Car stumbles terribly with MAF unplugged
Car stumbles terribly with MAF unplugged (trying speed density tuniing) which indicates to me there is a lean condition. I tried richening it up but that didnt help at all. So i went back to the stock ve table and doesnt seem to have helped it either. Ether way I think the stumble is caused by either a lean misifre or just being lean alltogether but richen it up doesnt make it any better and is making the car smell worse.
I am gonna try going in the other idrection but i dont think that will help
I am gonna try going in the other idrection but i dont think that will help
Last edited by HumpinSS; Jul 11, 2004 at 02:24 PM.
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From: Cave Creek, AZ- Canada Also.
Your title says "Car stumbles when maf unplugged" Now is think you mean by MAF is your mas air flow sensor correct? well if it is Doh of course its going to stumble its has to be plugged in, in order for the puter to adjust A/f and other parameters.
I think i may have figured it out. The car is using the low octane tables and is causing the stumble. I pulled a plug and i am running slightly rich so that puts that theory to rest. Because i pulled the MAF the Pcm automatically defaults to the low octane table as gameover specified in a previous thread. So as soon as i copy the H octane table to the low octane table hopefully i should be fine. Check back tomorrow for updates
It is not necissarily your low octane table. Unless you have reduced the low octane table on your own, the car should still run in the low octane mode.
Ironing out the VE table is tough. You have to have it pretty damn close before you can unplug the MAF. Even then, depending on the info saved in your PCM the a/f may shift.
If your VE table is fairly close to begin with, your car will stumble.
I see from your other threads that you have been using the LTerms to adjust the VE table. With your size cam, I wouldn't do that considering complications with overlap. The car should still run in closed loop with the cats in place, but it is going to error on the rich side.
The best/easiest way to go MAFless is to work off of a wideband. The formula's are a distant second, LTerms are dead last.
Good Luck
Ironing out the VE table is tough. You have to have it pretty damn close before you can unplug the MAF. Even then, depending on the info saved in your PCM the a/f may shift.
If your VE table is fairly close to begin with, your car will stumble.
I see from your other threads that you have been using the LTerms to adjust the VE table. With your size cam, I wouldn't do that considering complications with overlap. The car should still run in closed loop with the cats in place, but it is going to error on the rich side.
The best/easiest way to go MAFless is to work off of a wideband. The formula's are a distant second, LTerms are dead last.
Good Luck
Short timing (low octane table) should only make
the car low on power, not make it miss. Can you
tell from the in-car O2s whether you are lean as
you conjectured?
With the MAF out, I wonder if the spark computation
is hosed? It wants the CylAir value to index; did you
log spark advance and CylAir to see if there is a
nutso spark timing resulting from no MAF input?
the car low on power, not make it miss. Can you
tell from the in-car O2s whether you are lean as
you conjectured?
With the MAF out, I wonder if the spark computation
is hosed? It wants the CylAir value to index; did you
log spark advance and CylAir to see if there is a
nutso spark timing resulting from no MAF input?
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I went back to a table i knew worked with the maf plugged. It was the stock ve table with 400,800 and 1200 multiplied by 60-70-80 respectively.
Jimmy spark seems to be about -10* below what it would be if the maf was plugged up. Man the more i try with this tuning the more i see a wideband is imperative. Hopefully i will be picking one up in the next few weeks
Jimmy spark seems to be about -10* below what it would be if the maf was plugged up. Man the more i try with this tuning the more i see a wideband is imperative. Hopefully i will be picking one up in the next few weeks
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Originally Posted by HumpinSS
which indicates to me there is a lean condition. I tried richening it up but that didnt help at all. So i went back to the stock ve table and doesnt seem to have helped it either. Ether way I think the stumble is caused by either a lean misifre or just being lean alltogether but richen it up doesnt make it any better and is making the car smell worse.
I am gonna try going in the other idrection but i dont think that will help
I am gonna try going in the other idrection but i dont think that will help
PM'd you.
joel Update
After copying the hogh octane tables to the low octane tables 90% of the stumble is gone. Looks like there wasnt enough timing down low. Now onto getting rid of the rest of the stumble.
After copying the hogh octane tables to the low octane tables 90% of the stumble is gone. Looks like there wasnt enough timing down low. Now onto getting rid of the rest of the stumble.
