mis or shudder
 

hi guys,, i have a 99 lesabre,,3.8,, the car had 63500 miles on it when i got it,,nice old car,,well taken car of
but here is the problem
when i am driving down the road it has a mis or shudder,,this thing sometimes shakes the whole car,,then goes away,,comes back,,it can be very mild at times but it is there,,it does it at idle too like when stopped and changing from drive to reverse,,it will stuble,,so i kinda ruled out the tranny,,but i still have an open mind,, and too it seems to be worse the hotter it gets,,doesn't seem to affect mileage car runs and drives great other than this,,i know something is going on,,just can't seem to find it,,i have had my engine scanner plugged in,,everything looks good,,leave it plugged in and drive it to work checking along the way,,look at snapshot charts it makes,,i don't see anything going on,,,,,,WHAT UP here

things i have done
changed to dorman intake,,i thought may as well head this off early
changed plugs and wires
changed 1 coil,,post were corroded
also changed 2 of the tires,,belts had shifted in one of them,,the shudder kinda feels like a really bad tire out of balance,,but then goes away and comes back,,,when i found this i thought i found the problem,, BUT NO I DIDN'T

ok i am running out of things to change here,,,my next thought is this motor has a,, or more than one bad injector

i am open to any and all thought here guys,,,this is driving me nuts,,little help would be greatly appreciated

ANY IDEAS????

thanks
ocharry

Welcome to the forum. Have you checked the other coils to see if they were corroded too?

yes i have checked the other coils,,but just a visual,,not saying that there couldn't be a problem with one of the others

i did think about buying another new one and change one of the other two and if no change use the one i ake off in the last spot,,just a thought

come on guys,,,,i know somebody out there has the answer,,lol

ocharry

wow guys,,,no response,,well 1 response and i thank you

i would have figured there would be lots of motor heads here:confused:

you guys are letting me down on this:o

kinda looks like i am on my own to figure this one out:(

thanks anyway

ocharry

will it "miss/shudder" if you power brake?
you said ",,i have had my engine scanner plugged in,,".
were there any codes?
will your scanner show misfire history?
what brand plugs and wires did you install?

Also, is it speed related?

pafman;

well i have never tried to power brake the car
yes i have 2 scanners,,they both will show miss fire codes,,,NEITHER will show a miss fire code while plugged in to this car and the one scanner will take a 2min. history scan while you drive and then i can print out a graph or graphs of the things it is looking at,, not showing anything

they were ac iridium plugs,, think that's how you spell it,, and i don't remember the wire brand but they were the best ones they had with a lifetime warranty,,,well they did have better ones i think but they were racing stuff,,i didn't think i needed that for driving down the road every day

the problem i have is ,,, this motor was acting the very same way BEFORE i changed all this stuff,,,so nothing i have done to date has changed anything

hanky;

no it doesn't seem to be speed related,,it does the same thing at 25mph,,,65mph don't matter

i will say,,,it does seem worse at the low speeds,,that my be because the firing sequence is slower,,and at 65 it is firing pretty fast

i really think i have an injector that is having an issue,,,it definitely has something to do with heat,,seems like when its cold out it isn't as bad until the motor warms up,,,just like night before last,, when i left work,,it was running great for about 25 miles,,then it started again,,,it is always intermittent,,,,may be fine for 10 miles and then do the miss thing for 2 and quit for ten ,,, you never know for how long it will last or when it will happen

when i had the scanner on it i would wait until it started doing it and push the reset to start the running scan,,,or so it would take a snapshot of it while it was happening,,,i didn't see anything,,,comparing bad snapshot to good snapshot

i do know it is making my head hurt,,,lol

thanks guys,, keep thinking

ocharry

I didn't any mention of changing the fuel filter,has that been done?
Did you consider putting a bottle of injector cleaner or one full tank of premium gas .Either one will help with sticky injectors.

you should get misfire counts with faulty injectors. i would turn attention elsewhere for now.

give me a reading of your short term and long term fuel trims cold then hot. and do the power brake thing for me too, cold then hot.

hanky;

i haven't changed the fuel filter on this car yet
i did run premium fuel and injector cleaner through it for about 2 weeks,,that would be about 5 fill ups for me,, and i used 5 different cleaners,,lol,,, just in case,,,the reason for not looking at the filter is i get about 50 lbs fuel pressure key on motor not running,,,,and if i remember it was about 43-44 lbs motor running,,,i am not saying that isn't a good idea,,,but i have fuel at the rail and good pressure

i will say there was an improvement,,,it didn't go away,,BUT it was better,,by better,,i mean it didn't seem to happen as much AND when it did happen it was milder,,,,that's kinda what has lead me to fuel delivery

pafman;

i get no codes,,with either reader,,when i had the graph reader plugged in it was on the way to work,,so it was hooked up for over an hour,,i don't know maybe i don't know what i am looking at,,lol

do you think i would get a miss fire code even if it isn't a complete miss fire???? just a really lean mix,,, i don't think there would be a code if the injector was only about half working,,i don't think i am seeing a dead miss,,,just kinda like it isn't getting all the fuel it should into the cylinder,,or maybe more than 1,,if that makes any sense,,,and does it have to miss more the once to cause a code to show?? and will a code show if say an injector was fluttering,,like not a good solid pulse,,or not opening all the way or closing all the way,,,i have been talking to an injector guy ,,this is all he does ,,, and he says these rochester injectors have a bad rep,,,and the low miles on the care tells me it has sat around a lot,,well until i got it anyway,,he says that isn't good for the injectors,,i don't know about that ,,i have to rely on his expertise

ok i will try and get you some readings,,cold trim,,hmm when the motor is cold isn't it running in a loop that is a little rich until the temp sensors say ok we are at run temp start leaning out to run mixture,,,and warm after running for a few,,,ok i will see what i can do for you

ok i can do the power brake thing for ya,,are we looking to see if it is gona miss while the motor is under load??

ok guys i will try and get you the info you ask for,,may be monday or tuesday,,,but i will try,,,,anything else i need to look at??

thanks
ocharry