Now I know these engines are "supposed" to be able to run on just regular, but from what I've read they are sensitive to EGR clog...I've had an 85 Cutlass Supreme and an 85 Grand Prix (231 and 305 engines). I ALWAYS used premium gas in them because the engines acted like slugs if I didn't.

So I filled up my Toronado with 87 last week. I've been using premium but figured why spend the extra money. Well after about driving for 40 miles, the engine started to seriously bog down during acceleration...almost to the point of stalling...did the whole bucking thing and everything! It was pretty random, not doing it everytime I accelerated.

Do you guys think that is from the 87??? I have all new plugs/wires/distributor cap/rotor and O2 sensor so it shouldn't be a problem with those. Just seems weird that regular would do that to the engine...unless my EGR passages are really clogged.

I dunno...just thought I'd get some opinions...

Thank you!

 

Did you get it from the same station as normal? Could've quite simply gotten some bad gas.

 

Well I usually just buy gas at 2 stations...and I used one for the Toronado (Chevron). But I filled up with 87 at the Shell station for my Custom Cruiser (same 307 engine) and it runs just fine. So could be that it is just bad. The other thing I just figured out is that the Cruiser has had the EGR valve replaced while the one on the Toro is original, so maybe it is clogged. I'll have to do some testing to find out.

 

Contrary to popular belief (and oil company marketing), higher octane fuel, by itself, does NOTHING to increase or decrease power. If the engine is designed to use it (higher compression, more ignition advance) then the higher octane allows you to make more power, but if the car is designed to run on regular, then there is NO benefit to using more expensive premium.

In your case, assuming the car is stock, there is no way that simply changing from premium to regular would have caused the problems you describe. Your 307 does not have a knock sensor, so there's no way for the engine computer to "know" that you've changed octane level. More likely you simply got some gas that was either contaminated or has excessive water in it.

 

Thanks Joe, yeah that's what I'm hoping is the issue. It ran fine yesterday thankfully. Next time I'm under the hood I'll probably take the EGR off anyhow and clean it up just to be safe.

 

Excellent Joe, were do these urban legends start. The gas companies or Joe the mechanic? No pun intended Joe LOL

 

haha funny!

You know though, I think it really depends on the engine. Thinking back now my Grand Prix with a 305 had few issues with using 87 but I distinctly remember my Cutlass with the 231 2 bbl not liking 87 at all...it knocked and pinged like crazy if I didn't use premium, not to mention accelerated noticeably slower (if there is anything slower than a G body with a V6! LOL)