Hey rick, umm yea I think did right for what I can do. Codes I looked into and checked were the ones in dic. Held on/off button and up arrow wit key on. Found couple old history codes nothing to do with whats now. And I checked them on site I had to decifier them. Oh by way guys don't kno how much difference this makes but car is 99 wit 143k all stock pretty well taken care of and found records on plugs wires and changed them last thanksgiving day. All ac delco/ gm parts. And this didnt start until about march April 07 area. Really appreceiate all the input
mike

 

Just came in from pulling the coils off, everything look A ok, no corrision rust etc. All wire plugs were on snug removed N* cover all wires are still in great shape no look cracked/ arched. Coil post were clean clear. Now just think if a plug or two fouled out or something? next im going to pull first 4 easy plugs out, check them.

 

if any body is looking at this post for reference or info- i am in process of ordering new coils(pack). I will keep posted the status as it changes and once install new pack.

 

lol looks like im posting to my self now...but if it helps....I changed coil packs about 5-6 days back. So far same conditions still present. Rough when cold way better when warm but still vaguelypresent when warm. Help me out guys! O no codes either
Thanks-Mike

 

Fuel pressure? If you can check it, what isit anddoes it hold after pump stops running (key or prime)? Small vacuum leak at intake or boot between t/body and intake manifold. What type of fuel do you use? What kind of driving do you do?

 

Im not sureof the fuel pressure, but i do know if it helps that the fuel pump is brand new-fuel filter is new. Still shows same signs before/after change. At the intake i know the boot your talking about, usually found on eldorado but not on mine sts. Was at cadillac and we checked over that. I use 93 oct and fuel injector cleaner 3k mi (if it evenhelps)usually chevron/sunoco almost always. I have tried regular few months back when gas was really high..no difference. the type of driving i do is usally same highway 24 mi round trip morning city 22 mi round trip night. i like to WOT merging highway 50-80 no hesition. i would classify my self "spirited driver"

 

the only thing i can say, but peole keep denying it is..a year back i changed my radiator. installed new one filled up with new 50/50 dex cool. The minute i started the car i instantly felt the "rough idle" as if it just began that moment! i am very picky/obsservant and tend to notice "everything" so i keep thinking till now that somehow the new coolant..fouled or upset the ECT sensor. Everyone denies it but im very close to getting a new one just changing it. i have read online that that also controls fuel/air input mixture. and wont throw a code if bad.

 

Have you checked fuel pressure regulator for leaking fuel at vacuum hose connection. New pump and filter are good but regulator controls pressure. Correct pressure is more important on start up than when engine is warm. Carbon build up on can be a factor also during cold operation. Scanner is going to be required to monitor temp and O2 sensors. EGR valve not completely seating also possible. Grounds alway can figure in. I think you need a professional type scanner to figure it out. Also type coolant should not kill ect sensor

 

ok guys i know i am a year late, but i just came back from the shop and had it hooked up to the scanner. We checked every sensor, fuel, air, va*** leaks, settings possible. We went throu each setting, at different rpms..etc.. Everything checked out perfect. Engine temp,o2 sensors,iacv,maf,etc..Mechanic actually said it couldnt run better even with the miss for a vechicle this age and millage. What he did mention after the scanner, that it could be a valve not seating properly. He wants me to come back and do some check with a va*** gauge when engine is completely cold, And posibly a compression test.
Any ideas please reply

 

couple days ago i got the P0300 code, hooked up scanner it was 305 to be exact, and also pulled p0174, and 171 po420. always had 420. But the other three all pointed to either bad MAf,injector, o2 sensor or va*** leak. Well based on the comp they hooked up last month..my o2 sensor(s) are good, MAf as well, and said no va*** leaks. So hat leaves me injector. I put a screwdriver to it (number 5 cyl) and rest them, they all sound same. Next i unplugged it, the engine dipped in rpm then came right back to the same. I put it back and went up a tad then back normal..(immediately) so i tried another injector did the same thing..also yesterday did the seafoam cleaning thru intake procedure, kinda the same cant tell to much maybe better throtle response. i also bought another injector gonna pop it in there see if anything changes..post any thiughts~
MN