'ello all

97 Aero, 3.0 2WD extended 122000 miles
Symptoms started suddenly.

when climbing hills, in 3rd or overdrive and lower speed, ie 35-45 it would backfire through the intake.

Talked to a respected Ford guy, said it was running lean. had access to the Ford computer and did some on the road diag.

No MIL light, but had a code of misc non specific misfire, or something to that effect.

Changed the fuel filter, backfire pushed up in the rpm range.

Changed fuel pump and inlet screen, didn't think this would do anything, but at 122K, thought it was good insurance.

Changed the MAF sensor, still on the Ford computer, computer didn't like the pressure sender in the MAF.

Exchanged sensor for another. Pushed the backfire still higher in the rpm range. Now you have to have the throttle wide open going up the hill befoe it will backfire

You can make it do it sitting still by running the rpm's up and snapping the throttle open the rest of the way.

Guy at the parts counter said MAP sensor, the 97's don't have one, or at least I can't find it. I think it's in the MAF sensor.

O2 sensors check normal.

Any Suggestions? Floating intake valve spring?

Body and interior are mint, hate to replace the van just for this problem.

Besides, "She who must be obeyed" loves the thing

Thanks

Steve

 

97ext3.0:

I was wondering.....Did you change the Spark plugs & wires yet? Have you pulled and checked for plugged or weak injectors?

JaY

 

Could be a worn timing chain.

 

Autozone and some other local auto parts stores will read codes for you, call around....post codes here...we'll start there
the '97 has advanced OBDII engine control system with detailed stored and real time engine performance information...see if you can borrow a OBDII scanner from a friend or buy one, all new vehicles since '96 are OBDII and a scanner is a necessity to work on engine performance....one of the handiest features is that the PCU system stores engine parameters at time a code is set...can also see instantaneous computer ignition timing....

could be failing cam position sensor, failing crank position sensor, failing fuel injector...
no use throwing parts at it

122,000 miles on the O2 sensors and it's time to change per Ford and Bosch...correct fast response O2 operation is critical in hot closed high engine load operation

 

...Welcome Steve to Ford Truck Enthusiasts!

We are happy you have chosen the best source for Fords.

Enjoy FTE....and
JOIN CLUB FTE -SUPPORT THE FORUMS!
…..See you on the boards.

 

The first hypotesa: ignition timing (wron connected wires)
The second: Cranckshaft position sensor!
The 3d: to reach! may be o2 sensor
the 4th: timing chain
the 5th: bad spark plugs, coils, wires

 

Thanks for the replies all.

I appreciate the time.

I have a code reader, and that's how I got the random misfire code. I have a buddy that teaches at a votech school, and he has the official Ford computer, we were playing with that too.

Plugs and wires are 10,000 miles old. changed them shortly after I got it.

The cam and crank sensor are something I hadn't thought of. I will look into it. How can you check a cam or crank position sensor without just changing it?
If they aren't that expensive I will look into just putting them on.

I find it interesting that each thing I did that would increase fuel flow changed when the symptoms appeared. I am wondering if I am masking something, like a worn chain.

I 've become firmly convinced that cars with computers are just plain evil.

I have never had this kind of trouble diagnosing my 1971 Triumph spitfire.

Get back to you with what I find.

ps, the fuel pressure readings are 31 idle, 40 with the vacuum line off the regulator, or upong opening the throttle.

Steve

Never underestimate the maliciousness of an inanimate object.

 

with a high quality (read expensive) OBDII scanner you can watch both the crank and cam position sensor pulse waveforms for any erratic operation up thru the rpm and engine load range with alarm set points and data snapshot capture, a portable unit allows use in vehicle on the road....i have laptop with scanner software....search the web for OBDII scanner software and USB>OBDII port cabling

another potential failure/problem area is the camshaft postion sensor cable which is shielded to prevent ignition spark interference and other electrical interference...relies on good non leaking spark plug wires near the cable....there is a Ford TSB on failures of this cable, it's shielding and the spark plug wire insulation and spark plug wire routing... spark plug wire leakage increases as rpm increases...the driver's side bank plug wires are routed near the cam position sensor

 

Welcome!


I would say cam sensor or timing chain. Those are the only two things that would cause a backfire through the intake.

 

Thanks I will look into this.

Biggest hassle is that the family and I are supposed to be leaving thursday for a 1200 mile trip, in the van of course. and the schedule is such between then and now that it won't even cool off between runs.
96 4WD, do you have the number of the TSB? I could get it off All Data or something, or my friend at the votech.(if he's still my friend after all this)

I think that it's definitly running lean. My scanner isn't quite enough to see how lean.
(AutoXray EZ Link 5000) Which was all I could afford at the time.

I will definitly keep you posted when I find what, so we all can learn. Course it will never happen to anyone else

Steve
Never understimate the maliciousness of an inanimate object.