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Discussion Starter #1
Hi, I've gotten a lot of great info off this sites old threads, but never posted before.

I had "System Too Lean Bank 1&2" codes just as my inspection was coming up. I tried checking for vacuum leaks and cleaned the MAF (with MAF-cleaner), but the code came right back after reset. So I brought it to a shop and after multiple hours diagnosing decided it was the MAF and replaced it for a grand total of $450. I was in a pinch and got it, and had to drive it for a while to see if the codes didn't come back

Now there's "Fuel Trim Bank 1&2" codes that take ~10 min to come up.
Since it came up multiple times I could see the freeze frame data. Both banks at 24% long term positive trim at idle. 800rpm, 0.5 lb/min, 0 mph.
I caught it Freeze frames 3 times since and all were at idle except One. 33 mph, 1800rpm, 2.7 lb/min.
I even tried to highway it right after clearing the codes to see if it would get triggered under load, but it kept popping up with freeze frames that showed idle conditions Even when the code posted while on the highway (I was refreshing continuously)

It's affecting bank 1 and 2, so I'm fairly certain it's not a header leak, injector leak, etc.

I'm lost. a lean idle would almost have to be a vacuum type leak. Bank 1, our rear bank, lead the LTFT in every instance, but by .5-1%. Should I be checking for a vacuum leak there?
 

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Take your MAF off and look inside of it. The sensor elements should look like the first pic. If they look like the second pic with leaded parts (resistor, diode, etc.) then you need to replace it with a genuine OEM/Seimens MAF.



 

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...$450 to replace the MAF, even if it were a genuine part, is utterly ridiculous....
"utterly rediculous" is an understatement. it takes 5 minutes to replace a MAF, $450 is a complete rip off if they weren't doing diagnostics & just changing the part. if they charged you $450 for a MAF replacement, find yourself another shop.
 

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Discussion Starter #5
Thank you for the Info!
I'll be checking that asap.

Would a Non-OEM MAF cause enough of an idle lean condition to trigger a code?
Usually MAF failing or dirty is more Lean under load, correct?

Does anyone know what the idle ld/min should be on an OEM MAF?
 

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Discussion Starter #6
"utterly rediculous" is an understatement. it takes 5 minutes to replace a MAF, $450 is a complete rip off if they weren't doing diagnostics & just changing the part. if they charged you $450 for a MAF replacement, find yourself another shop.
They said that's including the labor diagnostics, but doesn't seem like it should've taken that long though. How long can it take to plug it in, fog it, and ****. $215 for the MAF itself, $200 for labor, $30 to the government.
It was not a good day, but I was trying to fix it in time for inspection. Now I need an extension now either way.
 

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Would a Non-OEM MAF cause enough of an idle lean condition to trigger a code?
Yes, I had a cheap aftermarket MAF and it caused my fuel trims to eventually max out and throw a code.

The shop probably bought the MAF from a local parts store like Autozone or something. They sell aftermarket (useless) MAFs at ridiculous markup.
 

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Oh, and to clarify why the OEM MAF goes bad and why cleaning doesn't help. Take a look at the sensor elements in the first pic I posted. The strips are quartz glass with a metal film on them. The metal film eventually wears away, either causing inaccurate sensor readings, or going completely open circuit. If you look at the lower strip you can clearly see the areas that no longer have the metal film on them. They can also break. I pressed on them after taking that pic and they just shattered.
 

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They said that's including the labor diagnostics, but doesn't seem like it should've taken that long though. How long can it take to plug it in, fog it, and ****. $215 for the MAF itself, $200 for labor, $30 to the government.
It was not a good day, but I was trying to fix it in time for inspection. Now I need an extension now either way.
that's not so bad not that I know it was diagnostics, it can take a while to pin a problem down. $215 for a MAF, I sure as hell hope it works right. buy cheap parts, get cheap results, but when you buy parts more expensive than OEM replacement, I would expect it to work as good or better than OEM.

you said the new codes are "Fuel Trim Bank 1&2", what are the code numbers exactly? In my old 06 i4, I had some code for a few months that said "P0170 Fuel Trim Malfunction (Bank 1)", but had perfectly normal trim numbers and no performance problems. this eventually went away on it's own after a few months, no idea what caused it. my point is, what are the new codes??
 

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Discussion Starter #10
Specifically P0170 and P0173

generic fuel trim codes, and the freeze frame shows Long Term Fuel Trim as pos 25%. I think this shop just screwed me over with a POS part. I'll be verifying soon based off h8isgr8's pictures and ordering an OEM one tonight if that's the case. This place better take the other one back, It's only been a few days and the issue was never even solved

I really appreciate your help guys!
 

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So for now I grabbed a decent looking OEM one from a salvage yard for $30. It seems to be working but I need to drive a little more before the scanner would let it pass inspection. Ordering a new OEM from amazon once I know that was the problem and this will work.

I'm about to go get my money back from this shop for the part price at minimum. Kinda bugging me that I can't find a decent shop around, so I just ordered a Bluetooth OBDII scan tool. I need to be able to see live Fuel Trims and the rest for engine diags

Hopefully this is /thread
I really appreciate the help and advice guys!
 

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To be fair, the shop did diagnose the problem correctly, and they *tried* not to buy cheap crap for a replacement part. sucks that they don't know how sensitive these cars are to aftermarket sensors, most cars I've owned are much more forgiving than Hyundai. I'd take the aftermarket MAF back and try to get my money back on that, but I wouldn't blame the shop. as far as I'm concerned, they did a fair job.

If the junkyard MAF is working, I'd just leave it in & get my moneys worth out of that one.
 

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Discussion Starter #16
100% confirmed, btw

Drove far enough with the salvage donor and no codes or CEL. Shop refunded me for their pos Duralast maf.
Thank you guys again, saved me at least $100 and more time/headache with my local autoshops.

P.S. just excited and want to share: My DUNLOP Signature HPs just arrived at AAA! replacing a tie rod end tomorrow, then getting everything dialed in at AAA (I've only ever had good experience at AAA with running gear maintenance)
 

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100% confirmed, btw

Drove far enough with the salvage donor and no codes or CEL. Shop refunded me for their pos Duralast maf.
Thank you guys again, saved me at least $100 and more time/headache with my local autoshops.

P.S. just excited and want to share: My DUNLOP Signature HPs just arrived at AAA! replacing a tie rod end tomorrow, then getting everything dialed in at AAA (I've only ever had good experience at AAA with running gear maintenance)
To the peeps that provided info here, I will see if I can give "greenies".

To the OP, glad you have a resolution path.
We appreciate a resolution to issues, helps others down the road (I hate dead end threads......).
 

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Nope, can only give a "greenie" to the OP, others......sorry, I checked.
:frown2:
 

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Hi all, just been reading the past post and I have encountered a similar problem of having the check light come on with the lean codes P0170 & P0174, both reading 25% on the long term fuel trim and -3-3 on the SFT. I have changed the MAF to a generic but the code still comes back. I did the smoke test and there is an ever so small leak at the throttle body, that it was so hard to see. I changed it out for one off the wreckers which seemed to be worst than the one I had. There are no other vacuum leaks I can pin point. My next step would be to check the fuel pressure and regulator and for that i will need one of those adapters..Any ideas anyone?
 
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