1_Bad_LS1

iTrader: (8)

I start the car, drive for a little bit... 2 minutes or so then it starts to miss real bad... idles like it has a huge cam... bogs real bad when leaving a light... SES light blinks... then after about 3-5 minutes its fine again... And I dont have a problem until I shut it off and drive again... then the process repeats itself...

I had this problem a while back, changed the plugs & wires still missed a little... I reset the pcm... and then after a few days it went away...

Last time it happened real bad like this we had about a week of rain... It started again after another week of rain...

Also... It only misses at idle and part throttle... at WOT it goes away, or seems to?

Any help, please?

GQ

iTrader: (5)

its unfortunate to see someone else with my problems, but i feel a little relieved that im not the only one this is happening to. i had a reply offering a few words of wisdom a few posts down.. titled part throttle probs..ill let you know how it goes. if you figure it out before i do drop me a pm on what you did. -g

1_Bad_LS1

iTrader: (8)

Yeah it really sucks... I was thinking the O2 sensors as well... I have LT headers and no cats so I am sure they are shot to hell... I have another maf from an 02 SS I will give that a shot and let you know...


Anybody else, any words of wisdom please?

Ravenous T\A

iTrader: (12)

Check all sensors for cracks and burnt wires. I had a mild miss (no SES light blinking) at part throttle for awhile, I cleaned my Idle Air holes and that help calm it down but it was still there, then I swapped in a New IAC and it helped it for a day or two but then it came right back when the weather changed (got cooler w/ more Humidity outside) Then one day on the way to work my SES light came on and I pulled the codes and it said High Voltage ECT sensor, checked the sensor and it was broke around where it fits into the brass fitting. Put in a new one and the car is back to normal. A change in weather would tell me it could be your intake sensor, 02's, MAF, airleak after the MAF, clogged or sticking idle air control, and of course my problem the ECT which is located on the driverside head in the front which could have been damaged with the header install. Good Luck man and lets us know what it is for future problems people have.

half-n-half

iTrader: (7)

heyt i am with you guys EXACT same problem, to a tee. starts to idle like ****, horrible part throttle miss, light flashes, etc.


i am ready to hear what your guys problems are as well, i have done quite a few thingsmyslef to try and figure it out.

Louie

ricknbird350

iTrader: (21)

i have an lt1 and i have a part throttle miss to..and my light flashes also..where is my ect located? what does ect stand for?

IOwnCalculus

I'm getting this lately in my truck ('00 SS LS1 in '70 GMC). It could be voltage supply issues to the ECM, but I think I've got those nailed (I'd think that would kill the fuel pump / speedo too, and it's not). Going to check that first anyway.

It seems like it's temperature related, when it crosses from open to closed loop...but I already fixed a dead O2 sensor.

Tell me...when you guys go to key-on and have your head under the hood...can you hear your IAC valve at all? Mine's getting noisy and I have a strange feeling that it's acting up. My symptoms are just like the OP's.

ricknbird350

iTrader: (21)

i had mine on a scanner and after 3 minutes of 1200 rpm it stayed in open loop and even awhile after that.. what tells it to go to closed loop?

half-n-half

iTrader: (7)

i have been listening to everyones input on this annoying problem that we are all going thorugh and i will share my thoughts and experience with it thus far...

first off i doubt that it is 02 sensors, or leaking exhaust, because i have had bad 02sand a worse leak in my exhaust before and it never did this.

secondly what happened to me yesterday was this:
i let my car run on the driveway for like 25-30 minutes and then went out to drive it...problem free!
i also let the car cool down completely and went to drive it, it was problem free for a little(about 2-3 minutes at best) and then started to missifre when driving right at or around 2-3k rpm and below it will miss, but WOT seems to be fine.

as far as the possible voltage issues to the PCM i can see that as a viable problem, i had originally thought it may be a voltage issue for no reason other than i can hear engine whine in my monsoon system when it is doing this stuff...that just seemed odd.

i checked my battery, and groundns, and everything but i never found anything.

ECT sensor i could see it possibly being this sensor bad because it seems that if i drive it before engine begins to heat up it is fine, or if i drive it after it has been warm for a while it is fine....

it is very difficult to say and i have been unable to scan my car to check the codes right now, so i will definately try to get them scanned an go from there...

