Why does my car rattle going uphill?

Question

I have a 1995 chevy tahoe and when im driving uphill about 30 mph when I try to accelerate I step on the gas about half way and it just does this rattling it sounds like its from under the hood.it wont stop rattling until i let go of the gas or floor it which then causes the transmission to go back one gear and the rpm goes higher,then its when the car actually begins to accelerate.my tahoe has had recently wheel alignment and a tune up but its been rattling since I got it. any ideas what it can be? and how much it would cost to fix it?

Answer 1

Sounds like pre-ignition ( known as "pinking" in the U.K. or "pinging" in the U.S.) normally caused by ignition timing being over advanced or carbon build up inside the cylinder head. have the timing checked first, that should'nt be very expensive. Its unlikely to be a carbon build up in a modern engine. Another cause could be the wrong grade of fuel. good luck.

Answer 2

Pinging or knocking, same thing just two names for it. The more proper name is detination.

It is caused by hot spots in in the combustion chamer where the pistons go boom-boom and make the power.

If your car is in tune then make sure you are using the proper octane. Did the tune up check your timing? Advanced timing may cause this. If it is not helped by uping the octane then you can try any number of fuel injector cleaners that claim to clean carbon from pistons. You may also be running lean. A worn fuel pump on the way may cause this. Normally a check light would come on if it were running lean...although since check lights didn't get really smart until 1996 it may not be reading it. Get the fuel pressure checked....if you can get it checked under load that would be even better.

No engine should ping but in most there is an acceptable amount of it. It does wear out the piston rings faster and can lead to oil buring. It may go away in the cooler weather.

Until you fix it or accept that the engine is old when you hear it you need to let off the gas a bit and go easy. The engine will thank you for many more thousands of miles.

How much to fix? It might be $2 for a bottle of injector cleaner. It may mean $0.10 more a gallon for higher octane. It might be a $300 fuel pump replace. It might be a simple timing adjustment....maybe free from the people who should have done this while doing the tuneup.

Answer 3

Try a higher octain fuel or put in an octaine booster. Over a period of time it will hurt your pistons. It's like hitting them with a hammer.

Answer 4

one possible cause of this is the low octane fuel and hot weather is causeing your vehicle to detonate. this a condition in which the cylinders become so hot that the fuel ignites prior to the spark plug. it is common on low compression (truck type) V8's. and the reason you hear it up hill is that is the only place you realy put a load on it, also the noise goes away once you down shift at the engine advances its timing under a downshifted load and the detonation goes away. more than likely this problem only shows up under low rpm heavy load scenerio's.

I wouldnt worry about it to much. if it does not feel like a vibration associated wtih it.