Engine/Transmission (1998.5 - 2002) Miss only with edge on, FIXED!

[NoSeeUm]

It's very noticeable on mine as well. It's instantly apparent once I start the pickup after putting in the resistor.



Paul

Yep, same here. Very noticeable change in engine tone / volume.



Jim

 

[Gary - K7GLD]

Yep, same here. Very noticeable change in engine tone / volume.



Jim

Just to clarify - are you talking about only in near zero temps - or at any ambient or engine temp?

 

[NoSeeUm]

Just to clarify - are you talking about only in near zero temps - or at any ambient or engine temp?

Two main conditions that I notice with the IAT fooled to 100F in cold weather.



First

OAT = Cold

WCT = Cold

Engine noise is much louder and runs fine



Second

OAT = Cold

WCT >= 180F

Engine noise is pretty quiet and runs fine



The engine itself runs no different as far as I can tell. I really can't tell any difference at all in performance. Only thing that I do notice is it runs quieter.



The only down side I can see to fooling the IAT permanently is that the WTS grid heater cycle is disabled and when the engine starts it runs very rough at first. This is no different than if I go ahead and start the engine without waiting for the WTS to go out on a cold day. I am sure you have done that a few times yourself. I intended to install a "Live Man" control circuit, but have decided to try and find a suitable DPDT time delay relay instead. That way a unknowing / unaware person can perform a normal start in cold weather.



My current theory is that the IAT timing adjustment is primarily for emissions or to aid in engine warm-up, but not to make the engine run better or worse. I could see how you could raise the combustion temperature by increasing the timing and how that would help. Also generally speaking, I would think that the emission standards would only be strictly required after the engine is at normal operating temperature. Either way, with a lower IAT and or a cold engine that most likely the combustion temperature would also be lower and so NOx production at those times would be acceptable even with advanced timing.



Jim

 

[NoSeeUm]

I finally got this bomb done. What sparked me was a trip up north. The OAT was 15F and the IAT was running around 50-55F. I had been running the XZT+ on the performance setting and I when I stepped on it to pass I got quite a bit of timing stutter.



#ad




I went with a time delay relay and a 5k-0k audio potentiometer all mounted on top of the fuse box using a DIN rail. And of course, the IAT wiring harness extender that I had already installed.



Currently I have the time delay set for 150 seconds. So for the first 150 seconds the ECM sees the IAT after that it sees the potentiometer.



The set-up seems to work well so far, with the indicated IAT = 105F @ 5k resistance. With the potentiometer set at 0k resistance the IAT indicated 292F and of course it threw a 0112 code.



Jim

 

[Gary - K7GLD]

Looks good Jim - nice pics - I may end up doing much the same.



Coldest driving temp so far this season was 27 degrees going up over a mile-high grade - engine fully warmed up. Truck was unloaded, and no timing studder issues - but I was driving with the 1K fixed resistor engaged, and whenever I would switch it out of the circuit, could instantly detect a small engine increased timing rattle - first I have noticed ANYTHING happening while driving or parked, and switching the resistor in or out.



Other than that, no changes so far, and increasing - or "fine-tuning" the IAT resistance with the 1 megohm variable gave no indication of effect - so I may well simply go with an in/out fixed resistor that is controlled by one of the small disc thermostats I bought with the rest of my IAT project goodies, and let that automatically control the whole setup. I have a miniature reed relay that I can tie into my unused Lift pump power lead to cut out the added 1K resistance for starting, then close it's contacts for the resistor to do it's thing - a nice side benefit is that doing it that way, the grid heaters will still function normally with ignition on, but engine not running...

 

[paulb]

I finally got this bomb done. What sparked me was a trip up north. The OAT was 15F and the IAT was running around 50-55F. I had been running the XZT+ on the performance setting and I when I stepped on it to pass I got quite a bit of timing stutter.



I went with a time delay relay and a 5k-0k audio potentiometer all mounted on top of the fuse box using a DIN rail. And of course, the IAT wiring harness extender that I had already installed.



Currently I have the time delay set for 150 seconds. So for the first 150 seconds the ECM sees the IAT after that it sees the potentiometer.



The set-up seems to work well so far, with the indicated IAT = 105F @ 5k resistance. With the potentiometer set at 0k resistance the IAT indicated 292F and of course it threw a 0112 code.



Jim

Very nice!!!



Paul

 

[GOT-Torque]

Nice job, how much do you have in the DIN rail, TDR, etc shown in the pic? I'm thinking of using the same sort of deal for a turbo timer (also using a button for activation upon shutdown).



To solve my timing issues this winter I swapped from my 250+ hp injectors back to some RV275's. No more issues...

 

[NoSeeUm]

Nice job, how much do you have in the DIN rail, TDR, etc shown in the pic? I'm thinking of using the same sort of deal for a turbo timer (also using a button for activation upon shutdown).



To solve my timing issues this winter I swapped from my 250+ hp injectors back to some RV275's. No more issues...

LOL :-laf Yeah, but what fun is that.....



