Hi folks, I've been chasing an issue for quite some time now so I figured I would finally reach out and ask. I've got quite a bit of mechanical experience and I feel that I have a pretty good understanding of the systems on my Monte. I have attached a picture showing a dash command readout on my iPod. As you can see, I've got a very high long term fuel trim. Also, I'm not sure how the other readouts compare to normal ones. Two years ago I started searching for the issue, starting with looking for vacuum leaks. I can't remember everything I've done now, but it's been a lot. It idles rough and tends to surge slightly when an electrical load is applied to the alternator. If anyone has any insight into this issue, I would appreciate it.

Thanks,

Bryan

 

The car is definitely running rich. What mods do you have?

 

Thanks for the reply. This car is 100% stock. I even went back to a paper air filter because when I bought it, it had an oily K&N, which gave me MAF problems.

 

Do you have any codes on your CEL? Sounds like an O2 sensor Bank 1!

 

No codes or pending codes and all the system monitors are okay. I replaced both O2 sensors with AC Delco ones last year and nothing changed.

 

Did you ever replace the MAF?

Plugs/Wires/Fuel Filter?

 

Yup I've been there.

 

I should also mention that my O2 sensor voltage shown in dash command spikes continuously at idle. I'm thinking this is not normal?

 

Rich, uhhmm no. The car is very lean +16.4 means u have a vac leak somewhere. Better check all your vac lines, something is letting air get out

 

That's what I thought. As far as I understand, that high long term percentage is the computer trying to add more fuel to compensate for the lean condition. Also, I forgot that I DO have a code that comes and goes. It's the P0171 I think.... I may not remember correctly. I comes on during long hauls of 1000+ kms. I have tried various times to find a leak. The latest time I used a can of ether and couldn't get a noticeable response. Before posting here, my next step was going to be the replacement of all gasket above the heads.