Hello gentlemen. I recently changed a fuel filter on my Blazer 98 4.3L vortec. After this a problem came. The engine doesn’t go higher than 1500 rpm. When I try to push accelerator more the rpm even gets down and P1133 code comes. If the engine is less than 1500 rpm any trouble isn’t seen. What may be the problem?

 

P1133 - HO2S Insufficient Switching Bank 1 Sensor 1

Sounds like your B1S1 sensor is getting lazy. To be sure, you could switch the sensors side to side and see if the code follows over to B2S1.

If it truly can not make it past 1500rpm, then you may have a restriction in the catalytic converter. When you switch the sensors side to side, leave one of the sensors unplugged and out of the y-pipe. This will relieve any build up of pressure that may be resulting from a clogged catalytic converter. Be aware that this will be loud, but rest assured that it won't damage anything if only attempted for a minute or so.

 

Thank you for advice. I will try to do so this weekend. Hope it will solve the problem.
The only one think that I am wondering why it happend exactly after the fuel filter was changed. Is there anything around the filter the may cause the problem if was disturbed ? Just one month ago the truck got passed emission test without problems.

 

So, left and right(B1S1)and right (B2S1) were switched today. No trouble codes come now. Anyway the engine speed doesn't go higher then 1500 rpm. The same is true with one of the sensors unplugged. Any other ideas what it could be? Thanks.

 

Check the fuel rail pressure. Make note and put the old fuel filter back in and remeasure. Just a quick thought. Hope this helps. Dave

 

But did you leave a sensor unscrewed out of the y-pipe to see if it relieves exhaust pressure? This will show if there is a plugged up cat.

 

deffinitly sounds like restriction issues follow the advice given on unpluging the sensor all the way for exhaust relief also another thing did it have any symptoms of blockage before you replaced the fuel filter?

 

It does sound like flow restriction in the exhaust. But in keeping with the theory of being thorough, I would suggest taking a look at the fuel filter again.........if this started after the fuel filter and was not a problem before you replaced the fuel filter.