Pontiac Aztek Hard Shifts (From 1 to 2) When Cold and No Speed!
Ok so this problem isn't a big one but none the less it has always been there but has gotten worse in the past few years.
When the engine is cold (not dependant on weather outside) and I drive my vehicle out of my garage (small slope very insignificant) and onto the street and put it in drive I will not see what speed I am going and it won't shift into 2nd gear. The moment I take my foot off the accelerator or hit the brake the speedometer will all of a sudden show what speed I am in and hard shift. I know how it is now so I don't get going as fast and at times avoid the hard shift.
In a possibly related note, regardless of engine or outside temperature when I am in stop and go traffic (crawling or going about 5 mph) my speedometer will (at times) jump from 0 ~ 10 mph (heads up display does too). It is a bit funny actually but by the time I get going again it comes to its senses and is fine no hard shifting.
Car is very well maintained, I put a lot of preventative maintanence into it. Milage is about 138,000.
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Have you checked the transmission fluid?
May be a bad speed sensor. Just guessing, but if the transmission shifts based in part on speed, and the sensor I'd jumping around because it's bad, then it's possible the computer is shifting weird due to a bad input.
If it's really cold where you are located, it could be fuel line freeze up. I always make sure I have a full tank of gas when it's cold. If you are low on gas, add a can of Heat and fill it up with gas.
Could be the gas cap,there are also canister purge and canister vent solenoids.The fuel system gets tested for vapor leaks when cold so clean the gas cap surface,always turn at least 3 clicks when putting cap on and have a parts store erase the code to see if that takes care of it.
Assuming your engine is in good mechanical condition, there are only a few options.
1. You may have a vacuum leak. 2. The pickup in the distributor may be worn to the point that it is sloppy at idle but normal at higher rpm. 3. Idle control valve/motor may not be working properly.
It probably isn't an ignition related problem as the problem would normally get worse as RPM increases. I've seen #2 about 5 times in the past year or 2 so it's not uncommon and would recommend replacing the entire distributor if you come to that conclusion, but would definitely check all vacuum hoses first.
After replacement of any brake componet that requires opening the lines (Brake lines, fluid loss) you have to bleed air out of system. In addition a master cylinder replacement requires a bench bleed before attaching to vehcile.
OK allot of people don't under stand transmission because they think a transmission is complicated. When the fluid is cold it is thick and can't move as fast and can't build pressure as fast as hot transmission fluid. There are small 1/16 holes in the Valve Body that the fluid has to pass through and Valve that get ***** out from allot of use. When a valve ware and fluid can go through the space that it couldn't before when it was new and the differences of hot and cold fluid makes a big differences. The fluid can move passed the valve and into the accumulators that operate the shift mechanism. So that why it shifts good when it's cold and hard when it's hot. Might be a sticky valve or shift solenoid or just need rebuilt. In the past if i had trouble like this and had to rebuild the transmission before i did that i would put a can of thick STP motor oil Treatment in the transmission because it thickens up the transmission fluid and make my car shift like new. Its not going to hurt nothing it mixes well with the transmission oil.