Hi my 96 saturn sL1 with 260.000km"s has had the check engine light on for
2 years i got it scaned at the dealer they say i have a misfire in 2
cylinders and slightly low backfires heard from the exhaust time
to time the car runs excellent aside from the engine light being on
dealer says i have carbon build up on the exhaust valves i have used

strong commercial grade cleaners like BG 44k in a full tank of premuim
gas the engine was stronger on power but i still have engine light
on also changed spark plugs using AC/ delco gapped to 40 mm
changed spark plug wires changed fuel filter ran some BG 104 cleaner
in the oil to clean out engine i also have re-set computer light goes
away for a day or so but comes back on after any clues or sugestions?

 

To be honest and realistic, the number of times I have worked on cars I have never seen before that were supposed to be running fine that were 16 years old with 170 or so thousand miles on them that had a check engine light on for 2 years or better and only were miss-firing on 50% of the available cylinders and have (according to reliable sources) carbon the the valves which can not be seen so there for guessed at and occasionally backfired but nothing was really wrong them that a couple of cans of motor fixit would take care of that actually had nothing wrong with them that a major diagnostice and repair program would not take care of has been, well zero.
Whats the compression like? Is it using oil? Are any of the injectors plugged? Or leaking? or both.
Vacuum leaks anywhere? Why does the engine light keep comming back on? What are the error codes? Why should it back fire? Is the catalytic converter plugged? Egr Valve functioning? Will it pass smog? Thats always a good one. I can think of a dozen different reasons why some of those symptoms might take place in unison or independantly. I have not had a reason to chase down vacuum lines in a Saturn so as I type, I guess I really don't know how many of them there are or what there importance is.
But one thing I can tell you. If some one says there is only one vacuuum line not hooked up correctly already there is a credibility problem. The do not come in odd numbers. If one is hooked up incorrectly, there is a second one hooked up where the first one should go. This means automtically there are two hooked up wrong.
That is not to say that after 16 years and 170,000 miles I have not screwed things up myself. I have. And it usually takes awhile to unscrew them.
But I have worked on cars with 30,000 miles that were only a few years old that already were balled up beyond belief.
So
Lets start with, what is a compression reading say?
What are the error codes.
Are you burning oil?
Can you verify the EGR valve actually works.
This is for starters. Give me time I will come up with more questions.
Although in my book, the credibility allocated to motor fix it in a can is well, pretty much zilch.
With out knowing other factors too.

 

last i checked a 4 banger doesnt keep spinnin on two cyls so the misfire must be intermittent

what do the plugs look like?

which plugs? 1/4 or 2/3? maybe a coil pack?

and yes compression and oil consumption info please
and which codes does it throw

 

Just an opinion on the plugs, with out being able to see them. Dark plugs would indicate running rich. Running rich would indicate getting a spark but too much fuel, on a fuel injected engine, that would indicate an injector that is leaking. Thus dumping too much fuel. Don't know what it is, but you got problems.

 

unc, don't forget the overly rich ects related situation which is not caused by a leak.....

 

Hi guys sorry for taking long to answer back been busy
yeah uhm the spark plugs were put in last year there AC delco oem
took them out 2 weeks ago to check them and the gap that saturn calls
for at .40 was perfectly still set and i seen no dark coloure have not taken
a compression test yet just because i think it doesent need it i mean the engine

turns over right away hot or cold and has good power too the engine
does use a little bit of oil about 1 bottle every 5.000kms using 5w30 royal
purple oil i see no blue smoke at start-up or while driving i use shell gas in
it and she starts runs excellent aside from the engine light being on all the
time i have seen it flashing the odd time under hard acceleration wich indicates

those 2 cylinders are missing and im sending raw fuel through the catalytic
converter killing it right? but the flashing shortly goes away if i keep my right foot
down at w.o.t someone sugested it could be the ignition coil i doubt it would
either not start or if it was a weak coil it would maybe start but stall the engine?