hoovied

Hey everyone-
great forum here! I have a couple problems I'm dealing with and I'm looking for any suggestions.
1. I accelerate to highway speed fine and smooth. I back off on the pedal to stop accelerating and just to maintain speed, and the engine starts bucking and I can hear some backfiring. Engine code reader mentioned something like random misfire and also one about the transmission, although I have no shifting problems. Replaced sparks with platinums twice and wires once but the problem persists. Any suggestions?

2. Braking is becoming hard lately. Very hard to initially depress the brake pedal- I wonder if it'll stop but always does. Then it seems ok for a time or two, then hard to depress again. I mean like there's virtually no travel in that pedal when it acts up. Fluid level is good, albeit kinda dirty. Front pads are ok, not sure about rear drums.

ANY suggestions would be greatly appreciated- THANKS!

Steve

lukemoore646

a little more info on the truck would be great, also look at the cap and rotor, it doesnt sound like your booster is working on the brakes

Speedy650

try bleeding the brakes.

mudmaniac

I wonder if the front calibers are frozen up, if they needed bleeding I think you would have a soft pedal.

hoovied

Thanks for the pointers, guys!
The engine is the small block V-8 (w/air) and it has about 175,000 miles on it. Other than these two problems I've had few issues in the 7 years I've had it. I will check into the cap and rotor. I've just replaced it 2 years ago, due to a starting issue. I'll check out the contacts inside but would think if there was a problem there it would be all the time, not like I'm seeing.

For the brakes, my Haynes manual briefly mentions the brake booster but is pretty vague regarding it. It says it can't really be serviced by shadetree mechanics. The pedal is hard to depress initially. If you get on it again fairly quickly, it feels normal. Wait a couple minutes, and it's really hard to depress again. Is the booster easy to swap out?
Thanks!
Steve

therewolf

Assuming you've got no distributor issues and the timing and vacuum advance are all in apple pie order, at 175(hack,hack) thousand miles:

1) You may have an exhaust leak

2) Blown head gasket

3)Valve train issues- such as bent pushrods,worn cam(my bet), collapsed lifters or valve springs, warped or scorched valves, or rocker arms very badly out of adjustment.

4)Your nylon timing gears also may have lost a few teeth by now...

If your exhaust is in order, and you don't have a vacuum leak, A compression test and valve train check may be in order.

All things being equal, and you want that thing back on the road quickly, you may just want to throw another short block in there and have done with it, hell,175K ain't a bad run.

jamesp2994

Check the vaccum lines to your MAP sensor. If a hose came loose or the sensor went bad it will cause the injectors to stay open. Also check the vaccum line for the brake booster. If it is cracked or broken it could affect what the MAP sensor reads.

Starboy

Random misfire is a generic code, the computer is telling you your truck is running crappy. Thanks for that, right? It does sound like you may have a vacuum leak in there. Can you hear anything? You can get a squirt can and squirt oil around the vacuum lines, sometimes that's useful. My 5.7 Vortec is showing about 191K miles, runs great, strong power for towing, 20mpg highway. 13 years old! Check the High Mileage thread in here: it's not unusual for some of those engines run 300K or more. Mostly that depends on the owner, maintenance, driving style, and mods.