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

[ERuhl]

IF the grid heaters are still operating at 50 degrees with the 1K resistor added, they DERN sure are also gonna work down at 30 degrees - resistor or not!

The length of time the heater is active varies with temperature. When it's really cold the heater grid is active for several seconds, so if you're seeing cold-temperature heater durations then something else is amiss in your setup. FYI with a stock truck the heater duration is noticeably different between 80°F and 32°F and it absolutely IS dependent on the IAT signal.

Wasn't it you who commented that the heaters would NOT work with the resistor added

Yup, when it gets COLD the short heater duration (zero?) due to the false IAT signal just won't cut it.

it apparently DOES NOT fool the ECM into shutting down grid heaters!

Wrong, it most certainly does affect heater duration.


So far I haven't led you astray, believe it or not I'm actually taking time to try and help you (and anyone else reading this). This period of rediscovery is admittedly taking more time than I had anticipated, but I feel compelled to correct your misdirections for the benefit of others.

 

[ERuhl]

FYI it was 39°F this morning and my heater grid was on for more than 10 seconds.

 

[Gary - K7GLD]

believe it or not I'm actually taking time to try and help you (and anyone else reading this). This period of rediscovery is admittedly taking more time than I had anticipated, but I feel compelled to correct your misdirections for the benefit of others.

Very "large" of you - I certainly appreciate your condescending willingness to help us dummies out... :-laf





How about this:

With a 1K ohm resister in series (ECM thinks it's about 100*), my grid heaters will still cycle once started, if it's cold enough.

IF the IAT is considered to be the ONLY controlling influence in regards to grid heater function - and perhaps other functions as well, WHY IS IT that the above poster who has DISCONNECTED the IAT completely, and has ONLY a fixed 1K resistance to affect ECM, still sees variations in grid heater function vs ambient temps - shouldn't it always operate the same regardless of ambient temperature, since the variable IAT is no longer in the circuit - or is he too only imagining things.



This discussion, and your input will go lots further and smoother if you leave your condescending attitude on YOUR side of the keyboard...

 

[ERuhl]

Very "large" of you - I certainly appreciate your condescending willingness to help us dummies out...

Actually as I've followed this thread you're pretty much the only guy having difficulty absorbing this. No condescension intended, just trying to help.

IF the IAT is considered to be the ONLY controlling influence in regards to grid heater function - and perhaps other functions as well, WHY IS IT that the above poster who has DISCONNECTED the IAT completely, and has ONLY a fixed 1K resistance to affect ECM, still sees variations in grid heater function vs ambient temps - shouldn't it always operate the same regardless of ambient temperature, since the variable IAT is no longer in the circuit - or is he too only imagining things.

He's not imagining anything, his is operating correctly. As Paul stated, with the 1k resistor in place the heater grid does NOT function for startup. This is exactly as I described and it is exactly what is going to cause you problems with a COLD start. What happens with the heater grids after startup is a different story, so I'll kindly ask you to stay on topic which is the IAT's affect on cold startup. Not once have I mentioned or suggested anything whatsoever about heater grid function after startup. FYI nothing he mentioned is abnormal, in fact it's exactly as it should be. On the other hand, it sounds like you may have some issues with your heater grids.

This discussion, and your input will go lots further and smoother if you leave your condescending attitude on YOUR side of the keyboard...

Oh my attitude is just fine thank you In contrast, we would be significantly farther along by now if we didn't have to stop and rediscover every aspect along the way. Not that this is a bad thing, however I do have concerns when you start throwing out erroneous conclusions. Other folks are reading this and will use this information to guide their own decisions. Post responsibly. So far I've had to make the following corrections for you:

1. Altering the IAT resistance DOES change the injection timing.
2. Retarding the injection timing CAN alleviate the cold-weather miss/surge that many of us experience.
3. When placing a resistor in parallel with the IAT circuit, 10k ohms is NOT sufficient resistance for cold (sub-freezing) starts.
4. The IAT resistance DOES affect the heater grid duration for startup.
5. Insufficient heater grid duration, combined with IAT-induced timing changes, WILL cause difficulty with sub-freezing cold starts.

Frankly I don't care how you go about resolving this, but PLEASE stop posting misinformation. FYI you're not breaking any new ground here Gary.

