poor acceleration

I'll start a new thread that's more on topic. The car is a 96 Monte Carlo with the 3.1 v6. I'm going to give up on the plugs being the problem. Took the thing for a ride and these are now the symptoms. First of all it idles fine through the entire warm up cycle. When you start out cold it runs pretty much ok. At about 2 or 3 minutes into the ride it starts to accelerate like crap. I mean really bad. First gear is not so bad but after shifting into 2nd it feels like someone tied a two ton trailer to the back. It will barely pick up speed. After it's completely warmed up it runs fine. You can drive it for hours and it performs flawlessly. I would guess it's something with a temperature sensor. Any help is appreciated.

Update. There is an exhaust leak and up until now I didn't pay much attention to it. Tonight I got a better look at it because when you first start the car the leak is bad (loud). Then as it warms up it gets quieter and pretty much goes away. And ironically the thing starts running better the quieter it gets. The leak is in the area of the ox sensor and the inlet tube for the EGR. At the drivers side rear of the engine. It may be in the coupling that joins the front to the rear exhaust manifolds. But I cannot get to the bolts because the things are surrounded with shields. And it looks like it would be a big pain to get the long shield off that covers that area of the manifolds. So my question is, would the exhaust leak and the poor performance during warm up be related? During the last ride I took I swear I could hear the thing suddenly get quieter just as the engine started running smooth. Again, any help is appreciated.

Normally during warm up the car is in open loop for a short period of time as the heated o2 sensor kicks in pretty quick, so it is possible the loss of exhaust passing over the sensor could affect performance.

Wouldn't it be giving me a service engine soon light if the ox sensor is involved? This has been going on for quite a while now according to the owner and he has never gotten an SES light.

May or may not do a full scan and what the o2 sensor is reporting to the pcm.

Wouldn't it be giving me a service engine soon light if the ox sensor is involved? This has been going on for quite a while now according to the owner and he has never gotten an SES light.

the exhaust leak needs repairing...this is dangerous as co can enter the vehicle and cause you to get injured...


this leak may be causing the knock sensors to retard timing and this will make vehicle have poor mpg and power......

It ended up being the knock sensor that was sensing engine noise. I was going to replace it but my daughter made a face when she found out she would have to pay for it. So I disconnected the sensor and it has been running fine now for 6 months.

It ended up being the knock sensor that was sensing engine noise. I was going to replace it but my daughter made a face when she found out she would have to pay for it. So I disconnected the sensor and it has been running fine now for 6 months.

So with the sensor disconnected, there's NOW a check engine light?

No that's the weird thing, no check engine light. The guy at the shop that did the manifold replace said we probably would eventually get the light but no. Lot's of clatter and tapping sounds coming out of the engine when it's cold but no hesitating during acceleration. Almost all the noise goes away after about 10 minutes of warm up.

No that's the weird thing, no check engine light. The guy at the shop that did the manifold replace said we probably would eventually get the light but no. Lot's of clatter and tapping sounds coming out of the engine when it's cold but no hesitating during acceleration. Almost all the noise goes away after about 10 minutes of warm up.

You got a history code in there. Promise.

Unpluggin' the KS will trip a code for 'POxxxx; Open Circuit KS'. Verbatim. :smile:

Default mode will then retard timing to near 0 degrees advance, low power, gas mileage tanks.

ever think that your catalytic convertor might be clogged???had the same sounds with my 95 camaro 3.4L v6 convertor was clogged and when warmed up made those sounds..abnd the car felt like a slug on accelaration...........

She has an oil change coming up so I plan to replace the knock sensor then. With the sensor connected it runs like crap until it's warmed up and the engine noise quiets down. So it is the sensor that is causing the retarding of the timing during warm up.