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Hey all, 2004 6mt base model with KN air intake and Corsa exhaust.
I've read probably 25 different threads here to solve my issue:
P0101 code has shown up once or twice. I also have some mild pinging only when oil temp is 200+ and WOT at 4000+ rpm. Any other condition, I.e. around town or even mildly aggressive throttle, no pinging and no check engine light.
I've tried:
1. Cleaned MAF sensor a couple times. This did have a big improvement with the throttle response and reduced some pinging (could be placebo though). P0101 showed up again after first round of cleaning.
2. Voltage check on sensor itself. All numbers were good, 5v, 12v, 0.1v.... yellow, pink, black.... 4.3v at idle as well
3. Double checked as many hoses and connections as I could to see if something was loose. Didn't see any visible cracks or gaps.
4. First thought on pinging was bad gas, I normally do Kroger premium (91), just did a half tank of shell v nitro (93) hoping that maybe a full cleanse of that might do the trick.
5. KN air filter not over oiled, not really dirty at all.
I'm not seeing a lot of people getting both the p0101 code in combination with pinging, wondering if they are even related or if I'm going in the wrong direction with diagnosis. Any thoughts or threads I could look at would be helpful.
Edit: Feel free to read entire thread. This has been solved. Summary Below: Skip the next couple of paragraphs for the TLDR.
Just thought Id update you on what happened (Its solved!!!). I started with P0101. You and a few others led me to MAF (among other things). I also had pinging under load. This issue morphed (or exposed) a P0171, P0174 issue.
I tried a variety of things, but the important thing here was the order in which I tried fixes. One of the FRIST things I did was check MAF voltages, and then ended up replacing the MAF entirely. I am sorry to admit I did NOT get an OEM MAF... (you might know where this is going...)
Issue not fixed. Still had P0171, 0174. I then tried Techron cleaner (2 back to back tanks worth). Pinging did go away. Hmm....
I checked vacuum leaks, exhaust leaks, pretty much EVERY possible thing I've ever read online about lean codes. Nothing.
Took it to a local vette tech. After a bunch of searching and double checking, I'm getting to that the Blue Streak brand MAF (which does have a lifetime warranty) that I bought was "working" but weirdly reporting numbers lower than it should. I also had a weird issue where the hood up/down condition was reporting different numbers. My tech took the MAF under warranty back to O Reilly for a swap, and the trims were instantly much better. I've been driving for a couple days now, and the long term memory has settled to about 4-10 while driving, a little higher at idle.
TLDR What I think happened was I had a 50/50 issue of a MAF that was on its way out, and I also had slightly clogged fuel injectors (pinging under load). I essentially traded one evil for another by replacing the MAF with a bad one, while also cleaning the injectors which made it look like nothing changed.
Last edited by Schmidtstain; Oct 21, 2024 at 03:06 PM.
Since the MAF sensor uses the IAT, ECT, RPM, and MAP sensor to calculate “predicted” MAF values if you have a scan tool I’d check MAP sensor “key on engine off” (KOEO) and you should see approximately 101 kPa (29.8 inches Hg) if you are at sea level…your MAP sensor may be skewed…after car sits overnight the IAT and ECT should be close to ambient air temperature…your MAF sensor at hot idle should read no lower than 5.7 grams/second with your scan tool.
Had a similar problem a few years ago without the pinging. Cleaned MAF a few times, it didn’t fix it. Got a replacement MAF from rock auto for a 100 bucks, also installed a VR intake. Then I had a surge problem on deceleration from 50 mph down to 40 mph after installing VR. Replacing MAF fixed the check engine light. Little did I know, VR connections need to be extremely tight, no air leaks otherwise it surges. Everything is fine now. And yes, I saved my original MAF.
I don’t have a scan tool to check electrical connections etc….
All the posts by @C5 Diag sound very interesting. I wish I understood that stuff
Since the MAF sensor uses the IAT, ECT, RPM, and MAP sensor to calculate “predicted” MAF values if you have a scan tool I’d check MAP sensor “key on engine off” (KOEO) and you should see approximately 101 kPa (29.8 inches Hg) if you are at sea level…your MAP sensor may be skewed…after car sits overnight the IAT and ECT should be close to ambient air temperature…your MAF sensor at hot idle should read no lower than 5.7 grams/second with your scan tool.
You need to check MAP KOEO not idling !!…and ECT and IAT after engine sits overnight…I don’t see those readings…right now don’t care about idle and WOT…are you at sea level ??
You need to check MAP KOEO not idling !!…and ECT and IAT after engine sits overnight…I don’t see those readings…right now don’t care about idle and WOT…are you at sea level ??
Ahh, I understand. My reading comprehension level wasn't at its fullest...
You need to check MAP KOEO not idling !!…and ECT and IAT after engine sits overnight…I don’t see those readings…right now don’t care about idle and WOT…are you at sea level ??
You know I didn't realize I left out the first part of my response. KOEO I was at 99kpa (800 ft above sea level) Trying to do this all from a phone att side, copy and paste failed me.
You know I didn't realize I left out the first part of my response. KOEO I was at 99kpa (800 ft above sea level) Trying to do this all from a phone att side, copy and paste failed me.
99 kPa is OK KOEO…MAP not skewed !!…compare IAT and ECT to ambient temp in the morning key on…you can find a VE calculator online and see you see if your engine is breathing normally…may just be a bad MAF sensor…do your fuel trims go positive under load ??
