hi,i have a 97 deville with the PO300 code,i try a lot of things to fix it and turn it off.when i star the car,the engine is like a little nervous and when i drive runs grate,but as son i stop on a red ligth or a stop sign the car feels like you push the gas a litlle and release it again and again.i am mechanic,i repair the engine,a complete rebuild block and heads,everithing like the oem specification,parts,torque.there is a list of parts i change or replace:
all engine seals,o rings,gaskets
all piston rings,rod bearings
all cranck shafth bearings
all heads tread whith NSl300 kit
spark plugs @.60 inch,wires,4 ignition coils
8 inyectors,fuel rail,fuel filter,fuel pressure regulator
all engine sensor,ecept oil pressure sensor
all oxigen sensor,catalystic converter
always use 93 octane fuel sunoco
egr
timing chain ,tensioners,guides,central sprocket
pcv
all fiters


if i remember something else,i let you know,when i put the scanner its said that the LT FTRIM bank 2 have 37.5%,but the bank 1 have 0.0% +/-.everybody tell me that the engine have too much air on bank 2 and that can be catalystic or air leak,but i replace it and also a fried of my have a smoke leak detector and theres no air leak.i start the engine and use starting fluid araund the intake gasket and seals but nothing happen,The engine compretion is 195 to 200 on all pistons,so i think it can,t be a bad seal valve,i claned and fix it one by one,also lifters are good and in the same position where they came from,i disconected the va***m hose and put a plug on it one by one,but the code still there.this year i put a waiver sticker,becuse the check engine ligth its on,but i can make that just one more time,so i really need to fix it becuse for the year 2011 the state dont let me use the car any more if it still have the code present.so please if anybody have ad idea or update please i needed.

att,abbyintegra

 

Please i need help whit my deville!!!!!

 

with scanner what are O2 sensors reading, p0300 - generic misfire code - disconnect and reconnect 1 injector at a time try to locate where misfire is.

 

thanks for your time!I try one by one and this is the results,all inyectors works but its feels like the numbers 2,4,6,8,bank 2,make the engine fail more than 1,3,5,7,bank 1,i put a tester on each inyector and all have 13.1 ohms.then i put a ligth on each conecctor and always turn on the same time and density,plus the scanner recognize when i take the plugs out.then i make the same thing with the spark plugs wires and i have the same results,its looks like the bank 1 dont make too much diference,but its the one that the scanner said its ok.any idea available i acepted with no problem,thanks

att,abbyintegra

 

what are o2 sensor readings at idle and 2,000? MAF and MAP readings at idle? also

 

thanks again for your time!there are some information,yesterday i take a trevel from lancaster,pennsilvania to ansonia connecticut,its like 238 miles,4:38 hours.i already have the P0300 code but now i have another one,P1645 DRIVER 1 LINE 5,its the first time i see it,i clear the code but came again P1645 with the P0300.

IDLLE
02 bank 1 0.55-0.835
02 bank 2 0.60-0.870
02 post converter 0.155-0.855
02 converter 0.60-0.855

MAF 0.89
MAP 10.9

2000RPM
same ratio,ST FTRIM 0.0-/+on bank1 and bank 2

MAF 1.93
MAP 8.0

att;abbyintegra

 

hi,i know finally whats wrong with my deville,after all ive done i forgot that i need to use a vacuum gauge to check if something wrong on the intake scenario.i do a test and i find that the vacuum in idlle its 18,but drops to 17.5 and come back to 18 at the same rhythm of engine misfire.it can be made by 4 reason;

bad intake valve seal
too much oil pressure
valve or valve seat goes up and lifter keep it slightly open
all 3 things

i made the mistake,for anyone that repair N* head,that i grind the valves at my home but forgot that, when you do lifter valves likes this ones you need to put everything rigth on place,for example if you change lifter positions maybe one valve keep open and the other one be retarded to open or you can grind the valve too much and the gap between the lifter and valve close and the cam keep it a litlle bit open,i think thats the problem i have,actualy i recheck the cilinder and the pistons 4,6,8 dont hold the same pressure like the number 2,its like no.2 holds 100% air on compresion but the others holds just 95 to 97 %,
im going to change the oil to 10w30w same brand to eliminate the posibility of too much oil pressure,i spent too much time doing the valves job and make sure they wont leak but i dont check if the valves or seats goes up and change the original positions relatives to camshafths.i have another set of heads,so maybe i buy valves and seats and takes the heads to machine shop to be sure this dont happen again,please take note of this and dont do the same thing i did , this days are not good to waste money and time.another thing is the other code p1645 its the selenoid on the rigth head,the EVAP selenoid,the seal stay open inside so i change the EVAP selenoid and its clear code now.
att abbyintegra

 

I would not put oil pressure OR lifter position on the list of possibilities. Engines can handle any oil unless you dropped 90w-120W gear oil in the crankcase.

What I would be looking at what slowroll said above.
The LT FTRIM bank error tells me that it is a fuel delivery and/or exhaust issue to me.

Also, these items can be important if not done correctly:

1. Proper honing/grinding of valves and valve seats with proper angles.
2. Timing chains installation.
3. New lifters

As a last note .. The Northstar, in IMHO & economically speaking, is not an engine designed for overhauling.

There are too many variables and cost. It often much cheaper to pull a low mileage engine with proper compression at a salvage yard, or buy a wreck and pull its engine, and fly with it without opening it up.

Of course, if you just like a challenge for the sake of a challenge, that is another story.







.

 

hello!thanks for your opinion,but oil grades can affect engines performance likes the oil pumps on services trucks,low oil grade more pressure,more oil grade less pressure,most machine shops always said that if you use the same lifters its better to put it on the same spot,becuse they dont have the same gap and position like they have when they are new,i think slowroll its thinking the same thing i am thinking rigth now because the numbers said that the problem its more air than the engine needs and we are stuck because it cant be other things ,the computer its reacting base in the info sensors give to it,the problem is not outside air coming into the engine,is pistons take a litlle bit of air out of cilinders by intake valves ,but like i said i know i did a good job honning the valves,i checked one by one before i put on the block,but when i installed cams the gap maybe change.when i put the cams on time everything was on rigth place thats why the number 2 its ok and the engine start beautifully.im not trying to overhaul the engine am just trying to fix it wit the original parts to have a normal stock engine.and also THEY ARE NOT CHEAP!!!! on junks yard i cant find it less than 1,800 also the parts are not cheap either i spent like 700 on timing parts only.and remember in my case i didnt pay for the labor part,if you buy the engine used you know soon you have problems whit the heads tread and you will spend more money and nobody change or fix N* for 50 or 150 bucks.i just said if you going to fix your engine make it right from the beginning and dont try to save money like me and then have problems like this.please dont get offended im not trying to look for a challenge im just trying to help everyone with my unfortunate case fixing the engine,remember N* ARE REALLY GOOD ENGINES AND ITS WORTH FIXING!!