Contour Enthusiasts Group Archives Forums General Troubleshooting Stumbling under load - worse when cold

Got an update on this. I've since replaced the fuel filter and ran a bottle of Techron through the tank. No difference.

Took it to the stealer this morning and paid to have the car diagnosed. Found a code P0176 (Bank 2 lean, no 02 switching). Did a check on this on the forums and found:

P0176 Flexible Fuel Sensor (which seems to differ from the description from this morning)


The sensor input signal to PCM is continuously moniterod. The test fails when the sensor exceeds or falls before a max. or min. calibrated range.

FF = flexible flue

Causes
-Open or short in FF sensor VPWR circuit
-open in battery ground to FF sensor circuit
-open in FF sensor signa; circuit
-short to ground in FF signal circuit
-fuel contamination
-short to VPWR in FF sensor battery ground circuit
-short to VPWR in FF sensor signal circuit
-fuel seperation
-damaged FF sensor
-damaged PCM

So...does anyone have any info on where this sensor is?

Check out the filter in the tank to see if it is clogged.

i would change the o2 sensors..the upstream ones..

ck42, you mensioned that you replaced the plug wires recently. Double check your wire routing. Two of the locations on the coil are REVERSE of the piston layout - I forget which off hand...

Matter of fact, I did. Everthing as it should be.

BTW...which manifold is the bank2 sensor on? Front or rear?

I may have stumbled across the cause of your stumble problem myself.

Take a look at the linkage which connects your front and rear secondary butterfly valves. This will be under the Upper Intake Manifold (UIM) just in from the manifold end nearest to the throttle body - it's round wire about the thickness of a coat hanger.

Make sure that that linkage is connected on both ends!

There is a little plastic retainer (at least on the front bank-side) that broke on mine - this disconnected the front butterfly valves. It may have happened with yours too.

An interesting thought on this...could it be that if the butterflys don't open and the ECU blasts extra fuel anyway, it would throw a HEGO failure code?

I expect it would because I didn't find a sensor on the front valve-shaft and the ECU would know that the fuel wasn't burned completely (this is measured by the HEGO) and infer the sensor was bad because the other bank was fueled the same way with a good HEGO signal.

Basically, the ECU would know something was wrong but miss-diagnoses the root-cause.

Perhaps the moderator could chime in on this idea. Frankly, a sticky about the missing retainer and what it can cause would be a good idea.

For sure the missing plastic retainer would allow the secondary valves to do something other than what they should.

Good thoughts there. It's coincidental that last night as I was looking through the service manual that I came up with a thought that maybe the secondary's control valve was not working right or maybe the secondaries were stuck in an open position.
I went to the car to see if I could even see under there and watch the linkage...but it's buried.

I may take some time this weekend and just pull the UIM and take a peek under there and make sure everything looks right. I can also pull a vacuum on the control valve and see if it opens the secondaries like it's suppose to (this is a '95 remember - vacuum operated secondaries).

You can see the linkage and vacuum motor on a 95 by looking under the manifold. The front side opening, by the water pump, has the linkage for the front butterfly array. I can stick my fingers in there and move them. When the engine is running I can see mine open/close when I snap the throttle wide open.
When you push the car hard does it miss or hold back in higher gears and RPMs? Does it knock even with the Techron in the tank? If so, it's leaning out. A lean mixture will knock more and give you lean bank one & two codes. When it's cold the engine needs a richer mixture too. I guessing the fuel pressure is low which can be caused by a bad pump or dirty filter(s).

"You can see the linkage and vacuum motor on a 95 by looking under the manifold."

I know it's under there....just can't see it with everything in place.

"The front side opening, by the water pump, has the linkage for the front butterfly array. I can stick my fingers in there and move them. When the engine is running I can see mine open/close when I snap the throttle wide open."

I'll try that.

"When you push the car hard does it miss or hold back in higher gears and RPMs?"

Nope....in fact, once the secondaries kick in, it seems to pretty much smooth out.

"Does it knock even with the Techron in the tank? "

Never has knocked to begin with.

"I guessing the fuel pressure is low which can be caused by a bad pump or dirty filter(s)."

Forgot to have the fuel pressure tested when I brought it in for the diagnostic But, I did replace the fuel filter...obviously doesn't help if the pump is having issues though.

CK42, I should've noticed the model year and didn't. The basic idea is still valid, I would think, but the description of where to look was certainly flawed. One of your later notes states that the engine smooths out at higher RPM - that sounds very familiar. Though with mine it seemed a bit variable, probably b/c the front valve shaft was rotating freely and not just stuck in one position.

Anyway, best of luck with it.

J