2000 Pontiac Grand Am 2.4
 

Car is a 2000 Grand Am with a 2.4 4 banger. So a couple weekends ago I swapped the new motor in. The old motor was knocking so hard I didn't bother paying attention to any other problems. Finally having time yesterday I finished everything up and fired her up. Started no problem, but stumbles hard intermitently. After a couple minutes I threw a P0300, multiple misfire. I also am getting a little smoke from where the exhaust pipe meets the manifold. I did spray some pb blaster on the exhaust manifold to get the nuts off so maybe it was burning a little. I am thinking clogged cat though? Any other thoughts. This is the first time I have worked on these 4 bangers.

Thanks, Kyle

Could be. Easy enough to open the exhaust and find out...

the smoke coming out from the headers and head is normal for about the first 10 to 15 minutes, its the penetrate that you used in the engine burning off, i got nervous about this when i did my headgaskets and put new headers in

Check the plugs if those are fine its usually the boots or the coils under the idi cover are junk

Sadly a on GMs a P0300 could be just one cyl misfiring, or all 4.. they like to be vague like that.

Any chance you have a scanner that plots live misfire data?? That is a godsend to narrow it down to one cyl, or check if it's effecting all 4.

I'm gonna go ahead and say almost for sure NOT a clogged cat, though. We tried to replicate a clogged cat vacuum test (vacuum drops as exhaust backs up) and plugged the tailpipe with a stopper that had a pencil sized hole in it, and the car ran perfectly even with that huge restriction. I'd assume to show any issue at idle it'd have to be almost 100% clogged and then it'd do more than stumble every so often.

With that said, do a vacuum test on it and see what the reading is. If you start it and it starts at 18" and drops as it idles.. then maybe a clogged cat.. You could almost use a pressure gauge to check exhaust back-pressure (screws in where the O2sensor goes).. should be under 4 psi or so IIRC.

I'd almost suspect a vacuum leak.. does the stumble go away off of idle?
If you have live data, look at STFT.. Is it high and idle and regular revved up? If so.. vacuum leak. Find it by smoking the manifold.

If those are dead ends, def seeing the other live data feeds would be a great start.


Also, what caboose said.. those boot things are crap. Give those a check.

There is a re-learn procedure for after a crank position sensor is changed. I'm not sure if that needs doing after an engine swap. ?

Good point. The new engine needs to be calibrated to the ECM in order to get proper operation. GM refers to a CASE learning procedure for these engines, IIRC a high quality code reader or programmer is required. There is also a process to recalibrate the TPS sensor that you can do.

Replacing the spark boots is always a good idea too since they are cheap.

Update, so it was a combination vaccum leak and bad spark plug boots so it idles fine.......

Now for the bad news, there is a noticable lifter ticking. I would say between all the trouble shooting the engine has ran for about 5 minutes or less. I also while under the hood (my retarded fault) neglected to notice the low oil pressure light. So I started to diagnose that problem. Cracked the new filter off that I put on the motor right after fill and install. DRY TO THE effING CORE!! roosterSUCKERS SENT ME A MOTOR WITH A BAD OIL PUMP!! I called them up and guess what! Oil pump is not covered under their 90 day warranty!!!

Mother effers!! Gonna fight for a day or two more with them before I call both my lawyer and the Connecticut Auto Recyclers Association.


NOW..........ohh let me calm down for a second...........the question is. If I get stuck with the motor, am I screwed, or do you think that with a new oil pump the upper end will operate properly?

Thanks, Kyle

it might depends how long it ran with no oil. I would be more concerned with the main bearings

Wow... typically the #3 rod bearing is the first to go. Top end is probably fine.

I was hoping the crank slopped up enough oil from the pan that the mains would be ok, i like to think optimistically, it helps me from wanting to kill people...