Acceleration cuts out when engine warms up

I've cleaned the throttle body, put new plugs in but I'm still having the same problem... I have a 2000 Saturn SL, when the motor is cool it runs perfectly, but when the engine temperature reaches the normal operating temperature that's controlled by the thermostat there's a about 35% power loss along with the enging cutting in and out around the 2/3 throttle area ... Anybody know what could be causing this...

any SES light?

No SES lights have come on since this problem has started.... By the way, the car has a manual trans. and it has the 1.9 engine with single over head cam...
Thanks and I'm still hoping for any thoughts about this problem I'm having...

first a side note,if those new plugs were platium plugs, change them. the 1.9L doesn't like platium plugs.

my first thought is an O2 sensor problem, because the computer doesn't use the O2 sensor until it reaches around 600F (that normally take about five minutes tops) it can't easily be checked unless you have a OBD2 scan tool, but you can remove it if the engine is cold(dead cold, like sitting over night) and see if it covered in crud. (FYI a blown head gasket can cause the O2 to fail, so if your head gasket did blow in the past...)

second idea: having no top end power(RPM, not speed) can be a sign of a clogged cat. convertor. but this unlikey because 1. i beleave all factory cats have 8 year warrentys(federal law) 2. i doubt heat would be a factor.

third idea - bad TPS(throttle position sensor), but again unlikey - 1. shouldn't be affected by heat, 2. even though they can deavlop(sp?) flat spots, it would take at least ten years

last idea, and this is a biggie, bad ECT. there were two designs - the old/crappy one and the new/reliable one. the new design(brass) is a direct replacement to the old design(nylon). i don't know what year saturn made the change. the old ones would crack and make the car run rich. and its only a $15 peice.


keep in mind these are only ideas, and since every problem has a different 'feel' its hard to diaginois without driving it.

Thanks for all the helpful suggestions.... I don't have platinum plugs in the car... I changed the ECT, I put a new O2 sensor in behind the catalitic converter, the O2 sensor on the exhaust manifold checked out in good condition and reads 6 ohms when checked with the engine warm and I've also changed the EGR valve....
In doing all this there have been very minor improvements and I'm still having a definate problem... The car runs great when it's cold, and I also found out it runs good with no problems when the EGR valve electrical connector is disconnected, this is and was the case with the old EGR and the new EGR...
After the car dash temp gage reaches the first line on the gage (About the 1/4 line), I loose about 1/3 of the cars power and as I depress the accelerator to about 3/4 throttle it can cut out also... But if I give it full throttle the problem seems to clear up....
I'm still bewildered and looking for any suggests that any one may have...
Bye the way, I wanted to thank you again Sierra for your taking the time you did and responding to this situation...

sorry that didn't fix the problem, you may want to ask on the forums on saturnfans.com

so if you egr is disconnected, and the motor is warm there is no problem?

the EGR is turned off at full throdde. but i think it still works during open loop mode(warm-up)

the PCM may still be adjusted to the old EGR, to clear the PCM's memory pull the PCM B fuse with the key out, after about 15-30 seconds you can put it back in. WARNING! - this will also erase the fuel maps, idle, and shift points. the car will run real bad for a while, the PCM will relearn everything after a hour or two(worst case - it will take a day, my 94 has a simpler computer, sometimes its fine in 10 minutes)

the saturn O2 sensor can't be properly tested with a ohmmeter, an osilioscope or scan tool are the only ways to get true reading.

whats the idle RPM?

This is where I'm at with the car today... I decided to get a code reader that I could check the pcm memory and see if there was anything in it... It cam up with the p0341 code, after doing some checking around (because these saturn don't have a camshaft sensor) I found out this code could indicate bad plug wires.... I changed the plug wires, cleared the pcm memory and gave the car a drive, the only good thing that came from that is the p0341 code hasn't came back... The car still has the same problem that it has had since this has started...

Along with changing the plug wires I took off the coil packs and ignition module, cleaned them up and made sure all the connections were good and put things back together....

I've also changed the IAC and the MAP sensor... Changing these things didn't solve my problem either...

So I connected everything including the EGR and took the car for a 150 mile drive and let it do it's power lose and cutting out stuff to see if any codes would come up, the computer still shows no error codes...

The last thing I've done is to put a piece of flat metal under the EGR to stop it's functioning so that I could have the electrical connected... By doing this one thing, the car performs fantastic, a lot of power with very smooth acceleration...

The car does seem to run a little lean, it idles at 750 rpm which is a little on the rough side but not too bad...

Could I have gotten a bad EGR, could there be something wrong with the PCM, could something be telling the EGR to open too much...

I'm still at a lose with this situation... I'd definitely be appreciative of any thoughts if some one has any...

Again I'd also like to thank Sierra for the suggestions that have been offered so far...

The car does seem to run a little lean, it idles at 750 rpm which is a little on the rough side but not too bad...

is that idle with the EGR blocked off or normal?

this is starting to get a little wierd. it possible you bought a bad EGR, but unlikey if it acts exactly the same with the new one and the old one.

did you replace the gasket too?

P0341 is not uncommon, but again wierd because the 1.9 don't have a cam sensor. the PCM uses spark plug #4 to fake a cam signal. this is not your problem.

does your scanner give you sensor readings or only codes?

Ok, problem solved... I had to get the car running so I took it to a mechanic that I've used in the past.... After 4 days he finally diagnosed the catalytic convertor as being bad.... He changed it out, not cheap, $300.00 for just the cat.. Picked the car up and its running great... Thanks for all the good suggestions... The car does have 180,000 miles on it so I know that even though the catalytic convertor was the final thing to get it running right, some of the other things needed to be done also... Thanks again for all the good suggestions and I'll be watching reading and commenting on all the other stuff that goes on here...