 

[NoSeeUm]

With a 1K ohm resister in series (ECM thinks it's about 100*), my grid heaters will still cycle once started, if it's cold enough. However, the grid heaters will not come on, until it is started. It seems that the ECM uses the IAT to turn on the grid heaters, before startup, and then other parameters once it has started.



Paul

I am getting 100F IAT with a 5. 6k resistor stuck in the ECM side of the IAT connection. Identical to your set up. I am thinking that maybe the ECM might not care about temperatures > 100F, because the timing adjustiment might be the same in all cases.



I agree with you. The logic for the "WTS (Wait to Start) light is not the same as the logic that drives the post start grid heater cycling. I am suspecting OAT. Because my grid heaters used to cycle post start, even after the truck had been plugged in all night. During those times I didn't get the WTS light and my WCT (Water Coolant Temperature) was around 100-120F.



However, I should add that since I modded the IAT I have not gotten any grid heater cycling at all, but I have also religously kept the engine warm on cold mornings.



Another thing I have seemed to have noticed with the modded IAT is that the timing really does not come out until the WCT has reached 185-190F, IF the WCT starts our below 70-100F or so. When I start first thing in the morning and the WCT is 120F (block heaters on) there does not seem to be as much timing. The WCT ensentially goes from 180F to 120F the night before. When I start after work and the WCT is colder (no block heaters), there seems to be more timing. In that case the WCT has dropped into the 50-70F range. In all cases my IAT = 100F with the IAT mod.



Jim

 

[Gary - K7GLD]

So far I've had to make the following corrections for you:



Altering the IAT resistance DOES change the injection timing.



Never at ANY time claimed it didn't - only questioned if the addition of the 1K resistor was the best or only correction method available - quickly agreed with you and others it apparently WAS, and put it to my own use.



Retarding the injection timing CAN alleviate the cold-weather miss/surge that many of us experience.



I've NEVER said it wouldn't - WHERE are you getting this stuff?



When placing a resistor in parallel with the IAT circuit, 10k ohms is NOT sufficient resistance for cold (sub-freezing) starts.



Never said it was, only offered that as a possibility I might try for MY climate!



The IAT resistance DOES affect the heater grid duration for startup.



Undoubtedly true - question is, is that the ONLY controlling factor for heater grid operation - in my case, only colder weather testing will tell.



Insufficient heater grid duration, combined with IAT-induced timing changes, WILL cause difficulty with sub-freezing cold starts.



Never said it didn't - only puzzled about so extreme an effect down at freezing temps - reinforced by the fact that the addition of the 1K resistor to my own truck produces absolutely NO discernable starting or running difference at 50 degrees, only 20 degrees up the scale - yup, NOT cold enough to form a reliable conclusion, but curious to me just the same!



Frankly I don't care how you go about resolving this, but PLEASE stop posting misinformation. FYI you're not breaking any new ground here Gary.



"posting misinformation" - Well, if asking questions and suggesting approaches *I* might try for MY specific truck, in MY specific climate can be construed as "misinformation", then you are correct - otherwise,...



Please try to realize, this is a subject that is NOT yours alone, nor are the actions that work to YOUR satisfaction the ONLY ones that will satisfy or work for all - there IS room for discussion and suggestions that may well differ from your own - as "tiring" as those suggestions and trials may be for you to deal with.

It's clear at this point that you have problems with those whose questions, suggestions and observations may differ from your own. Your solution to the IAT has worked well for your truck in your climate - the method in your case fits and does as you want it to - but YOUR wants and expectations are NOT necessarily what will fit all others, just as paulb is using the same METHOD, but a different application that so far, seems to work well for HIM, HIS truck, and HIS climate!



And *I* may well end up with yet a different set of resistance parameters that works best for ME - but only trial and testing will tell, and may well be quite different from your own "expert" solution!



There's nothing WRONG with questioning the results of others, as long as it's done (in this case) from under the hood, rather than based purely upon vague theory from a warm easy chair! Nor is there any reason for a true "expert" to feel annoyed or threatened by the questions and efforts of others that differ from his own.



BS and smoke will not alter your objectionable tendency to condescendingly talk down to other posters in this thread - so drop the "Well, if I *must* (as he sadly wipes forehead), I guess I'll offer my expert comment here to straighten out the ignorant peons, (golly, this is sure taking up lots of my valuable time... )" attitude - it's not needed, helpful OR appreciated - nor is twisting my words, comments or intended meanings of my posts to suit your purpose.



