stumbling around when warm ...

[dirtdemon]

howdie guys,

as it says -

fire it up, runs pretty normal
after warmup, lil probs coming up : when driving constantly ~40mph w/ small load on gas, it starts to stotter - in a small amount, but i think is no good :roll:
WOT feels nice and like it felt before the probs came up ...

so, could it be the ignition (done a good year ago - is 8K mls in there) ?
or could it be the fuel pressure (when installing the 255FP the threats on the fuel-lines where really bad, so they where dittched and replaced with a hose and clamps ...) ?
btw.: actually running 47psi w/ stockchip (still waiting for the ultimate :rant: )

... and yes, i did a search but came up w/ fairly nothing

hope for ya help,
pat.

 

[Jimmy]

Re: stumbling around when warm ...

Got a Datamaster file?

It's possible that your coolant temp sensor (on the driver's side) is bad or not hooked up.
If it is telling the ECM that the temp is -30 degrees when it's really 140,your engine will run like crap.

 

[dirtdemon]

Re: stumbling around when warm ...

sorry no DM file

understand me right - its not that bad , but quit disturbing :squint:

ignition is not a possibility ???

TIA,pat.

 

[Jimmy]

Re: stumbling around when warm ...

sorry no DM file

understand me right - its not that bad , but quit disturbing :squint:

ignition is not a possibility ???

TIA,pat.

IMO if it was ignition,it would do it all the time.
Any trouble codes?

 

[dirtdemon]

Re: stumbling around when warm ...

nope - no codes :squint:

... could be vac-leak ???

TIA,pat.

 

[MikeRenz]

Re: stumbling around when warm ...

47psi is a couple pounds high. after it warms up and starts fumbling a bit...try backing the fp down and see if it helps

 

[Jimmy]

Re: stumbling around when warm ...

47psi is a couple pounds high. after it warms up and starts fumbling a bit...try backing the fp down and see if it helps

Yeah that sounds good.Being open loop vs closed loop.

 

[dirtdemon]

Re: stumbling around when warm ...

@ mikerenz :
the high FP was my other intension, too - hope thats the cause ...
troubles seemed to start when geting warm outside :squint:

@ jimmy :
whats "open vs. closed loop" ???

 

[Jimmy]

Re: stumbling around when warm ...

@ mikerenz :
the high FP was my other intension, too - hope thats the cause ...
troubles seemed to start when geting warm outside :squint:

@ jimmy :
whats "open vs. closed loop" ???

From Dig:

Closed loop is generally used to refer to a cyclic
chain of sensor info that's used, rather than to simply say something
is derived from sensors. For example:

The ECM gets Air/Fuel Ratio data from the oxygen sensor, which is
used to alter injector pulse width, which increases/decreases
fueling, which changes the Air/Fuel ratio, which changes the data
the o2 sensor provides. Sort of an endless loop of change, where
a lot of factors provide input.

Open loop is where a sensor or a particular set of sensors (example:
MAP and Throttle Position) determine a particular parameter (such as
fueling) arbitrarily, without continual feedback to determine how
things are actually going. Sort of an arrogant view of engine
management.
.

About WOT: (which is open loop)

The thing is, the BLM *does* get applied if the BLM is lean at the
time you enter Power Enrichment mode (WOT).

In other words, if the ECM has "learned" over a long period of time
that the engine is lean, then it will apply that "fudge factor" to
the overall fueling equation, even at full throttle. This is why a
bad o2 sensor can potentially affect WOT performance.

If the BLM is reading "even" or richer than normal, it will not
add that factor to the overall fueling.

The BLM does't get calculated during WOT (Power enrichment) either.
It won't try to tell if the engine is too lean/rich if you're on
the throttle hard, it will only "learn" at part throttle and idle.


Basically what this means is that during open loop,the ECM is just working off of a set table of parameters,but in closed loop the ECM is actually using all the sensors to adjust the fueling and timing.

