Hello everyone. I hope everyone's new year is off to a great start. I need some help. My 2000 monte carlo ss has a strange problem. I had a high idle problem a while back. I did a throttle body service but it did not change. So, I replaced the IAC valve, the MAP sensor and the MAF meter. Idle issue resolved. Drove great for a few months. Kind of surges climbing a grade. But, I could live with that. Then it died like it was out of fuel. Would start then die, so I had it towed home. I replaced the fuel filer. It started right up and ran. I drove it and it still had the surging issue. So, I put a new fuel pump in it. That solved the surging. But, now if sitting in park, hit the throttle and off quickly the rpm goes up then all the way down and engine dies. If I feather the throttle it stays running. But, sitting in park at an idle the rpms will fluctuate up and down about 600 rpm steadily up and down. Can someone please help me? Thank you all in advance for any and all advice.

 

Simple stuff first.
1 spark plugs new old?
2. Air filter
3. Vacuum leak?
4. there is a fuel pressure valve on those cars too. (a leaking fuel pressure regulator diaphragm.) this will cause an explosion so you might want to check that out. symptoms are similar)
Now a big one could be the Catalytic Converter is plugged ?
they will act like that How many miles on the Car?

 

Thank you drivernumber3 for responding. I didn't mention in my original post. When I replaced the fuel filter and pump, I did replace the fuel pressure regulator. And I had a new cat put on about 2000 miles ago. Air filter is fairly clean I will look for a vacuum leak. Could it be the throttle positioning sensor? That's about the only one I haven't changed in the last 1500 miles. There is no check engine light on. Oh, and car has 183000 miles on it.

 

When were the O2 sensors replaced last? Both should be replaced at the same time. Could be clogged injectors, ever have them cleaned? Also how are your compression numbers?

 

Thanks xpage. I replaced only the bank 1 O2 sensor about 6000 miles ago. I ran sea foam through it about 2 tanks of gas ago. Before these issues began. I have not checked the compression. Thank you for the suggestions. All help is much appreciated.

 

What is the benefit of using the Seafoam? Sometimes when you over due the clean up it will give you some fits.