3300 misses & stalls Sometimes, awful MPG

[troy3000]

Ok, I have a 1993 Grand AM with the 3300 engine. Sometimes it runs like new. Other times it misses at low speeds. Other times it idles terrible and will stall when you let off the accelerator. It also gets terrible gas mileage (20 mpg or less). I pulled the trouble codes: they are 26, 27, 38, 49. Not exactly sure what is going on with this machine. It does appear though that the tranny is causing my irritation. Any help will be much appreciated.

[goredsox]

Originally posted by troy3000
Ok, I have a 1993 Grand AM with the 3300 engine. Sometimes it runs like new. Other times it misses at low speeds. Other times it idles terrible and will stall when you let off the accelerator. It also gets terrible gas mileage (20 mpg or less). I pulled the trouble codes: they are 26, 27, 38, 49. Not exactly sure what is going on with this machine. It does appear though that the tranny is causing my irritation. Any help will be much appreciated.

get a haynes to check the codes, i have never had a check engine light in my car in the 14 years we have owned it so i dont know what they mean.

could be the TCC Solenoid in the tranny. does it stall coming down from highway speeds?

i had missing at low speeds before as well, changed the plugs and wires to AC Platinums problem went away.

as for the bad MPG do you use to much happy pedal??? :lol: the way i drive it is "spirited" once and a while and i usually get 23.5 pure city mpg, and 25 mpg with a city/highway mix. All highway is around 30 mpg. Hope this helps... sad to see a 3300 sick...

[troy3000]

It will only stall sometimes coming down from highway speeds. The terible MPG is from driving at normal 50-55mph.

Now the car is dead, it cranks over, but won't start. I changed the ingnition module/ distributor, but it didn't help. I checked the haynes manual I have and then checked the wires to the ignition module and it appears that there is no power getting to the module. I am now wondering if the crank sensor is bad.

[pokesmot]

your TCC solenoid is sticking, which is why you keep stalling while coming down from highway speeds; the TCC locks the torque converter with the crankshaft, so when you slow down your basically stopping the engine from spinning when you hit the brakes.

repair means opening up the valve body and replacing the solenoid which is not easy; in the meantime to prevent it from stalling just unplug the TCC connector (4 pin grey connector drivers side front of tranny bellhousing)

the car will still drive fine in the meantime, but you will get poorer fuel economy on the highway, as the engine works harder to keep the car up to speed.

as for the no starting, check for a refference signal to the ignition module while cranking (if you have a tach or scanner that can give u tach readings, use that.) if there is an RPM reading while you crank the crank sensor is good.

Is the car flooding (strong gas smell from throttle body) while you crank it?
No spark on all 3 coils?


edit:

code 26 is quad driver module (ECM controlled ground for TCC)
code 27 is second gear switch (inside tranny)
code 38 is brake switch circuit, which could in fact be triggering all above 3 codes.

the brake switch is also used to disengage the TCC.


as for code 49, there is no such thing on this engine to my knowledge, however code 48 is a missfire code; start with spark plugs and wires also inspect ignition coils for cracks / sparking arcing.

[troy3000]

Replaced the ignition module again, now it starts and runs ( I think there may still be something wrong with the ignition switch though). I also unplugged the electrical plug from the transmission, which seems to have helped.

Thanks!

[GarciaNY]

my car does the same thing,anyone wanna explain this whole situation to someone who doesnt know much about engines? lol

[troy3000]

I replced the ignition switch on this car. Now it runs and drives fine. Best of all it now get 25MPG.

[goredsox]

Originally posted by troy3000
I replced the ignition switch on this car. Now it runs and drives fine. Best of all it now get 25MPG.

sweet!!! i used to get about 22-24 around town and 28-31 highway in mine.

[goredsox]

Originally posted by GarciaNY
my car does the same thing,anyone wanna explain this whole situation to someone who doesnt know much about engines? lol

Well i can explain the stalling when slowing, well sorta...

In our 3 speed transmission's there are 3 gears (obviously :lol: ) anywho, when you speed up and are in 3rd gear, at around 42 mph the Torque Clutch Converter Solenoid actuates in the transmission. All a solenoid is is an electric actuator. When it engages it locks the transmission and the torque converter.

The torque converter is the equivalent of a clutch in a manual transmission car. In an automatic it connects the motor to the tranny.

When this solenoid locks it lowers the rpms about 500 to boost fuel economy. Now when the sensor goes bad it will not disengage properly, see anytime you let off of the gas above 42 mph it disengages and "unlocks" the tranny. So if it doesnt disengage the tranny remains locked, and it remains in 3rd gear. So when you slow down and come to a stop it will stall, just like in a manual transmission car if you slow down and stop in gear it will stall.

That boys and girls is my novice attempt at describing the TCC Solenoid. If any one can do it better please, do so... :) :lol: