Car is a '95 Cobra. Stock engine. Long story short, I have one of the infamous switch chips with (I think?) a Bama 93 octane mail order tune. Primary reason I bought the chip (besides "better throttle response") was to eliminate the CEL for EGR as it's currently deleted. Well, the CEL started to come on consistently again about two years ago. I pulled codes and was only receiving one, for EGR.
I'm only getting around to this now because I lived in Germany for four years and didn't have the resources to really work out any issues with the car. Now that I'm back in the states and don't have to wait at least two weeks to get parts, I've decided to work on getting this car back to like-new condition.
I decided while charging up the air conditioning a few weeks ago to quit using the 93 octane tune and switch back to the stock tune using the switch; I honestly didn't notice any difference in performance other than it idles lower on the stock tune (idled at 1000rpm on the old tune).
I've been running the 93 octane tune for about six years or so. Is it perfectly fine to go back to 87 octane after all that time? I've never really read up much on octane ratings, and remember being told as a wee lad that you shouldn't go to a lower octane rating if you've been running at a higher rating. I can't find anything on the internet that would confirm this. In fact, I can't really find any information as searching for info regarding switching octane ratings only nets results for going to a higher rated fuel.
Besides just my concern about the fuel rating, I've also noticed in the time since I've switched back to the stock tune that I can hear a bit of a knock coming from the engine when it's warmed up at idle. It sounds very similar to the knock you'd hear from a diesel, albeit much more low key. The engine is all stock and has around 130,000 miles (not sure of actual mileage as the odometer gear gave up the ghost a few weeks ago).
While there were stretches where I didn't drive the car for a while in Germany, I never neglected it. I still changed the oil every three months or 3,000 miles. I can't remember where the timing is set, so I'll need to check that.
I'm sure these are very simple questions, but I haven't really messed with this car in a while and I'm just drawing a blank. Any help will be appreciated.
I'm only getting around to this now because I lived in Germany for four years and didn't have the resources to really work out any issues with the car. Now that I'm back in the states and don't have to wait at least two weeks to get parts, I've decided to work on getting this car back to like-new condition.
I decided while charging up the air conditioning a few weeks ago to quit using the 93 octane tune and switch back to the stock tune using the switch; I honestly didn't notice any difference in performance other than it idles lower on the stock tune (idled at 1000rpm on the old tune).
I've been running the 93 octane tune for about six years or so. Is it perfectly fine to go back to 87 octane after all that time? I've never really read up much on octane ratings, and remember being told as a wee lad that you shouldn't go to a lower octane rating if you've been running at a higher rating. I can't find anything on the internet that would confirm this. In fact, I can't really find any information as searching for info regarding switching octane ratings only nets results for going to a higher rated fuel.
Besides just my concern about the fuel rating, I've also noticed in the time since I've switched back to the stock tune that I can hear a bit of a knock coming from the engine when it's warmed up at idle. It sounds very similar to the knock you'd hear from a diesel, albeit much more low key. The engine is all stock and has around 130,000 miles (not sure of actual mileage as the odometer gear gave up the ghost a few weeks ago).
While there were stretches where I didn't drive the car for a while in Germany, I never neglected it. I still changed the oil every three months or 3,000 miles. I can't remember where the timing is set, so I'll need to check that.
I'm sure these are very simple questions, but I haven't really messed with this car in a while and I'm just drawing a blank. Any help will be appreciated.
