Hesitation when shifting to overdrive
 

Hello everyone!
I have a 1999 4Runner Limited 4WD that has developed a problem lately. The truck would hesitate every time I press on the gas pedal, shaking often violently. At first, this only happened at higher speeds, but as the problem got worse, it also happened from a standing start. After I used some injector cleaning fluid and replaced the spark plugs, the truck now only hesitated when shifting to overdrive. The problem seemed to occur between 1500-2000 RPM. Once the engine runs faster than 2000 RPM or so, then it seems OK, but if it slows down below 1500 and I accelerate to the point where the overdrive kicks in, it would hesitate and shake until I coax it past 2000 RPM. I can't decide if this has to do with the engine or the transmission. Any troubleshooting hint would be much appreciated. Thank you!

When I first got my 96 it had a slight miss also when it was in OD with the TC locked and I was under 2K rpms trying to slowly accelerate just like you are describing. I changed the plugs and wires and that solved it for me. You said you changed the plugs, how bout the wires? If they are the originals I would do the wires also. When I changed mine the wires said 1996 on them and the plugs were Denso on one side and NGK on the other so I think the plugs were originals with 181K miles on them!

Thanks for the reply, kball! I'll follow your advice and replace the spark plug wires. I thought of doing that when I bought the spark plugs, but I didn't expect that spark plug wires would have this kind of effect. But since replacing the wires worked for you, I'll try it too. Now that you mentioned it, these wires have at least 100,000 miles on them, so they're probably due to be replaced. My truck has 186,000 miles. Thanks again! I'll let you know how it goes.