AxisOfOil

99 Camaro with an LS1. 120k miles, lt's, lid, !cats, otherwise stock.

Lately I've been having reduced gas mileage (down from 25-27mpg to 18-20mpg), and occasional times when the car won't start right away, sometimes for as many as 10 or 15 attempts to crank it.

I have P0171 and P0174 codes that come up as soon as the engine warms up while driving... stop/go or highway, low acceleration or high.

I occasionally also get a code for idle RPM being higher than expected. P0507

No hesitations or rough driving or idling.

So, is this a headgasket problem? Somewhere I read that burning coolant can set false lean readings... but it's set on both banks, so I don't think so.

I couldn't find a vacuum leak with carb cleaner. I don't have access to a scan tool (unless someone in the prescott/prescott valley, az area wants to lend me one), and don't have the money to just throw parts at the car until the problem is fixed.

Any ideas?

joshp14

iTrader: (5)

Sounds like a fuel pump. I would check fuel pressure to start.

AxisOfOil

~52psi ignition on, not started.
~60psi idling.

Just tested. Sorry 'bout the delay, don't have too many nice tools like a pressure tester, had to borrow it from autozone.

joshp14

iTrader: (5)

What happens to the pressure when you turn the car off? Does it bleed down or stay steady?

Did the idle change at all when you were spraying down the intake to head area?

Other possible problem is a MAF sensor. I would take it off and clean it and see if that does anything...especially if you have an oiled air filter (ie K&N)

AxisOfOil

Stayed steady... but was near 0 when I first put the tester on, so I suppose it might bleed very slowly.

The idle made a different noise (not sure how to describe it, but it was almost an electronic noise), the engine didn't really change rpm or noise level like it was accelerating or decelerating) when I sprayed At the front of the intake-head on the driver's side... if I hit the small metal tube that bolts into the head that is at that location.

Already cleaned the MAF, didn't help. Forgot to mention that I already checked that one. Also replaced the fuel filter and air filter.

AxisOfOil

Just checked for sure on the pressure drop after turning the car off.

As soon as the fuel pump stops, the pressure drops from 60 to 52 almost instantly.

Then, it takes about 30 seconds to drop to 50, about a minute past that to hit 48... and goes down super slowly after that.

Edit:

Just to be thorough, I thought I'd check for vacuum leaks again... and when I sprayed the front of the heads where they meet the block, the engine revved up slightly.
Does it make sense that they (head gaskets) would fail at the same time, both on the front of the block? It seems to me that that is what's occurring if that's where there is a vacuum leak.

O2Form

You have a vacuum leak someplace, checking with carb cleaner is about useless in closed loop........ !st thing to check are intake manifold bolts.

joshp14

iTrader: (5)

I beg to differ. Checking in closed loop is advised because you can monitor fuel trims while spraying the intake. If the trims go way negative when you spray it, you've found the leak. In open loop the trim learn isnt active and and the only thing you are relying on to find the leak is the chance that your idle may change or it may start to misfire. This method will find large intake leaks, but small leaks are best found monitoring fuel trims.

O2Form

Not if he isn't watching the fuel trims geez! Using carb cleaner in closed loop is completely useless unless you have a good scanner and know how to use it. Using carb cleaner is old school AND works fine in open loop WITHOUT a scanner. Hell in open loop when my intake was loose it barely ran....as soon as it got into closed loop it ran perfect!

I see see you are ASE certified..........................

AND no one should be using carb cleaner to check for vacuum leaks, proper way is to 1st visually inspect then use propane or a ultra sonic tester. Carb cleaner can equal a very long hospital stay or a visit to the local morgue. Do you have any idea how many possible ignition sources there are on the engines of today...if you diid you woooodn't EVER use carb cleaner. An unlit propane torch cracked open will not start any fires and will locate the vacuum leak just as well, infact better because it doesn't linger and give false readings. Try it before you post any stupid comments about it. BUT knowing you are ASE certified they must of taught you all the proper methods.

joshp14

iTrader: (5)

I guess I'm old school then because I use brake clean to find them and never had any ignition. I have used this method to find HUNDREDS of intake leaks on older saturn cars as well as the earlier truck engines that had so many intake gasket problems.

