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

[timbo]

My latest idea actually worked and its so simple its pathetic! I'm in pa and this past weekend it was 65 deg on sat, and the truck didn't miss a beat! It just dawned on me! the water temp don't run up to 195 in the chilly weather, mine is lucky to get 180. So for hell of it i cut a piece of cardboard 23in wide 20in tall and put in beween the radiator and the intercooler. Drove this coldblooded peice of iron about 8 miles,and got 190deg. I rolled into throttle in 5th NO MISS Oo. I had smoke flyin the whole way home! It was 40deg on the way but before it would miss at any ambient temp below 60. Its all about this thing being nice and toasty! Even in the summer time i drive the truck about 5-10 miles before getting on the dyno. it just runs better hot! I don't tow anything with my truck, so i dont know how good it will work for that, might heat up!! This is just my daily driven HODROD!! :-laf Hope this helps others!

 

[ERuhl]

Thanks for posting your results for this and for your tests on the IAT sensor. What thermostat are you running right now? I have the one from the tsb but I've disliked it from day 1. It doesn't hold a steady temp so I've been wanting to try a different thermostat. I'll give the 190° thermostat a try and see if it helps. Thanks!

 

[timbo]

As far as i know it's the stock thermostat,every thing seems factory orig. as it was a one onwer truck. it runs a hair above 190 in the summer time. Today it was in the low 30s, that temp gauge had to be dead on 190( help from cardboard) for it not to miss! I'm still sure it's timing, and i'm still not entirely happy with the solution! I have a smarty coming, it will be here friday! After i receive it i will resume testing!!

 

[ERuhl]

I'm still sure it's timing, and i'm still not entirely happy with the solution! I have a smarty coming, it will be here friday! After i receive it i will resume testing!!

It's definitely timing. When I had my TTPM I put it on the "timing only" setting and it still had the miss. Unplugged it and it was back to normal. I noticed the Smarty comes with several "fueling only" options, I'm anxious to hear if those work for you.



I'm picking up a new 190° thermostat on Friday, hopefully that helps. If not I'll try blocking off the radiator and at least verify that the operating temp makes a difference.

 

[timbo]

It's definitely timing. When I had my TTPM I put it on the "timing only" setting and it still had the miss. Unplugged it and it was back to normal. I noticed the Smarty comes with several "fueling only" options, I'm anxious to hear if those work for you.



I'm picking up a new 190° thermostat on Friday, hopefully that helps. If not I'll try blocking off the radiator and at least verify that the operating temp makes a difference.

Hey, ERuhl i see you also joined not to long ago. Please fiil your signature in, im curious to know what you have! Well today it was in the high 20s and when the temp gauge got to 190 i rolled into the throttle, it misses. On the way home it was 35, No miss! The extra coolant temp seems to retard the timing enough, to not "go over the line", but it only works to 35deg. I,ve been seriously considering slotting the holes on my old vp,on the mill at work(slot them only in the direction to retard). This would absolutely prove it's timing. My old pump has already been TAPPED :-laf I would like to keep the new pump untapped and on the shelf so i always have a troubleshooting aid, and a back-up just in case.

For a living, i troubleshoot hydrostatic drives and hydraulic systems on construction equip. along with the 24v cummins found in most CASE trackhoes. This is just one of those problems that will drive me nuts until i find an answer! And it's just another JOY of being a mechanic!

 

[ERuhl]

Hey, ERuhl i see you also joined not to long ago. Please fiil your signature in, im curious to know what you have!

Truck details are in my profile Much less aggressive setup than yours but I still get the miss, so that's more evidence that it's a timing issue and not fuel demand that causes the miss.



Please keep me posted on your results!

