timing problem; stumble

[#2875]

well i figured out why my syclone is stumbling; now i need to know how to fix it. my timing is being pulled way back. why, i don't know and no, it's not knock retard. my sofware came with a couple of typhoon data records that i have been using as standards. anyway, when the tps reads 24% on a slow acceleration (when i'm behind a ford and 1/4 throttle is all i want) the timing will go from 24 to 10 deg. advance. i did not observe this in the typhoon data. does anyone know why my computer is pulling out all my timing? since somebody will most likely say this anyway... there was no knock retard!!! please help.

 

[ItsMyTy]

any DTCs?

verified that it has a stock PROM?

that low of timing doesn't make any sense with a stock PROM if there's no DTCs

 

[ZavzTy547]

I have the same exact issue. I could be way off here but based on some troubleshooting, I suspect that it may be a bad ECM.
(stock prom is seated properly) I double checked my timing with the brown wire unattached at 0 degrees and idles fine but when I reattached the brown wire and clear the codes, it acts up, just as you decribed. I noticed that my ECM casing gets very worm at the touch (relocated it to the glovebox).
I have another ECM on the way so I'll let you know if it fixed the problem.

Could proms go bad too?

Zav

 

[#2875]

zav, i don't think it is a bad ecm because i just bought a new one and it didn't fix the problem. i am using the stock prom and the ultimate chip + stock prom. problem occurs both with the chip and without. the ultimate uses the esc from the stock prom so this may be the problem but i am really guessing here. ecs means elec. spark control right? but i have also read that this part of the chip "LISTENS TO KNOCK". both of these statements probably are true but is doesn't bring me any closer to solving my problem because i have no knock.

 

[#2875]

oh yea... no codes either.

 

[jwaller]

how about you guys post some data files so we can all look and see whats goin on. then we may be of more help. when you go from idle to part throttle the timing will go down some and it continues to go down as rpm and boost come up.

eng temp, mat temp, load, rpm, boost, everything plays into the spark equation.

 

[ZavzTy547]

Same issue, no codes, it starts right up, idles normal for 30 seconds, then stumbles and dies. If it's not the ECM I'm stumped. Have you tried changing out the stock chip? That will be my next step.

Has anyone else on this board experienced this type of issue?
Zav

 

[#2875]

i would be more than happy to do that, send me your email or tell me how to post it. i don't want to break one of the 50 rules of syty.net and i couldn't find any info on posting files. as for the variables that contribute to timing they all are in the norm compared to other data i have been lookin' at. maybe you can find something i missed. thanks.

 

[BPATT]

I am having the same problems. I changed my ecm and chip still the same thing going on.

 

[ZavzTy547]

Your right it wasn't my ECM. The other ECM did fix part of my problem (used to get a false code 43)
Truck still stumbled/missed which caused the timing to pull at 0 degrees like you mentioned.

Solution.
I advanced my timing about 8 degrees and now it idles fine and does not pull timing at idle. This tells me that I may have a dampener issue and I"m not at 0 degrees (with the brown wire unlugged). Looks like I have to find true top dead center and remark existing...

So adjusting my timing did fix the stumble but the issue lies in the ballancer not being acurate for me.

Granted this stumble could be from multiple causes so I'm curious to hear about how other peeps fixed similiar issue. It seems to be happening to alot of trucks.

Oh yeah, thanks Roland Black (SYTY VET) for your advise on this topic.

Zav.