Ignition timing, 1997 4.0?

[2seater]

New here and have had little luck searching for what the expected ignition timing spec's should be. I have Google searched and tried a couple of key words on this forum, but no luck. This is a 4x4, 85k miles, 3.73, five speed auto, 31"x10.5 factory size tires. It has been a problem child since new, and has always had poor mileage, which is apparently a very common complaint. I just replaced the EGR valve and tube so I was doing a scan of parameters while driving. There are no issues with starting, idling or general performance. The one area I noticed was ignition timing numbers, which seem very low. I see 27 degrees in coast mode and low 20's @ 65mph cruising across the flat. Does this seem normal?

 

[alwaysFlOoReD]

I'm in for the info.
I've never really thought about checking the timing while moving as I don't have the capability but I can see where I might want to. Also I'm pretty old-school ( points and carbs ) and I don't know a whole bunch about the newer systems but have been trying to learn. From what I understand the initial timing should be 10* and the computer sets the rest according to sensors and its programing.
What are you using to capture your data?

Richard

 

[2seater]

I'm using an Auto X-ray for OBD-II. It doesn't do a perfect job but does read most sensors on the move. The fly in the ointment is this: When it goes through the initial scan it says the O2 sensors and heaters are okay, but, I get no actual readings from the sensors? It also shows bank 1 & 2 as -100%. My guess is the two things go hand in hand? I had an EGR code before but no issues after tube and valve replacement. I do get an occasional code 171 and 174, bank 1&2 lean. It will go two weeks or more before those codes set. I do have a new DPFE coming. As I mentioned before, I have no issues with engine power or actual operation. The reason I ask about the timing, is the very low values I see. I would expect a much higher value under cruise conditions and light load. My comparison is a 3800 Buick engine, 1990 vintage. Similar crank fired ignition and waste spark coil setup. The one difference is the Buick uses a knock sensor where the 4.0 appears to not. My conjecture is Ford is using a safe timing map which is not conducive to decent mileage, but to keep everything happy under all conditions the truck may be used in, since it has no knock sensing. The Buick shows upper 40's to 50 ish degrees under light load and mid twenties at full load. I know it is a sort of apples and oranges comparison, but I would expect more timing lead with EGR flowing and moderate manifold vacuum, which leads to relatively slow combustion. I have had this vehicle since new, and it has never done well in the mileage category. I chalked this up to the nature of a 4x4 which has a small factory lift with the big tire option, but this has got me to thinking? Disregarding the cruise readings, even the initial timing at idle is very different. The Buick shows 20 degrees at hot idle in neutral which increases by two degrees or so when dropped in gear to help pick up the load. As the weather cools, timing increases two to four degrees in response to cool inlet temps. I know the 3800 Buick is much closer to the 3.8 Ford V6 in design, not the 4.0. The thrust of my initial question is to determine if I have a defect in the PCM or is this normal? Thnks for listening.

 

[FritzTKatt]

I don't have any real input on this, but you have definitely posed quite a question...

I'm surely curious as to the answer. Ford should have the specs somewhere. Maybe in an actual calibration spec sheet, you could diagnose the PCM and ECU to see if it is performing properly.

 

[adsm08]

That seems like it would be a good timing for that kind of operation. There aren't any real spec sheets for the timing because it isn't adjustable.

 

[97RangerXLT]

I have pretty much the same set up as you. 97, Supercab, factory lift and 31" tires, 3:73 gearing in an 8.8 and the 4.0 OHV engine. great running truck, has quite a bit of torque and overall no issues. I get an average of 16-17 mpg mixed driving and about 19 and sometimes 20mpg on the highway. I am also interested in some of the answers that come up here...

And welcome to TRS

AJ

 

[Road Angels]

Emissions engines, your not going to get what was once concidered normal, 32 degrees wide open throttle above 4k rpm with a baseline in the teens degrees at idle, on old school stuff, even when coasting you have a speed sensor coming into play, o2 sesors coming in to play after closed loop, you need to check it in the very few minutes that you have open loop operation, cold, would give you a close reading as to what its doing before sensors come on line, on the newer cars and trucks there is no longer open loop operation

 

[2seater]

Thanks for the input. This is really a question I could have asked fifteen years ago when everything was current I agree it is probably safe timing for almost any occasion. Unfortunately, if true, it is less efficient than it could be for the vast majority of daily driver needs. I would guess the chip or reprogramming vendors would have some idea, but I would guess they wouldn't want to share. I shall ask.

 

[Road Angels]

One last thought have you put a inline programmer for your speed sensor so that it is sending correct info to the ecm for the larger tire size,

 

[2seater]

As a slow typist, a couple of posts showed up while a huntin' and a peckin'. Interesting suggestion to check while open loop. I would guess it is even more conservative? We shall see. Thinking about this a littlle more and I am guessing that a knock feedback mechanism was not included in the truck programming as a corporate decision due to the perceived use? Certainly commonly used in pursuit of mileage/performance in cars for more than a decade prior.