 

[timbo]

Well after a bunch of research today on the phone with EDGE, When i explained its symptoms, they said WE know there are a couple of gliches in some of PCMs on these year trucks, in cold weather. I then explained my idea about slotting the holes on the pump. They did not recommend that! They told me to call sheid diesel for some help. I found out slotting the mount holes on the front flange will not change timing. the ecm senses TDC by the CAM sensor. Timing and fuel delivery is entirely controlled by the ecm closeing the bypass valve. Twisting of the pump body would do nothing, the ecm would just compensate for it. Thats what the guy at sheid diesel told me,and i also agree with him! So i got thinkin again, i went the electronics place and got a 30k potentiometer. I wanted to do this IAT fooling again, but this time i got pins that fit snug in the connector and ran the wire into the cab. I also hooked up the ohms meter so i can see actual ohm values. The values are on genos garage,40k at 32deg and 667 ohms at 212deg Then i went for a fairly long ride. Just let me say, I must not of had a good connection last time,because this really changes timing! At 30k on the meter it misses like crazy and you can hear timing. I then took it to 1k, the miss was almost gone. then i set at 500 ohms NO MISS Oo. I realize this is less ohms then the sensor would actually send back to the ecm, but the ecm only sets a code on an 'open' sensor. It did not set a code for me. I'm going to mount it in the cab so i can adjust it. COOL another thing to tune, I LIKE IT :-laf

 

[timbo]

well i just got my smarty! but its raining here in pa and 55deg when the temp gets back down to the 20s i will plug the IAT back in and do some experimenting to see if it misses with just the smarty and 190deg water temp.

 

[timbo]

Here is everything i went through to solve this issue! I thought i would shoot back to the top again since all the discussion! I have also found 1k. works just fine and ERuhl has also proven it. Thank you ERuhl, for helping to prove this!

 

[Gary - K7GLD]

OK, sounds like a possibility, and a fair number of guys with the VP-44 24 valve trucks have reported the same problem - but just one question:



Is your IAT resistor "fix" treating the real CAUSE, or only the SYMPTOM?



I want to make dern certain I'm attacking the real problem, not merely a symptom OF that problem!



Is it possible that the affected trucks are displaying an out of tolerance or defective IAT issue, rather than the suspected base timing? Has anyone experiencing this problem tried simply replacing the IAT - or swapping with another one from a truck NOT having the cold weather miss problem?



Case in point, I experienced the cold temp erratic/random miss or "bucking" last week while towing our 5er, Smarty was on stock setting, Comp in EZ mode, on setting 1x1. Miss got worse if I increased the Comp level - but even turning the Comp completely off did NOT stop the miss. Only thing I didn't try, was loading in one of the Smarty levels to see what effect that might have. Once the truck gets fully warmed up, the miss is gone. I first noticed this effect about 4 years ago when towing our 5er in below freezing weather - last week was the first time we had towed in cold weather since then, and the problem quickly returned...

 

[NoSeeUm]

This topic has come up before. It seems that, in at least from what I read, that too much timing / higher fueling rates seem to cause the miss. The fix in the past has been a resistor in paralled of the IAT. The resistance seems to be in the 1k to 5k ohm range.



In my case I have only experienced the miss one time. I was running Smarty SW 1 (Fuel Saver) and I got in it pretty hard.



I know that my engine noise seems to be much louder until the IAT gets around 100F and the CWT comes up to normal. I always thought this was caused by more timing. Much like the difference in noise from running stock vice a timing SW. At any rate I notice it before the engine is fully warmed up.



Jim

 

[Gary - K7GLD]

This topic has come up before. It seems that, in at least from what I read, that too much timing / higher fueling rates seem to cause the miss. The fix in the past has been a resistor in paralled of the IAT. The resistance seems to be in the 1k to 5k ohm range.

Which, of course, is the reason why I ask if the REAL issue is possibly a defective/out of tolerance IAT. If that IS the basic problem, I'd rather simply fix THAT than screw around with a band-aid "fix"...



I have in the past, seen posted the range of "normal" resistance readings provided at specific ambient temperatures for the IAT - think I'll dig back for the thread(s) they're in, then pull mine off the engine and check it out...



