So I've looked all over this site at the different ways to fix the 3500-4000rpm stumble. I'm leaving for college again at the beginning of the weeks, finally , and I want to get this fixed before I go. I don't have a lot of money to spend before I go. My plan is that I'm giving the engine a tune up, yeah it needs one badly, and I'm changing the oil to a winter weight. I've already bought some fuel injector cleaner that I'm going to put in either today or tomarrow when I go to the pump. Now, what should I do about the 3500rpm stumble? I've seen different post that say about the ground connections and how to do them, then other's that say, removing your intake manifolds to get to the 5th and 6th ports and taking them out and cleaning them, and another post that just involves you turning them to 6 and wiring them open. This engine thats in it has only 30,000 miles on it, the previous owner bought the engine new from Mazda like 7 years ago, and the engine has only 30k miles since. I can do some good work to it all weekend, but I really can't spend much at all because of my trip soon. Whats your advice to do? Also, what else should I check out on the car before I go? Thanks for the help guys.

 

A full 60K tune up should be done first.

Then if you still have problems the grounds should be updated before anything else. In 90% of the cases this solves any hesitation problems.

You only need to clean the Aux ports if they are not functioning correctly.

Wiring the aux ports open will only result in low RPM performance and not gain any high RPM HP.