97 miss between 45 and 55 mph

[jph2424]

I have a 1997 3800 engine SE model. I just bought the car with 167,000 miles on it. When I go between 45 and 55 mph the engine starts to miss. If I hit the gas hard it does not miss.
Any help
thanks,

[jay69dogg]

My 99 GT's RPM's would fluctuate and it would hesitate around those same speeds. I'd mash the gas and it would come out of it. It mainly happened when I was going up hills and it never activated my SES light. You could have your computer read to see if it has sent any codes. There are auto parts stores that will let you read them for free.
I ended up changing the spark plugs, wires, fuel and air filters. It got better but did not completely go away. I ended up having to change my MAF sensor later on due to it failing. The fluctuating RPM's have gone away since then. I'm not sure what the exact fix was but I would go for the cheaper solutions first (plugs/wires/fuel filter) since your car has that many miles on it and you just purchased it so who knows if/when they have ever been changed.

[Cbierniat]

mine did that and it was the fuel pump resistor

[GTP Dad]

Unfortunately unless you have a GTP you don't have a fuel pump resistor. I would have to think that you have either a bad plug or wire causing the engine to miss. The other issue may concern the TCC solenoid. It usually locks between 45 and 55. If it does not lock properly or fails to unlock it will do what you are saying. Does the miss stop when you hit the brake as well as the throttle? If so then that is your problem.

[richtazz]

I agree with the other posters to try a tune up first. At that speed, the engine is under a heavy load (without downshifting) and a bad plug or wire will cause a miss. IF plugs, wires, pcv and fuel filter don't fix it, you may have a sticky TCC solenoid like GTPdad said, as that is the range that they engage/disengage.

[maxwedge]

A scan with a trans capable scanner will eliminate or confirm a tcc problem by looking at slippage percent errors when in lock up.

[jph2424]

Originally Posted by GTP Dad

Unfortunately unless you have a GTP you don't have a fuel pump resistor. I would have to think that you have either a bad plug or wire causing the engine to miss. The other issue may concern the TCC solenoid. It usually locks between 45 and 55. If it does not lock properly or fails to unlock it will do what you are saying. Does the miss stop when you hit the brake as well as the throttle? If so then that is your problem.

The misfire goes away when you take your foot off or hit the gas hard.
Thank you guys for all the great tips on what to look for. Where is the TCC solenoid? Any ideas on the cost to replace it?
Also, the last few days the car will just die. In a turn, going straight, slowing down. It will start right up again. Could it be the map sensor going bad?

[GTP Dad]

The TCC solenoid is located inside the transmission and replacement is not a diy job. Costs about $500 to replace. The description you gave when you take your foot off the gas pedal indicates that the TCC is disengaging causing the issue to go away. As for the stalling the problem there is probably caused by the Crank position sensor going bad. I would replace the CPS before doing anything, if it is weak it could cause this issue and can account for misfires. The stalling issue is the critical one at this point.

[troy1]

A worn out PWM TCC solenoid on the trans sometimes will make a engine miss feeling because it cant regulate properly anymore, under light throttle the TCC is slipping under hard throttle it sould have almost no slippage. so if the PWM TCC solenoid is worn out it cant control the slip anymore either bringing the TCC on completely which the computer does not want with light throttle so it unlocks it alittle but then the computer sees it slipping to much so it brings it back on then the cycle just keeps repeating its self, or possible a worn out VB could be possible also. 167K that’s a lot a miles!