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View Full Version : Stumbling at low rpm...advise?



kimletrim
06-28-2005, 11:36 AM
OK, here is the situation. I have had a stumbling problem on my engine ever since I had HKS cams installed. At low speeds of 1400 to 1500 rpm, my engine stumbles, hiccups, hesitates, whatever you want to call it and then picks up as normal after such point. I don't know what could be causing the problem.

I recently had my car tuned by Dr. Gray with the SAFC, 660 injectors and the other requisites mods. As far as BOV, I have tried the Greddy Type S and the JDM MR valve and the car will stumble at exactly the same point for either BOV. The bogging at low rpm is really bothering me so any advice?

EugeoEvo
06-28-2005, 12:18 PM
I might be a dumbass, but does it stumble when your trying to get into 1st gear or does it happen when your already in gear and just at low rpm?

Cause this happens to me when I try to get into 1st gear, something about not gassing it enough and having my clutch in a certain way that makes it stumble for me...

Skiracer
06-28-2005, 12:26 PM
I have a similar problem when i drive around really slow for example a parking lot, but i don't have cams installed. . I "think" it might have something to do with the larger injectors. fyi, i'm running 720cc injectors.

kimletrim
06-28-2005, 12:29 PM
My car stumbles when I am already in gear and light throttle (heavy throttle will simple make the car bog).

Skiracer, I have had the stumbling prior to the bigger injectors.

Blaze
06-28-2005, 12:44 PM
I had that problem for a while.

I would try two things:

1. First Pull the ECU fuse and reset. Then re-test.

2. If that doesn't work, note the LO settings below 2600 and change them back to zero. Retest. If this solves your problem, you may need to re-tune your STFT and LTFT.

Good luck,

Blaze

kimletrim
06-28-2005, 12:54 PM
Thanks, I will give it a try.

Blaze
06-28-2005, 04:34 PM
Thanks, I will give it a try.

Make certain you don't loose your LO settings!

earlyapex
06-28-2005, 05:27 PM
My car stumbles when I am already in gear and light throttle (heavy throttle will simple make the car bog).

Skiracer, I have had the stumbling prior to the bigger injectors.

Sounds like it's too rich.

How does the car "feel" at that point? sharp or soft?

Did you re-tune your SAFC after you put the cams in?

DTunedEvoX
06-28-2005, 05:37 PM
My car stumbles when I am already in gear and light throttle (heavy throttle will simple make the car bog).

Skiracer, I have had the stumbling prior to the bigger injectors.

Sounds like it's too rich.

How does the car "feel" at that point? sharp or soft?

Did you re-tune your SAFC after you put the cams in?

I believe he got tuned after everything was put in ...

kimletrim
06-28-2005, 05:43 PM
That's the thing. I had 272 cams put in and the thing stumbled at 1400 or 1500 rpm. I have read that this is somewhat common.

To clarify matters: I had the stumbling just after getting the cams put in. At the time they were put in, all I had extra in terms of fuel was a Walbro pump; no injectors and no tune of the SAFC.

I still have the stumbling even after installing the injectors and the SAFC tune.

earlyapex
06-28-2005, 05:48 PM
That's the thing. I had 272 cams put in and the thing stumbled at 1400 or 1500 rpm. I have read that this is somewhat common.

To clarify matters: I had the stumbling just after getting the cams put in. At the time they were put in, all I had extra in terms of fuel was a Walbro pump; no injectors and no tune of the SAFC.

I still have the stumbling even after installing the injectors and the SAFC tune.

Whats your SAFC settings below 2500?

leaveit2bevo
06-29-2005, 01:55 AM
mine does the same thing.........

kimletrim
06-29-2005, 07:52 AM
So if it is something that I have to drive around (live with), will the stumbling cause problems enginewise down the road?

DTunedEvoX
06-29-2005, 09:02 AM
So if it is something that I have to drive around (live with), will the stumbling cause problems enginewise down the road?

Your already running 300+whp LOL I'm sure all those things combined would just cause a bit more wear lol :lol:

I think you'll be fine bro! 8)