17 Elantra 2.0L low end torque misfire

Hello friends! Im Lew. I hope i poated this correctly, admin please correct if needed, forum layouts mess with my head lol
Heads up, this is a long one. If you do read and decide to respond, thank you greatly in advance. Seriously.

Let me give you a quick backround on myself and my car.
Im no mechanic. Just a simple lube tech manager that loves cars fast or slow. Iv always loved cars but never thought about getting into the field since i was busy getting in trouble. Last year when i got this car i decided to do my own work since pepboys tried to tell me my rear drum brakes were the reason my brand new front brakes and rotors were grinding. Now iv worked with around mechanics and have asked millions of questions. I knew that wasnt the case. And i was right. So here i am...a year later still full of passion.
I own a 2017 hyundai elantra 2.0L.
(Its not modded, just custom exhaust, and intake and suspension)
Got it last year at 111k. Currently at 149k.

Anyways, let me show you how deep my rabit hole is. Ill make it as short as i can aha..

August 2023- P0017. Timing chain jumped due to a dowel pin inside the vvt phaser getting stuck inside the exhaust camshaft. Manufacturing error. Hole drilled too deep.
This was my first big job on a car. Yes i did it. And yes i also screwed up. Off timing by few degrees. Car still ran till febuary this year. I had to constantly restart the car twice to get out of limp home mode. No bent valves, etc.


Febuary 2024
Dropped my brother off at airport at 1am. On my way back, right before my exit i started losing power.
I had just replaced the spark plugs an coilpacks in November. So im assuming fuel injectors since they take forever to warm up and were noisy.
For several weeks the car ran a bit but had this weird thing when starting. The car will start normal and idle normal. But when i needed to turn car back on to get out of limp mode, the car starts up rough barely tryna turn on.
Replaced injectors and catalytic converter. Nothing chnged.
Heres the rabit hole.
I started with the fuel pump. But ever since that day, the car was immovable. Never the same. I avoided the risk of making things worst so its been sitting.

Other symptoms:
Hard start after engine is hot.
Long start
Contant Misfire (no misifre code)
And the most weirdest! If i get the car running, ill try doing some revs and itll misifre by 3k so bad nearly stalling. The higher rpms sound fine. ill also hear this popping noise in the intake as i rev and it starts misfiring. Doesnt happen every time, maybe 3-5 pops out of the 10 revs.
ENGINE CODE:
P0171
P016c
So after much much research i started replacing the following according to what i understood.

Fuel filter/ Whole assembly
Fuel pressure sensor
Fuel injectors again (i assumed i clogged them since the issues got worse when i started messing with the fuel pump)
Throttle body/ wgasket
Intake gasket
MAP sensor
Purge valve solenoid
Both intake/exhaust vvt solenoids
Pcv valve
Engine temp sensor
Crankshaft p. sensor
Vcm intake motor
O2 sensors Up/down
Ignition switch
Checked all fuses
Did many smoke test in different areas
Theres no vacuum leak whatsoever.
Refurbished top head (had leaky intake valve at 160psi)
Compression test each cyl. was 125psi.
(I tried to get the correct psi but could not get info anywhere, even the dealer so i wasnt sure if 125 is normal.) I ignored and replaced the top head. Then discovered cyl1 piston had alot of play. Worn out piston ring. So....i got the engine rebuilt. Paid only grand, i was expecting more.
A week ago i got the car running but still misfiring like before.
The other day, as i was adding freon, the engine boggled down and misfired along with rough idling. Lasted for 4-6sec then returned to normal idle 645-50rpm.

At this point, im starting to think its the ecu. Iv sprayed starting fluid all over the place (carefully),even the fuel lines and gas cap. Purge canister box next to tank also was inspected, sprayed an nothing.

Any idea? Its been 6months...this car needs to get up and running asap. I refuse to take it to a shop since 1 shop failed me already trying to diagnose and couldnt find anything. Plus iv done so much already to this car that many starters like me would certainly not have the balls to do. Out of determination and preserverence i kept learning an pushing thru all 15+ disappointments of buying parts and strongly believing i fixed it but to see i didnt. Iv come too far to miss out of another opportunity to learn something and deepen my knowledge within this field.
Please help me fight thru this. Thank you again for reading.

**im certain i did the timing correct btw. Took this engine apart too many times back in may and july. I followed hyundais repair procedure each time. But we'll see soon once the cars running after 20miles. 

