Hello all,

I have a 1998 Chevrolet Lumina LTZ. The chassis and transmission have 138K on them, and the motor (out of a boneville) has around 90K. As far as I remember, the SES has been on after the swap. The motor is a Series II 3800 V6.

I had it scanned at Advance Auto, and the codes returned misfire on cylinder 2, and something about the idle RPMs. It likes to fluctuate idle rapidly when I first start the car, sometimes I have to hold the accelerator down slightly for just a second to keep it running. Also, the Service Engine Soon light flashes on WOT..but only at higher RPMs..

I have performed a full tune up on the car: plugs, wires, filter, and I even replaced the whole coil pack module. I had the original coil pack from the old motor, swapped it, and it still didn't make a difference. I also sanded off most the corrosion and crap to make sure it had a good contact. I have sprayed the vacuum lines with injector cleaner to see if the motor would rev up due to a vacuum leak, but to no avail. I unplugged the injector on cylinder 2, and the idle went down. That tells me its probably not the injector. I replaced the fuel filter after the swap, and have ran sea foam through the car.

From doing a search on this forum, I read for misfiring it could possibly be the catylitic converter? Is this last option that it could be?

Thanks!

 

you say that when you unplugged the injector the idle went down? did the car stall out? have you checked compression in each cylinder? how bout an injector flow test? can u feel the misfire? also was it an on demand code or a memory code?

 

i have not done a compression test, or injector flow test. i don't have the tools to do so, nor very much money! the car sounded like the idle went down when i unplugged injector #2. the car did not stall, but i did not have the injector unplugged very long.

it sounds like it could be an injector though since the SES light flashes at WOT doesn't it?

thanks for the reply.

 

it could b but at wot ignition is advanced as well and if your car almost dies at start up it could b ignition as well. on the other hand your fuel pump may not be able to keep up wit the demand at wot and cant build up pressure right away when u start the car.

 

hmm..i replaced the complete coil pack..not just the one coil that cylinder #2 is on..still no difference. i did plugs, and wires..i am going to take cyl #2 spark plug out and make sure it still looks good tomorrow..and see if i can get a hold of a compression test..otherwise i don't know what to do! any ideas where to start?

could it be the fuel pump? i want to rule out the easier stuff to check first before i have to drop the gas tank! you don't think the cat is possibly clogged? it does have 137K on the stock exhaust system...

 

well yes the cat could be clogged but that generally throws misfires along both banks not just one cylinder. since uve already replaced almost everything ignition id start checking out fuel. check the compression and u really cant measure injector flow without the diag software. now that i know everything uve replaced, an injector sounds pretty good. but do the compression first

 

thanks..i will try to get the compression tested on all cylinders..if the compression is good, i can try to test the injector..and if that is good, then i imagine it could be something in the exhaust.

i forgot to mention shortly after, or right after, the swap the car developed an exhaust leak i believe it to be one of the doughnut under the hood..where one of the couplers are..which may mean the cat is clogged and forced an exhaust leak through the coupler? either that, or i didn't tighten the coupler down good enough after the swap...but even after, i tried to tighten it afterward and it didn't fix it..i think it needs a new doughnut.

 

also, in neutral the car idles at about 1,250 or so RPMs...should be aroun 1,000..its always above 1,000.

 

my buddy is coming over with a compression test tomorrow..i will let u know what the results are.

 

after a day of testing, we figured out the idle problem. the idle air control valve was stuck open..car idles at 1,000RPMs as it should now and it runs better in that department. it still has some sort of misfire problem. after we fixed the IAC, the service engine soon light came on again..last time it ran sluggish, it was 58 degrees out and the car had not been started for 4 1/2 hours. it runs sluggish when you first start it for about 5 minutes or more on the low end..its nothing major though. i just wish i could figure it out! compression is good, ignition should be good..only thing we did not check was the fuel flow on the injectors.

any ideas?