This may or may not be normal IDI behavior, however, I don't usually have a very heavy foot in the morning or whenever the truck is cold, so I've never noticed it before. I was running behind this morning, and after letting the truck "warm up" for about a minute, maybe two, I had to go. I admit, I gave it a lot of go pedal, but that cat just about jumped out of it's skin. It was still on the (warm-up advance?) high idle setting, and seemed like it had a great deal more power than what it has when it's at operating temp, or even after the high idle switches off. Is this a normal IDI behavior, or am I looking at replacing something sooner than I had anticipated? When I say it had more power than usual, I'm not even remotely kidding. I hit 6lbs of boost about 1/2 way through 1st gear with an empty truck, so I grabbed 2nd and eased it out. For comparisons sake, when the truck is "warm" and empty, getting on the go pedal usually builds about 2 to 4 lbs of boost by the top of 1st gear. I was impressed with it's go-power, but it made me nervous enough to post about it. Truck, for what it's worth, has about 330,000 miles now, and an ATS 088, 3" down pipe to 4" out a single stack, T19, and I believe 3.55 gear ratios. So, I guess the question is, am I closing in on an IP replacement faster than I originally thought, or is this normal behavior?
Was in a bit of a rush this morning, and noticed something
- Thread starter JesterPgh
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Cincinnati Guy
Registered User
When your high idle is on it advances your timing.
LCAM-01XA
Full Access Member
^^^ which can have the "whoa!" effect, but if you try it with the engine all warmed up you end up with a semi-runaway engine that revvs up to 2500 rps by itself, then idles down, then revvs up again, and so on. Guess how I know that 
So, this is a normal behavior of the IDI in the timing advanced/high idle setting then. Judging by my guess on how you know that, I wouldn't want that setting "on" all the time. But damn if it ran like that ALL the time, it would have much better wow factor 
. I guess I better learn more about the timing situation on my truck right now, and figure out if I should advance it slightly. I only am on that train of thought, because when the timing is advanced to where the cold advance/high idle setting is, it's a pretty big difference, and if I could achieve just *some* of that, I think I would be pretty satisfied.
. I guess I better learn more about the timing situation on my truck right now, and figure out if I should advance it slightly. I only am on that train of thought, because when the timing is advanced to where the cold advance/high idle setting is, it's a pretty big difference, and if I could achieve just *some* of that, I think I would be pretty satisfied.
sootman73
Registered User
yea you should have felt when the high idle/ cold advance went off too. I have my timing advance on a switch on the dash as i'm not one to let my truck idle for 10+ minutes before i leave. this way i can turn off the timing advance and not eat glows when i start getting the egts up on the road.
i'm gonna try this this summer with taking my glow plugs out like dyoung and running the advance on. should help i hope. i get better boost thats for sure with it on!
i'm gonna try this this summer with taking my glow plugs out like dyoung and running the advance on. should help i hope. i get better boost thats for sure with it on!
LCAM-01XA
Full Access Member
When I first wired in my manual switch for the high idle I didn't use a diode, so voltage was back feeding from the high idle solenoid to the cold advance one. it worked okay for a while, then I advanced my base timing and it started acting up when warm - noticed it while idling in my driveway, never had the spirit to try it in gear I have since revised the wiring to include a diode to isolate the cold advance from the manual switch, so now she works like she should. There have been several threads on proper timing of these engines, and there may be someone in your area who owns a timing meter and is willing to give ya a hand with timing your engine...
I have since revised the wiring to include a diode to isolate the cold advance from the manual switch, so now she works like she should. There have been several threads on proper timing of these engines, and there may be someone in your area who owns a timing meter and is willing to give ya a hand with timing your engine...
dyoung14
Is getting worn out
higher timing to a certian point makes more power in these engines, i have played alot with timing and so far i never found the limit of too much timing because my pump was turned as far as i could turn it, so was the fuel screw
Yes its normal to notice more power when the advance is on because your timing is advanced more
Yes its normal to notice more power when the advance is on because your timing is advanced more
plywood
Recovered N/A
I tried hooking a jumper to my CAS to see if I wanted to advance the timing and also noticed major pep up around 2000-2500 rpm.
