Thread: Getting tired of this...

Hello all,

Car: 2003 GT, 150k

Quick rundown of recent engine work: Rebuilt trans, front O2 sensor, catalytic converter @ 136k. Upper and lower intake manifold gaskets, plugs, wires, pcv valve @ 140k.

It idles smoothly and under light acceleration you would never sense an issue. Half throttle or more, or highway passing reveals a noticeable lack of power with the a/c on or off. Between 3-4k rpm seems the weakest. There is no check engine light. It just seems to wind up and not go anywhere fast. Overall fuel mileage is 19-20mpg per tank on a pretty easy drive cycle, which is 50% highway. It just feels like it is dragging an anchor and making more noise than power. Never feels rough or off balance though, just weak. I did notice a few days ago, when the wife was driving off, some bluish smoke coming out of the right tailpipe only. Not much, but it worries me nonetheless. It has been using about 1qt of Castrol GTX High Mileage every 2k miles.

I will be checking the plugs today and will probably unhook the muffler assy to see if the left muffler is clogged and causing back pressure (i know, not very likely since the dual mufflers are just for looks).

Has anyone experienced these symptoms? Could this be some sensors getting lazy and unable to compensate for the summer hot air? I know the AC Delco O2 sensor isn't particularly sensitive... The MAF was cleaned when I did the intake manifold gaskets. Fuel mileage on this car has never been great, maybe 21mpg average at best.

Any pointers or things to check would be most helpful. This car has had well over $3k in parts and repairs over the last year and I am about ready to trade it in and take the suck on a car payment again.

Just checked the plugs... All 6 Delco plugs look good and have a slight gray tint as I would think they should. I am concerned about compression though. I let it idle for a few minutes and then held it at 3k rpm and the smoke show was very unsettling. I could see it having weak rings after the wife ran over the oil change interval a few times and drove it with the low oil light on a couple times, only mentioning it a few days after the fact. This is her car and I work otr so I can't be in total control of its care. Grrrrrrrrrrrrr. Well, a replacement motor wouldnt be the end of the world, L67 or L32 perhaps? I will get the tool and check the cylinders for compression. Im hoping it may just be valve guide seals, but the way it was blowing smoke leads me to believe not.

Dtrick, thanks for the reply. I dont know of anyone else with a GP or any 3800-powered ride for that matter. The car ran like poop before the LIM gasket job. It had bad idle, got 14mpg, and smelled like coolant. It never really used oil until the last 3 oil changes.

Where in St. Louis are you? I've got an 00 GT w/ 150K on it. Not sure it drags an anchor but it doesn't seem to be too much of a slug, even for an N/A car. Although I'm beginning to suspect my cat is done for. Technically it has 240K on it to the best of my knowledge.

Have you checked the PCV valve/replaced it? That could cause a buildup of crankcase pressure and may account for the oil burning/smoke. It's a cheap fix if it hasn't been done recently.

Maybe give it a Seafoam treatment and see if it helps the smoke.

I'm on the east side of the river in Troy, FordMan. The PCV was changed when I did the LIM gasket. I did make sure the o-ring was removed and replaced properly.

The wife and I took it for a spirited drive yesterday evening and it seemed lively enough after awhile, pretty much like you describe your car to be. I get to drive this thing about 50 miles per week running errands (~25% of its total usage) and it seems like a computer/heat-related cut in performance. Does this sound crazy? What sensor(s) will afflict the ecm with this? Not that I'm trying to infect this post with ADD, but here's another one... is the ecm adaptive to the point where enough granny driving will induce this kind of fuel trim?

Might the cause of the smoke be related? Last time I checked, the car doesn't grill steaks... Next step in my mind is a compression or leakdown test. That should reveal if the smoke is a mechanical breakdown of some kind.

The smoke is definitely not coolant. I did a coolant flush when I did the LIM gasket and the coolant level has been static since. The smoke is bluish and does not smell sweet at all. With the engine using 1qt in ~2k miles I pretty much assumed the smoke was oil. Bad assumption?

Fuel mileage on the whole doesn't seem out of line from where this car usually gets on a tank. Typically we get 300-320mi out of it unless its a roadtrip, then the average goes up significantly. Our last trip I got 440mi before we needed to stop. Abrasive, I like the idea of small cheap parts going bad and causing all the symptoms. I'll throw an fpr on it and see if it improves. Im hesitant to buy a MAF or any other sensor since those are typically pass/fail electrical units and definitely not cheap or refundable.

My willingness to throw money at this car has dwindled severely after a transmission rebuild, cat, LIM gaskets, full brakes and full suspension all in the last 10mos. Are we beginning to understand the title of this post yet? lol

Also, maybe of no consequence.. The exhaust sounds incredibly raspy after you let off from a good stab of the throttle. Like wtf raspy. Never really had the occasion to rev it in neutral before now, dunno if that's normal.

So Troy, Ill then. Wierd, I'm near Troy, Mo, lol...

Anyways, the exhaust sounding raspy is normal. I've heard it on mine before. It will espsecially do it in Park. I've only rapped mine that hard once though.

