stumble under certain loads
05-29-2008, 04:13 AM
#1
Race Car
Thread Starter
stumble under certain loads
OK ...I'm not too proud to ask for help 
I have been chasing a weird problem for a couple of months now.
I am having a stumble/flutter problem at certain loads. Heres what it will do:
1st gear: it will just hesitate slightly at around 10psi but then will clean up quick and run out fine
2nd gear similiar to first but the stumble lasts longer
3rd gear starts to flutter at around 7 psi and it will if I am trying to run it hard continue up to about 12-15 psi then clear up
4th gear starts to happen at as low as 4 psi if I am cruising at min throttle position. If I am running through the gears it will hapen at about 7-10 psi but may continue up to 17 psi but will clear and run out
5th is somewhat unknown other than it will start at 3-4 psi under low throttle with load.
It will also have a slight miss every so often when cruising at low throttle- part throttle
when it cleans up it is like I just released a rev limiter and runs right to whatever boost I want.
I thought I had this cleared up before I blew the turbo on my last outing
. It was running great at that time but only for about ten runs then the turbo went. I must have just got lucky
here is what I have done:
new plugs 7's at .025
known good coil and new wire
new cap and rotor
checked wires they ohm out to about 3.5 they are magnecore
new TPS
new knock sensor that seems to be working well
extra gound to engine ohms to 0 at all points
no vacuum leaks
checked AFM per clarks and moved wipers and rechecked 2x's now (last time I did this it seemed to go back to normal)
looked at the DME and KLR boards and nothing seems to be wrong
the A/F ratio is rock steady 12-13 when it does this.
to reiterate it acts like it has a 1/4-1/3 rev limiter when loading then once it clears it is like a switch is flipped and completely normal. Feels like nitrous on a POS engine.
it seems that when at the point of any real load on the engine it does it. That is why I am looking at the ignition so much.
I read that someopne had this issue with the AFM and it was testing well too. What coud the AFM do to make this happen ? short out ??
I am going to go to a differnt setup to replace the AFM but I would like to get this sorted first.
Also I have been behaving myself very well with the boost... I would like to stop now
Any help is appreciated.
I have been chasing a weird problem for a couple of months now.
I am having a stumble/flutter problem at certain loads. Heres what it will do:
1st gear: it will just hesitate slightly at around 10psi but then will clean up quick and run out fine
2nd gear similiar to first but the stumble lasts longer
3rd gear starts to flutter at around 7 psi and it will if I am trying to run it hard continue up to about 12-15 psi then clear up
4th gear starts to happen at as low as 4 psi if I am cruising at min throttle position. If I am running through the gears it will hapen at about 7-10 psi but may continue up to 17 psi but will clear and run out
5th is somewhat unknown other than it will start at 3-4 psi under low throttle with load.
It will also have a slight miss every so often when cruising at low throttle- part throttle
when it cleans up it is like I just released a rev limiter and runs right to whatever boost I want.
I thought I had this cleared up before I blew the turbo on my last outing
. It was running great at that time but only for about ten runs then the turbo went. I must have just got luckyhere is what I have done:
new plugs 7's at .025
known good coil and new wire
new cap and rotor
checked wires they ohm out to about 3.5 they are magnecore
new TPS
new knock sensor that seems to be working well
extra gound to engine ohms to 0 at all points
no vacuum leaks
checked AFM per clarks and moved wipers and rechecked 2x's now (last time I did this it seemed to go back to normal)
looked at the DME and KLR boards and nothing seems to be wrong
the A/F ratio is rock steady 12-13 when it does this.
to reiterate it acts like it has a 1/4-1/3 rev limiter when loading then once it clears it is like a switch is flipped and completely normal. Feels like nitrous on a POS engine.
it seems that when at the point of any real load on the engine it does it. That is why I am looking at the ignition so much.
I read that someopne had this issue with the AFM and it was testing well too. What coud the AFM do to make this happen ? short out ??
I am going to go to a differnt setup to replace the AFM but I would like to get this sorted first.
Also I have been behaving myself very well with the boost... I would like to stop now
Any help is appreciated.
05-29-2008, 07:51 AM
#2
The rubber in Magnecores is very soft, especially those boots.
If you are the kind of guy who removes them frequently, I would suggest you roll your own MSD 8 MM.
Just a suggestion.
If you are the kind of guy who removes them frequently, I would suggest you roll your own MSD 8 MM.
Just a suggestion.
05-29-2008, 11:48 AM
#3
Race Car
Thread Starter
Agreed and I am .
However, at this point I don't feel they are they are the cause considering once the stumble is overcome they have no misfires/problems at high boost and rpms. Even a stock wire should be fine at the lower boost.
You agree???
However, at this point I don't feel they are they are the cause considering once the stumble is overcome they have no misfires/problems at high boost and rpms. Even a stock wire should be fine at the lower boost.
You agree???
06-02-2008, 03:36 AM
#4
Race Car
Thread Starter
FYI I finally got it figured out.
turns out I had 1 bad injector and it was shorting out the driver at a certain load and then would clean up.
The good news is that in the process I now have a MAP setup installed. It is a AFMlink setup and so far I am liking it very well. I have the idle well sorted and all the cells seem to be very easy to get tuned in with E85. That along with my supplemental fuel nozzle and the A/F ratio is looking very nice. So far I am running at 22 psi with the small turbo.
After all this time I am so relieved. I have been living in the garage changing everything to figure this out.
Now to get the big turbo back on it 
Oh wait I need to get the paint done first, have to keep reminding myself what I am doing here.
turns out I had 1 bad injector and it was shorting out the driver at a certain load and then would clean up.
The good news is that in the process I now have a MAP setup installed. It is a AFMlink setup and so far I am liking it very well. I have the idle well sorted and all the cells seem to be very easy to get tuned in with E85. That along with my supplemental fuel nozzle and the A/F ratio is looking very nice. So far I am running at 22 psi with the small turbo.
After all this time I am so relieved. I have been living in the garage changing everything to figure this out.
Now to get the big turbo back on it
Oh wait I need to get the paint done first, have to keep reminding myself what I am doing here.
06-02-2008, 03:49 AM
#6
Race Car
Thread Starter
depends on how hard I drive it. If I am taking it easy I can get over 400 miles per tank. If I continually flogging it (like I have been lately to figure this out) I get around 280. I have been filling up at around 17 gallons.