Thanks
Louie

half-n-half

iTrader: (7)

ok just now again this morning i went out to my car to check some things out real quick...i unplugged teh ECT just for ***** and giggles and the car definately idled much much worse and the high fans came on all the time, i think that i am going ot cross that off of my list, even though i still may be wrong.

i also revved the engine while it was still cold/freshly started and it would on its way down drop to about 300 rpm. it even died once.

along with these things i let the car run for a while on my driveway and then took it for a ride....it idles perfectly, ran perfectly and when i got home i could rev it a little and it would go right back to 800 rpm.

i really just dont get what the problem could be for it to act this way only when cold, then if i let it warm up for 10-15 minutes all is well.

i reset the pcm yesterday so i doubt that it is in the pcm, has to be somewhere else i am going to assume....

98TA_vert

I mean this is probably pointless, but my 96 S10 4.3 vortec did the same thing with the same symptoms, It was a bad distributor i know thats not much help being our cars dont have distributors but its probably ignition related and not a sensor.

half-n-half

iTrader: (7)

it is definately possible that it is ignition, it is one of the things that i considered... i will be changing the plugs first, then possibly the wires...

if it is a coil i would have to get it scanned and then check which cylinder is misfiring, possibly swap coils and see what that does....etc.

Louie

1_Bad_LS1

iTrader: (8)

I figured it was a coil...

Somebody told me to get it to where it was idling rough again... then start pulling plugs one at a time. Cylinders with good coils would make the car idle much worse... If the idle stays the same... thats the bad coil... Makes sense... I'm just not sure How I feel about pulling these wire with all that voltage running through them!!

Any inputs?

02_Blk_RamAir_TA

i have the same problem on my stock 02 TA it says #1 missfire . so i switched the plug to #3 ... it did the same thing then i switched the plug wire to #3 ...it still missed so i switched the coil pack to #3 ... still says #1 missfire same **** it misses at part throttle with SES light flashing . I changed the crank trigger and it still misses it, misses after it rains or on very humid days . Two visits to two diffrent dealerships and one shop, my neighbor who is 15 years ASE certified and no luck . i'll let you guys know if i find out what it is

half-n-half

iTrader: (7)

...not plug, not plug wire, not coil, not crank trigger, it says it is #1. did you ever think to try the fuel injector?

also i heard that sometimes the computer has the wrong cylinder when it says shich is missing....

i dunno just a thought.

wont i did notice is that it ONLY happens when warming up...it seems like if my car is not completely cold and not completely warm it will do it...but if i first fire it up it is fine...and after 5 min of driving(3 minutes it is missing) it goes back to being perfectly fine and running PERFECT again...it is so wierd.

there has to be something with it switching from open loop to clsed loop...etc. i just am not sure what all happens when this takes place...

also i have tried to make it missfire after it "fixes" itself when warmed up.

i will tried everything in power to bring the missfire back without any luck...

6th gear at 7-800 rpm WOT.
WOT in low gear then letting off.
shifting early
shifting late
everything that i could think of...and nothing...

half-n-half

iTrader: (7)

ok guys today i got a scantool and checked some things out on the drive home...

What i have come up with is teh following....:

The only time my car missfires is if it is closed loop. Whenever it is in closed loop mode my short term fuel trims bank 2 will begin to work its way to -40% and then the car will start to miss real bad. the trim will stay at -40% until i give it a little gas to "power through" the missfire and then the fuel trim will back to low negatives numbers like the rest of them...


What does this mean...i have no idea. hopefully you can help and i will ask in PCm and tuning too.

It also says that fuel system 1 and 2 are both in fault regardless of OL or CL.

When in OL all the fuel trim tables sit right at 0% and it runs great....

i dunno hopefully i can get some help.
Thanks

BTW DTCs were...
1133
1153
0300
0140
0160

Thanks
Louie

half-n-half

iTrader: (7)

ok guys well i just went through the scanner a little more, asked int he pcm section and noticed that my passenger side 02 sensor was not responding at all!

i changed it and everything works good.

gsformula99

im having simalar problems slight miss throught rpm range and a idle that gets worse after theer car warms up and it seems to be down on power but no ses light as of yet

mc01ta

gsformula99, me too. Same probs as you state but no light. its been doing it for awhile. I've done new fuel filter, cleaned maf, air filter, seafoam, new plugs. I'm about to get new wires and o2's next. you have any luck?

IOwnCalculus

I swapped out my ECT sensor and so far it seems to have cleared up. Not going to say for sure until I get throug a whole tank without any troubles...

...which won't take too long with my right foot