strange problem w/ 3.8l impala

Hello-I am new and have a 2000 3.8l Impala with approx. 100k and a tranny rebuilt about 10k ago, and within the past several thousand miles and half a year, the coolant has been flushed, the plugs, wires fuel filter, etc.
Now to the problem- I just got back from about a 40 mile highway trip, about 5 miles from my exit I had to accelerate to pass a slow moving truck. I was going approx. 45 and as I started to accelerate it wasn't responding, the engine made a continous noise like it was going to fall apart, rpms weren't really going up as they normally do and the pedal was all the way to the floor threw all of this and was just barely responding. The check engine light started flashing durring this time and when I was finally able to get past the truck and back into the right lane the light stayed on. I tried giving it more gas several times more on the highway but it was sluggish to respond and the light started flashing-I noticed it seems to be when you have the rpms near 4500. (It does eventually redline but it doesn't upshift).When I got to my exit I pulled off at a well lit station and my brother who is more mechanically savvy checked all the fluids and everything seemed proper although there was a slight fuel smell in the oil.
I am truly puzzled and extrmely concerned seeing as this is my only vehicle. Any replies would be greatly appreciated.
Thanks-
Tim

Most of my experience is with older 3.8l engines but it sounds as if you might have jumped time. I used to rotate the engine backwards stop at tdc mark the dist and turn by hand if it went over 15 to 20 degrees I replaced the timing chain.
You could do this by watching through the camshaft position sensor hole. Stop when the tooth for the sensor just starts to move.
Your description sounds like a mechanical problem to me. Is this what you are trying to convey.

Thanks for your response, I should have mentioned that it idles smooth so I don't think that the timing is affected, but I'm far from an expert so is it possible that it could still be the case? Also the slight gas smell from the oil?

This is really confusing me and stressful as it's the only transportation I have.
Thanks for your response-
Tim

Latley I Have Experanced The Coating On The Inside Of The Exaust Manifolds Braking Loose And Clogging The Converter If It Has Less Than 120,000 The Dealer Will Replace It For Free There It Tech Service Bullitan On This Problem.i Have Seen This 3 To 4 Times In The Past Few Months Same Symptoms Good Idle Poor Drivabilty

Sounds like it is time to have the PCM scanned. All your timing and fuel metering is done by the computer. Sounds to me like you might be getting too much gas. When the MIL light came on there are dtc's or codes that the computer throws that will tell you the area of the fault. Random replacement of parts very seldom corrects any errors. Have you checked your air filter to make sure it is not clogged, also could be your cat is slightly clogged, will never know till tests are made.

The flashing CEL (check engine light) indicates a mis-fire condition. If you used quality parts when you tuned it up (not Bosch, multi-electrode JUNK plugs), then I would have it scanned and see if any codes are stored (A-Z and Advance can scan for free if the CEL is on). Trying to track mis-fires can be frustrating if you don't do you homework.

As I read your comments and replys it appears nobody understands exactly what you are trying to tell us. If part of the exhaust headed towards the converter was the noise more under the seat as the converter started to plug up. Was it in the center of the engine as a piston dropped to the oil pan. Was it on the pass side and sounded like plastic pieces hitting the engine. If just the engine is shaking from running rough then the engine scan is the way to go.

The noise was coming from the engine compartment, it seemed more centralized as oppossed to one side or the other and it didn't seem like anything dropped or fell off the car and it wasn't riding rough untill you got it in the 4500 range or so.
Does this seem like it may possibly be a simple problem with a simple fix or something much mor e involved and costly?
Thanks for your replies-
Tim

Do not worry about the noise, concentrate on the car not running right, get a scan to find out what codes you have. There is a greater then average chance what ever is causing the car not to run right is linked to the noise. thats it.

yes as the other posted stated, get rid of the junk plugs, get A/C DELCO PLUGS AND NEW WIRES.

