RPM's unstable after getting 87 octane

I installed a 3.4 pulley and neglected in getting premium gas. Would that cause my car to sputter and have the rpms go low and then hi? This is the first time I get gas after the pulley install.  It ran fine last night then today started acting up.  It died out on me a few times at the light and the SES light came on.  I also noticed the engine bay felt hotter than normal

what codes is it throwin?

I havent checked, I guess I'll check that tomorrow. It almost feels like a misfire but its wierd cause it was immediate after getting gas

No, just using 87 wouldn't cause any of that, even though it's a terrible idea with 3.4" pulley. It's probably bad quality gas causing the issues. Or, you have some maintenance to take care of (spark plugs, wires, injectors, filter(s)).

If you got on the gas and went into boost, the engine would cut timing to protect itself, which would cause to car to become a bit slower. But seems like you caught it before going WOT, right?

Drive as easy as you can through the remainder of the tank. Refill with 93 and should be good again. If you can find some 100 octane race gas at Sunoco, fill up when 1/2 empty. This will get you back to near 93.

I was thinking injectors actually or clogged fuel filter. Im going to start off replacing the fuel filter today.

Unstable RPMs could also be a dirty MAF or throttle body.

Yep, good one Albert. I actually went to Autozone and they said it was throwin the code for the MAF sensor. I found a leak in the vacuum T under the SC snout.  The T is pretty much disintegrated.  I could hear the hissing of the air leaking. I also sprayed with carb cleaner at the T connector under the SC snout and the RPMs would fluctuate.  WOuld that vacuum leak cause the code and would it cause the RPMs to go up and down on occasion?

Vac leaks are a classic cause of uneven idle. Fix that and see if the MAF code comes back.

I blew a head gasket using 87

robotennis61 wrote:

I blew a head gasket using 87

Sure it wasn't your nuts from the head???

87 octane in a S/C Riv? Really?

Yea sorry guys, I feel bad about it too.  I drive a ford e250 for work and didnt even think about what I was doing. I hadn't gotten gas in the Riviera in like 8 months. I hope I didn't blow a head gasket!  I Just replaced the T's with the hard plastic ones from Oreillys by my house.  I disconnected the battery and pulled the PCM fuse to try and clear the codes.

I fixed the vacuum leak but its still having issues. I think the MAF sensor crapped out. Im gonna try and find one at the pick n pull by my house.

I would first take 10 mins to clean the sensor using a can of electronic parts or MAF sensor cleaner. MAF sensors can be pricey to replace with good condition parts.

i just sold 3 on ebay for 15 a peice but they where off a newer regal gs's and a lil diffrent than ours but i do have one more for ours that i havent tested yet. ill test it and if its good when i put it on ill give it to ya if ya want, a brand new one from autozone is only 120 bucks with tax btw. my old one was super hot when i took it off a sure sign that it was bad

Driving as much as I do I have been using 87 in my '99 SA for over a year now, it has never acted up and gets between 25 and 27 MPG on the average. I try not to "get on it" at all, just drive it easy, and it hasn't given me any problems?!? Might be something else as stated?

I never use anything but "super" in the "good" SA and the '95, but the 87 hasn't caused any problems "yet" with the SA that has 224K miles on it!?!

Thanks Rivman, I also have used for the most part 87 octane in the Riv for the 10 years I've had it. I just thought since I just replaced the pulley with a 3.4 inch pulley that could have changed. But nope, I was wrong it ended up being the MAF sensor after all. I was going to clean it like Aaron suggested but when I took the MAF out of the Throttle body the housing was cracked! I ended up pulling one of a 98 regal gs at my local wreckers and cleaning that off. I installed in the Riv and problem solved. I think I might have sprayed it with the Gunk Engine degreaser when I was doing my valve cover gaskets. That probably killed the sensor. Thanks for everyones help. I was flying down the expressway finally:3gears: 

Glad to hear it's fixed. Since you've put on the 3.4" I wouldn't run 87 octane anymore, or you could have a more serious problem, like a cracked piston. A stock Riv can deal with 87 if you baby it all the time, but if you're swapping SC pulleys, you won't be babying it, so 93 only!

The 87 octane might or might not give you problems, if you don't call for heavy or brisk acceleration and if it is good gas to begin with. However, given you shrunk the pulley I'd switch up to at least 91.

99Rivman wrote:

Driving as much as I do I have been using 87 in my '99 SA for over a year now, it has never acted up and gets between 25 and 27 MPG on the average. I try not to "get on it" at all, just drive it easy, and it hasn't given me any problems?!? Might be something else as stated?

I never use anything but "super" in the "good" SA and the '95, but the 87 hasn't caused any problems "yet" with the SA that has 224K miles on it!?!

Generally people who have smaller pullies, low octane and no tuning will shortly be replacing a piston at minimum. If you are going to continue using 87 octane at least put the stock pulley back on and just baby the gas pedal.

I'm upgrading my gas to 93 from now on. I'm almost on E with this tank of gas. I'm gonna fill it up with premium. No Way I'm putting the stock pulley back on! Im planning on replacing the mufflers since the cat and resonator have been removed. A pcm and shift kit are in the near future also. I can't imagine messing a piston up