Nor is your vague offering that any variation in my own installation that I may notice and comment upon that differ from your own are probably due to incorrect installation on my part - the simple addition of resistance across a pair of harness leads is hardly rocket science - even for a dummy like me... :-laf



I don't intend to expand or continue this discussion with you any further - I'm sure I have all the *helpful* info from you I'm likely to get, you've provided lots of excellent info and help, thanks - unfortunately, the rest from you is tedious, self serving and irritating - so I will block all further posts from you from my display, and allow you to sanctimoniously preach to the rest of the assembly as you wish...



And for that matter, there is little more for me to add here in regards to my own setup testing until winter temperatures drop to, and below, freezing - so I will remove myself from this discussion and leave further comments to you and others. Anyone wishing to toss comments my way concerning IAT testing are free to use PM's.

 

[ERuhl]

LOL, ok Gary... you "win". All this because I pointed out that it's still too warm... sheesh.

 

[paulb]

I agree with you. The logic for the "WTS (Wait to Start) light is not the same as the logic that drives the post start grid heater cycling. I am suspecting OAT. Because my grid heaters used to cycle post start, even after the truck had been plugged in all night. During those times I didn't get the WTS light and my WCT (Water Coolant Temperature) was around 100-120F.

Jim

It sure seems to be related to OAT to me also, and it does make sense from a logically point of view. I just can't believe that they would use that cheap sensor that is used for the overhead display. There must be another sensor someplace.



On a side note, with the Redline box on at least 60% and stacked with the drag comp, I don't have a timing problem. With the drag comp by itself, it does once, the OAT gets below about 48 degrees. The timing "should" be the same both ways, as only the Comp adds timing.



Paul

 

[WTBurke]

I have to agree and also I recall the long thread many years back regarding the high-idle and 3 cylinder activation issues. It's a long thread and lot's of guys were being jacked around by dealers who didn't know how to load the program or activate it once it was loaded. None the less, I make this observation because the sensor under the battery had some play in the activation process. Hence IAT, OAT and Battery temperature may very well all tie together. This too is not breaking new ground but, today perhaps some of this old data may shed some light on this particular issue of focus.



William

 

[NoSeeUm]

It sure seems to be related to OAT to me also, and it does make sense from a logically point of view. I just can't believe that they would use that cheap sensor that is used for the overhead display. There must be another sensor someplace.



On a side note, with the Redline box on at least 60% and stacked with the drag comp, I don't have a timing problem. With the drag comp by itself, it does once, the OAT gets below about 48 degrees. The timing "should" be the same both ways, as only the Comp adds timing.



Paul

I don't know if the FCM temperature back feeds into the ECM, but other than OAT I don't know of any "other" temperature sensor(s) that can effect the grid heaters. At least that have not already been explained. I am almost possitively sure that IAT controls WTS, but after the engine starts it is something else that makes the grid heaters cycle.



If it is the FCM temperature sensor that is possibly effecting timing independent of IAT, OAT or WCT. Makes sense a little. The OAT is a thermistor, maybe I'll hook up the 5. 6K resistor there and see what happens.



You have any idea what value of boost the Comp clips at? I know that both the XZT+ and the TST clip at 37. 3 inHg. Either that or the ScanGauge is confused equally in both cases. Roughly 5 psi boost at our altitude.



I re-connected my IAT today, using a harness extenter with a couple of wiring loops for access later on when I get some more parts. I noticed the engine noise from timing is very noticably louder when cold. Like I said before, it sounds like the timing does not come out until WCT reaches 180F. The IAT will come up into the 70F range rather quickly. Later in the day, OAT = 65F, WCT = 185F and IAT = 100F(+) and the engine runs quietly.



Seems almost like a set-reset type logic function.



Jim

 

[Gary - K7GLD]

but other than OAT I don't know of any "other" temperature sensor(s) that can effect the grid heaters. At least that have not already been explained. I am almost possitively sure that IAT controls WTS, but after the engine starts it is something else that makes the grid heaters cycle.

Possibly a programming issue, rather than just a sensor one? Is it possible the the pre-start ECM program related to grid heaters is different, or uses different table values than the one that functions AFTER the engine starts, even though the same sensors are at work?