At 150K your list of replacement parts sounds about right on par with the rest of us. Just normal wear items for an 8 year old car so I wouldn't junk it just because stuff is starting to break. My 00 has 240K+ on it and I've replaced just about everything on it except rear struts and the front control arms. Of course doing all the work myself helps w/ the bills.

The ECM can adapt to driving conditions to a point. Maybe have her take it on a highway run once in a while just to get a mix of city/hwy driving. Your fuel mileage sounds about right. I average 400mi/tank and most of my driving is highway since I live in the sticks and drive 100mi+ everyday just to get to work and back.

Have you replaced the fuel filter? How about the air filter? Also, how long ago did you start using the High Mileage Oil? Was it 3 oil changes ago, or longer? I'm wondering if you switched oil and now it wants to burn it.

I would run a cranking compression test first. Also you might want to check the condition of the valve stem oil seals, could be the cause of the oil consumption.
If you are able to see blue smoke out the back, oil is getting on there from somwhere. And if oil is getting into the combustion chamber, that leaves less room for air and fuel, wich inturn means less power.

With ~50% highway driving, I always thought this car should get better than 19mpg overall. Heck, my 2000 Expedition gets 18mpg on average with a similar drive cycle.

My head is swimming with all the possible causes of this sluggishness. A compression test is my first priority. I would think if it were a fuel or spark condition there would be some kind of notification from the computer. I say that, but the entire time the LIM was leaking it never threw a code, but kept adding more and more fuel to compensate for the leak. Enough so that it clogged the cat and brought the whole thing to a halt.

It sounds like its doing the work, just not making the power. In fact, it almost seems like there is an excessive whine/whir sound in the 3-5k rpm range, instead of the usual 3800 purr. Like I said, though, down low you would never think anything is wrong. It leaves the line with good torque, but midrange and top-end power is absent.

Has anyone had these symptoms without a check engine light? I am really trying to avoid paying for diagnosis, mostly bc I think it's going to turn into a wild goose chase and they're going to want to replace many things that are fine but just old and time consuming to test. No thanks.

I just fixed a long term problem with mine by cleaning the Intake Air Temp sensor. I used MAF sensor cleaner. I was getting 20-22 mpg consistently and now I'm getting 27-29 mpg. I had power problems long ago but replacing the CAT fixed that issue.

Of course, I had the poor fuel economy after that repair until the AIT sensor cleaning and it didn't start until the CAT and O2 sensors were replaced. I'd hook it up to a computer and see what your sensors are reporting before I dumped any more info. You could also try the MAF on your AIT. It's cheap, easy and you'll notice the improvement right away.

Also, if you're using a clean and oil filter, limit the amount of oil you're using. I was informed I was using way too much. Just a spritz is what I've been told. If it's a paper one I'm sure you've already tried changing it.

Good luck.

I just re-read your post. Every car I've ever had an experience similar to yours ended up having a bad CAT and no engine codes. I even took one car in to have the transmission checked and the transmission guy took one look at it and dropped it off at the exhaust guy across the street for me.

I know you had the CAT replaced (OEM or universal?) but it sounds to me like it's not breathing properly on the back end.

I've done this more than once, disconnect the exhaust before the CAT if you can and run it to see what happens. It won't run right but it should run better than a plugged exhaust.

Thanks mtsav8or. I will try taking the front o2 sensor out and see if relieves some restriction. The cat that's on the car now is aftermarket and has about 14k on it. There's a chance it got partially blocked having to run it for about the first 2k miles until I did the LIM gasket job.. I would think we'd have seen some symptoms before now though.

I wish I had access to a computer advanced enough to tell me something. My local dealer wants $80 just to plug theirs in. $120 if I want them to go for a drive with it. I'm in the wrong freakin' business...

Originally Posted by Mr Chill

Thanks mtsav8or. I will try taking the front o2 sensor out and see if relieves some restriction. The cat that's on the car now is aftermarket and has about 14k on it. There's a chance it got partially blocked having to run it for about the first 2k miles until I did the LIM gasket job.. I would think we'd have seen some symptoms before now though.

I wish I had access to a computer advanced enough to tell me something. My local dealer wants $80 just to plug theirs in. $120 if I want them to go for a drive with it. I'm in the wrong freakin' business...

If you have a laptop you may want to buy the connector and software to scan it on your own. I haven't shopped the market lately but digimoto was a pretty reasonable solution $99 when I bought mine. I went super cheap though and got a elm327 interface but they're not as advanced as what you can get today and no one is writing new software for them.

I don't know what the dedicated units cost but you can probably find them used for what you're dealer wants for a single scan.

Mine has paid for itself at least a dozen times over.

Good luck.

Id try dissconect the down pipe from the rear manifold and see how it runs kinda sounds like all the same problems when my cat was plugged in my 02 GP GT. Besides its free to check out instead of throwing parts at it.

Also you can go to oreillys and use their scanner to check codes like misfire count, o2 stats ect. Your car also sounds like its going in and out of limp mode. Too many misfires will send the computer into limp mode which limits the fuel trim and timing.