Ford 302 FI issue

My '99 Mercury Mountaineer with 156K miles had the CHECK ENGINE light kick on. This is associated with the engine bucking around 2,000 RPMS. When I give it gas under way, the bucking gets worse. At highway speed as long as I don't give it gas, there's no bucking. Idle is semi smooth, a slight cough every now and then. FYI, my gas mileage has gone down the crapper since this issue began.

History: Replaced plugs, wires, air filter within 20K miles. I don't think the o2 sensor, EGR or PCV valve has ever been replaced. Is it possible it's one of those little monkeys acting up? I'm hoping my engine isn't giving up the ghost.

I also dumped some dry gas in the tank, FI cleaner and filled it up with fresh 93 gas.

Ken

The CHECK ENGINE light indicates a fault in the closed-loop EFI system and needs to be addressed ASAP. Have the dealer read the code from your engine computer and tell you what needs to be fixed. It could be any of the EFI sensors.

Completely guessing, maybe since it's associated with increases in throttle/load it's the MAF sensor which senses intake manifold pressure changes. We shall see though...

TRBenj wrote: M3Fan wrote: Completely guessing, maybe since it's associated with increases in throttle/load it's the MAF sensor which senses intake manifold pressure changes. We shall see though... Not a bad guess. The symptoms sound similar to the time the MAF failed on my Maxima. Ken, Id suggest a Ford dealer over a chain like Midas. A good independant shop (if you know of one) might be even better. You might even want to consider going to Autozone and have them pull the OBD2 codes for free. If the problem is something simple that you can fix yourself, that will save you a $90 diagnostics fee.

I didn't know they'd read it for you- that's awesome. I actually meant the MAP sensor. MAF measures air density- but hey, if I was still correct then I guess that's what I meant!

Nautique - I had similar symptoms on my old windstar & what had happpened is that the head gaskets leaked (common problem) took out all 4 O2 sensors, (which caused over rich mixture) & did a number on my cat converter. As this all happened over a period of time, Ford covered the head gaskets, but I got a blue job on the rest, because I didn't connect the dots until way later.

Ok,now for my current puzzler:

My Honda Odsessy has (had) a engine rattle that was prevelant upon acceleration, particularly when cold. It seemed to be getting worse lately.

I asked my Honda dealer about this noise (which they heard on test drive) & they said I need a $400 valve adjustment. I took the bait & actually had an appointment to get hosed Monday.

In the meantime, yesterday we went on a skiing trip (snow, that is). It was pinging really bad. Today, I filled up with BP 87 octane. No noise! (which I now realize was knock or ping). No expalnation on the difference in gas - always use 87 or sometimes E10.

When I (happily) cancelled my service appointment, I asked the dealer if the pre-ignition sensor could be tested, as it is supposed to sense knock & adjust timing for octane.

The dealer said if the sensor was bad it would throw a code. His credibility is not so good with me right now. I am wondering if any of you gearheads know if this sensor could be tested.

Thanks in advance for any & all free advice.

Chris

SNobsessed wrote: The dealer said if the sensor was bad it would throw a code. His credibility is not so good with me right now. I am wondering if any of you gearheads know if this sensor could be tested.

He's probably right- there arent many (if any) sensors on the motor that wont throw a code. Not all codes will trigger a check engine light. Hook up an scanner and see if there are any stored. Some auto parts stores will read them for free (like Autozone).

MAF , mass air flow,or cfm ingested
MAP , manifold absolute pressure, or vacuum.

MAF gives a known when combined with air temp, also receives info from the TPS or throttle position sensor....

MAP gives a known value to air pressure at sea level then the decrease as the throttle plate is opened.But it only uses this info,vacuum.

O2 Sensor , monitors amounts of unburned fuel and constantly adjusts injector pulse width to add or subtract fuel ratio.This will put your mpg in the single digits quickly .

Just my TWO CENTS WORTH......boat dr

His Mountaineer might have up to 4 O2 sensors. One upstream and downstream of each cat coming off the headers. I had an 02 sensor go in my old V6 4Runner with no noticable change in how it drove- it was the downstream sensor FWIW. After I saw how easy it was to do, I kicked myself for having a shop do it at an outrageous expense.

Nautique2001 wrote: By the way, my 6.0 HP Craftsman mower runs like a champ. Ken

Dont forget to winterize your lawnmower!

Thanks Mark...it was getting kinda serious here...almost hadta reach for the Beam. I really do think I might be learning a thing or 2 on these threads. Between the dr, Tim, eric, and Joel we got the bases covered.

john

way over my head Joel.

john

now you found the ONLY reason to use premium fuel, that is the only reason on earth to use the premium (and i will back this statement up) if you are getting detonation or valve rattle with 87 it will clear up with higher octane.
It really is hard to diagnose check engine lights with out a scanner, I scanned a Cadilac yesterday which was still drivable and it has 2 crank sensors in which one failed,
I bought the scanner to mainly diagnose transmissions in which it does well, depending on what type of vehicle you have most of the times it leads to one main computer and ties everything in, i recently rebuilt a 4l60e out of a gmc and the engine light is on and it wont shift into 3rd, the scanner goes on to tell me it is the maf, which is tied into shifting and also a bad cam sensor which is also causing the trans to break away, and i can cover my ass because the customer thinks he has a trans problem, BTW it was a bench rebuild, he pulled the trans if your wondering, but at this point he wants me to repair under warranty and i wont untill he gets the other issues worked out. I did a real time test driving down the road showing him exactly what was happening on the scanner.
its hard enough rebuilding boat trannys and i get myself wrapped up car tranny's, but without the scanner you really are in the dark

   Ken,
Go for the free code check as suggested.At least you'll see first hand what it says so you don't get jerked around.Nothing against Midas,but I tend to stay away from those types of places.
Eric is correct,in today's modern systems you can speculate all you want but you're dead in the water without the proper diagnostic equipment.So many things can fail and exibit similar symptoms.
I'm not familiar with multiple crank sensor cars,but have never seen a Harley that would run if the crank sensor was bad.I have also never seen one that WOULDN'T run with a bad map sensor.Either way,get it fixed in time to drive to the boat show


    Mike

sounds to me like the converter is clogged or bad!

Is Brunstucky on the map?

Can you get a trip tick to get you there?

john




ps to eric: Lots of luck in the New Year. Been a pleasure talkin' to ya.