I have a 1994 Vauxhall Astra 1.4ltr injection Automatic. It has had two lady owners before I purchased it and only had 63,000 miles in the clock. It had not done any motorway driving before I had it as the two previous owners never had need to drive on the motorway. However I do alot of motorway driving and this greatly increases the amount of fuel I go through as to get my car up to speed of 70mph I have to put it into sports mode which greatly increases the revs but it does get it to the speed I need otherwise my car would be quite happy to chug along at 50mph. When I am on the motorway I have to keep my foot pretty much to the floor to keep it at a constant speed of 70mph. I do not have kick back like most automatics have as I have noticed there is a restrictor under the gas peddle to stop you from flooring it. My car is not very efficient on speed or fuel I have replaced the spark plugs, put some special fluid into it that cleans the components as it runs, its similar to red ex but it is specifically for injection engines. I dont know what else I can do to try to fine tune it and get it to run as it should do.
When I am on the motorway or if I have had my foot pushed down on the peddle for a while I will suddenly get a scrapping noise of metal rubbing on something, easing off the gas does not help it sometimes makes it worse, to get it to stop I have to decrease my speed and let it cure itself. Which it always does but one day I am afraid it is going to break down on me, and I will be stuck in the middle of nowhere as I do not have breakdown cover. When this scrapping noise occurs I hear it first then I feel it in the gas peddle.
I hope this is nothing too serious as I really dont have the money to fix anything major. Was going to take it to a garage but would not have a clue what to say or what they would do for that matter? Also money is scarce so any useful advice you may be able to give me would be greatly appreciated.
I am in the United Kingdom by the way in case that helps. Thanks in advance