Surging engine

I have a 2000 Olds Alero with a 6 cyl. It surges between 2500 and 3000 rpms (aprox) when I’m accelerating and especially climbing a hill. I have tried fuel injection additives, had the injection system cleaned at service shops and replaced the fuel filter multiple times with very limited results. Any ideas?

Add a few ounces of ATF to your gas tank each time you fill up. It will lube those old injectors.

What usually happens in any engine under acceleration? The fuel injector rate (pulse width) increases, air flow increases as you open the throttle more, and timing may change.

What if the amount of fuel injected varied, when it should be steady? Why would it do that? The engine computer could be telling the fuel injectors to increase and decrease fuel flow irregularly. Why would it do that? Some sensor inputs to the engine computer may be varying, causing the engine computer to vary fuel flow causing surge. The fuel pressure could, also, be varying because the fuel pressure regulator is allowing it to; or, the fuel pump can’t “keep up” (weak). Both, the fuel pressure regulator and fuel pressure stability, need to be checked.

Attach a fuel pressure gauge, with a long hose. to the outside rear view mirror. Take a drive. Try to get the engine to “act up” as you monitor the fuel pressure. Fuel pressure which swings high, then swings low, could cause surge. Take note, and let us know.

Does it happen on all hills, or just on a certain grade and only at highway speed? If it is the latter, it might not be an engine problem at all but a lock-up torque converter that cannot decide whether it wants to engage or disengage. My wife’s BMW does that, but ONLY on one hill, the grade heading north out of San Luis Obispo CA. We just lock it down into 4th gear until we hit the top of the grade and it stops doing it.

What is the vehicle speed when the surge occurs? Do you have a way of “locking” your automatic transmission into a certain gear, as Manolito has done on his BMW?

It’s not limited to the alero. I own a 2000 GRAND AM with 140K MILES SE 3.4L. ENGINE ALSO SURGES WHILE DRIVING. IT HAPPENS AT A LITTLE OVER 2k USUALLY GOING UP HILL. BELOW 2K, ONCE IT’S IN OVER DRIVE AND THE LOAD IS LESS OR AFTER YOU GIVE IT GAS AND ACCELERATE THE SURGE STOPS. THE SURGE IS NOT RANDOM BUT IS VERY REGULAR EVERY COUPLE SECONDS THE ENGINE SPEED JUMPS TO ROUGHLY 2.5K and will continue to do this until the condition changes. if this information helps get the answer we’ll both be better off.


I believe that I am currently having the exact same issue. Did you figure out the cause? I have replaced the fuel filter as well. This was never an issue until the local shop cleaned my mass air flow sensor. Maybe it was damaged or still dirty? Does this sound like a potential cause?

It sounds like a lot of guessing about the fuel system when the problem could be elsewhere.
First off, I suggest getting the codes pulled. AutoZone, etc. will do this free.

An EGR system fault can cause a surging condition. A vacuum leak can do the same thing (and an EGR is also a vacuum leak of sorts).