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fuel problem

fordfan's Avatar
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07-08-04, 08:08 PM   #1  

I have 1990 Hyundai Excel. A month ago filled the gas tank after work. Next morn on my way to store, started missing and assumed it was water in the gas. Put in water treatment in tank and didn't change. After driving about 50 miles, went through 1/2 tank gas, filled up with premium gas, miss continued. Took it to a garage and they hooked it up to check it out. Said they cleaned fuel injectors and changed the fuel filter.Missing has not stopped. Misses while it idles and driving it, blowing out black smoke. Checked fuel injectors,one wasn't working, cleaned it, cleaned the plugs. After plugs were cleaned it ran good for about 30 seconds and then back to the same. What is the next step to figure out what is the problem? I was told it could be the mass air filter. Or can one injector be pumping too much fuel?

Last edited by fordfan; 07-09-04 at 03:01 PM. Reason: change title
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davo's Avatar

Join Date: Apr 2002
Posts: 2,417

07-11-04, 05:41 AM   #2  
Check the air filter first then check/test the O2 sensor,mass air flow sensor and map sensor.One of these is the most likely problem.Check the fuel pressure regulator for leakage or for being stuck on hi pressure.

jeff67's Avatar

Join Date: Dec 2001
Posts: 616

07-11-04, 11:34 AM   #3  
Have you done the basic things when troubleshooting a misfire such as replacing the sparkplugs and wires? Were you able to narrow the problem down to one particular cylinder causing the misfire? Make sure you are getting spark at all cylinders.

If you have ruled out an ignition system failure, my advice is to check for vaccuum leaks and a split or lose connection at the air intake hose before moving on to more complex and expensive sensor problems.

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