 

[NoSeeUm]

Possibly a programming issue, rather than just a sensor one? Is it possible the the pre-start ECM program related to grid heaters is different, or uses different table values than the one that functions AFTER the engine starts, even though the same sensors are at work?

Yeah maybe, not sure.....



Here is what I notice:



OAT = 40

IAT = 40

WCT = 40

WTS and cycling after start



OAT = 40

IAT = 100 (5. 6k resistor)

WCT = 40

No WTS and cycling after start (runs very rough, but starts)



OAT = 40

IAT = 100 (5. 6k resistor or plugged in)

WCT = 100 (plugged in)

No WTS and cycling after start



OAT = 75

IAT = 100 (5. 6k resistor)

WCT = 75

No WTS and no cycling after start



I know that going over about 20 mph will discontinue grid heater cycling. I have never waited to see if any temperature / time the grid heater will stop cycling on their own.



I am thinking for grid heater cycling, possibly something like:

OAT = 50 then set

WCT = 180 then reset (never been tested by me)

Speed = 20 then reset



As for the timing advance, something like:

OAT = 50 then set

WCT @ RPM = timing advance per F(x) curve (function curve)

WCT = 180 then reset



Other examples:

IAT@ RPM = timing per F(x) curve

TPS @ RPM = timing per F(x) curve

Boost @ RPM = timing per F(x) curve



Fueling, the same:

TPS @ RPM = fueling per F(x) curve

Etc... .



When I say F(x) curve, for me it is basically an X-Y curve. The ones I have seen have essentially been in a table. The X-Y data points entered in the logic form a curve. You could see, for example, [0,0,10,30,12,42,20,60,20,60] in the table. Typically the tables I have seen will contain around 5 X-Y points.



Plot this on a piece of graph paper for each point:

x = 0, y = 0

x = 10, y = 30

x = 12, y = 42

x = 20, y = 60

x = 20, y = 60



Draw a line between all the points, that is the function or F(x) curve. For any input (process) value of x what ever point that correspondes to y on the line would be the output value of the F(x) curve.



For example:

x = 8 then y = 27

x = 15 then y = 28

x = 22 then y = 60

x = 33 then y = 60



Where, for example, x could be a process value of a beer glasses beer level and y could be output value of how many sips until the glass is empty. In this case, the curve describes the shape of the glass. Notice the glass will not hold more than 20. Bogus I know, but an example.



I can only immage that in the ECM each process would have its own F(x) curve determining a multiplication factor. The total timing would be calculated using a mathamatical algorithm including all the multiplication factors.



How it would work would be like this, example only:

Timing = 100 (base)

IAT = 57 through F(x) = . 925

Timing = (100) * (. 925) = 92. 5

WCT = 115 through F(x) = . 987

Timing = (92. 5) * (. 987) = 91. 3

RPM = 1300 through F(x) = 1. 047

Timing = (91. 3) * (1. 047) = 95. 59



Example, engine is warmed up:

Timing = 100 (base)

IAT = 57 through F(x) = . 925

Timing = (100) * (. 925) = 92. 5

WCT = 180 through F(x) = 1. 000

Timing = (92. 5) * (1. 000) = 92. 5

RPM = 1300 through F(x) = 1. 047

Timing = (92. 5) * (1. 047) = 96. 85



Sorry for the book;

Jim

 

[NoSeeUm]

Can anyone recommend a good 12 volt holding relay with at least one NC and two NO auxilliary contacts?

Jim

This Relay work? Just solder the connections?



The 1 NC for cold start having IAT switched in. The 2 NO, one for seal in and one for switching the resistor in. This relay looks to have 3 NO/NC contacts.



Jim

 

[paulb]

According to the redline box the Edge Comp limits the max boost to about 20psi. I usually run it with the redline box hooked up to the map and then the Edge, because the redline is total pass thru, and the Edge then see's total boost. One other interesting note. I replace the map sensor, and the old map sensor, would read up to 57 psi, the new one only reads up to 52psi. The new sensor did fix a "flair up" condition that I was periodically having on startup with the Comp on.



I agree that the IAT controls the WTS. I also agree that something else comes into play once it has started. I don't think it's coolant temp related (at least not directly), because with the truck plugged in, the grids will still cycle after startup. I have also had them cycle when starting up hot at the drag strip, when the weather is cold. The heater grids will stop cycling after 3 minutes, or once the vehicle reaches 18mph (it won't stop in the middle of a cycle though).



