CudaJoe

iTrader: (1)

Hey guys, long time no chat.

Cars current setup:

-2009 Cobalt SS
-107,000 miles
-bolt ons with stock tune. (K&N intake, ZZP charge pipe, TR8 intercooler, Forge recirculating BPV, Exhaust and DP).
-LTFT normally floats around 5 to 7.

-Normally the car is tuned in the summer but Ive decided to leave it on the OEM tune since my summer tires are spent and I want to get some more mileage out of the all seasons before they are 6+ years old.


SYMPTOMS:

- CEL is on. code is p2188 "rich at idle?"
- wont boost past 5 psi.
- as the car accelerates the LTFT climbs rapidly, short accel went from 8 LTFT to 15.
- staying out of boost, the LTFT drops back down to 7-8 LTFT
- No sounds heard during initial CEL light up, (no blown off Charge pipes are exploding ICs, etc.) Light just popped up, and it feels like a leak.

Any ideas? I am going to make a boost leak tester, if someone can give me a link to a solid DIY boost leak tester, that would be awesome.

ECaulk

iTrader: (6)

Here is a boost leak tester how to https://www.cobaltss.net/forums/how-...ss-lnf-223319/

Looks like others have had issues with the hpfp leaking causing the code, might check that out also.

CudaJoe

iTrader: (1)

Thanks, I will check fuel pressure on Aeroforce to see if its changed. Past threads say that if the pump is failing, you'll notice a fuel smell. Im not sure Ive smelled any fuel beyond the fuel line issue I had 5 months ago. Since then, I havent smelled fuel. But maybe it leaks into the oil. If the boost leak test doesnt yield any results (im pretty sure it will tell me something), I will focus on the HPFP.

CudaJoe

iTrader: (1)

Today I noticed a fairly rough idle this morning, felt like it was stumbling and possible about to stall. After driving around for a bit, the idle became normal.

Yesterday, I put a clean intake filter on the car and reset the code. Car feels like it drives normal, still possible boost leak as Ive only notice a PSI peak of 14 on a short pull but it is cool this morning.

This weekend I plan to check the Forge bypass valve, its been on the car for 6 or so years without me touching it. See is the spring is faulty or the piston is loose. Quick look over the charge piping and vac lines didnt show anything real evident. I peeked at the intercooler from underneathe and through the grill as best I could without taking the bumper off, no cracked welds visible but doesnt mean they arent cracked on the back side. I will take the bumper off this weekend to check.

The car now hit 107,000 miles. Ive never replaced the sensors so Im thinking it would be a good idea just to replace, the MAP/ TMAP/ MAF/ and Upstream O2 for preventative maintenance if that may also solve the issue, great.

I think I will also give the home made boost leak tester a try as well but something tells me its a failing O2 sensor. Another check would be to switch to the 2nd PCM I have which has a 24 psi tune and see if I hit 24 psi or if the symptoms carryover to a 2nd PCM.. Would rule out failing PCM.

CudaJoe

iTrader: (1)

So Update: I am confused now.

Code has not come back. Fuel trims are holding around 7.8 to 8.0 under acceleration. Does not feel like a boost leak, fuel trims not climbing during acceleration. I am hitting 15 psi on the stock tune with ambient temp around 48*F.

Everything seems normal? I am still checking the BPV this weekend because I think a possibility is the Forge units spring is worn out or too soft and created the boost leak symptoms. Another possibility is the sensors are old and need to be replaced. Looking at replacing the O2, MAF, MAP, TMAP still. Im worried about replacing the one on the lower charge pipe as I know that plastic charge pipe can get stripped when messing with the screws.

Can anyone provide the GM part# ACDELCO part#s for those sensors? I believe I found them but want to verify and I am not sure about TMAP and MAP. Which ones located where?

C0balts5

I've noticed with my lnf, any fuel or emissions related codes with make my idle rough on start up and I will either never have enough boost, or it will spike 30 psi and hold 25 when it's only tuned on 23psi, I don't know if it's the tune the previous owner put on it or what, but it sounds identical what happened happened with yours. I know mine eats 02 sensors every other year and one time I missed a shift (due to the clutch taking a crap) and my car somehow sucked map sensor through the engine. I've already had to replace the hpfp but that was due to it completely failing and the car fell on its face because it was running solely off of the low pressure pump. I honestly don't know which direction to tell you to go other than drive it and see what pending codes pop up.

CudaJoe

iTrader: (1)

yep Im just driving it now and waiting. Nothings happened. Drives normal, everything appears normal. Code might have been a fluke?

My LTFTs at +2.1 now and holding. so weird. Ive done some hard pulls and it doesnt move. I do think replacing the sensors would be a good idea but im also the type of person that follows the principle "If it aint broken, dont fix it". replacing sensors might open a new can of worms lol. I'll buy they and sit on them till something wonky happens again.

CudaJoe

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And the code came back yesterday afternoon. Same code p2188. So after a much thorough scrub of Css.net about leaky HPFP, I saw a comment about checking the dip stick after a few hard pulls and seeing if there was a raw gas smell.

