NoPistons -Mazda Rx7 & Rx8 Rotary Forum

Quote:

Originally Posted by dblboinger (Post 833052)

This weekend I installed a Bonez Hi-flow catalytic converter and Racing Beat Cat-back exhaust. Last night I finally got to take a test drive and found I have a problem. It's very difficult to explain what I was feeling, but here goes...

I had driven the car for about 10 minutes or so and it appeared to be running very well. Then I got on I-5. The acceleration was great but once I got up to highway speed and tried to hold a steady speed the car started "surging". What I mean is every couple of seconds it alternated between feeling like it was going to die and running alright and it kept repeating as long as I tried to maintain a constant speed. If I pushed throttle it would straighten out and ran good until I tried to level off again. I didn't mess with anything under the hood, so I don't think I knocked any connectors off. Anyone got any suggestions of what I could try to remedy this?

Previously I neglected to mention that before the modifications my CEL would come on after about 10 minutes of driving. When I checked the error code it reflected a bad EGR valve. Yesterday, when I went for my test drive, the CEL didn't come on at all. I didn't mention that because I thought maybe replacing the cat cured the problem that was causing the CEL. So this afternoon I removed the ground wire from the exhaust and the car ran great....but the CEL came on again after about 10 minutes of driving. I got to thinking about it and realized that about 10 minutes into the test drive was when the car started acting up yesterday. So one theory is that the bad EGR solenoid is somehow grounding out my ECU and causing the car to run poorly.

But that's not the end of the story...I drove the car for about 2 hours and it ran great. Tons of power and not one instance of missing, until it got dark and I turned on the headlights. The stereo and the AC had both been on nearly the entire time I was driving and not a hint of a problem. When I added the headlights it started again, but not nearly as bad as yesterday. If I turned off the stereo, the AC or the headlights the problem would clear up. It was dark/raining yesterday when I went for my test drive so I had the headlights and the AC on then too, but not the stereo. Once I got on the freeway I turned on the stereo and shortly after the problem started. But like I said it wasn't nearly as bad today, with the exhaust ground removed, as it was yesterday with it on.

My thoughts now are that I may have 2 problems...a bad EGR solenoid and insufficient alternator output. Tomorrow afternoon I will put the ground back on and try it again with all large electrical loads OFF. If it doesn't mis-fire like that then I will add electrical loads until it starts mis-firing.

The alternator thing doesn't really surprise me because I've been concerned about that for a time. I've got about 1800 watts of Alpine in this car and I was concerned the 90 Amp alternator was not enough to feed the stereo and the rest of the car at once, but I hadn't seen any problems up until now. I've already been looking for a high output alternator, but they're hard to find for this vehicle. Unique Audio says they can supply me with a 240 Amp unit that is a direct replacement for my stock unit...but it costs $699 (ouch!). Of course I'll check the battery too, but it's a fairly new Optima Yellow and the voltage doesn't seem to be dropping much, so my guess is the alterator. Stay tuned for the conclusion.