Lol "poated". Posted******

August 2023- P0017. Timing chain jumped due to a dowel pin inside the vvt phaser getting stuck inside the exhaust camshaft. Manufacturing error. Hole drilled too deep.
This was my first big job on a car. Yes i did it. And yes i also screwed up. Off timing by few degrees. Car still ran till febuary this year. I had to constantly restart the car twice to get out of limp home mode. No bent valves, etc.

Following so far. I had one this year that sheared the cam phaser alignment dowel in the camshaft and needed a new camshaft and phaser. 

So at this point in time, the PCM is putting your engine in reduced power mode in response to an actual timing problem. You changed the camshaft, phaser etc. and drove from August to February trouble free?


Febuary 2024
Dropped my brother off at airport at 1am. On my way back, right before my exit i started losing power.
I had just replaced the spark plugs an coilpacks in November.

Okay, so maybe not exactly trouble free since you had to change plugs and all the ignition coils in November.

So im assuming fuel injectors since they take forever to warm up and were noisy.

Now you're thinking fuel injectors on the ride home because it started "losing power". What codes were set at this time?

For several weeks the car ran a bit but had this weird thing when starting. The car will start normal and idle normal. But when i needed to turn car back on to get out of limp mode, the car starts up rough barely tryna turn on.

This part I really start to lose the thread. Starts and runs normal but when it's time to restart it to cancel reduced power mode it's not happy. Doesn't sound like it was running very well of it is going into reduced power mode in the first place. In my experience, if a PCM decides to enter a reduced power mode, a code will be set. Why was this continually going into reduced power mode?

Replaced injectors and catalytic converter. Nothing chnged.
Heres the rabit hole.
I started with the fuel pump. But ever since that day, the car was immovable.

Up until you changed the fuel pump the car would start and run and move, and once you finished that job the car is "unmovable". So that finished it off, i think a fuel pressure test would be in order. Better late than never.

Never the same. I avoided the risk of making things worst so its been sitting.


Other symptoms:
Hard start after engine is hot.
Long start
Contant Misfire (no misifre code)
And the most weirdest! If i get the car running, ill try doing some revs and itll misifre by 3k so bad nearly stalling. The higher rpms sound fine. ill also hear this popping noise in the intake as i rev and it starts misfiring. Doesnt happen every time, maybe 3-5 pops out of the 10 revs.
ENGINE CODE:
P0171
P016c
So after much much research i started replacing the following according to what i understood.

Fuel filter/ Whole assembly
Fuel pressure sensor
Fuel injectors again (i assumed i clogged them since the issues got worse when i started messing with the fuel pump)

So now counting the original injectors this is on its third set of injectors. Hopefully they are good quality and the appropriate injectors for this engine. It's very easy to install problems and lean codes with incorrect injectors.

Throttle body/ wgasket
Intake gasket
MAP sensor
Purge valve solenoid
Both intake/exhaust vvt solenoids
Pcv valve
Engine temp sensor
Crankshaft p. sensor
Vcm intake motor
O2 sensors Up/down
Ignition switch
Checked all fuses
Did many smoke test in different areas
Theres no vacuum leak whatsoever.

I'm guessing you went down this path to correct the lean codes. I'm still not convinced that lean codes would have resulted in reduced power mode, I feel like there's missing information.

Refurbished top head (had leaky intake valve at 160psi)
Compression test each cyl. was 125psi.
(I tried to get the correct psi but could not get info anywhere, even the dealer so i wasnt sure if 125 is normal.) I ignored and replaced the top head. Then discovered cyl1 piston had alot of play. Worn out piston ring. So....i got the engine rebuilt. Paid only grand, i was expecting more.

Now we're spending money! What lead you to do a leak down test that exposed a leaky intake valve? Especially if it doesn't run after a fuel pump replacement. Doesn't sound relevant to diagnosis of two lean codes either. Curious, how did you find play in the piston rings after reinstalling the cylinder head, did it continue to have low compression? All this makes me think there's missing information...

A week ago i got the car running but still misfiring like before.
The other day, as i was adding freon, the engine boggled down and misfired along with rough idling. Lasted for 4-6sec then returned to normal idle 645-50rpm.

At this point, im starting to think its the ecu. Iv sprayed starting fluid all over the place (carefully),even the fuel lines and gas cap.
You could remove the gas cap, douse the filler neck in brake clean and never see any response. You don't need to waste brake clean like that anymore now that you know.
Purge canister box next to tank also was inspected, sprayed an nothing.

