Cchris1109

iTrader: (11)

So I am having problems pinpointing this misfire..its an odd misfire in my opinion. Car has all new spark plugs and wires to begin with. After the car runs for a little it will hesitate on idle and chug like a misfire, then it will continue to misfire unless I give it more than half throttle and it picks right back up *and puts me back in the seat haha *

This generally happens after the car runs for maybe 15-20 minutes or longer and sometimes doesn't happen at all. I am not throwing any codes so I am not sure whats going on.

Any help would be appreciated.

DiabloFormula

iTrader: (58)

Did this only start to happen after you put plugs and wires on??

Cchris1109

iTrader: (11)

no i thought it was bad plugs or bad wires so i replaced them, they were getting old anyway so I figured it was a good time

DiabloFormula

iTrader: (58)

ic, i would have guessed a cracked plug, but since it was already doing it.......

Cchris1109

iTrader: (11)

yeah i thought it was too but i changed em all and it has the same exact symptoms and its occasional, sometimes it doesn't happen at all.

the only things i can think of left are fuel pump, fuel filter, coil packs, oxygen sensors. I am not sure if the symptoms I am describing are even related to those, but I don't want to start guessing you know?

edit: I also checked the MAF and its fine.

flirtnwithdisaster

iTrader: (6)

what year car?

Cchris1109

iTrader: (11)

its a 1999

5.slow99

what kind of plugs?

Trev_SS

iTrader: (17)

Is the car cammed? If so it probally has something to do with the tune. My van started driving like this before the fuel pump went out. Are you still running the stock fuel pump, if so might think about that

F-Body Lover

check your coils my friends 99 z28 got the same thing he changed almost everything at the end his coils were dead

7camaro7

iTrader: (15)

I say swap coils to brand new, and you checked the maf, right? Did you clean it? A buddy of mine had a problem with his maf, but in his situation a wire dry rotted. That may be your problem too. good luck, and check the plugs again to make sure that none are cracked. Did you check your old plugs for cracks?

shaun

try cleaning the maf they sell a cleaner made for maf's at the parts store.how about a fuel filter? maybe you have got a bad wire. i had a new set of wires be bad and caused my 98 gtp to missfire up hill and on heave throttle but it only did it when the car warmed up so go figure.

Cchris1109

iTrader: (11)

maf is new and was tested no problems, the plugs are ngk tr55s, just long tubes and an x pipe with lid, no cam to my knowledge unless its a cheater cam the car traps 108 and no stall so I am assuming its just bolt ons like the person advertised when I got the car.

I have not yet bought a new fuel filter, think that it could be it? They aren't too expensive so I may go get one and swap it in.

how do i check if coils are bad? a certain test or anything? the car runs and has full power with decent gas mileage *around 22mpg mostly city* so I know the problem does not happen all the time, its just an odd misfire like I put it, im really stumped.

o1ls1ssmaro

those are the right things to check..... the only other things i can think it could be is spark plugs gapped wrong, timing is wrong, or a vacuum leak at the intake manifold. or the injectors could be dirty. also some of the emissions components could be messed up... with the bolt ons that the guy before you had the car put on, did he keep the emisions components or did he get rid of them ?

drone

iTrader: (5)

Mine is doing something similar. Kinda hesitates and runs like a turd at low rpm's/low throttle. Sometimes I feel like a small misfire feeling at idle. Sometimes the rpm's will drop and the car will struggle to stay alive at idle speed. Its only after driving it for 10-15+ minutes. It runs like a beast when you first start it up. Im throwing a small evap leak code but im not sure if thats related since that has been an older problem that I havnt cared to fix yet. I have a k&n filter, and i did a quick cleaning on my maf a month ago. Im gonna try to clean the **** out of it and see if it clears up and I need a paper filter.

Egr was removed and tuned out. Air pump tubes gone, but the air pump is still in and working? I hear it go off when im driving. all done by the previous owner.

Cchris1109

iTrader: (11)

well I am still stumped, I will be buying a fuel filter and if that doesn't solve it then I am going to have to take it to a shop. It could be fuel cutting out because it hesitates so much and a clogged filter could be a result of that, will also feed in injector cleaner.

redhotSS

iTrader: (1)

my car is doing the same thing, new plugs and wires, new fuel filter. cleaned the throttle body and MAF and still it does it. i plugged it into our snap on modis and it says theres no problems, one thing i didnt do is do slow rpm pulls to see if maybe the throttle position sensor is dropping current somewhere. has anyone pin pointed a direct problem yet? the only thing that makes me think its not a coil problem is it only does it in a certain rpm range, then runs amazing in higher rpms... if a coil was bad id think itd run off par through all rpms... maybe im wrong tho. my car is bone stock btw

survival

iTrader: (1)

Also simple check is the vacuum line between the throttle body and the pcv they tend to get soft with age and temp and collapse.This causes poor idle or stalling.Check pcv while your at it.Just had this problem after ls6 intake swap,a new piece of vacume line and it was a better.

redhotSS

iTrader: (1)

i checked my tps today and it was failing, so i took it out and it actually rattled when i shook it. so I was confident id found the problem and i installed a brand new one and the throttle response is alot crisper... but i still have the hesitation in that spot. i guess tommorow i will check that vacume line.

2000Z28ls1

iTrader: (18)

I was told today Gm is known for failing coolent temp sensors, which read cold so the computer dumps fuel causes the miss or hesitation. I havent tried anything yet but where is the temp sensor that goes to the computer not the gauge location, on the front of the drivers side head?