UPDATE: unplugged the EGR and it stopped the missing/stumbling, so the EGR must be fubared

ok, i know i have 4 VERY OLD passenger side plugs that needs to be changed, and i'm almost positive thats whats making it miss....
but why would the car misfire only at 2K and below? it wont miss at idle, it wont miss when i give the car some oomph gas... only a lil gas at around 1500 makes it misfire...
is the spark intensity increased as u give it more throttle or something?
cuz since my plugs are bad, i'd assume i'd misfire uptop too? (or that its there, but minor so i dont feel it or something?)
well, i'll change the plugs this saturday, and that should fix it, but still curious why it only does it at low rpms when i'm giving lil gas only
hmmmm
edit:
on a diff post i saw this
"Do you still have the EGR? They're good for low rpm stumble."
i noticed this started to happen after i got my cats taken off...
can it do this because of low EGR pressure since the cats are gone?

 

most likely your EGR. I believe your EGR is hooked up BEFORE the cats so havin them removed shouldnt affect it. Did you try sqeezing the diaphram to see if it is stuck open?do that first and work from there.Usually when somethins wrong its the simplist things.I beleiev the EGR closes at around 2500-3000RPM and at wide open throttle it remains closed,so the EGR will never be a problem at WOT. Also, when u took off your cats,what did u do with the oxygen sensors? Most sensors are shut off at WIDE Open throttle so if it misses at WOT then its a mechanical (hard parts) problem,if it doesnt its electrical (sensors and such).

 

aren't the low rpm stumbles also a very comon sign of a bad opti?

i'd do the plug though...that could very easily be it

 

Im sure the plugs play a part in it but the main problem is probably within the EGR as MauriSSio said


Later,
-JOhn

 

i think its a sign when u start missing at high RPMs

 

i got my hand back there, and started to feel it, but i dont feel a diaphgram that i can like move around with my hand, its all metal crap :P

 

theres a big metal circle thingy on the back of the intake manifold with a vacuum line going into it...disconnect that vacuum line and see if the miss goes away. if it does your EGR valve is dirty/shot.

 

if you cant move the diaphram then its probly stuck open.im not sure what its made of but it feels like metal i believe.theres not too much room for you to put your fingers in there to press it but if you know what exactly what youre doing/looking for it SHOULD be simple.where r u located?maybe someon from this board can help you out?

 

When you experience the miss, is it just showing a DTC P0300? (indicating a random miss) and/or is the engine noticeabley missing at 2k rpms and lower as you mention above?

 

I hope we all find a cure for this low RPM miss.

Someone said we drive a cheap GM car and I disagree completely (was other post). If a 4 cylinder car pulling 20Hg of vacum can run smooth I dont see why an LT1 with stock cam and pulling 20Hg vacum can not do the same.

We have 4 more cylinders per cranck rotation that by itself should smooth things out. This problem we are experiencing is something we have yet to discover. I have even thought about my MAF being so close to the Ignition coil maybe picking up electromagnetic noise from it... I mean most of us have done just about anything and I dont see many people fixin their problem.


One more note. Perhaps is just not one problem but several problems that show up as a low RPM miss therefore not all of us will have the same cure. For as long as my car is running I can methodically test all of my theories one at a time and see what fixes it. Another theory is that perhaps the Alternator (old ones that is) is making electric noise and the PCM maybe picking up that noise through sensors (unlikely but possible). I will be filtering power supplys to sensors (only where applicable) to see that fixes up the problem. It could be a ramdom voltage jump inside the Opty Crap too...

Please keep posting your results after you fix the problem... I am thinking of starting a database of ramdom miss fixes too...


Thank you

Marvin

 

i havent checked for the errors i'm getting, because i dont have an access to a machine that can check it for me =/

i will remove the vacuum line going to it, but will that hurt the car, and should i just keep it off if the miss goes away?

 

I had a low rpm miss on my Caprice (same engine). I did just about every dignostic technique. checked EGR & also plugged the vacuum line, compression check, vacuum check, cleaned maf, checked o2 sensors, checked and cleaned injectors, put new plugs in, put new wires in, then finaly replaced opti. Yep, it was the opti. 135K mile car and it was still on the original wires and opti. The opti will wear out. It has posts and rotor just like any other distributor. I got a 'rebuilt' one from autozone for $129. Works like a charm. Anyway I had a low rpm miss with light throttle, especially noticable at cruise speeds when the torque converter would lock up. The car ran great at 3/4 and WOT. Also idled ok. I checked all the small things before replacing opti and it was the only thing left.

If you think EGR remove the vacuum line from the solenoid and plug it. take for a test drive and see if you notice any change.

 

well what if it drives fine with the egr plugged? should i just keep it like that?

i hope its not the opti errrr

 

mine did that when my o2s were bad. the car would idle fine but would miss like crazy till i gave it a decent amout of gas.

 

ARGH!! Thats why im just gonna fix up my 68' Mustang, no sensors EGR smog or unneeded headaches!