EDIT:



Here's a pointer to info regarding IAT related problems, as well as info on checking and cleaning one:



IAT sensor - Ram Diesel Problems and repair

 

[NoSeeUm]

Here is another thread Gary. GOT-Torque ran the full route. I believe from his investigation it was software and too much timing.



IIRC Diesel Freak of on NWBombers, had pretty much the same problem and same result only on cooler days. DF, initially fixed his with cardboard in front of the radiator.



In my case, with Fuel Saver, the one and only time my truck ever missed a beat.



Edit: Diesel not Deisel I got to noticing the circa of this thread. LOL I am a Dork... .



Jim

 

[ERuhl]

Is your IAT resistor "fix" treating the real CAUSE, or only the SYMPTOM?

The cause is too much base timing. To correct it, the base timing is being adjusted indirectly via the IAT sensor signal.

Has anyone experiencing this problem tried simply replacing the IAT - or swapping with another one from a truck NOT having the cold weather miss problem?

Surely you're joking? With the obvious relationship to intake air temperature the IAT sensor was the prime suspect. I swapped it out for new, researched the calibration curve, tried a sensor with a different calibration (so it effectively reads "warmer" than actual), and looked into sensor relocation options. Yes, the health of the IAT sensor was thoroughly examined. Given that the sensor is functioning properly, the root cause is too much timing. Without a means to directly alter the base timing via the CPS signal, altering the IAT signal was/is the easiest solution. To mechanically shift the base timing you need to pull the camshaft (no thanks, see search for more info if interested).

Otherwise the "fix" is to not run a timing box and stick with fueling-only options. Incidentally this is where I'm headed, but for now the IAT mod gets me by.

 

[WestTN]

Timbo, as an old, retired electronics guy, I like your diagnostic approach except for one thing. You have paralled a current source (your ohmmeter) with the circuit you are analyzing. This will affect the results. You need to adjust the potentiometer without the meter attached until the 'missing' stops. Then shut the truck down, disconnect the pot and check its resistance. This will give a result that will work your truck's IAT. That value may or may not be right for another IAT or truck. Of course you could just leave the ohmeter in cicuit full time and just replace the batteries when they need to be!

 

[Gary - K7GLD]

Thanks for the added info - and I was also curious as to what you guys mean by "base timing" - as in MECHANICAL. or ELECTRONIC base timing - it seems you are specifically referring to the MECHANICAL timing, perhaps centered on the camshaft timing in relation to the crankshaft?



Hard to figure how that could be so far off in normal engine manufacturing/assembly that the electronic side couldn't compensate, just as the VP-44 will if rotated s bit off - and by the way, this effect has occurred for me with 2 different VP-44's...

Otherwise the "fix" is to not run a timing box and stick with fueling-only options. Incidentally this is where I'm headed, but for now the IAT mod gets me by.

AH, but in MY case, I'm running the Comp in EZ mode, no wire tap (I can plug or unplug the Comp/VP-44 tap as I wish) - and even turning the Comp off didn't help. Also, this same cold weather effect has been noted by others in STOCK trucks - and it did it on my own even with STOCK injectors.



I have NO doubt that at least for the 2 of you guys, the IAT "workaround" works, and if all else fails, I will try it on mine - just trying to get more specifics on exactly what's going on here, and why this "fix" is even needed...



Please correct me, and/or comment on exactly what you are referring to in "base timing" - mechanical, electronic, or a combination of both.



And I'll emphasize, once normal engine temps are reached, the effect disappears, and the truck runs GREAT!

 

[WTBurke]

I agree with Dennis... .

Any of us doing these DC resistance measurements (parallel) should be done with a decent digital style DVM. The input DC resistance should be around 20 megohms per volt so as to not swamp the actual circuit you're reading. Old style Simpson analog type meters are down around 1000 ohms per volt and a $2. 99 meter is a sure bet you're swamping the circuit. There are many DVM's today around $20 bux that have 20 meg input resistance and do provide high isolation.



