Misfire? Won't hold steady RPM.
 

So I went to do emissions, besides failing (miserable and I'll address that later) I noticed my car would not hold a steady rpm. The test was at a steady 2500 rpm and every full cycle the engine would droop to about 2200 rpm and then back up to 2500. I went home and tried the same test at a few different rpms between 2k-3500 and it did the same every time.

Any ideas what could be causing this?

It's a very brief cutoff and according to TunerStudio the fuel load seems to spike slightly at the same time (from about 30% to 35% load).



Not sure if this is related, but when I start the car it idles perfect right around 1000 rpm however when I drive for a short period of time it idles at 1500rpm. Still smooth, but it won't go beneath 1500. A few times it will idle closer to 2k rpm, but I can touch the throttle once or twice and it will come back down to 1500.


:dunno:

log\msq of said happening?

Perhaps something in your car is creating a load. Is your fan kicking on and off?

What do you mean "every cycle"? Every RPM? Every Minute?

If you had an on/off load kick on while holding the throttle constant, your RPMs would quickly drop. To compensate, you would have to increase manifold pressure, which would cause a "fuel spike" in order to return the car to the previous operating RPMs.

post your msq, it could be a number of things, idle could be idle settings, the weird surge could be an untuned VE cell

The fan is on constant, both of them. The original owner had them wired that way and I haven't bothered fixing it yet. So no extra load is being put on the car past that, which is why I assume the idle hangs around 1k normally.


I should have been more specific with the description, it isn't every engine cycle but it is timed exactly. It's approximately every three seconds, but constant and like clockwork.

I will try to post up an msq tomorrow.