Ok, at wide open throttle only the car sputters and jerks. At 3/4 or 4/5 throttle it does not. It starts fine - idles a bit choppy but it always has.

I'm considering a few causes, but my custom air intake is not one of them.
Here's why.

The car only does it under sudden acceleration. If it were the intake, it would do all the time, including idle. My first thought was "well, the mixture is getting lean when I go full throttle because the new intake is allowing more airflow, and the fuel system can't keep up with it." It made some sense at first because my fuel filter probably could use changing and fuel pump is a little old. I rejected that idea though for the same reason as the first. If I go more smoothly into full throttle rather than punching it, it doesn't jerk much, if any. A lean engine would still sputter at high rpms even if I gently brought it to full throttle.

I know it's getting plenty of air...

That left about one other possibility - the ignition. The plugs and wires were about about due for a change. I intend to check them pretty soon. I know the throttle body looks fairly dirty from the EGR. There's soot built up on the butterfly valve. I'm thinking a gimpy ignition is unable to ignite the sudden dump of fuel when I accelerate hard. My dad's Chevy truck had the same problem. If you throttled gently, you could get it up to speed eventually, but with a hard throttle push you'd be off to the rockin' rodeo.

The ignition was probably about ready for a change, so it couldn't handle the extra demand placed on it by the custom intake bringing in more air, which meant more fuel added, and so on.

Just to be on the safe side, I poured a pint of isopropyl alcohol in the tank for good measure. Who knows, I could've gotten some bad gas, or there could be crud in the fuel system. It never hurts anyway.

The plugs should tell most of the story.

DK

Make sure you fuel filter is clean. Get new plugs and wires (perferably 8mm wires) Make sure you timing is on and I would throw some injector cleaner in. Also what type of fuel octance are you running?

We're thinking along the same lines, it seems. The isopropyl alcohol will clean the injectors, along with removing whatever traces of water might be in the tank. The fuel filter, I do need to check. The wires and plugs are in a pretty definite need for change. The only issue is money. I only have so much, haha, and I wanna get good plugs and wires.

DK

does it only miss and buck from a dead stop? or is it even if you floor it while cruising? if its from a dead stop only you might have a transmission problem. 2 of the times i rebuilt the trans in my car it was because the first gear band wears out and starts to chatter (the other times it was because a defective torque converter smoked the trans and the other time it just stopped shifting) so if you, quoting the guy who rebuilt my trans the last time "drive aggressively" the transmission is certainly a possibility.

it was kind of tricky to diagnose the first time because it did it even when torquing the engine up (revving it in gear holding the brake). so i thought it was a miss at first. but when the coil goes bad it will start to miss before wide open throttle usually.

good luck

I sure hope it isn't the tranny, though I suppose it could be. However, it seems more of an engine problem than a tranny problem to me. It happens when it gets a quick burst of fuel into the engine. The SES light has come on a time or two also. Sure does get annoying.

There's one other possibility that I've been considering - the MAF. It tends to go bad about every 10 or 15k miles, long before I put on the intake. When it goes bad, it acts a lot like this.

DK

first i'd suggest checking the computer to see if there is a code. and a MAF going bad every 10-15k miles is not good, there is possibly something else wrong that makes it go bad or maybe you keep getting bad MAF's.

what did you do with your IAC sensor when you made your custom intake duct?

normally a bad MAF would set a code. i have seen some different things happen with bad MAF's, but not missing or bucking. from the ones i remember, one just set a code and the SES light came on, and the other (which was on a Delta 88) made it run full rich and blow black smoke.

also, you never answered my question, does it do it only from a dead stop or if you floor it while cruising too?

Well, it doesn't do it at all now. It has stopped. When I think about it, it didn't start until the very time I was pulling out of the gas station. Since it started then, and has now stopped, I'm thinking it was just a bad batch of gas. The isopropyl alcohol I put in helped, I'm pretty sure. It usually does.

To answer your question, it did it from cruise, from a standstill, or any other time I went to full throttle.

I tested it out thoroughly tonight at my favorite spot. The car ran back to back 8.94 0-60, which is as good or better than it has ever run. That ain't bad considering that these cars ran 9.2 or so totally new, and this has 323k on it now.

As for the MAF, they are notorious for going out on this model of car. It's just a part of the deal. Never seems to hurt anything though.

So, in a nutshell, there you have it! The car is back on its feet, and running faster than it has in quite a while.

I went and got some Autolite Platinum plugs (I wanted copper core, but they didn't have them for my model). Last plug change was about 292k, I think. I put in Splitifires, which have served me well. It's time for the Platinum, though, I think.

DK

i don't know who told you that those MAF's fail alot, because i have several customers with a 3800 that have never had problems with it.

personally, i wouldn't waste my money on platinum plugs, i tried them once, too expensive, didn't feel any difference, and if the car doesn't call for platinum plugs why bother? besides, on a high mileage engine they will probably get fouled and need to be replaced before you can benefit from the longevity aspects of a platinum plug.

More than one trusted mechanic has said that the MAFs are one of the weak spots of the 3800. At many message boards having to do with the Series I 3800, it is also common knowledge.

As far as the spark plugs...I've never had one foul, and I don't expect them to start. At 323k miles, my Olds is just getting broke in, so I'm not putting any crap in it. I'm going for 400k. Besides that, with the stock ignition coils and wires, I've decided that it's probably best just to use a more concentrated spark. The Splitfires are great, but they spread the spark out. They would probably work better with an aftermarket ignition that would have the power to better utilize that split ground electrode.

My car calls for 87 octane, but I don't use it, because it runs better by far on premium (no, it's not just in my head). It's the same with plugs. The platinums have a narrower, more focused positive electrode which should make a more intense, focused spark. I tried the platinum just because I wanted to, and also because they were the only ones at Walmart which matched my car. I didn't want to go anywhere else, I wanted them then, darn it! haha

DK