Random Misfires

[dkard]

I have a 96 4Runner 143K miles 6 cyl 3.4 L. HAD the timing belt replaced at 140K miles.

Check Engine light came on at 143 k miles. Codes for random misfires all 6 cylinders

Replaced plugs and wires, no effect.

replaced coils no effect

replaced MAss air flow sensor no change

replaced cam shaft sensor no change

replaced crank shaft sensor no effect.

Engine runs fine, below 3500 rpm is smooth, above 3500 rpm can hear the cylinders missing.

Got the car back with the CEL still on but running. after about 50 miles the alternator belt came off.

Took it back in and the harmonic dampener is wobbling, looks like the key might not have been installed properly.

Currently looking for a dampener for it.

anyway any ideas on cause of misfires, could the harmonic dampener cause this

The problem seems to have come out of the blue though.

dave

[jetwhine]

dkard,

Welcome to the T/N.
The first thing I would do is to get a code reader and find out what codes are being triggered. And then we can try to help from that point. You have an OBD II system. You might have dirty injectors. Might be more noticeable above 3500 rpm's when they need to deliver more fuel.

[dkard]

The codes were 300 to 306, random misfires on cylinders 1-6.

We may have found the problem, the car threw the alternator belt this weekend. the Harmonic balancer was wobbling. Turns out it was not reinstalled correctly after the timing belt change. the timing belt sprocket was about 1/2" up the shaft so the crank shaft sensor was not getting a good signal. I hope that is it as I need my car back,

Unfortunately a new harmonic dampener is 3-5 days out.
dave

[jetwhine]

dkard,

I think a new mechanic is in line for you. That is too many mistakes for a timing belt change. Especially when you are paying for someone to do it right.

[dkard]

I had the local college automotive program do the timing belt change.

I only drive this car to and from work, only put 3k on the car since January. Which is probably why the problems took so long to show up.

Way too many mistakes on a rather straight forward job.

dave

[kball]

I believe the balancer and the crank pulley are one and the same. The crank bolt is supposed to be torqued to 217 ft-lbs. Apparently someone thought zapping it on with an impact gun was good enough...

[jetwhine]

An impact is good enough if it has enough torque and is not worn out. I use mine all the time and has not let me down yet.