I know dozens of excellent techs that find them this way without any problems. So until one burns to the ground, then I'm going to keep doing it this way because its proven and it works.

By the way, ASE doesnt teach you anything, it tests what you know. I dont take much pride in having my ASE's, I take greater pride in the World Class status.

O2Form

Bet the insurance that covers your work place doesn't know you are spraying highly flammable liquids on hot engines. We all learn, usually the hard way. Not to mention spraying crap like that can ruin sensors and cause extremely toxic exhaust conditions. I know of at least one garage that had a IDIOT try spraying freon onto a running engine inside the shop.........the entire shop ended up in the hospital and the IDIOT that sprayed it died.

Bet GM doesn't recommend it....WORLD CLASS pffft......


When you are older and all effed up from spraying of all things chlorinated! solvents ! into a engine you will remember bk how someone tried to warn you.

And the dealers wonder why they have no business!

CLASSIC!

AxisOfOil

Well, since I don't have a good scanner... can't really watch fuel trims. :/

I'll double-check the intake bolts. happen to know the proper torque for them? none of them are loose enough to finger-tighten and I'd rather not break them.

And, sorry to add another question... but could someone give me a super-simple explanation of closed-loop/open-loop?

joshp14

iTrader: (5)

You're probably one of those whos out buying potassium iodide pills right now right in fear of radiation poisining from Japan right?

Yea it can ignite on a HOT engine, but typically the plastic intake isnt drastically hot. I could care less what GM says is "recommended" way to diagnose things. If you saw half the diagnostics I stared at everyday you would laugh and wonder why we have to make up so much of our own diagnostics.

Yes world class. I'll bet you dont have a clue whats involved to get it. Don't care what you think. I get paid very well for having it so "pfft" all you want. I'm done.

O2Form

89 inch lbs NOT FOOT lbs for the intake bolts. Also look at the rubber hose going to the PCV valve coming off the intake manifold. They usually need replacing.

AxisOfOil

retorqued the intake bolts. No change.

Is there supposed to be a valve somewhere on the line between the throttle body and valve cover on? (That IS the PCV, right?)

What size of hose do I need to replace it with? Seems loose, may as well re-do it, it's a pretty short piece of hose.

O2Form

Its 3/8 inch fuel line and yes it attaches to the PCV valve. If you are hangy you want to check over the entire pcv system. There is a rubber union or T at the very back of the intake that sometimes breaks open.

AxisOfOil

I feel like an uuber idiot. The hose has a tear right at the throttle body, in the little weird looking part that's about 2" long. idk how I missed that!


Hopefully that's the problem. Will let you guys know.

//edit//

Yep, that did it. No more lean codes, starts up almost instantly again... now THIS is the car that I remember.
Hopefully the gas mileage comes back.

O2Form

Yep the hose is a common problem.

Lets see the "WORLD CLASS" ASE had you down for a fuel pump and a maf sensor..........


geez I'M so glad i never got "WORLD CLASS" certified cause it seems to have a reverse effect!

I had one of these "WORLD CLASS" certified idiots work on my rear once at the local pontiac dealer uner warranty. HE RUINED THE RING AND PINION. The idiot put the factory shims back in the wrong sides after replacing the bearings. He also used a brass drift to hit on the pinion bearing races to install them and never cleaned the brass chips out that came off the drift. So the rear was full of brass chips. Cost me 900 dollars to get it fixed someplace else a week later. Yes he was "WORLD CLASS" ASE rated !!!!!!!!! <<<<run the fk away if anyone ever tells you that AND DON"T bend over any where near them!


Its clear to see why people stay away from dealers and why people waving certs around usually are bone heads.