OT car bucks when I accelerate

01 chevy cavalier, no codes, no service engine light, changed out coilpacks/module and wires with known good ones and no change. any thoughts, thanks

Try a new fuel filter.
Good Luck

Put some water remover in the tank.

Fuel filter, 2 cans of dry gas, and at the worst case, a low fuel pump pressure. Have a pressure check if injector cleaner, filter, drygas does not work.

No codes indicates an obviousity, in my opinion.

Check manifold vacumn-if low at high speed could be partially clogged cat. If you have over 100,000 miles on car it is a possibility- might not have a bad code yet. Other posibility outside of fuel is ignitiion advance under open throttle- could be a bit retarded from knock sensor holding it retarded, wouldn't affect part throttle run even with somewhat poor gas. Some gasoline deliveries can have a bit of water or extra ethanol now.

Big plug gaps.Friends car had 3 plugs with little ground electrodes left.Gas problems usually show up pulling long hills.

Or a few tankfuls of E10 (1 gal. of alcohol per 10 gals fuel), plus a little higher octane. Engine computer will "tune" engine to run with better fuel.

It seems a pump is a common prob on these with high miles, this one has 150k. How do I check fuel pump pressure ? there is no scraider valve on the fuel rail? The filter is an obvious thing to try but I must admit I have not done, but will tomorrow. The onset of the problem was quick however. might add that it is much worse when warmed up. No engine light makes me think something "simple" as well. thanks for the ideas

I put a valve on the side of my Chevys fuel filter so I could check the pressure once. You will need a new filter but is one way to do it.

To check fuel pressure you need a special adapter that goes in between the fuel rail on the engine and the fuel supply line from the pump. I would check the fuel filter. Not very expensive and probably needs one any way.
The only "dry gas" products that remove water have alcohol in them. Too much alcohol and it will run lean. I don't recall the cavalier having E85 capability back then. Most of the time the pump either works or it doesn't. That being said I had a 07 Avalanche today with a lack of fuel problem. Fuel pressure held with the engine off over the weekend. The fuel pressure was a little slow to build and fell off when calling for more than 10% throttle while driving. Either the pump was bad or the fuel filter was clogged. Don't know for sure. The filter is built in to the pump. To change the filter you have to change the pump. A new pump and all was well.
Check the plugs. Gaps too wide can cause hesitation. Bad enough would set misfire codes. Running poorly over a long time period can clog the catalytic converter. A clogged catalytic converter won't make it buck. It will just be a real turd.

If it Bucks, that means it's not broke in yet..

Had an '01 Sunfire in the shop with similar problem.Found a bulletin for a reflash on it and took care of the symptom.Here it is:

File In Section: 07 - Transmission/Transaxle

Bulletin No.: 01-07-30-026

Date: September, 2001

TECHNICAL

Subject:
TCC Surge/Chuggle/Slip at 72-96 km/h (45-60 mph) with Automatic Transmission 4T40E (Reprogram PCM)

Models:

2001 Chevrolet Cavalier
2001 Pontiac Sunfire
with 2.2 L engine (VIN 4 - RPO LN2)
and automatic transaxle (RPO MN4)

Condition

Some owners may comment on a TCC surge/chuggle between 72-96 km/h (45-60 mph) under a light load with the engine at operating temperature and TCC applied. There will be no stored DTCs. When in the condition, a Tech 2 will reveal that TCC slip will oscillate for multiple consecutive cycles (3 or more) between 20-300 RPM slip. The driver may notice a fluctuation in the tachometer at steady highway speeds and may also notice a vehicle surging sensation.

Cause

Condition may be caused by a variation in the torque converter clutch slip speed.

Correction

Test drive the vehicle. Look for a fluctuation

of 20-300 RPM in the torque converter slip speed with a steady TCC duty cycle of 25-50%. Commanding the TCC fully on (99% PWM) will eliminate the concern. If the vehicle exactly duplicates the above conditions, recalibrate the PCM with the appropriate calibration. Remember that the calibration is VIN specific. When you enter the VIN, the correct calibration will appear. The calibrations listed are electronic calibrations and are NOT available from GMSPO. Calibrations will be available from Techline starting June 2001, on the TIS 2000 version 7.0.

i agree with the good idea's about plugs,fuel pressure and such . one test i started doing on cars that die,buck ,is to check the ohms on each injector.i think that car's injectors should have 10-12 ohms . one bad injector can shut down or scramble the drivers in the computer that control everything,,all with with no c.e.l showing. lucas

Lucas is partially right. If the resistance of the injectors starts dropping below 10-12 ohms, the PCM will disable that injector and in this case only drop that cylinder. Older fuel injected GM engines used a batch fire system (non sequential) meaning that half of the injectors are pulsed then the other half are pulsed. If you had one or more injectors resistance going low you lost one or both banks of injectors delivering fuel. No fuel no start. Most common complaint would be a no start on a hot engine. In this case only the one cylinder would drop and the appropriate P200 code for the injector circuit and a P300 for misfire detected would set with the MIL on.

Hi Jay,

Since there were no codes set, I'd would look at the CV joints looking for a bind in a cross "T".

On any puter controlled vehicle, the first sign of any trouble I reset the ECM to the system defaults, (disconnect the battery). If there was truly a problem, new codes will be reset and the problem will persist.

T_Bone

(quoted from post at 16:52:16 12/01/08) The onset of the problem was quick however.

Click to expand...

Any screwy weather changes that would cause your tank to sweat while you didn't keep it full? Did you change fuel recently (octane?) I've gotten bad gas before also, no matter how much the station tried to explain their filtering system. Maybe take you a can of gas from a different station, take a drive and run the car completely out of gas, put in the can and go fill up at the station that gets the most business. Maybe a bottle of injector cleaner and dry gas also. May take care of you.

Dave

that gives me an idea about my injected 2.5 it is hard to keep running at start up after it is warm and if you drive it across a parking lot it is fine

sounds like the answer to his problem gooooood info

I had a Chevy pickup that did that.Fuel filter and new fuel pump fixed it.