My 99 s10 2.2 turbo seems to be running rich. My cheap ebay guage maxes out on the rich side anytime I'm on the gas. When I watch the upstream data on my scanner I see as high as 1.1v when on the throttle. I replace the upstream 02 with a new denso and put a fresh set of tr 6 plugs in it. This did seems to help a little but not much. I turned the boost up from 6 -8 psi just tinkering with it and it made no difference. Could I get some input on the next set to correcting this. Also it's Werth mentioning that the truck was tuned in the middle of winter in a shop that was around 50f and it ran great in the cold weather but ever since it started getting worm out ( in the mid 60-70s. This problem has started

Have you checked you fuel pressure? Have you tried looking for a boost leak? Is it rich in normal operation at all or just when in WOT? Is your MAP functioning properly? There are some places to start.

Thanks for the reply. I have ruled out a boost leak and replaced the upstream 02. The 02 reads 1.1 most of the time and it seems like it is having trouble going in and out of closed/ open loop. I have not checked the map. Or fuel pressure yet though my next thought is the regulator. How would I check the map sensor?

Also do you know off the top of your head what fuel preasre I should be looking for? I borrowed a guage from a friend. I was also reading a write up on the fuel pressure regulator and it sounds like this could be my issue. When I'm just cruising my 02 volts will read good between. 0.2-0.9. It's when I give it throttle that it goes lean and voltage is pegged at 1.1. I'm thinking this is causing the system fail reading in between open/closed loop. Sometimes it will stay open untill I turn the car off and restart. Does this make any sense?

I checked fuel preasure today. With key on not running I have 40psi . When running I have about 38psi. When I disconnect the regulator I have around 47. It on goes rich at wot. But sometimes it will stay open loop. It has been hit or miss getting closed loop when just crusing. The
Map seems to be reading but today when driving the high way and closed loop was working I had a pending code for the map sensor but that went away and know the 02 voltage high code is now pending. I don't see any issues with the tps. I'm at a lose on this. ..
Any advise?

Also regarding the fuel I forgot to mention that when I have the gauge hooked up and turn the engine off the guage drops so it's not holding preasre when I turn it off

Also regarding the fuel I forgot to mention that when I have the gauge hooked up and turn the engine off the guage drops so it's not holding preasre when I turn it off

More than likely not going into closed lop could be 02 sensor related, but the fact you have codes coming and going that very well could be your issue.

Now when you go WOT you are running off the tune, so if the car is lean or rich it is either tune related or fuel system related. how is your fuel pressure under boost at WOT?





FU Tuning

I was not ablet to check it @ wot today but I will get back to you on that tomorrow. The turbo is not mounted to the manifold, it has a 12inches connecting pipe in between and last week I built a new pipe so I was wondering is a couple of pin hole leaks In my welds could cause this? I replace the 02 when I made the new pipe because the old 02 was in the old connecting pipe and it was killing gthe sensors being pre turbo

The fuel pressure will slowly drop over time after you shut the car down, faster if you have most aftermarket regulators. If you are running a scanner that can monitor sensors, you can see the MAP either work or not. If I remember correctly, closed loop should enable once the O2 heater finishes cycling and the reading is within correctable tolerance, I don't think it should be effected by anything else. Now, any exhaust gas leak pre-O2 will skew the sensors reading, would I presume a couple pin holes in the weld would cause your issue, not but can't rule it out completely. Can your scanner read you injector pulse duration?

holes in the exhaust would make you read lean not rich. You'd be lean because you have extra air entering the exhaust, hence more air then fuel.

Thanks for the reply. So today after wracking my brain over this and pretty much out of options and things to test I just decided to do a hard reset. When I disconnect the battery I noticed that one of the negative cables had broke off its connection to the frame rail. I replaced it and I now have closed loop at idle!! I did not get to test drive it tonight but I will first thing in the morning. Keeping my fingers crossed.

Put some miles on it today and the pro lemme seems to fixed as I figured it would be. A good ground goes along way....lol. at least it was something simple. I still need to move the 02 sensor a bit closer to the turbo. I think down stream a bit far but everything is working well. Thanks for the advice guys. Much appreciated

Glad you found it, good grounds do indeed mean quite a lot. Thanks Austin for adding more detail to what I botched up. I did mean to type wouldn't presume rather than would.