP IN NO DIFFERENCE. CHECK TPS VOLTAGES W/OTC GENISYS GOOD. ENGINE VAC. GOOD WHEN I SPRAY 2+2 UP TO 4,000 RPM.CONVERTER O.K.
then something has fouled the injectors, poor or dirty fuel would be my guess
U can give me a call on this 925-459-0571 if u really do need help, have 35 years of experience, know GM really well
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NEED HELP BADLEY.
has no vac. leaks.
please look over previous conversations and get back to me . thanks
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