2002 Grand Am GT losing power

[Axe_1]

Hi guys, my Grand Am 3400 has just over 100K and it started losing power. Now the top speed is about 35 MPH. It sounds smooth at idle but acts like it's either starving for fuel, or drowning in it. I have changed the Air Filter, Spark Plugs, O2 Sensors, Fuel Filter, and that's what got me from 25 MPH to 35 MPH.

I have a bad back and really hate to work on transverse engines, but need to get it running. I do have some mechanical knowledge but it's limited on newer cars and I'm old, lol. I've tested the fuel pressure and it was good, though I can't remember the numbers right now. Any other suggestions or things that are common with this engine? The only other things I can come up with are:

Timing Chain
Various Sensors
Blown Head Gasket
Blown Intake Gasket

It doesn't smoke or steam out the exhaust and the last time I looked there was no water in the oil. It does however leak coolant somewhere and shows signs of it on the bottom Intake. If it needs very much I'm more likely to pull the engine and fix everything at once, outside the vehicle, but I don't have a great place to do so.

Any suggestions would help.

Axe

[Azrael]

Check the throttle position sensor.

[Axe_1]

Thanks Azreal, I have done a visual check but not tested it yet. That would be an easy repair that I would do today if needed. Is there a link I can use to test and/or set the TPS? I have done them before but it's been a very long time. I have a Micronta Digital Multimeter that should work fine, I just don't want to screw something else up or short anything.

Axe

[60dgrzbelow0]

The possibility of fuel starvation or flooding prompts pulling the Vacuum Hose off of the Fuel Rail Pressure Regulator and see if any gasoline smell is present or liquid fuel leaks out. If so... the bladder or diaphragm inside the FPR is "Tits-Up" and a check with www.rockauto.com will allow you to get a replacement. If none of these symptoms are present... attach an analog Fuel Pressure Gauge and Hose to the Fuel Rail Schrader access port and raise the RPM through a reasonable range to determine if the Fuel Pump is the culprit after comparing its behavior against the recommended factory FP pressure specs. If power loss is coming from bad valve seats or burned valves... a trick I have used is to take a piece of printer paper about 3" X 11" and just drape it over one (or if you are lucky... both exhaust pipes) and watch as the paper flutters rapidly... but should the paper slip get sucked up inside the tail pipe... one ore more valves are compromised and allow exhaust gases to be pulled back inside the cylinder(s) around leaking valves during the intake strokes.

If you are not in immediate possession of the GM Factory Repair Manual for your car... This item might be of great help...

http://cgi.ebay.com/ebaymotors/Pontiac-Grand-Am-Prix-Service-Repair-Manual-2002-2003-_W0QQcmdZViewItemQQhashZitem255b336eb2QQitemZ160443887282QQptZMotorsQ5fManualsQ5fLiterature

PS... I'm an Old Dog myself... and one trick I have found very helpful to avoiding severe back problems is to jack up the front of the vehicle to a comfortable height and then safely "Jack-Standing" the car at a level that makes bending over and reaching down inside the engine compartment much less of a PITA...

[MidnightriderZ24]

unbolt the downpipe from the rear manifold and go drive to see if its the cat.

[Axe_1]

Thanks guys, great replies.

A guy from work brought in his fuel tester and we both agreed it was within range. I don't have one new enough to fit the rail, but they aren't that expensive so I'll look into that again. I'll also check the fuel pressure regulator diaphragm. Good call!
Also I've seen the exhaust trick before, I've just been out of the loop for so long I completely forgot about it.

I do raise the vehicle on occasion, but I've had 2 back surgeries and I'm leaning towards another. I'll probably have another one in the next 8 years before I retire.

As far as the Cat, it actually runs better as the RPM's go up. I thought of that but thought it would be the opposite if the exhaust was restricted. If I find that is the culprit do they sell a high flow or Cat-Back type system for this? I didn't know there was so much available for this engine until the first time I surfed this site.

I'm an old V8 builder and have a special love for Big Blocks.

Axe

[robertisaar]

and none of this throws any kind of SES light?