Problem for me was that right about as close to that time as I'm aware I started having an IP problem that may or may not have been coincidental.
I had a broken thrust (wavy) washer in the governer. My IP rebuilder says he dosen't think I caused it but it has certainly kept me from trying it again now that I have a fairly fresh rebuild.
I've read the CAS advances by 2 degrees and I've read 6 degrees.
It sure would be interesting to know for sure by a timing meter which is true and if it is linear, meaning is it the same amount of advance throughout the rpm range or is it possilby more like 10 degrees at higher rpms????
Problem for me was that right about as close to that time as I'm aware I started having an IP problem that may or may not have been coincidental.
I had a broken thrust (wavy) washer in the governer. My IP rebuilder says he dosen't think I caused it but it has certainly kept me from trying it again now that I have a fairly fresh rebuild.
I've read the CAS advances by 2 degrees and I've read 6 degrees.
It sure would be interesting to know for sure by a timing meter which is true and if it is linear, meaning is it the same amount of advance throughout the rpm range or is it possilby more like 10 degrees at higher rpms????
MIDNIGHT RIDER
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Timing at the high-idle advance and actually rotating the pump in relation to the mounts are birds of a completely different feather.
Some even go so far as to skip a tooth on the gear.
Advanced timing will give lower than realistic pyrometer readings due to the hot gasses remaining within the cylinder for a longer time, thus increasing the chance of melting through a piston.
You might get away with it on a play truck, but a work truck would not be able to control EGTs.
Some even go so far as to skip a tooth on the gear.
Advanced timing will give lower than realistic pyrometer readings due to the hot gasses remaining within the cylinder for a longer time, thus increasing the chance of melting through a piston.
You might get away with it on a play truck, but a work truck would not be able to control EGTs.
DeepRoots
Tug Engineer
Sure the Timing Advance has something to do with it.....
another theory:
A small air bubble in the filter or system from a very minor leak. Normally it would work itself out while you are at idle or slowly leaving the yard. Due to more throttle the air pocket ran through the pump.... truck jumps with immense power.
Drew
another theory:
A small air bubble in the filter or system from a very minor leak. Normally it would work itself out while you are at idle or slowly leaving the yard. Due to more throttle the air pocket ran through the pump.... truck jumps with immense power.
Drew
dyoung14
Is getting worn out
but if he were to try it again a couple times and it were to do it again after again it wouldnt be air,
And when my truck was running
it would do the same thing that one would when i had it timed to specs, but after i began playin with the timing i unhooked the advance, so i dont know how mine would have acted with the advance
DeepRoots
Tug Engineer
not so certain mr young.
I've had a minor air leak (slightly loose connection) that didn't leak air, or at least not badly until I got on the skinny pedal....
the added vacuum of the pump speeding up while the truck lurches forward and fuel pushes backward is enough to get a pocket of air.
guess we'll see, I'm just trying to bring up another option that may have been overlooked.
Drew
I've had a minor air leak (slightly loose connection) that didn't leak air, or at least not badly until I got on the skinny pedal....
the added vacuum of the pump speeding up while the truck lurches forward and fuel pushes backward is enough to get a pocket of air.
guess we'll see, I'm just trying to bring up another option that may have been overlooked.
Drew
I do agree that the air intrusion could be a viable alternative, however...we had a nice chilly morning here, and I let the truck sit awhile, but not long enough to have the cold start solenoid snap closed. Same result: Lots of go fast power. Once the truck was back to low idle, it had the normal power again. I've had air intrusion before, and this doesn't feel the same. When I did have it, the 6.9 would try to run away, and it's not, it's very throttle responsive both winding up and letting off.
Fordsandguns
Fords Rule
One way to find out is to run a jumper to the cold advance and drive it. Wait till it clicks off then do the jumper. I realize it might not be good to drive it like this for very long but it will let you see if it is the cause or not.
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