Engine/Transmission (1998.5 - 2002) hesitation with no codes

[DavidC]

Some have already tried changing the IAT with no success. I believe I have seen at least one post with the front covers on radiator and that seemed to cure his problem. If that is the case it may lead to coolant temperature. Is it possible the fan is coming on with a long hard pull, the coolant going low temp, ECM reads and tries to adjust fueling?. Just a thought.



Dave

 

[Big P]

I don't believe it is the IAT either, I'm just thinking about altering the IAT's signal to the ecm. Actually I think it was Gary that first thought of doing that.

 

[DavidC]

Coolant sensor. Is it possible to bring engine temp up to normal operating range, shut off engine, unplug temp sensor, read sensor resistance with ohmmeter and leave plug off with a resistor across the wires in the plug. If this could be done it would fool the system into thinking the coolant temp is ok. Maybe a way to at least eliminate coolant temp.



Dave

 

[WadePatton]

Originally posted by DavidC

Is it possible the fan is coming on with a long hard pull, the coolant going low temp, ECM reads and tries to adjust fueling?.

Dave

There is no "long pull" on my truck. Any WOT romp (after coolant is up to temp) with air temp under 30F is going to make it happen.



The loaded situation might make it happen at higher temps, but I'm rarely loaded. Ordering some "winter front" panels from TDR member. Will try cardboard on the brushguard if temps drop again.

 

[Gary - K7GLD]

The resistance of the IAT goes LOWER as intake air temperature goes HIGHER - so in "fooling" the ECM with what would appear to be higher intake air, you would need a lower resistance at the colder temperatures where the hesitation is usually being experienced. To do that, you would have to add a selected resistor ACROSS, or in PARALLEL with the IAT. The proper resistor might be a value of around 100K ohms - assuming a nominal IAT resistance (stock) at around 32 degrees is about 35K - a 100K resistor would then look like a bit over 25k to the ECM.



Problem with that scheme, is that the OTHER end of the IAT temperature scale is affected as well, and at a normal temperature when warm, the ECM would see a larger than actual resistance, and think is is hotter than it actually is... .



(SIGH!)



There ain't no free lunch...



It's beginning to look as though some of us are just gonna have to LIVE with this problem, unless something radical comes charging over the horizon!

 

[ALittlejohn]

OK, I started this and after alot of research I found in the Technical Service Bulletins. Bulletin # 18-24-99 states that the intermittent may occur at any time during operation of the vehicle and a change to the Cummins CM551 Engine Control Module (ECM) software corrects this condition (calibration change 99CalT9A). I do not know if you can get this done by the dealer or cummis it self. I hope this information helps.

 

[WadePatton]

AHA! almost

This ain't that- "intermittent stumble". I HAD that. Got it flashed at a D/C store. (can't say "dealer"-rhymes with "steeler" and my fingers get crossed). But thanks for bringing it up John.



The intermittent stumble was the VP cutting completely out for just a split second. Just like you cut the key, but faster. It would only happen once, and almost always when at part throttle or lifting. Never with hammer down. It might do it twice in one week and then skip two weeks. IMPOSSIBLE to reproduce on demand or predict.



No, this here is a different doggie.



OKAY, so I thought I found something tonight. As temps dropped into mid-30's again, I covered the brush guard with a Rotella box. Plenty of room for air to get in, but a major reduction in flow. No change.



Then I noticed that the system was in Heat/Defrost, so I punched it and it stammered. Then I switched out of defrost to heat only--punched it and got no stammer. I did this a couple of times and thought BINGO! There's a glitch in the A/C circuit.



But then later in the night I could not reproduce that situation.



Oh, and also the stammer just about DOUBLES in severity when (right after) I lift--if I lift before 2700 defueling. I would drop under 2k and pull about 25# of boost to "feel" for the condition. Damn stammer is not consistent. It might happen seven times of ten. But I can't make it happen 10x in a row. Actually I'd rather not.



One thing I'm convinced of is that it's in the ECM or inputs and is NOT healthy for the VP. So after miles of messing with it, I kicked the box off to sooth my VP44's nerves.



But WAIT there's more: I almost forgot that I pulled a 0122 code! TPS. Now I don't know if that's left over from the other day when I keyed-on with the TPS disconnected or not. I'll check further.



Good news is--I can make 36# of boost with the box off.

 

[Huff N Puff]

With all the high tech electronics

We sometimes over look the simple stuff. Really low temperatures can effect sensitive electronic circuits,and can also effect weak or loose fuel fittings, gaskets and orings. You guys might have minute amounts of air getting drawn in the fuel supply to the injection pump. When the fuel is cold it dos'nt want to move easily, therefore air can get drawn in. When the fittings are also cold and may be slightly loose ,a little heat can make the fuel move easier and tighten the fitting or clamps on your fuel lines. Small amounts of air would be hard to find. One way to find air is to splice in a clear test line near the injection pump. Get it real cold and snap the throttle,look real close for air in the clear line. Hope this helps. Merv

 

[SteveE]

Ramdom thought

Read through your thread and thought this might be an answer.



This is an old thread that I just copied, the important info from

and filed it away.



I think that you wore out the AIT sensor end of it.



Might as well wear on the MAP sensor now.



One thing nice is that you can check with scan tool.



Steve



Hesitation off the line

I took my 99 out today for a little ride and noticed that it was a dog (hesitated) badly before boost built up. I thought this is strange, and took it over to Blue Chip. Chip new exactly what the problem was; it was low voltage from the map sensor. A new sensor from Dodge was $96. 00, however Chip removed the old sensor and stuck a small screw driver to slightly bend the diaphragm to a get the correct voltage from the unit.