Sure enough, pure gas smell coming off the end of the dipstick. Gentlemen, I think the answer is clear here. I have a leaky HPFP. Apparently what happens is gas seeps by the seals and mixes in the oil, the fuel vapors end up getting sucked into the PCV which routes back to the intake system this causes the rich fuel code even though I personally am not seeing crazy long term fuel trims. It did not feel like a boost leak when I reset the code so it actually makes sense that this is the issue.

I am going to attempt this repair myself. I think I am pretty good with a wrench and everyone is saying this is an easy fix. I know the pump is a good $350 - $450 so Im sure the dealership would be a money bath.


Before I make the committed jump on a $350+ pump, does anyone have any other suggestions or possibilities for gas smell in oil or what the p2188 code is for if not the pump?

Edit: Also while im doing the HPFP replacement, what other things can I easily replace or should replace?

On ZZP website, this is what I need correct?
https://zzperformance.com/collection...sure-fuel-pump

It says bolts and gasket not included? I am sure I can reuse bolts but what about the gasket?

ECaulk

iTrader: (6)

Well that sucks. I dont hace sn experience with that issue but interested in the fix.

CudaJoe

iTrader: (1)

Someone on my facebook group suggested that the gas can also get in the oil from a leaking injector. Im not sure thats true though. I think if anything you would smell gas outside the vehicle when you park the car, not in the dip stick. He also mentioned the car would be running lean and not flag a code for p2188 rich at idle.

I can understand how the car would run rich at idle with fuel vapor getting sucked into the intake. It does actually have a very positive LTFT at the moment so that backs his statement of running lean.

ECaulk

iTrader: (6)

Going from memory but the injector is completely sealed off from the oil system

CudaJoe

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I am sure enough its the fuel pump to go ahead and buy a replacement. Ordered from Rockauto although that ZZP one was probably cheaper, I wasnt sure about the missing gasket thing. rockauto also sells the fuel line release tools and new fuel line so its easier to grab everything at once. At 120k miles, I will replace spark plugs, O2 sensors, MAF, and MAPs. maybe injectors if I think I can do it. Looks like a pain to get to.

ECaulk

iTrader: (6)

If you have the fuel pump off do the injectors also, you just have to pull the intake manifold which half the stuff you pulled for the hpfp will be out of the way. Plan on doing some valve cleaning while there since you're at that point. Get some gun brushes and some picks and carb cleaner

C0balts5

I replaced my fuel pump with the zzp performance one, came with the gasket and 0 ring, g.m. states that the fuel line is one time only use that goes from the pump to the rail but I did the old good and snug method and didn't have problems. I don't know if I would go messing with the injectors since it's direct injection, i know with Acuras they have a one time only use set of seals on the ends of the injectors since they go directly into the combustion chamber and have to seal against combustion pressures. If you had a leaking injector more than likely you would get misfire codes, hard starting and plug fouling due to flooding from the injector bleeding off rail pressure overnight.

CudaJoe

iTrader: (1)

Thought didnt even cross my mind. Thanks. I could see whats going on in the valves. How does one remove the lower charge pipe? lol. I have never actually seen it connected to the throttle body.

I will need to rotate the engine to close valves correct? What is the easiest method to rotate crank? Will I need to remove plugs if intake manifold is off?

ECaulk

iTrader: (6)

A long ass screw driver to go through the front grill to access the clamp on the throttle body.

Yes you have to rotate the engine, but you can access the crank bolt to rotate it. It helps if the plugs are pulled, but you can turn it over with them in (just requires more force).

CudaJoe

iTrader: (1)

ive added spark plug and Cam solenoid replacement to my list of things to do. I remember awhile back I was having a code for the intake solenoid. Spark plugs were last changed near 60k miles so that probably a good idea. Also PCV valve.

Any recommended gun brush? I know they come all different sizes and styles, I am assuming you mean the spiral brass bore brushes right? like this?

Access to the crank bolt is visible where passenger wheel is correct? take wheel out and I should see an access space? or am I gonna have to take all the liner out of the way?

ECaulk

iTrader: (6)

That one seems a bit large, although for the main part of the intake runner it could work well.

Something like:
Or harbor freight sells a engine brush kit that works well https://www.harborfreight.com/engine...-pc-63732.html

I don't recall from memory about the wheel liner, but I think it has to be at least partly removed for access

CudaJoe

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alright thanks, thats what I was trying to figure out. I didnt know what diameter the brush should be. I actually have some beer line brushes and tap brushes that look like the 13mm reagent bottle brush you posted there.

ECaulk

iTrader: (6)

They'll be destroyed and certainly un-usable for cleaning beer lines after the valve gunk gets on them

CudaJoe

iTrader: (1)

Oh yes Im sure lol, I bought the new brushes. Funny thing, so I said the code came back. It never tripped the CEL but I saw it pending on the Aeroforce scan gauge and notice boost only hitting maybe 5 psi (limp mode). Its gone without me clearing anything and the boost is back to normal. so strange, I thought once a code was logged, it stayed until it was cleared.

Im going to be brewing beer next Saturday May 4th, then I have vacation May 10th, so the fuel pump change/ valve cleaning will have to wait till the weekend after that. I should be okay with gas in the oil right? it doesnt wreck the internals or combust?

ECaulk

iTrader: (6)

As long as it's not to much fuel, to much fuel and it can wash away the oil film. If you go on long drives it shouldn't accumulate enough to be an issue.