 

[dirtdemon]

Re: stumbling around when warm ...

thx a bunch, guys - hope will work it out :tup:

regards, pat. :2cents:

 

[sleepy]

Re: stumbling around when warm ...

Maybe have the injectors checked/cleaned - this went a long way on mine. If you have one that's not flowing right - It may work under certain situations , but cause issues at others... My two cents - good luck

 

[dirtdemon]

Re: stumbling around when warm ...

Maybe have the injectors checked/cleaned - this went a long way on mine. If you have one that's not flowing right - It may work under certain situations , but cause issues at others... My two cents - good luck

ahhh, thx for the hint, man - worth to try :tup:

regards, pat.

 

[71Mopar440]

Re: stumbling around when warm ...

Ok fairly new here. This is the only thread that I have found that really sounds like my problem. Got a 91 Syclone that stumbles horribly right around 2500 to 3000 rpms when in overdrive. Once you reach 2500 rpms, the turbo blows off and you lose all power no matter how much pedal you give it. If you manually shift it from 1 through the gears it is not near as bad. Once the rpms crest 3000, it runs rather normal, it actually pulls hard past 3500 rpms. Boost is fine, tranny is serviced, no codes (except for a few brake system codes that have been there forever), new plugs and wires, everything hooked up. The truck revs fine in park and neutral, no stumbling. Temperature doesnt seem to have any effect on this. Any help would be greatly appreciated.

 

[dirtdemon]

Re: stumbling around when warm ...

check engine light ?

are you sure your ECM does store codes ?

does fuelpress rise with boost ??

did check the fuelfilter ??

... any mods yet ??

another quick brainfart: ignition-module, cap+rotor checked ??

have the problems at any speed, in any gear ?

do you have sparkretard ?

IMO from here it seems like you have issues with fuel-deliverence or ignition or both :squint:


HTH,pat.

 

[gjp]

Re: stumbling around when warm ...

mine had a stumble when warm. Search my posts for "missfire". Its about 100000 posts long.LOL
Never did find the problem. Did a top end engine build and its gone. Lowering FP before helped but caused Knock in my truck if I went to low. I had to find the perfect pressure. It was 37lbs on my truck but that was with 50# injectors.

 

[71Mopar440]

Re: stumbling around when warm ...

Alright...... I just changed the cap and rotor. No change. Brand new wires and brand new plugs.

As far as the ECU storing codes.... Dont know. I ran the truck with the Snap-on system hooked up and it threw no codes for the ignition or the fuel, just brakes. I was thinking it is a fuel delivery problem but havent changed anything yet. Im going to put in a new pump and filter and see where that gets me. I just really dont want to shotgun parts at the truck.

No mods except suspension and a K&N intake. Other than that, it has had an alarm installed, none of which was done recently. The problem is only a couple of weeks old.

It happens at any speed, in every gear, but is it always at 2500 to 3000 RPM's. Maybe the torque converter? But if it was I think it would be doing it at lower RPM's also. The truck isnt that high in mileage either. 80K on a 16 year old truck.

It really has me stumped. ???

 

[kentuc]

Re: stumbling around when warm ...

Curious about the spark plug gap. Try .035, then back down to .032.

 

[71Mopar440]

Re: stumbling around when warm ...

Checked the gap. I went with .035 and .032. both were about the same. Still had the bad stumble. The stumbling is now creeping up the RPM's. I checked the fuel pressure and I am only at 33psi. I have a new fuel pump on the way and I am going to change it out this weekend.

 

[Kybol]

Re: stumbling around when warm ...

Checked the gap. I went with .035 and .032. both were about the same. Still had the bad stumble. The stumbling is now creeping up the RPM's. I checked the fuel pressure and I am only at 33psi. I have a new fuel pump on the way and I am going to change it out this weekend.

Mine was doing this also, never had a FP guage to check it. then my pump went out not to long after, changed it out and it seemed to fix the bogging problem when hot.

 

[MikeRenz]

Re: stumbling around when warm ...

i'd next test fuel pressure, coil, voltage (when stumbling)...plug wire resistence, rotor buildup...