Edit: The tire size is factory stock (actually the infamous Wilderness AT in 265/70R15 was stock). I have checked mileage over a known fifty mile course and against a GPS, and it is accurate.

 

[feellnfroggy]

VMPTUNING IN ORLANDO FL. His name is Justin and he used to work for SCT. he is a whiz with the Xcal 3 or whatever the newest thing is. Timing is def a prob, buy must be fixed with a programmer.

 

[FritzTKatt]

Adam, i was more referring to what ford specified the computer should do. This COULD be checked by someone a hell of a lot more knowledgeable on electronics than i, but it would alsp require a complete teardown of the electrical system andwould require specifications made by the computer programmer. So im thinking its possible, but would likely cost more than putting in a crate motor lol

 

[martin]

funny that this question should come up at this time, I'll tell you the story and then my theory. A friend has a 2k something f150 4 x 4 with the infamous 5.4 and he wanted the plugs changed. After reading the horror stories of broken plugs I told him to take it in somewhere as I was not interested. long story short, the plugs were changed a one of the major chains and it came out of there with all kinds of running problems and cel's. Pulled everything apart they would have had to remove to change the plugs and put everything back together properly. We then plugged in his thingy that interfaces with his laptop and went for a ride while I watched the live data from the sensors. The truck was running fine again but I noticed the ign timing was 0 to 1 degree at idle and only went to 28 on over run. I thought, that's weird, where can I find another obd2 vehicle for comparison. Tried it on a 2006 jeep wk with the same result, umm. My son has a bluetooth scanner thingy and a small four cylinder chev so we tried the same thing with his, same thing. Tried his scanner on the Jeep and same thing.

My theory is that the scanner is receiving degrees above base timing only, not total advance. The reason I'm thinking this is that emissions are lower with maximum timing advance. I was thinking of how to verify this, timing light would work but the three vehicles I have access to all have coil on plug ignition and no timing marks.


just my five cents (no more pennies in Canada)

 

[2seater]

Thanks for all of the input. I guess there is no definite way to know what the scanner is telling me, but my gut says it is reading the actual advance. I did check the system with the engine dead cold, actually 21 deg.F. It took a lot of willpower to not start the engine while I was scraping frost from the windows, but in the interest of science, I perservered. The scanner was a little hard to read since it has spent the night below freezing as well and the LCD display was slow and some digits had to be guessed at. The scanner showed 14deg advance in park when started and in the low to mid 20's while driving at moderate speed while warming up. After approx. two minutes I was at hiway speed of 55-60 mph. Timing was in the mid-twenties but never higher than 27.5 degrees. After warming for a couple of miles, I accelerated fairly briskly and timing dropped to 12-14 degrees while accelerating and back into the twenties at cruise. Interestingly, timing showed 24 degrees at warm idle in gear and droped into the high teens in park. This is likely higher than previously observed since the incoming air is well below freezing and it likeley has a table similar to the Buick that adjusts for air temperature. The warm idle in and out of gear shows timing not much different than my reference Buick engine. The power timing numbers in the low teens are very similar to my 10psi boost chips for the Buick. The only thing missing is high timing numbers for low load and cruise speeds. I am pretty certain this would have a positive effect on mileage, but without a knock sensor for feedback, it could get a person in trouble fiddling with it blindly. Unless I find better information, my guess is everything is working properly. The numbers move around in response to throttle, the MAF readings appear to be in order although I am used to seeing grams/seconds and will need to convert lb/min to see if they make sense relative to the approx. hp.

What size are the injectors? My guess would be in the 19# @ 3bar range? I have toyed with doing a Squires type rear mounted turbo on this old truck off and on for years. I have a brand new 40 year old Garrett turbo of unknown origin. Even Garrett can't or won't tell me. The best info. I have found is it is from a IHC diesel engine for a military genset. Definitely old tech. but the layout of the pickup looks tailor made for a turbo in place of the muffler. Maybe best to leave the timing alone and boost it a bit?

One other tidbit: the check engine came on again, so it appears this is getting more frequent. Again it was a pending bank 1&2 lean. It now occasionally has a loping idle. Very short lived and minor but that is what it did before, only then it was much more severe. The EGR had stuck partially open, causing engine vacuum to drop to 9"Hg, which rendered the brake boost almost non-existant. Plugging the EGR brought engine vacuum back to 21"-22" at idle. The new EGR and tube kept the codes at bay for two weeks, but now it is gradually creeping back to similar behavior.

 

[FritzTKatt]

You may have caused a simple vacuum leak somewhere else fiddling with it. Probably a loose line or such.

If your banks are lean, timing should get retarded, and a rich bank needs advanced timing, correct? Have you considered your rich/lean problem to be in fuel delivery? Or a post-maf air leak?

Have you removed your stock hot-air intake off the pre-filter hose? The one that draws air heated by the passenger exhaust manifold... that is also vacuum operated so if the engine vacuum is messed up that won't work properly. You also have to think bout that air temp sensor, giving a false reading causing poor mixture...

Just some food for thought...