Engine/Transmission (1998.5 - 2002) uneven idle

[Wyatt 1]

Installed all the parts in the sig it runs good but at idle it doesnt idle smooth is this normal with the mods installed? Anyone else have this problem and can give a solution or things to check for? Thanks,

 

[RJPotts]

What is the spec on the cam? That may have something to do with it.

You say it doesn't idle smooth, does this mean it lopes (like a gasser with a cam) or it shakes like its lugging?

-R. J.

 

[2-ND TIME]

bad idle, power above 1600

Well I can tell you that you unfortunately have the same thing as I have been having since new. Nobody has a clue what it is. EXCEPT ME. What I have found mine to be is bad voltage from the PDC. I have mine apart sort of and have been measureing the resistance of the buss connections in it.



The only thing I have found to now is poor fitting studs in the buss connections for positive and negintive. Probably causing the arcing. I hve also started to redo the ground connection below the drivers battery case. You can put the one lead on the stud and the other lead of the meter on the buss and have no continuity. Marvelous such a poor design. :{



With the oscilloscope I have seen the poor voltage from the buss conection and this is seen in the voltages to the VP-44 The poor voltage to pin 7 is likely upsetting the 5 volt logic. This is embeded in the sync pulse and has ruined the pin 5 fuel shut off voltage. I have 1 volt peak to peak. So with this I fugire that it shuts the fuel off very regularly. It is probably just above the hold in voltage. When the peak voltage falls it starts to close and then reopens. Cryslurrr,Cummins and Bosch have been no help to date. I have some of the scope info on my readers rigs if girlfriend can figure how to get more on she will. Can fax or send them as an attachment to you if you like. Does your buck at all or an rpm band???? Hope this helps. :-{} :{

 

[Wyatt 1]

It only has uneven RPM at idle I dont have any problems cruising. When I got on it for the first time it cut out real bad in third and fourth, I mean real bad when I was into to it hard boost about 35 to 40 and then to or three real bad bucks shifted into fourth and got it going again same thing so I shifted into fifth and let off the throttle smooth sailing at about 85mph????

 

[CumminsFarmer]

Mine idled normal when I bought it stock. It started fluctuating roughly 50 RPM at idle after I honed the injectors. For those of you that dont know, the 'Stage 2 injectors' in my sig. are stock injectors that have been hydraulically honed to change injection patterns. Gave me about 80-90 extra horsepower. Nice mod really, but it made it idle rough. I just got used to it.

 

[Texas Diesel]

Here is what I did and it dramatically reduced my idle surge.



I got the idea from my BMW (fuel injected). The BMW would hunt or surge badly at cruise speed. The problem was traced to loose and corroded battery connections. Clean and tighten them and the worst of it went away. It seems that some BMW's surge a little due to EPA mandated lean-burn engines. I fixed that too with an adjustable fueling box



EPA KMA :-laf



Back to the truck, I cleaned all 4 battery connections and then sealed them good. Problem solved. This step alone removed 90% of the idle lope. The remainder might be due to an old VP-44, bad connections elsewhere (arent you glad you dont have a P-7100 :-laf) or who knows what, but it is very tolerable now.

 

[Wyatt 1]

What is the spec on the cam? That may have something to do with it.

You say it doesn't idle smooth, does this mean it lopes (like a gasser with a cam) or it shakes like its lugging?

-R. J.

No RJ it doesnt lope, or really surge, it is more like a stutter if you will, there is no pattern and it did it worse sometimes than others, and you could hear more than you could see it on the RPM guage, which fluctuated slightly.



I cleaned the battery post and connections already Texas, you were there, how are things, I had to go back, it sux here, no truck!!

 

[Texas Diesel]

Hey Wyatt1, give me your address over there in Iraq so I can send my consultation fee bill :-laf



I posted that for the benefit of others, I think your shower head injectors may be your source of uneven idle.



You need to add "custom machined flywheel" to your sig.



Do you want me to test run your truck while you are gone? Oo.

 

[Wyatt 1]

Do you want me to test run your truck while you are gone? Oo.

Yeah maybe you can work the bugs out. I wrote piers and between the custom flywheel deal I am trying to trade the stage 3's for some 4's or 5's what size would be better, bigger the better can sometimes bite you in the *%$. :--)

 

[2-ND TIME]

bad idle

Do you have a certian RPM that you have to get over for it to accelerate? Mine is 1500. Is it gutless or slow to pickup below that???

The cutting out at 35 to 40 lbs boost is very enviable :--) is likly the ECM seeing the over boost and cutting back the fuel. I describe the cutting off of fuel as turning on and off a transistor ( would be at that speed).

 

[Wyatt 1]

yes thats about it, around 1500 rpm or maybe a little more and then the boost guage jumps up quick. Also like the flip of a switch and back on again thats what it was like. Could be the fuel cutting out but why? Doesnt the comp adjust for boost, boost fool the ECM??

 

[Wyatt 1]

also found out why it spools so slow I think, there was a peice supplied with the piping kit it was a piece of 2" od pipe or around that dimension and about three inches long. I was told it should have been put in the backside of the HX 40 exhaust housing to block off the waste gate flute to the exhaust wheel and forces the wastegate gases to help boost the HT3B spool quicker at lower RPMs. I hope that is what it is because right now it has NO low end, but when it comes on its nice!!! I trust my source (PDR).