1996 Camry engine stumble or hesitate

I love my 1996 Toyota Camry wagon – It’s a V6 and for the last 6 months or so, has had this problem while accelerating – I first noticed it while speeding up on a freeway on-ramp – It would stumble under hard acceleration, but accelerate fine if I went easy on the gas – Over the months, it’s gotten worse – It stumbles on the freeway, just cruising along when going over 70, or any time at all that I try to accelerate – But not until after I’ve driven for 15 or 20 minutes – When I first start driving, it will only stumble under really hard acceleration – Otherwise fine – Until 20 minutes or so has passed – Sometimes I even seem to notice it stumbling a bit on the freeway, when I take my foot off the gas. Check engine light does not come on.

My mechanic’s first suggestion was to replace the MAF sensor, which I did – Then he replaced the plugs and wires – still no improvement.

Any suggestions on what to do next?

When was the fuel filter last replaced?
Has your mechanic checked the pressure of the fuel pump?

Thanks for the quick response! – The fuel pressure was checked and was fine – I don’t remember about the filter, but would it be safe to assume it was OK if the fuel pressure was OK?

I’d clean the egr valve. Take the thing off, shake the gunk out abndclean it with some carb or intake cleaner spray.
It is located on top of you engine. Two bolts and it comes off.


It is possible to have good fuel pressure, but insufficient volume

The fuel filter is cheap. If in doubt, replace it.

For the benefit of anyone with similar symptoms – I took the car to a shop –
TriStar Automotive in Santa Rosa, CA – with a good rep for diagnostics and Japanese car knowledge – They charged $110 to look at it – Hooked up oscilloscopes, dwell meters, and who knows what else – They said it was most likely the crankshaft position sensor – Only way to know for sure was to replace it – another $240 – And it was fixed!

Filippo thanks for the feed back. It’s nice to get the fix!