The TD relay - $40

Mouser 528-TDR782XBXA-12D

Magnacraft TDR782XBXA-12D

DIN Screw Terminal Relay Base - $4

Mouser 528-461

Magnacraft 70-461-1



IAT wiring extender - $20

ZZPerformance - 18 inch IAT Extension Cable



Potentiometer - $5

Fry's - 5k-0k Audio Taper Potentiometer - $3

Fry's - Knob for Potentiometer - $2 [Edit]



The DIN rail and the 5 retainers I scavenged from work. I bet you could get them from Mouser as well.



I mounted the potentiometer sandwiched between the retainers using the hold down nut on the shaft of the potentiometer. It was just lucky that the nut fit perfectly in a slot the retainer had molded into it. A little LocTight on the nut. Hopefully that will not vibrate and become a problem.



I tried to find some nylon 1/4 inch long bolts (and nuts) locally, but had no luck and so I used some galvy 1/4 inch long bolts (6-32) with barrel nuts to mount the DIN rail to the top of the fuse box cover. I had no clearance issues with the hood or the fuse box cover internally.



Jim

 

[NoSeeUm]

Coldest driving temp so far this season was 27 degrees going up over a mile-high grade - engine fully warmed up. Truck was unloaded, and no timing studder issues - but I was driving with the 1K fixed resistor engaged, and whenever I would switch it out of the circuit, could instantly detect a small engine increased timing rattle - first I have noticed ANYTHING happening while driving or parked, and switching the resistor in or out.

Missing your intent for text in bold Gary?



Jim

 

[Gary - K7GLD]

Missing your intent for text in bold Gary?



Jim

UMMmmmm - What "bold" text?



All I posted was :

first I have noticed ANYTHING happening while driving or parked, and switching the resistor in or out.

I capped the word ANYTHING purely for emphasis, since as indicated, that incident was absolutely the FIRST (emphasis again!) time I had seen any effect from the added IAT resistance circuit...



Maybe you're seeing something in my post my screen isn't displaying?

 

[PRout]

Since e=mc^2 the only conclusion possible could be that this is an ecm issue, and if it is an ecm issue then I suggest adding a 47Mh coil in series with the next version of smarty beta software (#0). If that doesnt resolve the issue I suggest buying a heathkit ecm inducer and running it in horizontal oscillization mode. :-{} Dangit!

 

[Gary - K7GLD]

Since e=mc^2 the only conclusion possible could be that this is an ecm issue, and if it is an ecm issue then I suggest adding a 47Mh coil in series with the next version of smarty beta software (#0). If that doesnt resolve the issue I suggest buying a heathkit ecm inducer and running it in horizontal oscillization mode. :-{} Dangit!

I've suspected something along those lines as well - but I'd be VERY careful with that 46mh coil - too much RF restriction is quite likely to fracture the fragillatior, and create excessive oscillation in the inverse refraction circuit...

 

[NoSeeUm]

I've suspected something along those lines as well - but I'd be VERY careful with that 46mh coil - too much RF restriction is quite likely to fracture the fragillatior, and create excessive oscillation in the inverse refraction circuit...

LOL



Well, at least that makes some sense... .



Jim

 

[PRout]

I've suspected something along those lines as well - but I'd be VERY careful with that 46mh coil - too much RF restriction is quite likely to fracture the fragillatior, and create excessive oscillation in the inverse refraction circuit...

Good point. Prolly should lower the value a bit. . Just throwing the info out there in case it might help for the benefit of others...

 

[timbo]

Well it's been a long time since i've been on here and did not realize this thread went this far. WOW You all did some serious research and experimentation! My final fix for this was last year. I took a 50k pot wired it in place of the IAT then took a 1k resistor wired in paralell to a hobbs press. switch to be activated by oil press. When i turn the key on it is reading high resis. value about 25-30k, grid stays on 30 or so seconds. and when the engine fires the hobbs switch closes and the 1k takes over. The neat thing is i can make the high idle kick in even in warmer temps if i turn the pot to about 40k. My neighbors, are very happy about that i'm sure:-laf:-laf This was just MY approach and it's fully automatic unless i want give the neighbors an alarm clock:-laf:-laf I'm not downing anyone's ideas or approach at fooling the computer this was just my way of doing it and i'm very happy with it Merry christmas to all !

 

[PRout]

This is the kind of fixes we like to see - Thanks & nice job. .

 

[Gary - K7GLD]

WELL, at this point in time - and only running the truck empty and lowest temps in the 25 degree or so range, the variable resistance portion of my setup seems to have no value. I could as easily just use the fixed 1K resistor and some form of switching in/out, and that seems to cover it so far.



I have all the electronic components to do all the switching fully automatically, either on a timed basis, or on a temperature controlled basis - haven't decided which to use, and for now, the switch is already there, so no great motivation to fool with it further at the present time.



Also, with temps not very close to zero degrees, the hard starting issue hasn't been evident, and the truck starts and runs just fine with or without the resistor switched in - altho as commented further above, I *have* detected an audible change in timing rattle in slightly below freezing temps when switching the resistor. So it does seem to have the expected effect, just haven't been in a situation - heavy towing right after cold temp startup - to really test it fully.

 

[RSimmons]

For anyone looking for an IAT extention cable, this appears to be a good (read inexpensive) source. Home » Shop » Connectors » Delphi / Packard » Extensions » GM Delphi / Packard - IAT / MAT / ACT Extender Harness