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Discussion Starter · #1 ·
I have been trying to troubleshoot this problem for awhile now but it has beat me... so im here to ask for some help.

Recently, I bought a 98' c70 HPT with an m56 and a ton of other mods such as a k24 turbo, cat delete with 3" all the way back, rip kit, WOT box, RICA ECU, and tons of other goodies... and I have been loving it. I bought it from an owner who used to have it out on the track but moved on to other projects and has had it sitting for about 2 years, so he decided to sell it. I saw the ad and I immediately fell in love with it so I bought it and it did not seem to have any clear issues that I could see.. though it obviously needed a tune up after sitting for so long. It ran great for sitting that long and I changed the oil and checked everything over, then drove it for a few days and had absolutely no problems.. except an intake hose after the MAF that popped loose which I quickly hooked back up. After that I noticed the MIL wasn't on at all so I got kind of curious and checked if it lit up with the key on and of course it didn't...

I decided to scan it and pulled up about a thousand codes so I ended up clearing them and taking it on a drive to see what it really had going on. Fortunately, most of the codes did not come back except p0171 (running lean) and not too long after p0505 (Idle control system malfunction), which meant that I was most likely not seeing the full potential of the car. I also pulled a code for the acceleration sensor which I found had a cut wire so I fixed it and the code seemed to go away. For the other 2 codes, I ended up believing that the MAF was somehow malfunctioning possibly due to the hose popping off, so I ended up changing it with a good one off a parts s70 t5 and nothing has really changed.. though there was a slight improvement in power from before.. and that's when I noticed that the car did not have as much power as it should.

I also checked every hose I could see and looked everywhere for vacuum leaks but found nothing. I am beginning to dig more into it to hopefully figure out what is causing these codes if they're related so that I can fix it and get it inspected.. but until then i'm stumped for now. I also ended up checking the o2 sensors which my obd2 scanner claimed both to be good. The voltage on the first sensor fluctuated from 0.1 to 0.8 volts as the second one was kind of all over the place. I also noticed that when I revved the car the second sensor would drop to around 0.1 volts and stay there for about 10 seconds before it would rise back up... but im not sure if that's normal.

There is also an air to fuel ratio gauge in the car but I am not sure if it is at all accurate.. but it seems to read 14.6:1 at idle but drops to all the way down to 10:1 under acceleration... but isn't that a rich condition?

I am hoping that someone can help with the situation I am having as it would be greatly appreciated... and I apologize for the mouthful I attempted to fit into a few "small" paragraphs. Thank you!
 

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10:1 is very rich

AFR Values & Characteristics in Four Stroke Engines
6.0 AFR - Rich Burn Limit (engine fully warm)
9.0 AFR - Black Smoke / Low Power
11.5 AFR - Best Rich Torque at Wide Open Throttle
12.2 AFR - Safe Best Power at Wide Open Throttle
13.3 AFR - Lean Best Torque
14.6 AFR - Stoichiometric AFR (Stoich)
15.5 AFR - Lean Cruise
16.5 AFR - Usual Best Economy
18.0 AFR - Carbureted Lean Burn Limit
22.0+ AFR - EEC / EFI Lean Burn Limit



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Discussion Starter · #3 ·
Thank you for the response!

I havent noticed the ratio drop below 10:1 but as I said it may not be an accurate reading. If it is, then I am wondering why im still getting a lean code. I will look further into it today with my scanner and put a set of copper plugs in it... since the old plugs could likely be causing a rich condition. Either way I was going to as I have noticed a slight missfire on hard acceleration and as I said the car has been sitting anyways. I will also get better readings of the voltages from the o2 sensors and perhaps try another MAF off one of my other cars in case the one on the s70 was bad.

I will continue to post updates. I appreciate the help!
 

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When my C70 T5 was pulling that code, it ended up being the MAF that was causing the problem, and no amount of cleaning it helped. Ended up just installing a new one, problem solved


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