Help with P0174 and rough idle

[Sinister]

So, a while back the car started stalling out under hard braking. A long time ago this happened and it was the large vacuum hose on the passenger side which was replaced. I just got the car back from my brother and now it wont hardly start or idle.

I hooked up the scan tool and it was showing a P0174 Lean bank 2 and cat IM not ready. I cleared the codes and hooked up the live data.

Everything looks pretty normal as far as I can tell except the following:

O2S B1 S2(v) = 0.0 (opposite side of lean code)
LTFT B2 = 29.7 constant

STFTs look reasonable, code hasn't returned yet but car is barely running.
MAF=0.7.5
Fuel P=37.9
MAP=16

I am going to pull the MAF and give it a spray.

Any help is greatly appreciated!!! And thanks for the forum!!!

[Sinister]

I made some live data while revving motor about 2k rpms.
STFT bank 1 = +8
STFT bank 2 = -9

if that helps

[vegasmarauder]

If that FP is Fuel Pressure, its too low. 40# is minimum value, should be in the mid-50's to 59-60 for optimal.

First order is to change the fuel filter if a low pressure reading. And stay away from the Made In Taiwan ones, they go bad in about 10K miles and wont maintain pressure at RPM's.

If you still get a low reading look at fuel pump to be failing.

[Marauderjack]

40# FP is too low?????

My FP with the high output Walbro pump and ProCharger is only about 38#-40# at WOT....been that way since 2005 install and even now with 158K miles on it!!

Pressure does go up when the engine bay is HOT to prevent fuel vaporization but normally runs around 39#!!

I suspect he has another problem.....bad O2 sensor......bad cat??:cool:

My $0.02 FWIW??:beer:

[justbob]

What he said^

What's your mileage? Probably time for an o2 sensor is all.


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[Sinister]

It's only got 172000 miles on it.

[Sinister]

I replaced the upstream O2 sensor bank 2
Cleaned the MAF
Checked all vacuum hoses
Replaced the plugs on bank 2

There is some residue around the upper intake manifold gasket, I ordered a
replacement gasket but suspect that would cause both banks to lean.

Still running rough, hard starting, exhaust sounds like a twin cylinder.
Sounds almost normal under part throttle.

Thanks for the responses!

[justbob]

Was it replaced with a motorcraft one? Most FLAPS only carry one part number for front and rear, and the one they sell is really only the rear. The fronts run ten times the voltage of the rear.

Rockauto.com offers the best deals.


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[Sinister]

I could only get a bosch 15717 today, and it is indicated same upstream and downstream.

Oh yeah, the live data is showing high negative #'s for STFT Bank 2.

[justbob]

It is not and can not be the same. Do you have an Xcal? You could data log and make sure both fronts are bouncing rich to lean around eight times every ten seconds.

The front ones monitor the gases and tell the PCM to richen or lean out that bank and run up to 1 volt. The rears monitor what the gases are exiting the front cats and report back but only run .1 volt from what I recall. Either way you are over double the lifetime for o2's. I think I paid $78 for both shipped from Rick auto at 60,000 and she ran better than ever. Data logging showed one lazy at rich and the other lazy or pretty much stuck at lean. They are what determines you STFT's.


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[justbob]

Something else to consider would be a bad EGR / DPFE.


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[babbage]

I say look for a vacumme leak. Is there a hose clamp on drivers side air hose, throttle body coupler etc.

[sailsmen]

Idle control valve? It can stick. You may have more than one issue.

[Sinister]

OK, finally did a compression test. No compression on cylinder 1. Pulled the valve cover and two exhaust rockers just laying there. I popped them back in and they are hella loose.
Guess it's time for a cam.

[MyO4Rawdur]

OK, finally did a compression test. No compression on cylinder 1. Pulled the valve cover and two exhaust rockers just laying there. I popped them back in and they are hella loose.
Guess it's time for a cam.

With 170k + I assume a cam but it might be something else. Also id do all 4 at once and go with crower or comp. Both really good and reliable. Going to cost you a nice penny. If its not the cam then just your rockers got loose. Check the pushrods make sure they arent bent.

[fastblackmerc]

With 170k + I assume a cam but it might be something else. Also id do all 4 at once and go with crower or comp. Both really good and reliable. Going to cost you a nice penny. If its not the cam then just your rockers got loose. Check the pushrods make sure they arent bent.

Push rods?

[WhatsUpDOHC]

Push rods?
He was up all night posting. Gettin a bit loopy.

[Krytin]

I would worry about dropped valve seats in the head.

[Sinister]

I would worry about dropped valve seats in the head.

What is the best way to determine if this is the case? I took my calipers to the lobes and didn't notice a major difference between the seated rockers and the unseated ones, but it was late and dark. How much difference would cause the rockers to be that loose?

[Sinister]

Update, visually appears that the springs are compressed and the exhaust valves are stuck open. Otherwise I should have seen compression, right?

[RF Overlord]

Update, visually appears that the springs are compressed and the exhaust valves are stuck open. That does sound like dropped seats, but on both exhaust valves at the same time? Pretty rare... You may have to take things apart to determine exact issue.

[Krytin]

Update, visually appears that the springs are compressed and the exhaust valves are stuck open. Otherwise I should have seen compression, right?
Yep. The seats are dropped or the valves are bent. Could be something could be stuck between the valves and seats but on both valves at the sametime...

Good luck with the fix. At the very least that head needs to come off.

[MyO4Rawdur]

He was up all night posting. Gettin a bit loopy.
Haha hes correct. Tipsy and loopy haha I dont even remember posting that

[Sinister]

And, here's the dropped seats...

[Krytin]

Good Luck w/the fix.
Take a look at the cam chaine guides and hydraulic tensioners while it's all apart.