Technical > Automotive > Car running rough

Car running rough

Have you checked the plugs? That can give you a very good clue.

reply to lostinms
An exhaust leak can burn valves just like a vacuum leak can and either will cause a very rough idle. Time to look at the plugs and run a compression test and also repair all leaks found.
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reply to lostinms
"I do have a exhaust leak some where on the manifold would it cause it to run rough?"

If the O2 sensor has the wrong reading it can affect the fuel mixture going to the engine. Usually it will cause a Check Engine indication.
A clogged catalyst will also cause the wheezing you are describing.

reply to lostinms
Unfortunately this car does not have a check engine light wish it did sometimes.

Yeah I really don't want any burnt valves its hard enough to get parts for the old car. My wifes grandmother had regular check ups on the the car before I got it and i have been doing my best to keep her running. Was planing on looking and the Plugs and find that exhaust leak if the weather will warm up. Wish I had a enclosed garage.

reply to lostinms
Just because the spark plugs are new doesn't mean one didn't go bad. I had a spark plug die at 12,000 miles in a brand new car.

If it runs rough at idle, disconnect the plugs one at a time and see if any do not have a detrimental effect. That may help narrow-down the problem.

For that matter, make sure the spark plugs aren't loose.

reply to lostinms
In addition to the spark plug suggestions made by others,

What wires did you put on?
Name brand or value brand?

I have only found NGK or OE Mazda wires to be any good.

If you have a compression gauge, why not do a compression test while the plugs are out. If possible please attach a clear photo of the business end of the plugs.

Does the car use any oil? If it has been using oil for a while, then I would be more than a little concerned that you have a compression issue - this is an OLD car.
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reply to lostinms
You mention plugs and wires, what about cap and rotor? I cannot believe well maybe a car from '86 made it this far with original dist cap.

What is the actual make and model of the vehicle?

reply to lostinms
Just fyi this car does not have points. It is fuel injected plus it has a computer in it. The Cap and rotor has been replaced just I don't know when. My wife's grandmother really took care of the car and had it serviced by the book.

It had sat for a while cause she was getting to that age where she did not need to drive so I she gave it to me.

i have found the exhaust leak and it appears the manifold gasket had gone bad so I am waiting for one to get in from the parts house and that won't be till Thursday. Gota love the holidays.

The car in question is a 1986 Mazda 626 non turbo with stick shift. It is the last year that model was made in Japan and shipped to the US. '87 and on was made in the US.

The reason why I change plugs and wires, the wire leading form the coil to the distributor had gone bad. The Plugs I didn't like what they had in there which was Bosch so I put NGK's back in it when I did the car ran like a champ. Like she was brand new. It won't be till after Thursday that I will update do to having to wait on a part.

Its getting harder and harder to find parts for it in stock with out having to order it.

Granny had a stick-shift? I'm impressed!

reply to Bob
if it was automatic it would not be running today. From what I am told the automatic versions would die around 60k miles.

I have worked on many of these cars in the past and have seen many things go wrong with them. After rereading your original post, have you tried doing a compression check, or cylinder leak test make sure head gasket and valves are ok? Has the timing chain ever been replaced or checked? Car this old could be anything, even a possibly a cat starting to go bad.

yes the timing belt has been replaced. Found the old one in the trunk and it had look pretty good. After I get the exhuast manifold gasket replace and that won't happen till the stupid part gets in on Thursday. I could go to one of the dealers in town to see if they have the part but they love to charge you a arm , leg and kidney for their parts.

Oh and Merry Xmas.

reply to Sr Tech