William

 

[ERuhl]

Timbo, as an old, retired electronics guy, I like your diagnostic approach except for one thing. You have paralled a current source (your ohmmeter) with the circuit you are analyzing. This will affect the results.

I'm guessing you're talking to me? If so, you misunderstood the approach that timbo and I took.

You need to adjust the potentiometer without the meter attached until the 'missing' stops. Then shut the truck down, disconnect the pot and check its resistance.

This is in effect the method we took. We found a substitute resistor that worked in place of the IAT sensor (which is nothing more than a temperature-dependent resistor). This tells us the net resistance needed to prevent the miss. The IAT sensor calibration is known as is the equation for resistors in parallel. I measured the resistance of the potentiometer and marked my housing so I know pot resistance based on knob position. With the pot in the cab and plugged into the IAT circuit I can adjust the resistance on the fly to maximize timing without inducing the miss. I can also look at my markings to determine the associated pot resistance.

Of course you could just leave the ohmeter in cicuit full time and just replace the batteries when they need to be!

The meter was never part of the circuit.

 

[ERuhl]

I agree with Dennis... .

Any of us doing these DC resistance measurements (parallel) should be done with a decent digital style DVM. The input DC resistance should be around 20 megohms per volt so as to not swamp the actual circuit you're reading. Old style Simpson analog type meters are down around 1000 ohms per volt and a $2. 99 meter is a sure bet you're swamping the circuit. There are many DVM's today around $20 bux that have 20 meg input resistance and do provide high isolation.



William

All good info, and something for others to keep in mind if they intend to do something like that. I took the easy route.

 

[ERuhl]

Thanks for the added info - and I was also curious as to what you guys mean by "base timing" - as in MECHANICAL. or ELECTRONIC base timing - it seems you are specifically referring to the MECHANICAL timing, perhaps centered on the camshaft timing in relation to the crankshaft?

Base fuel injection timing, which is read off the cam position sensor. The sensor is non-adjustable.

Hard to figure how that could be so far off in normal engine manufacturing/assembly that the electronic side couldn't compensate, just as the VP-44 will if rotated s bit off - and by the way, this effect has occurred for me with 2 different VP-44's...

In order to "compensate", it needs a point of reference (base timing).

AH, but in MY case, I'm running the Comp in EZ mode, no wire tap (I can plug or unplug the Comp/VP-44 tap as I wish) - and even turning the Comp off didn't help. Also, this same cold weather effect has been noted by others in STOCK trucks - and it did it on my own even with STOCK injectors.

I have NO doubt that at least for the 2 of you guys, the IAT "workaround" works, and if all else fails, I will try it on mine - just trying to get more specifics on exactly what's going on here, and why this "fix" is even needed...

What I can tell you, is that a resistor costs less than a dollar and in the time we've spent writing these messages back and forth you could have answered this for yourself already. Unplug your IAT sensor and insert the resistor into the connector in place of the sensor (make sure you have a good contact). Go for a drive, if the miss is gone then you're in the same boat as timbo and I (and others, search for the Edge miss). If not, then you have other problems. I'm not familiar with the comp and whether or not it still changes timing while "turned off". Perhaps yours is so far out that it misses even without the added Edge timing.

For timbo and I adjusting the base timing via the IAT sensor eliminates the miss. YMMV, but fortunately for everyone it's a very cheap and easy test to confirm. You just have to make the effort to try it.

And I'll emphasize, once normal engine temps are reached, the effect disappears, and the truck runs GREAT!

Mine too on some days if it wasn't too terribly cold, and the IAT was raised high enough by the engine to not cause the miss. Look into it, you may be surprised that the IAT temperature is not the smae as the outside air temperature. So when starting with a cold engine it could miss and when the engine warms so does the IAT and the miss goes away. Likewise there are days that are warm enough not to ever have the miss, and there are days that are cold enough to miss even when the engine's warm. BTDT, came up with a fix for it, wrote a post on it, and somehow still reliving it.