Apparently the sensor needs to output minimum . 5 volts before any fueling will take place. Mine only had . 2 volts output, thereby I had to get the boost up before fueling would take place and this created the hesitation.



Chip used his scan tool to measure the voltage, however a standard voltage meter could be used for the job. After this quick fix, the truck ran perfect with no hesitation off the line.



This is my first post to this forum and wanted folks to know about another possible problem to hesitation issues. There were no codes set, and the problem came on quickly. Also, this is a easy fix, however one must have a 1 1/4 deep socket to remove the map sensor, and the ability to measure the voltage from the unit.

 

[Gary - K7GLD]

Steve, I think the key to the above is HERE:



"Hesitation off the line

I took my 99 out today for a little ride and noticed that it was a dog (hesitated) badly before boost built up. "



Looks like the above relates primarily to ACCELERATION, especially from a dead stop - whereas what most of us here are fighting is a light stumble at STEADY or light throttle during cruising situations, or under a higher than normal load, such as towing.



Not saying the above is NOT part of our problem only that it seems to address a somewhat different scenario - plus, it apparently only exists in COLD weather for most of us... I can't speak for others - but even when the cruise hesitition was occurring with my truck, pure accelleration was fine!

 

[Gary - K7GLD]

TTT



This subject continues to crop up - even some of the 3rd gennies are displaying similar problems...

 

[Sticks]

I have been having the same problems as well. Mine is oddly enough occurring when the temps are around 40*. I am getting mixed issues. Sometimes just sitting at the stoplight, clutch out, the RPS will ramp up 100 - 250 rpms. I also get the sudden lurch forward in city traffic (1600 - 1900 rpms).



I went through the engine compartment and pulled, ground, cleaned, dielectric greased, and torqued all the grounds that I could find. Still have the problem.



My thinking is the TPS/APPS assembly may be the culprit. There is an overgrown rheostat that controls the throttle (fly by wire). Grit, dust, metal shavings will break contact or bridge the coil to give random throttle senor readings, within 150 rpms. It's metal on metal, so you can't tell me that there is not wear going on in there. Supposedly there is grease (dirt magnet) to lube the parts in contact.



#ad

 

[WadePatton]

Okay, now I have a code...

You'll never guess. --460 APPS voltage low.



I've been noticing a slight fluctuation of RPM (25-50) under steady throttle. Would be dandy if APPS replacement fixed the hesitation as well.



Anybody swapped APPS units for this problem?



Another thing that might point at the APPS is that I have found that FULL THROTTLE will cure the buck--but it'll also get you a TICKET!

 

[HillCountrykid]

Just doing a search and this came up.



Wade, I replaced my APPS yesterday, and now I am the pround owner of a perfectly good $450 paper weight. It did'nt fix a thing. I've about had it with this stubble. I can make it do it just about every time I get it up to 2500~2600 rpm and let off gently. I even had it blow a little white smoke today. I have had it pour white smoke and die several times before, so I don't know if it's related. I also unhooked the Comp (unplugged sensors) today and it does'nt help one bit. The temps have been in the 60's and 70's, so it's not limited to cold weather.



Brian

 

[Gary - K7GLD]

I didn't really think it was related - but it might be - a couple of us are working on dissecting APPS units to determine why they seem to fail prematurely, and if we can find a common, easily repaired solution to the "$450 paperweight" mentioned above.



One remote posssibility for BOTH the APPS and hesitation bit is possible "noisy" electronic components/circuitry inside the APPS - sorta like when a volume control starts going bad and delivers lots of scratchy static when you try to change a stereo or radio's volume - that could sure create problems down the line at the ECM...



Buy apparently didn't work for Brian...

 

[HillCountrykid]

This only started two or three weeks ago and is getting worse. Just for grins and giggles I pulled the IAT and MAP sensors and cleaned them yesterday with no change. I'm pretty short tempered and don't have alot of patience, so this is really starting to get my panties in a wad. I'm not part swapping anymore, since I was almost possitive the APPS was bad.



Is it just me or has there been a big increase in the number of complaints of stumbling lately?

 

[HillCountrykid]

I went out and checked codes again. I remember the 0122 (reason I replaced the APPS) but also have 0216 and 0253! Not good. Has anybody with these symptoms and codes fixed it with a new VP? I really don't want to replace a expensive pump, but maybe that's the problem. After searching around, some have had similar symptoms and replaced the pump, fixing the problems. Also it seems to be clattering more lately under 2200 or 2300 rpm, like loose valves or bad timing. Since the 0216 is a pump timing failure code, maybe.

 

[WadePatton]

216 is almost always the pump--I'm told. sorry.

 

[HillCountrykid]

Replaced the pump and everything seems to be o. k. (knock on wood).



Brian

 

[ThrottleJockey]

Slight, temporary flooding of the combustion chamber due to.....



You got it, timing advance. Not enough to damage anything, mind you. Just enough to annoy the crap out of the driver! See the cold temps of the water and the intake air cause the ECM to advance the timing of the injection event and this coupled with bigger injectors sends a bunch of cold fuel into a cold combustion chamber filled with cold intake air surrounded by cold coolant. Brrrrr! It's a wonder the thing runs at all. The early injection of the cold fuel tries to put out the very 'fire' the combustion chamber is trying to create. This would be okay if it were a Cummins powered Peterbilt pulling the Grapevine with a 50000 pound chill coil 'cause boost would be coming on right about now. But in our pick ups with virtually no load and low cruising boost a slight flooding condition occurs. Remember, the ECM doesn't know you changed injectors.