Except for the noise you are trying to describe, all your other symptoms could be caused by a clogged CAT... Due to manufacturing defect problems your CAT is covered for 10 yrs/120K miles by GM... But the dealer would have to test and confirm the clogged CAT problem before he replaced it for free... Since your CEL came on get the codes scanned (Autozone will do that for free) and see what the codes are... Post back here with the scan codes...

You easily put the car on jack stands and loosen the bolts at the front of the converter in an evening. At this point if this don't work get it scanned.

i am going to agree with the conclusion of the plugged convertor. but the noise could very well be caused by the converter being restricted. if the engine can't breathe correctly(good exhaust flow) then it will start to choke. i have acutally seen a grand prix burn a hole in a piston due to too backpressure caused by the restriction.
also a side note. why does everyone like the idea of going to autozone to get you codes pulled. a trouble code is just a syptom of a condition that is occuring. if you go to the doctor and tell him you knee is hurting does he just replace your knee

I always check the primary side first if that doesn't work. I find out more information from my scanner than codes. I can monitor temp,volts and other things. This helps pinpoint problem areas. I have found when a problem area is repaired other codes go away.

You easily put the car on jack stands and loosen the bolts at the front of the converter in an evening. At this point if this don't work get it scanned. Probably would be easier to unscrew the 02 sensor. Actually if the car is cold it runs in open loop not using the the 02 sensor and running off of the VE tables till the heated ox 02 sensor warms up then switches to closed loop using the 02 sensor.

I had it taken to a local mechanic last week- It wasn't throwing any specific cylinder misfire codes, it was a general code for a misfire. He examined the coil packs and 2 of the 3 had some corrossion. He cleaned that off and cleared the light; he wasn't sure that was the exact cause but we didn't want to throw parts at it either, said I should drive it and see how things go. I've driven it about only 10 miles since (due to injury), when I started the car up and started accelerating it made a slight jump but that was the only thing out of the ordinary although the true test will be taking it out on the highway so it can open up a little bit with some mid to high range acceleration. When I am able to do that I will post what happened and how it's running.
Thanks for all the replies

I took the car out tonight and it started doing the same thing-I drove to Advance as others here have recommended and they gave me the code of po300
random/multiple cylinder misfire detected- I was wondering what would be the best course of action considering the problem can't be pinpointed.
Thanks

I have this more detailed posted on the impala forum but lately I've been having a problem when I get past about 4500rpm range. I've had the car examined by a mechanic and the coil packs were cleaned. I took it to Advance and they scanned it and came up with po300-multiple/random cylinder misfire detected. I was wondering what would be the best course of action considering the problem can't be pinpointed.
Thanks for any advice

When was the last time you had your injectors cleaned?

Sorry Tim2006, we do not allow multiple posts/threads on what appears to be the same issue since you have a recent post at Impala. It gets confusing and 9 times out of 10 the same people will weigh-in to help out. Non-specific is not intended to be utilized this way.

I'm going to have to merge/move this one with the post at Impala which should bump it up automatically.

I haven't had them cleaned and I've had it approx. 5k miles. By the way my gas mileage is 13 city and 22 at best highway driving. You think it is the fuel injectors?
Thanks for the response

I haven't read thru all the posts but I would have the cat back pressure tested at the o2 sensor port, Bosch plugs are known to be short lived in these engines also.

As you paid to have it checked I would ask the mechanic to check your converter and put it on a scope so he can watch what cylinders are misfiring.
The scope will pick up a bad coil,wires,plugs,gap and ect.

When my CAT clogged I would start to hear this rattling under the car like the exhaust was loose. It eventualy wouldn't excelerate and didn't want to shift under a load. The brakes were even effected, I guess because of vacume. I would have never guessed that was the problem but the dealership said that I was only running off 2% effeciency from the cAt. After I had saftey brake and muffler replace it witha HI PO ,CAT it ran fast! Better than new. Chevy paid for the repairs.