[Axe_1]

None at all. I was told that if the TPS was out of position the computer may think that's what I'm asking for and may not throw a light?
Don't know for sure.

Axe

[Azrael]

You can use an ohm-meter across pins A or B and C. A known good one of mine reads between 700-4K ohms off the car (might be narrower installed). The important thing to look for is a smooth linear change between the extremes as the throttle is opened. A scan tool is also useful as it'll show a percentage of the throttle open.

[Axe_1]

Thanks again guys. I haven't taken the time to mess with this yet but will soon. I had to borrow the battery for another car but will install one in it tonight.

If this should have been somewhere else like "Pushrod Maintenance" then feel free to move it... (sorry)

Axe

[Skeith]

Does you gas tank draw a vacuum when its running? If it is you could have a clogged EECS vac line or a clogged filter in the evap emissions canister. Im having a similar problem with my car, But If I crack the gas cap a bit It will accellerate faster. If its idling fine its probably not the head gasket, head gasket usually leads to overheating as well.

Also as mentioned above too much exhaust back pressure comes to mind. try disconnecting the the pipe before the cat and see if that helps.

How are your spark cables? A visual and resistance check is usualy all thats needed to make sure they are in decent condition.

[Axe_1]

OK here's what I found today.

TPS - 1750-5.72K seemed pretty smooth watching the meter rise/lower.

Fuel Pressure Regulator Vacuum Hose was dry and didn't smell like gas before and after driving tests (I would have bet against this one)

Valve/Seat Paper Test was deceiving at first. It has duals with the dual tips so I had to block 1/2 of the tip to get a reading. Tried with 4" wide paper, 2.5" wide paper, and then 1/2" slits 6" long with no sign of intake valve leakage.

EECS - Loosened gas cap with no gain, possibly a very slight loss of power.

Spark Plug Cable Resistance:

1) 2.36K 3) 2.59K 5) 2.72K
2) 3.78K 4) 3.48K 6)3.74K

The numbers vary quite a bit but it seemed to be proportionate to the cable length. They don't look great though and are all suspect. I'll change those whether they are the problem or not. I have a new set of Excell 8.8's I was saving for one of my V8's that I may cut down and use.

Downpipe/Cat Converter Test - It was already hot after doing these tests so I didn't get to this . I also want to do a
Compression Test in a couple of days. I'm working outside and it's supposed to rain tonight & tomorrow.

Also the oil leak looks like it's around the LIM to me, without cleaning and getting too far into it. I know I will eventually change the UIM and LIM gaskets, but was hoping to not have to this week. If I'm that far I'd like to go ahead and pull the heads and get them checked and resurfaced.

Thanks again for any suggestions you may have.

Axe

[fastback4]

Hey guys...Should i have replaced the TPS when i updated my throttle body from the smaller 3100 inlet to the larger 3400 inlet on my 1997 3100 engine? I got codes P0121 & P0122...TPS pedal position sensor chk. range & chk. low input

None at all. I was told that if the TPS was out of position the computer may think that's what I'm asking for and may not throw a light?
Don't know for sure.

Axe

[fastback4]

Hey Axe, Follow my threads as I'm kinda dealing with some similar performance problems. I did a 2000+ 3400 heads, intakes, fuel injectors, throttle body swap on my 1997 3100. Runs smooth but my milage is 21MPG. Used to get 27MPG. Car has a sloppy hole shot. Also I'm throwing codes like crazy. I may have contributed to some codes, like pulling sensor plugs while the engine was running (damn OCD)...Any way it may help you out......Tom
P/S I'm 30 miles south of Cinn. Ohio in California, Ky., 58, Work at Generous Electric Evendale, 32 years...

[Axe_1]

Thanks Tom, I have been following yours and a few other threads looking for similar info.

I'm 49, Cincinnati Firefighter/EMT FAO (driver) for 21 years, and living in NCH, OH. Hey I lived with my grandfather on Shepherd Ave for about 3 years right after high school. I could see GE from my front door, lol. Our local drag strip in the 80's was Gate 17 to the bridge.

Axe