Any idea? Its been 6months...this car needs to get up and running asap. I refuse to take it to a shop since 1 shop failed me already trying to diagnose and couldnt find anything. Plus iv done so much already to this car that many starters like me would certainly not have the balls to do. Out of determination and preserverence i kept learning an pushing thru all 15+ disappointments of buying parts and strongly believing i fixed it but to see i didnt. Iv come too far to miss out of another opportunity to learn something and deepen my knowledge within this field.
Please help me fight thru this. Thank you again for reading.

**im certain i did the timing correct btw. Took this engine apart too many times back in may and july. I followed hyundais repair procedure each time. But we'll see soon once the cars running after 20miles. 

If lean codes are really all you have to go by and it you could use it before the fuel pump replacement but never again afterwards, I would start with a check of fuel pressure and fuel quality. Make sure nobody put diesel fuel or two cycle fuel in it.

Im sorry. I had literally answrred every question you had, then when i went to submit my reply, the session expired. Ill reply later after work. Im not retyping it, im pissed off rn.

That's frustrating, the forum logs you out if you take a while to type a response. I copy my work now before I click Submit.

Ok, so some details were left out to avoid writing a whole book. trust me i would be willing to share literally every detail but much of it is not related to the problem or is just not worthy info or i dont remember exact details to even mention. 1. No engine light was on when i thought injectors were the issue. I replaced the cat manifold a week later since i also had a bit of a exhaust leak. that was a disaster. another skill i had to learn. tappin new threads since the stud started spinning non stop. Eventually i got the cat in with no leak present and they car drove like 2 weeks. only concern at that moment was, the car still sounded funny on 2nd start up. thats when i started messing with the fuel pump. thinking itll start up if its cold just fine but that second start may not go well if the pump is failing since i was constantly turning it on and off doordashin, etc back in November when i lost my job. so doordash being my only source of income from November to mid January. Every single day. cold weather, car was off an on triple the amount of someone with a bunch of errands to run.


The car was constantly going into limp home mode since i had screwed the timing job up by 3degrees. no damage to valves or pistons. That mode is default when timing is off. tops 30mph.


The thing about the fuel test is that for my 2.0l engine, there is no port to check pressure. Only sign of pressure i have is on the topdon scan. it said something like, 0.03630psi. i just seen this today but im not sure what this number is tellin me. maybe i looked art it wrong. ill try again tomorrow based off your response.



So lets forget about the reduce power mode. The focus is the devils favorite letter and numbers p0171.

"what lead me to do a leak down test? The code p0171 mentioned many different reasons. intake valve was one. The car ran. i could turn it on, but it didn't run like it should. i let it sit to avoid making things worse.

"How did i find play in the piston rings after the head was on?" Im not sure if i mixed my sentences is but thats impossible. other than oil burning you can physically check with the head. I apologize for the mix up. Im depressed, lonely, sad, tipsy and high as ****. anytways..next.


Where do i get a fuel pressure that has some design thatll work since this car does not have a port to click or tighten on to?

Thanks for the detailed reply, I know it sucks when you loose your post, very frustrating....

I was just trying to get the time line of repairs and symptoms straight, hope you didn't take it as being critical.
So if youre focused on fixing the lean condition, you will need to know when it's running lean.
Freeze frame data will let you know under what conditions the code finally sets.
If you have the capability with your tool, graphing the fuel trim will let you know for sure.
Graph the Long Term Fuel Trim & Short Term Fuel Trim (LTFT & STFT here on out) along with engine RPM to determine if it is only lean at idle, or more or less lean as engine speed increases.
Vacuum leaks will be defeated the throttle is opened so trims that improve at higher rpm point to a vacuum leak. Trims that get worse at higher rpm or higher engine load indicate a fuel delivery issue or load measurement error.
I know you are certain the timing is correct, and I don't doubt you, but it is worth noting that if the timing did happen to be off, it would effect the engines ability to breathe, and could effect fuel trim.

might get a compression reading again and i know of bad after market parts , those oil pressure sensors need to be good , test with your scanner, they will give those symptoms.

My reply did not post. So i was forced to tow car to hyundai. Glad i did, allowed me to breath. Anyways, you were right. Fuel delivery issue. The fuel pump i had replaced was only pushin 30psi. Should be 50. Dealer wants 2200 parts an labor. Im considering having them do it. Or just save money. At this point, i just want it running.