high mileage 3.3 trouble

[WSU_EE_PhD]

A close personal friend of mine has a pretty nice 93 grand am with the 3.3. It is up to about 150k miles. A week or so ago the car itself was nice, no squeaks or rattles, trans seemed fine, etc. There was a hesitation right off idle. Anyway, her battery had gone bad and a new battery went in about 3 days ago, now the car is totally sucking. It needs very light gas to get going (slowly) but it does eventually make the speed limit. No check engine light so far.

My questions:

I have heard about computers needing to "re-learn" the engine after a battery swap. Since this happened right after the new battery, is this a probable cause of the recent extreme lack of power? About how long/many miles should I expect it to take to "re-learn." We have run maybe 10 (painfully slow) miles so far.

As far as the underlying problem(s,) what should I consider as far as the hesitation right above idle that was there even before the battery swap? I assume whatever was causing that is now being compounded. If it was a small block chev, I would guess the timing chain was really stretched. If it were a mid 80's Buick 3.0 V6 I would say the cam is rounded off. Are these options? What is the first to go in a well-maintained high-mileage Grand Am 3.3?


Thank you all very much in advance for your help.

[92CamaroRS]

check and clean the MAF sensor as that could be a problem. also how old are the spark plugs and maybe have the plugs and coils checked. just some ideas

[sublime922]

also check the 02 sensor....fixed mine when i changed it

[WSU_EE_PhD]

Hey guys, thanks for your quick replies. The oxygen sensor, plugs, and plug wires were all changed pretty recently, so I ruled those out for now. Again thanks for the help though.

Here's what I did to fix it if anyone's curious. I pulled the MAF sensor and carefully cleaned the "pins" with gas, an old toothbrush, and gentle compressed air. Next I undid the hose from airbox to MAF housing and took out those 4 philipps screws and pulled off the housing that the air flow sensor screws into. I cleaned the inside of the housing with gas and a toothbrush, and wiped the inside with a rag. It was black, and it cleaned up very well to shiny. Then I used a piece of wire to hold open the throttle and cleaned the butterfly valve and the inside of the throttle body. There was lots of black, gummy buildup inside there. I used gas, a toothbrush, and the wood end of an unsharpened pencil on the heavy deposits. I got down into the idle air bypass as much as I could. Then I went over it all with gas and a toothbrush again and wiped it all out with rags. I left the throttle body on the car while doing this. The inside of the throttle body went from black and gummy to almost mirror-like. I paid special attention to the black "ring" of goo that had formed around where the butterfly valve rests at idle.

Right off the bat I could tell the car was better. I took it out for a drive and the car now runs better than it did 50k miles ago. If anyone else has a similar problem with hesitation right above idle or rough idle, I would recommend you consider this as a possibility. It only took an hour and costs zero. Tools used; a philipps screwdriver, a coffee cup full of clean gas, an old toothbrush, a pencil, and old rags. Now this weekend I'm going to try it on my Ford Probe that is running fine, because it can't hurt and it made a big difference on her Grand Am.

Anyway, thanks again for your help.