Ok, for u guys who don't check the registry, It's a 2000 Z24, automatic.

Now, this problem has only been happening for the past week. At idle, the RPM's will stay at ~600 but every now and then it'll drop real fast to ~400 and pop right back up. The engine shudders and rocks the car a little bit, interoir/headlights dim, no blinking CEL. At first I thought maybe the engine was cold, so I let it run for awhile and it does the same thing.

When I'm driving, it's fine... give it some gas, it'll go. It's just at idle. I thought it could have been the gas (it was under 1/4 tank), so I filled up with some 89 octane. No difference really. I'm thinking about checking the fuel filter and running some injector cleaner through it today.

I'm gonna pull the plugs when I get off work to check the gap, I got some Bosch Plats in there which I might get rid of and throw the Delco Plats instead. IT's 0.60 gap right?

Oh, 1 more thing, it's throwing code P4020 (I think), O2 lean in bank 1. I don't know if it's the cat or the first O2 that's the problem... would that effect performance?

???

dude i am having the same problem u are right now

Ex-girlfriend's 2002 2200 auto did exactly that, exactly as you describe it in every way. Unfortunately for her, the "ex-" was added to her title right before I was gonna check it out, so she's SOL

My thought process got me leaning away from an ingition problem or a fuel problem, and more towards alternator output, how good/old the battery is since it's needed as a reservoir for alternator (I think...), cooling fan since it might be putting a load on your alternator as it cycles on and off, possibly sensors like O2 (not sure which would be most likely), maybe something to do with A/C since it puts an intermitted load on engine sometimes.

So I'm not exactly full of answers, but there's how I might approach it. Hope that helps a little

Hmm.. good thoughts, but this is with A/C off, and no fan kick in... hmm...

Places like AutoZone and Advance Auto sometimes will check things like alternator output and battery for free... maybe very small fee.

Idea of replacing plugs may not be your problem, but let's face it, replacing your plugs never hurts, so go fir it

Corsica Dude wrote:Oh, 1 more thing, it's throwing code P4020 (I think), O2 lean in bank 1. I don't know if it's the cat or the first O2 that's the problem... would that effect performance?

Bank 1 makes me think it's the one in the manifold, not the one after the cat. I got a similar code (P0402) and it was for the one after, so maybe yours is for the manifold sensor. That will definitely affect performance. No idea why you'd be running lean, especially since our cars are notorious for being a little rich...

Well, I pulled the plugs, traded out the Bosch Plats for some nice Delcos, at $6 a piece they better be good!!! The plugs looked a little whitish, not that nice brown we want... so I think it's running a bit lean. I have the battery disconnected right now to reset the computer, I'll let it warm up in about 10-15 mins and see whats up...

just an FYI, bank 1 can be either the upstream or downstream o2 sensor. All the 3rd gen J's have 4 cylinders, so theres only 1 bank, unlike a car with a V6 or V8, then theirs 2 banks. The full description of the code should be something like Bank 1 Sensor 1 or Bank 1 Sensor 2. Sensor 1 is the the one in the manifold and Sensor 2 is the one after the cat.


Lifes too short to drink cheap beer.

Thanks man, I'll get it re-scanned tomorrow or something.

Also, the AC Delco's fixed whatever the problem was. The idle is steady at ~600 with no drops. I drove it around for about 20 mins, accelerating normally, then hard letting off about 5000 rpms. Idle in drive was steady.

Bottom line:

BOSCHES SUCK.

green98cavy wrote:just an FYI, bank 1 can be either the upstream or downstream o2 sensor. All the 3rd gen J's have 4 cylinders, so theres only 1 bank, unlike a car with a V6 or V8, then theirs 2 banks. The full description of the code should be something like Bank 1 Sensor 1 or Bank 1 Sensor 2. Sensor 1 is the the one in the manifold and Sensor 2 is the one after the cat.

ohh... that kind of "bank"

I had the same problem using bosch plats.. just changed over yesterday. The plats where alittle white also, but as soon at I put the delco ones in, ran smoother, and no shudder at idle... the plats where only 3 months old too

same thing is happening to me too, and i have the Bosch Platinums

hopefully changing them will fix my problem.

This is what my vin pulled
Part Number Cal.ID# CVN Description
12222103 12222102 N/A New calibration to address cold hesitation issue
9373243 9373172 N/A New calibration corrects concern related to knock sensor false light
9368543 9368542 N/A New calibration to correct hot restart problems
9365343 9365288 N/A Control module calibration

http://tis2web.service.gm.com/tis2web

I personally changed IAT both O2 sensors, coil packs, spark plugs etc.. No help what i have posted gave me the most help but did not solve it


2004 Grand Prix GTP (Competition Group)
SOLD-->1999 Z24 5M-#30 to register on JBO
"You can please some of the people some of the time but you can't please all the people'
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