Help! 99 OBW hesitates on accel

[G K Russell]

When engine cold no problems. When warm, engine stumbles from idle (700rpm) on accelaration in neutral & 1st gear, all other gears stumbles upto ~1200 rpm on accelaration. I'm running 94 octane & tried fuel injector cleaner through the tank (mild temporary improvement) & done the throttle body with an aerosol cleaner. I can't find any air leaks. What next? I'm thinking maybe IAC valve or plugged cat? Car has 125000km & had the 'big' service done at 100k by dealer. I have noticed that the fan cycles on & off at ~1 minute intervals almost as soon as the car is started way before it gets to operating temperature, not sure if its related. Any thoughts/suggestions appreciated.

Gavin.

 

[Jim Stewart]

When engine cold no problems. When warm, engine stumbles from idle (700rpm) on accelaration in neutral & 1st gear, all other gears stumbles upto ~1200 rpm on accelaration. I'm running 94 octane & tried fuel injector cleaner through the tank (mild temporary improvement) & done the throttle body with an aerosol cleaner. I can't find any air leaks. What next? I'm thinking maybe IAC valve or plugged cat? Car has 125000km & had the 'big' service done at 100k by dealer. I have noticed that the fan cycles on & off at ~1 minute intervals almost as soon as the car is started way before it gets to operating temperature, not sure if its related. Any thoughts/suggestions appreciated.

I'm surprised you don't have a check engine light.
If if were mine, I'd first check for trouble codes.

 

[oothlagre]

A plugged cat will kill your power big time.Acceleration will be very sloppy.

My guess would be to check throttle position sensor, crank sensor and maybe cam sensors.

Take it in to AutoZone and have them read the codes for you to see if there are any.

Henry

 

[X-Eliminator]

check the fuel pump pressure, and replace the fuel filter.

 

[JW]

When engine cold no problems. When warm, engine stumbles from idle (700rpm) on accelaration in neutral & 1st gear, all other gears stumbles upto ~1200 rpm on accelaration. I'm running 94 octane & tried fuel injector cleaner through the tank (mild temporary improvement) & done the throttle body with an aerosol cleaner. I can't find any air leaks. What next? I'm thinking maybe IAC valve or plugged cat? Car has 125000km & had the 'big' service done at 100k by dealer.

Hi, when mine acted this way and I did the same as you and got a temp improvement after running injector cleaner through it, I was plagued for weeks. Turned out my fuel filter was mostly plugged!

 

[John (archive)]

check the fuel pump pressure, and replace the fuel filter.

Fuel filter will get you every time.

Does your siggy suggest you had an Eliminator? What year?