I have a 1998 F-150 4X4 with a 4.6. I added a superchip, K&N intake filter kit and a new performance muffler. I primarily used it to haul my 21ft boat. I was laid-off a week or so ago and I've been driving the vehicle much more often lately. Damn..... this truck gets BAD gas mileage. (13-14 mpg) I had a company truck prior and now I realise how expensive gas really is. I've been putting regular unleaded in ever since I was laid-off. I've put 89 in once or twice. I know the superchip is programmed for 92 octane. I've notice the truck is lacking power and knocks and pings at any load on the engine. I've been driving the truck without the boat. I know the truck has always lacked some power due to having larger tired. I wish it had the 5.4 in it. I went from the stock tires to 285's. There BFG AT's. I almost had new gears installed, but couldn't afford it. Are my problems due to not using the correct gas? I just had the oil changed and added some expensive fuel injector cleaner. I've heard some of the fuel injector cleaners are worthless and are not worth the money. I figured it couldn't hurt. The truck just went over 40,000 miles. It's pretty low miles for a 98. What should I do? I know one option would to take out the chip until I land another job. I'd really like to get the gears, but that's out of the question right now. Please help me out.

 

richgonfishn,

Sounds like you have two options; use a higher octane gas or remove the chip. I can get away with using 89-90 octane with mine. I currently use Pioneer 93 octane or Sunoco 94. When I am traveling I use ESSO 92. With my 97 I could get away with a few tanks of 87 but then it would start to ping.

Regards

Jean Marc Chartier

 

Rich,

The best help (and the only *real* help) you'll get about this is to help yourself by using the Superchip correctly. You *know* you have to use premium gas with the Superchip, so either do it or REMOVE THE SUPERCHIP.

Also, I know you remember from all the times we've discussed this before in numerous different sections of these message boards and in email, what is requried to allow the engine to turn the rpms at a given speed it was before you installed those taller tires. Either do a gear ratio change or go back to the original tire size. The answer is not going to change.

You are obviously experiencing, and are going to *continue* to experience, the problems that happen when you attempt to burn cheap low-quality gas with the Superchip; no power gain and detonation. You will also continue to experience poor performance and poor mileage with those taller tires, until you either change gear ratios to compensate or put the original tire size back on it.

Good luck!

 

Hey Mike, thanks for getting back to me. I'm not an automotive/engine person. I had no idea I could cause serious damage to my engine by running lower octane gas in it. I wouldn't take that chance over 15-20 cents a gallon. I had a half tank and went and filled up with premium. Since I went to a higher octane, changed oil and added the fuel injector cleaner the truck seems to be running much better. I haven't heard any knocking or pinging. When the engine knocks and pings what is actually happening? Please educate me. Thanks again.

 

Hi Rich!

OK, thanks for your responses, both here and in email, that helps me to understnad much better how to go over this with you.

I explained this in some detail in our email response to you, which you should already have by now, but briefly, what's happening is that you are experiencing pre-ignition, uncontrolled explosions in the combustion chamber as a result of too little octane for the level of spark advance being used. These uncontrolled and improperly timed explosions create and transmit tremendously powerful shock waves directly to the piston tops, rings, ring lands, connecting rod bearings on both ends, main bearings and the crankshaft. If allowed to continue, this will cause severe and catastrophic engine damage, usually melting holes in pistons.

Octane is a specific rating standard, it's a scientific numeric rating to express the fuel's resistance to detonation in a specially designed octane rating engine with variable compression ratio. In your case, you do not have enough octane, and thus you're getting detonation.

By this time, as you mentioned, you have already gone back to the higher octane fuel and the detonation has been quelled, and I can't tell you how glad I am to hear that!

Take care & have a great weekend,