Yes, the 3300 is multiport.......

Strange things happen when cars shut down for a couple of years.....

These engines were not known for a smooth idle, at 600-650....nature of the beast.....if you raise the rpms 50-100, it smoothes out....some people would open the throttle a little, but then you would have harsh tranny engagement, and it would also throw off TPS %......

It'* possible it could be vac leak, intermittent MAF, or it could quite possibly be injectors......this is multiport....so 1-3-5 fire at the same time, as does 2-4-6....

Now if you have flow problems in an injector, this can cause your hesitation problems......unfortunately, you need special equipment to test injector flow.....then if flow is off, you try to clean them, again with special equipment at the fuel rail.......adding injector cleaner to a fuel tank, is just for maintenance purposes......the only way to clean injectors is at the fuel rail....then a flow test has to be done again....if the injector still fails, then it has to be replaced......unfortunately, have seen aftermarket injectors not match OEM'*....not saying this is your problem, just a possibility.....

I was hoping I wouldn't have to mess with the injectors. It seems that I have read something about injectors going bad on these 3300--or at least being loud. The only thing I haven't really checked are the coils. It seems now that is hesitates very bad when it'* cold, then smooths out. But after it'* fully warmed--like 30 minutes of highway--it starts to buck. The idle is relatively smooth, but every once in a while, it will suddenly dip way down and then go back to normal. I haven't tested the fuel pressure at the shrader valve, but I wouldnt suspect a fuel pressure issue because of how it runs when it'* lukewarm. It'* definitely throwing me off..

If it'* bucking, do a coil output test with a spark tester....

Could bad coils drive perfectly normal when warm? It revs up great when warm, but not hot.

Coils tend to misfire, when they have the greatest load on them.....this happens when the engine is warm, you are going up a slight hill, and the TCC is engaged.....

Typical test for a misfire, drive the vehicle on the highway(normal operating temp), at 50-55....as you approach an upward grade, lightly start to accelerate(hard accel will disengage the TCC).....if the vehicle starts to buck, it'* usually secondary ignition(coil, wire, or plug)....

Okay, so I drove the car about 200 miles today. Getting on the interstate, it was bucking worse than ever, so I was waiting for the next exit to turn around. But after like 2 minutes, it drove just fine. I put on another 100 miles without a single issue--going up hills at 70 mph, merging with about half throttle. On the way back, it bucked once, then was fine again. I'm definitely confused, because I know it'* going to buck again tomorrow.

Like I said, do a coil output test with a spark tester....

Okay, guys. It'* been a while. Still driving the car with the issues.

Here'* a complete list of parts/work done so far:

New plugs/wires
Air Filter/Fuel Filter
All 3 Coils
ICM
Crank Shaft Position Sensor
Coolant Temperature Sensor
Cleaned MAF Sensor
All 6 Injectors
Cleaned Throttle Body and IAC Valve
New PCV Valve
New TPS (Professionally Calibrated Now)

Sometimes upon starting the car, it will run poorly and buck at all speeds.
Other times, it will drive perfectly fine, even at WOT.

It will never rev all the way up if I floor it--or even gradually accelerating.

It will occasionally buck on the interstate. Other times, it will drive perfect for hours.

It will still stall out--sometimes unexpectedly and sometimes after running poorly first.

It will sometimes miss while idling, it never idles perfectly--as expected, of course.

And the last time I floored it, it bucked as usual, but the CEL came on with code 42. After turning it off, it went away.

From my understanding, the parts I've replaced and code 42 tell me that the problem rests with the ECU. Code 42 supposedly only comes on from a wiring issue between the ICM and the ECU, a defective ICM or defective ECU. Since I've replaced the ICM, I figure it must be the ECU.

If I had not gotten the code 42, I would have suspected the MAF sensor, because I just cleaned it and didn't buy a new one.

I'd really like to get this figured out. It'* a one-owner old-lady car, so it'* pretty much new inside and out. Thanks guys

this is a good explanation of the code. you cant just jump on replacing parts(the pcm is the last thing on the list), the wiring needs to be checked

Why the computer flags this code.

The ignition module and the computer are in constant communication when the engine is in operation. (Over 400 RPM.)With the computer telling the module the correct timing. If communication is lost or a circuit becomes infected with false signals (bad grounds, short to battery +, Electro Magnetic Interference {spark plug wires to close to circuit wiring}, oil contamination of the circuit connectors and wiring) then the computer will turn timing control back to the ignition module and flag the code.

Possible causes:

· EST circuit open or grounded.
· Bypass circuit open or grounded.
· Reference Ground circuit open or shorted to battery +.
· A bad computer to engine circuit ground.
· A defective ignition module.

· A defective computer.

If you are testing a vehicle for this code check the routing of the spark plug wires making sure they are not to close to the EST circuit(*) wiring. Check the connector terminals making sure they are not over-sized or oil contaminated. Check the entire wiring of the circuits for chaffing,
short(*) ground.

I've come across this information before. It wasn't useful to me because I have no idea where the EST circuit is. The plug wires don't seem to be routed next to any wires. The code 42 light only showed up once and then went away the next time I started it. I think it may have been a fluke.

Today, I was accelerating to 40 and it died at about 35. I rolled it to the side of the road. It didn't start back up. It almost did a couple of times, but never started. It'* still sitting there. I tried turning the key to the "on" position for 15 seconds to see if the fuel pump was weak, but it didn't help. It'* still sitting there. I'm definitely stumped on this one.