It seems at times to me that a "block learn" functionality comes into play. It almost seems that if the grids were used when the coolant temp was cold, then it is more likely to cycle the grids on a hot coolant, cool OAT restart. Just an impression...



Paul

 

[Gary - K7GLD]

From the "Inside the ECU" thread:

I am not 100% sure yet, but from what I have looked at, once the engine is running, the program switches from a 'preheat' operation of the grid heater, to a different mode. This mode appears to use the engine speed, road speed, and possibly coolant temp to determine how the heater should operate. Finally, a flag is set when the grid heater should no longer be operated. This flag bypasses the grid heater program altogether, until the next time the key is turned off/back on.



When I have some time, I'll peek into the grid heater control a bit more.



Road speed apparently comes from the CCD bus, that is a part of the code I have not looked into due to the proprietary nature of the CCD bus. I may have to build some kind of 'CCD Bus sniffer' to figure out the messages that the ECU sends/receives from the PCM.

SO, if true, I wonder what OTHER aspects of IAT/engine function might also be affected if the ECU somehow switches from a "start", to a "running" mode, and how that affects added IAT resistance as the engine warms?



Once colder weather arrives, I'll be very interested to see if my added variable potentiometer is of any noticeable value once the engine reaches operating temperature, such as "fine-tuning" base engine timing electronically.

 

[ERuhl]

Once colder weather arrives, I'll be very interested to see if my added variable potentiometer is of any noticeable value once the engine reaches operating temperature, such as "fine-tuning" base engine timing electronically.

Hopefully it works for you, I can only say that it has been of noticeable benefit for me. With a fully warmed up truck you can clearly hear the timing change when I flip the switch (usually takes a second or so). Significantly quieter, but what really makes me happy is that the miss under load goes away. It was cold enough the past few days for me to play around with this again, but now for the rest of the week it's back to warmer weather.

 

[Gary - K7GLD]

Hopefully it works for you, I can only say that it has been of noticeable benefit for me. With a fully warmed up truck you can clearly hear the timing change when I flip the switch (usually takes a second or so). Significantly quieter, but what really makes me happy is that the miss under load goes away. It was cold enough the past few days for me to play around with this again, but now for the rest of the week it's back to warmer weather.

Well, I'm not really expecting anything radical, but at a steady speed out on level road, would hope to see some small change in performance or slight change in the instant MPG readout on the overhead...



If no change or advantage at full warmup is evident, the next approach will be simply the 1K or so fixed resistor, keyed to a small reed relay and the ignition switch to eliminate cold starting issues, and whichever of the small disc thermostats will work best vs engine temperature to drop the added resistance completely out of the circuit when it's no longer needed - that setup would at least be totally transparent in operation, with no operator action needed...

 

[paulb]

Hopefully it works for you, I can only say that it has been of noticeable benefit for me. With a fully warmed up truck you can clearly hear the timing change when I flip the switch (usually takes a second or so). Significantly quieter, but what really makes me happy is that the miss under load goes away. It was cold enough the past few days for me to play around with this again, but now for the rest of the week it's back to warmer weather.

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



Paul

 

[ERuhl]

Well, I'm not really expecting anything radical, but at a steady speed out on level road, would hope to see some small change in performance or slight change in the instant MPG readout on the overhead...

My seat of the pants dyno says no difference. I tried watching the overhead mpg while switching the resistor on/off and I can't tell a difference. I think the only way to really check any mpg changes is over the long haul (ie. I think it's pretty subtle). Once we get some steady cold weather I can try a few tanks stock and a few tanks w/ IAT fooled and see how they match up. These days I'm commuting 65 miles each way, so I go through a tank pretty quickly ($$$)

 

[NoSeeUm]

It seems at times to me that a "block learn" functionality comes into play. It almost seems that if the grids were used when the coolant temp was cold, then it is more likely to cycle the grids on a hot coolant, cool OAT restart. Just an impression...



Paul

Yeah... .



I notice the same thing, it seems the the logic flag needs to be reset by bringing WCT to normal. If it isn't then the logic stays set and the grids will cycle after start, even though the engine is fairly well warmed.



Jim