97 Sonata SE V6 178k miles
Had a circle of events on this car. Problem free until now. Sorry so long. There is just too much detail!

I may occassionally need to try and start the car twice in the morning. It has happened more since my change out of the Air flow meter (IAT and MAF sensor too) last month and the other items placed on the car to try to relieve secondary symptoms.
I have a rough idle. Worse in the morning or after a long sitting. However, the car's idle improves after about 4 miles or so. Then it is an occassional hiccup here or there.
I start it later that day and she starts right up and an occassional hiccup here or there.
I have to say that I can not report that I am having any performance loss. She seems reved up higher than before the TPS replacement. She is in idle sitting at 900 where as she us to be at about 650. When I take my foot off the brake, she has no problem taking right off. I can feel the gas cut off and kick in when I put my foot back on the accelerator while driving at 80mph. I also know that means my car is getting way too much gas as she will make little puffs of light smoke and I can smell a little gas in the exhaust.
This happens almost everyday. But since they are not happening back to back, the car is not detecting the malfunction and giving me a code.


I would like to add that the CEL does work. I created a random misfire to test it and I was successful. I cleared the P0300 code.
I have pulled the spark plugs and they are only 4 months old. They recently underwent a fuel injection cleaning and flush. I know that is hard on plugs and olderplugs usually do not make it after injection cleaning. There was an accumulation of carbon on plugs 5 and 6, but the spark is adequate. A compression and leak down test shows the car to be fine despite her miles. I have had the TPS replaced, the timing inspected, the sensors tested, vacuum checks, injector checks, fuel injection cleaning, distrib/cap/rotor replacement in August and another inspection during last shop visit, air filter replaced, fuel filter replaced, NGK plugs in July and wires, catalyst looked at, oil leaks (very small valve cover, but doesn't drop on ground), transmission fluid levels, ECT inspected, replaced PCV valve, o2 sensors replaced only 20k miles ago with timing belt replacement (volts fine).
My shop is telling me that they firmly believe that since the car did better after the fuel injection cleaning. Then the car slipped back into a rough idle because something may have gunked up the fuel line or some junk may be restricting fuel flow or a vacuum issue. However another peson had a similar intermittent problem with idle (but his car shut off on him) and states I should be looking more into the ignition coil. Something about the injectors being fired up at once rather than a sequence. What do you think? Any opinions on this?

 

fuel filter.

 

Thanks for the suggestion. In 4 forum websites I have asked the same questions and you have been the ONLY response.
I did have my fuel filter replaced in August with my spark plugs and wires.

Since EVERYTHING was checked out and sound...I allowed my tech to drop the tank. Tank and fuel lines have no restrictions. Fuel filter is clean, fuel regulator working and so does the fuel pump.

AFter dismanteling the fuel rail...it was determined I have the following:
2 good injector with good spray pattern
2 leaking injectors (which he is getting resealed for me)
2 hairline cracked injectors that have faulted.

HE is having it replaced tomorrow. He has a valid point...the fuel injection cleaning really helped smooth everything out, but within the week...it was back to no good. I hope this fixes it. At 85.00 per injector....I can't complain...but throwing all the other parts as mentioned above has totaled 550.00. I would do anyhting to just have her run normally again.
I will let your all know if this injector was the fix!

 

I am so glad that they found everything, I had an idea that it was fuel related, at least I was close.