Replaced coils, plugs, filters, pvc valve, cleaned MAF and IAC units. All vacumn lines are connected, no leaks found. Engine idles fine, but when you accelerate the engine jerks and seems to misfire. Slow steady application of the throttle, then engine does better. No check engine indicator activity and no codes. Any ideas?

 

Plugged cat?

 

Makes sense, Its the original catalytic converter; any way to test for this? Have replaced all 02 sensors

 

You could take the exhaust apart ahead of the rear cat and push it to the side and drive it around the block. Would probably have your answer pretty quick if it was that one. The front ones would be a lot harder to diagnose, although you would think a pre-cat would throw a check engine light.

 

Sounds like a good course of action. Will give this a try and get back to you. Appreciate the prompt response.

 

May still be worth connecting OBDII reader to see if you have any pending code.

Salim

 

Thanks, just checked, no pending codes. Forgot to mention this unit has 226k on tt with all original exhaust components. Notice that there are leaks at the donut gaskets. Will start with replacing the front section and leave the middle and back alone since there is no leaks. Noticed that the center pipe, muffler and cat are all one piece. Checked on OEM parts, very pricy. Do you all know of a more reasonable priced alternative source?

 

Walker makes most of it. Rockauto is usually pretty competitive on price.

https://www.rockauto.com/en/moreinfo...373879&jsn=336

 

 

EGR. That's how it manifests. EGR and ALL plumbing to it needs to be cleaned.

 

Cat doe snot really give jerking. Gives slow loss of power, but it's linear. Car simply gets very sluggish.

 

 

 

Have replaced Cat Converters, has definitely helped the issue. Still has hesitation at higher RPMS. Slow steady application of throttle when in park yields smooth transition from idle to 3000rpm, then the engine hesitates, doesn't appear to be misfire, just cutting out. Throttle application can take it to higher rpm, but it runs rough and jerky. In drive the vehicle shifts fine through all gears when throttle is applied slowly and steady, however if you aggressively accelerate the problem returns. Idles fine, transmission seems to be fine too. Not sure how to check fuel pressure, but it seems to start and run fine, unless you are aggressive with the throttle.

 

But it's EGR like symptoms. So yes, indeed, VVT took over EGR function so maybe something is not right with VVT? Dirty strainer filters, failing solenoids?