2002 Ford Expedition - 4.6L No Guts

[BOUNTYHUNTER29]

GOT A 2002 EXPEDITION 4.6L THAT CAME IN THE SHOP WITH COMPLAINT OF NO POWER.

AFTER TEST DRIVE, FELT VERY SURE CATS WERE STOPPED UP. RAN BACK PRESSURE TEST AND TO MY SURPRISE THE CATS WERE OK. IT ONLY AT 1# OF BACK PRESSURE AT 2500 RPMS AND 0 AT IDLE. CHECK FUEL PRESSURE AND VOLUME. BOTH ARE WITHIN SPEC. REPLACED FUEL FILTER AND CLEANED MAF. STILL NO GUTS. MAF VOLTAGE INCREASES TO ABOUT 4.6v UNDER HARD ACCEL. FOUND NO TPS GLICHES.

VEHICLE RUNS LIKE IT HAS A POTATOE STUFFED UP THE TAILPIPE. THE ONLY CODE IN ECM WAS A DPFE LOW VOLTAGE CODE WHICH I FIXED BY REPLACING DPFE SENSOR AND HOSES. I'VE EVEN FLUSHED FUEL INJECTORS AND PULLED PLUGS TO INSPECT. PLUGS LOOK GOOD. NOT EXTREMELY WHITE FROM LEAN CONDITION.

I'M AT MY WITS END. ANY IDEAS?

[steven kiser]

i've had maf's do this. check the timing advance during rpm increase.

[ricmorin]

How about base engine? Any problems? Timing? Compression?

And what are the fuel trims at idle and under load?

Did you do your fuel pressure tests on the road or just in the bay?

[Tim Martin]

I'm old school and would hang a vacuum gauge on it. This would tell me alot. Vacuum should be at least 18 and be steady.

[liljoe]

I would look at the grams per second on the scanner, it should be around 110 gams per second at 3000 rpm at WOT, if it is much lower suspect the sensor is dirty or bad.

[BOUNTYHUNTER29]

THANKS FOR THE REPLIES FELLOWS.

I DID PERFORM MY FUEL PRESSURE TEST UNDER DRIVING CONDITIONS. I ALSO TRIED A MAF FROM ANOTHER IDENTICLE VEHICLE THAT CAME IN TODAY AND IT MADE NO DIFFERENCE. INTAKE MANIFOLD VACUUM IS BETWEEN 17-18 AT IDLE. TODAY WHEN I DROVE IT, ACCELERATING WOT UP A STEEP HILL, THE CAR WOULD BARELY PULL THE HILL.

I THOUGHT AT ONE TIME I ACTUALLY HEARD A BACKFIRE THRU THE INTAKE, BUT 3 MORE TRIPS UP THE HILL AND I COULD NOT DUPLICATE IT AGAIN. ONE THING I HAVE NOTICED, WHILE WATCHING SCANNER DATA, SPARK ADVANCE IS ALL OVER THE PLACE. FROM -8 DEGREES TO +28 DEGREES. IT SEEMS TO RETARD TREMENDOUSLY UNDER HARD ACCEL. MAYBE KNOCK SENSOR RETARDING TIMING? OR MAYBE CAM TIMING OFF. I DON'T KNOW OF ANY WAY TO CHECK CAM TIMING ON FORD MOD ENGINES WITHOUT PULLING VALVE COVERS.

SEEMS LIKE IF CAM TIMING WAS RETARDED, INTAKE VACUUM WOULD BE REAL LOW. THE CAR IDLES SMOOTH, AND ONCE YOU GET HER WOUND UP IT GOES DOWN THE ROAD FINE, NO HICCUPS OR MISSES. LT AND ST FUEL TRIMS FLUCTUATE BETWEEN -4 AND 4. PLUGS AREN'T REAL WHITE LIKE IT SUPER LEAN.

I'M GETTING PERPLEXED AND FRUSTRATED. ANY MORE IDEAS?

[steven kiser]

I'd firmly feel like "gibbs" and follow my gut. pull the front 02's and drive it. back pressure readings can be deceptive. if tested at just idle (didn't read about higher rpm's) you could get good readings. my lead tech will yank the 02's even if all the tests show that they're ok and has had cat issues before. speaking for myself i can overcomplicate tomato soup and a tuna sandwich.

[Jeff @ Able Auto]

This is a long shot BUT I have had cam sensors go bad and not throw codes. The ECM will use defaults. At that point you would see the timing jumping around and lack power. Never on a 4.6 but several 3.8 windstars. Just a thought.

[brianp87]

What are the fuel trims

[fortknoxx]

we had a car in on friday. just didn't have any pep. would drive ok up till bout 40 mph, but no more with pedal all the way down on the scrunched up floor mat.

[BOUNTYHUNTER29]

WELL GUYS....I GAVE UP ON THIS ONE. CUSTOMER GOT A LITTLE ANTSY, AND I BECAME FRUSTRATED TO TEARS OVER THIS ONE. CUSTOMER IS GOING TO TAKE IT TO FORD. I'VE BEEN IN THIS BUSINESS LONG ENOUGH TO KNOW WHEN A JOB IS NOT PROFITABLE, BUT GIVING UP ON ONE SURE DOES HURT MY PRIDE. I FEEL LIKE THIS VEHICLE HAS JUMPED TIME BUT CUSTOMER WOULD NOT AUTHORIZE ME TO TEAR IT DOWN. I'M SURE HE'LL LET ME KNOW WHAT THE FORD DEALER FINDS OUT. CUSTOMER WASN'T UPSET OR ANYHTING, SO I THINK HE'LL BE BACK IN OUR SHOP AGAIN. I'LL KEEP YOU POSTED...AND THANKS FOR THE INPUT!

[wbuxton]

Sometimes a good run is better than a bad stand.

[wminnichbach]

How about a clog egr tube from egr valve down to the exhaust manifold ?

[steven kiser]

How about a clog egr tube from egr valve down to the exhaust manifold ?

welcome to the forum.

[steven kiser]

i've replaced intakes on these for other issues and am wondering if this is the answer. a jumped timing chain would have effected vac and the engine would have sounded like a cement mixer. i've seen these chains jump before and the customer only come forward with the noise information after being queried in a dark room under a spot light surrounded by a bunch of sweaty guys smoking cigaretts........ sometimes i feel that the customer holds back information because they think we can keep the vehicle because they haven't taken care of them. "when did this noises start"? long pause..... "i want my lawyer". it's sad but true...........