Throwing Both Lean Codes No Fix In Sight...

[onefstsnake]

Well Ive posted a thread on here a while back about the car running rough. Turns out I had a bad injector...
I replaced all 8 with FMS 19's

But the car still idles rough and surges from 900-2,000rpm (yes I checked the checklist...)
I get codes for both banks being lean and the car reeks of gas when running. At WOT I can see fuel coming out of the car....

I recently changed to the Cobra intake and all Vac. lines are on correctly and there are no leaks. IAC, ECT, ACT and TPS have been replaced with Ford Parts.

TPS is at .98v, FP is at 35psi w/ vac off, Timing is at 10* w/ spout out, O2 sensors are brand new Bosch sensors...

Any chance I got a bad sensor?

I also noticed there is a huge vacuum on the filler neck vacuum nipple...and by pinching this line the car nearly stalls...

Needless to say im stumped...

 

[BlownFiveLiter]

I'd bet on the fuel pressure being the problem. You're probably on the outer limits of the adaptive strategy in the computer with the pressure that low, so it's basically dumping fuel to compensate for the lean codes. If you have an AFPR, reset the pressure to 39-40psi, reset the computer, and then take it for a drive to see if your issues are resolved.

 

[302RollinHard]

X2. 35 is low. 40 psi is stock

 

[jrichker]

The 41/91 code is often the result of a vacuum leak. When you replaced the injectors, did you use new injector seal kits with new pintle caps?

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Testing the O2 sensors
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.



The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

 

[93 LX]

2nd vacuum leak!

Allen

 

[onefstsnake]

Well I seriously doubt its a vacuum leak.

I used a propane torch to propane the entire engine bay while the car was running. No change in idle...

 

[93 LX]

Lets see. You used a torch to to check for vacuum leaks? I use WD40 or Carb cleaner but to each is own. Your codes say lean, then engine is surging, your FP is 35 psi which is low. Disconnect all vacuum lines, it still sounds like a leak. I had several leaks in my 86 Stang which I just fixed and it passed smog. I had several leaks, one was the PCV hose under the intake, the second was the power brake booster, not the gasket but the booster itself had a small pin hole where it was rusted at the very bottom of the booster canister, then the hose that leads to the charcoal canister was cracked and very soft. All of these made the car seem like it was running lean with a surging idle and all.

Also check the MAF if its dirty it can cause poor idle. If you have fuel pouring out the exhaust then you could have a bad injector or a sticky injector. I would not drive the car around if this were true, you know fire hazzard and all. How does the oil look and smell, if the injector is sticky it could wash down the cylinder.

Pull the codes one time and let us know,

Allen

 

[jrichker]

Well I seriously doubt its a vacuum leak.

I used a propane torch to propane the entire engine bay while the car was running. No change in idle...

Propane leak check? Brings to mind the words of black comedian Richard Pryor " Fire is a wonderful depilatory" after he roasted himself with second and third degree burns while freebasing cocaine. I would hate to hear the headline "Man roasted while working on car" on the evening news.

I would avoid using anything that had a low flash point like carb cleaner or propane. Propane flashes very easily and a hot engine compatment makes for a greater hazard. An old fashioned squirt oiler can with motor oil is a much safer and easier method. The oil gets sucked into the leak and the engine changes speed. It is messy, but it is safe.

As metioned by 93 LX, vacuum leaks can be hard to find. Diligence and inspection of every line and gasket seems to be the only way of finding many of them.

 

[onefstsnake]

I was worried about the propane igniting but the engine was pretty cold at the time.

Ever since I put this Cobra intake on it just hasnt run right.


I checked the FP earlier today and it was at 42psi w/ vacuum off and plugged...
RPM was at 1,500... Strange.

If I had a vacuum leak wouldnt a vacuum gauge show that? Wouldnt the needle jump around?

Also when I started the car this morning I got quite a bit of smoke out of the exhaust... I couldnt tell if it was gas or oil...

Ill be doing an oil change tomorrow and Ill see how it looks and smells.

 

[jrichker]

Bad vacuum leaks tend to show up as low, steady readings. A sweeping reading is an indication of too much ignition timing or a sticking valve.

Small vacuum leaks may not show much change using a vacuum gauge. The range of "good readings" varies so much from engine to engine that it may be difficult to detect small leaks. My engine pulls about 16.5" of vacuum at 650-7250 RPM, which I consider rather low. It is a mass market remanufactured rebuild, so no telling what kind of camshaft it has. Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM. The only sure comparison is a reading taken when your car was performing at its best through all the RPM ranges and what it is doing now.

 

[onefstsnake]

Update:

Changed the oil. Doesnt smell like gas. No coolant in it... No metal...
Changed the plugs on bank 1. 2-4 look pretty lean (white) but not terrible. #1 plug was covered in oil or fuel maybe both...
Checked all the vaccum lines and they have no cracks or holes...
Checked the FP again. Still reading ~42-43psi w/ vac off and plugged.

So why is the computer saying the car is lean when the FP is high and the car reeks of fuel?
I cleaned the MAF and nothing... Disconnected the IAC and idle stays the same...

I also noticed when I first started it that if I pushed in the clutch the idle would decrease ~200rpm. As the car warmed up it was almost unnoticable.

 

[jrichker]

There is a vacuum leak somewhere or you have O2 sensor wiring problems. See my first post for help in how to check the O2 sensor wiring.

 

[onefstsnake]

I also noticed when I first started it that if I pushed in the clutch the idle would decrease ~200rpm. As the car warmed up it was almost unnoticable.

so what would cause this?

 

[93 LX]

Dude you have found the trouble by what you said above. The problem started when you changed the intake. Could be a bad intake gasket or the gasket between the upper and lower intake.

 

[onefstsnake]

Dude you have found the trouble by what you said above. The problem started when you changed the intake. Could be a bad intake gasket or the gasket between the upper and lower intake.

I guess it could be pulling extra air from the crankcase. Could explain why its burning a little oil, which it never has before.

I really took my time with the gaskets making sure they were seated properly and even put a little RTV on them to hold them to the heads. And for the front and back seals I used the Permatex "Right Stuff" sealant, which alot of people recomend.

But heck it wouldnt be the first thing Ive messed up.

Im taking the car to Ford Tuesday. I know a few guys up there anyways. So they can mess with it. And at least ill have a 90 warranty on the work they do.

 

[MikeC]

.

 

[93 LX]

to my knowledge you do not use RTV on the sealing areas of the intake. If it dries it can casue the gasket not to seal. Edn seals are ok but never use it on th sealing surfaces of the intake or head.

 

[onefstsnake]

sorry it wasnt actually RTV it was the Indian Head stuff. Just keeps the gasket from moving.