99 kPa is OK KOEO…MAP not skewed !!…compare IAT and ECT to ambient temp in the morning key on…you can find a VE calculator online and see you see if your engine is breathing normally…may just be a bad MAF sensor…do your fuel trims go positive under load ??
Stone cold engine, key on engine off -
IAT 77F
ECT 75.2F
Ambient air 40%RH @ 78.3F
Answering previous questions as well as VE calculator data for a couple of pulls -
Pull 1
Long term fuel trim prior to WOT +21.88
WOT Short term fuel trim ZERO
VE per online calculator 72% (95F, 5769rpm, 226.82g/s, 5.7L)
Pull 2
Short term fuel trim still ZERO at WOT
VE per online calculator 67% (yikes)
Long term fuel trim settled at +6.25
I didn't see, and don't have the data for it, but these pulls were only at about 190-200F oil temp. Check engine light still hasn't come back, but lots of pinging high up still present. To my understanding, fuel trim being 0 at WOT equals more air, which would cause pinging?
No, it’s normal for fuel trims to go to zero at WOT…you can use the O2’s at WOT to see if you have issues..O2’s should go rich at WOT…I ran my VE calculator (the same one that is in the video) with the numbers you gave me and your VE is 70%…you saw 67% so we are close…80% is good so it’s looks like a bad MAF if all the wires check out OK…I used 78 degrees so if it was 95 I’ll redo tomorrow.
Than you @C5 Diag for all your help. I salute you for your Corvette diagnostic services!
I'll grab a new sensor on my way home from work tomorrow and give it a go.
Ran your VE test at 95 degrees and came up with 73%…since your engine has difficulty “breathing” maybe look for cats that are starting to clog….one quick check is to see if your IAT is increasing under load…hot exhaust gases are backing up into the induction system.
Ran your VE test at 95 degrees and came up with 73%…since your engine has difficulty “breathing” maybe look for cats that are starting to clog….one quick check is to see if your IAT is increasing under load…hot exhaust gases are backing up into the induction system.
The IAT was definitely warmer under load. However, there was another post from 2013 on another forum saying they only experienced 10-20f difference between ambient and IAT (while under race conditions). I understand that sitting still after a few pulls that difference might be higher. My unconditioned garage was 78f ambient, but outdoors was 85ish. My second pull IAT didn't increase anything tangible (again while moving), so unless you think that's odd, I don't know that I do. I'll also note when I bought the car I checked the uncleared history codes through the dash and none of them indicated a catalytic converter or exhaust temp code. I've also never smelled any sulfur or anything like that.
Side note, speaking of previous codes that have never come back but might be noteworthy, one of the preexisting codes was a P0171 h code.... I've put a few thousand miles on the car since that was cleared out and it has never come back, I attributed it to never being cleared after the air intake was installed (prior to my ownership).
The IAT was definitely warmer under load. However, there was another post from 2013 on another forum saying they only experienced 10-20f difference between ambient and IAT (while under race conditions). I understand that sitting still after a few pulls that difference might be higher. My unconditioned garage was 78f ambient, but outdoors was 85ish. My second pull IAT didn't increase anything tangible (again while moving), so unless you think that's odd, I don't know that I do. I'll also note when I bought the car I checked the uncleared history codes through the dash and none of them indicated a catalytic converter or exhaust temp code. I've also never smelled any sulfur or anything like that.
Side note, speaking of previous codes that have never come back but might be noteworthy, one of the preexisting codes was a P0171 h code.... I've put a few thousand miles on the car since that was cleared out and it has never come back, I attributed it to never being cleared after the air intake was installed (prior to my ownership).
P0171 is saying that your Long Term Fuel Trims on bank 1 reached 24% at some point.
Well...
Wasn't the MAF sensor. Replaced the MAF sensor, let idle until it got to 200 oil temp.
Drove around a bit, had to come back as my right rear tire pressure was blank on the dash... not sure what that's about. Checked pressures and started the car again. Within about a minute or two of idling I get P0171 and P0174...
Reset the codes (saved the pdfs) and went down the road a bit to see if it would come back
Hard pull with oil temp at 228 (just wanted to see what the other data looked like)
136.4F IAT, 5834 rpm, 122.52 MAF g/s, 5.7L (41% VE calculation, this was at the highest rpm, the previous "frame" was 60%)
So So So much pinging.
Well...
Wasn't the MAF sensor. Replaced the MAF sensor, let idle until it got to 200 oil temp.
Drove around a bit, had to come back as my right rear tire pressure was blank on the dash... not sure what that's about. Checked pressures and started the car again. Within about a minute or two of idling I get P0171 and P0174...
Reset the codes (saved the pdfs) and went down the road a bit to see if it would come back
Hard pull with oil temp at 228 (just wanted to see what the other data looked like)
136.4F IAT, 5834 rpm, 122.52 MAF g/s, 5.7L (41% VE calculation, this was at the highest rpm, the previous "frame" was 60%)
So So So much pinging.
Do you have the freeze frame data for both DTC’s ??…at WOT are your O2’s over 800mv’s ??
The 2 DTC’s set at idle so with high fuel trims…that tells me it’s a vacuum leak…if fuel trims are elevated at idle raise RPM to 3000…if fuel trims decrease you have a vacuum leak.
P0101 (again...)
