I have a short bed 1990 4wd with a 5.0 crate block and svo heads, headers, mass air kit, aod with a wide ratio kit and 411 gears with a 3 inch exaust and factory cats, also an eldelbrock truck intake manifold. It has 19 lb injectors. The cam is stock explorer, with 1.65 roller rockers.
It runs strong on winter 92 octane chevron fuel. In the summer running 92 summer grade fuel it looses lots of power, I suspect the timing is being cut back due to the small injectors.
It has no codes. Is my cure going to 24 lb injectors and a matching mass air meter? I have been using octane booster with the summer fuel and need lots of it. Berne

 

It has nothing to do with the injectors......the methanol blended fuels.

 

I think the stock 19# injectors are plenty big enough for that engine with those mods. What you need is a true cold air intake, not one that draws air from under the hood. The MAF and computer also have to be specifically tuned for whatever intake you are using.

By the way, they don't use methanol in the fuel, they use ethanol. Can you get pure gas where you are?

 

He said it loses power in the summer, like on the better fuel. That doesn't make any sense to me.

Why does this truck need such high octane if it's not boosted?

 

It has a k&n cold air intake, and runs good on winter grade non corn fuel. I have tried summer grade non ethanol fuel and same result, it's a dog. My 5.0 93 injected T Bird did the same thing until I cleaned the injectors then it got it's power back and quit pinging. The f150 has newish motorsports 19 lb injectors and all new sensors. I forgot to mention it has all msd ign and dist and 6al.

 

It's not a "cold" air intake if it's an open filter under the hood. The K&N oil can also foul the MAF.

If you think the injectors are dirty, throw some Techron in the gas.

 

The Techron works great esp the consentrate. that's how I cleaned up the old T Bird. On the Pickup the injectors are almost new, and yes I have used cleaner in it. I have often wondered if the exaust system could use some back pressure. When the truck was new and unmodified it didn't care what the fuel was, but back then it was better fuel. I first put shorty headers and a 3 inch catback system on it. My memory is fuzzy, but thinking back, it was fuel sensitive then. Maybe related to the exhaust mods? Or the coming of crappy gas?

 

I have cleaned and also replaced the Maf sensor. All the sensors are newish.

 

With factory cats, you should have plenty of backpressure. But it shouldn't be related to that, I wouldn't think, anyway

 

If I don't get any new ideas, I think my next move will be to have an exhaust shop make me a reducer insert to stick in my tailpipe just for a test. I need to wait for summer fuel though. The last couple years I have been storing winter fuel in jugs, that is highly dangerous though.

 

Have you tried different brands and grades of summer fuel?

 

I have tried all the major fuel brands, even in winter, esp out of town I run into stations that still have summer fuel in their tanks. I guess they don't sell too much of the premium.
Seems no one else has run into this problem, or at least have no cure.
From my research the winter fuel is more volatile (easier to light off). So it has additives that make it more explosive.
So how am I going to find a tuner for a 24 year old pickup with lots of modifications, that can tune the computer?

 

http://www.tweecer.com/

 

I have another thought, I've always run a 180 thermostat, it came new with a 195, I'm thinking of trying the hotter one just to see if it makes any diff. It might affect the egr valve that would affect timing.

 

realize it would cost money but would be interesting to see what kind of rwhp you are making, a run on each grade of gas. everyones definition of "lots" of power is very different.

on the older engines you can actually still turn the distributor for gains or lower octane. have you tried messing with that, the old 5.0 mustangs responded well to advancing the initial timing.