BOV hell...
- Thread starter airtroop01
- Start date
If it was still drawing air through the MAF with the BOV disconnected (and assuming that the IAC wasn't going full-bore), I wonder where it was going?
And, even more curious, why is the truck going lean?
And, even more curious, why is the truck going lean?
camcojb
Active member
FMOS Racing said:If it was still drawing air through the MAF with the BOV disconnected (and assuming that the IAC wasn't going full-bore), I wonder where it was going?
And, even more curious, why is the truck going lean?
I don't know that it draws more air with the bov disconnected; he briefly tried that and it was much worse so he hooked it back up.
The higher dashpot settings have cured it everywhere except when fully warm. I think the lean issue is what nearly all these trucks do when you shut the throttle, at least mine always did. Injectors shutting off on coastdown. I really want to get a look at it myself to see what it's doing, but he says it goes lean, the maf counts seem to hang higher than the idle speed would indicate they should be. Then the idle speed drops way down to 300-400 rpm and it dies.
airtroop01
Active member
Yeah, the BOV might have been fully open when I tried disconnecting it. It wasn't until later did I realize that the fine print on the Greddy paperwork on the other side which wasn't written in Japanese said the BOV comes from the factory on the softest setting. But now, with the BOV adjusted a bit stiffer, I'll try disconnecting it again and see if it makes a difference.
As far as the lean issue... I know and understand the truck will go lean when you shut the throttle. Jeff was also checking that I knew that as well.
The lean issue exhibits itself in two ways. I may back off the gas, but I'm not fully off the gas. Consider a coast with light throttle. Maybe I'm merging on the freeway and after a little romp I back off a bit to go with the flow of traffic. Maybe I pass a school and ease off the throttle to slow down but keep going. A/F shows rich initially then goes lean under throttle. Engine stumbles under the 17:1 a/f. That's one of the moments I'll see the maf counts hang when rpm and load are lower. Now getting back into the throttle after this, the truck stays lean at 17-18:1. After a few seconds of sputtering, then i get full rich 10:1. If it doesn't die there, then I'm usually surprised.
The second lean condition is stepping on the gas from a stop. At idle I'd see the normal 14.8-15.1:1 a/f. Stepping into the gas, when fully warm, the a/f will go lean on me again to 17:1 and then cause the truck to run bad. More gas and richer but back off again and I get the condition I mentioned previous to this one.
Both conditions mainly show themselves when the truck is really warm. At that time, the truck is usually much more fun to drive because the turbo is spooling up, I'm hitting boost quickly, and then when trying to return to some level of sanity is when it wants to die.
So, if you think what I thought, the first thing I say was well, that lean condition from a stop must mean your maf transfer is jacked. So I've been datalogging the hell out of it. In neutral, noting a/f and short term fuel trim counts and making sure the numbers are right. OK. Still does it. So what do I do? I decide why not richen it up and make it fat with an open loop tune. But that didn't work out as I thought it would as low throttle besides idle was horrible.
The dashpot settings made this much better in addition to increasing the range of learning the computer can do. If I can keep it from doing the lean issue it might actually be a streetable ride. I should check my TPS voltage.
As far as the lean issue... I know and understand the truck will go lean when you shut the throttle. Jeff was also checking that I knew that as well.
The lean issue exhibits itself in two ways. I may back off the gas, but I'm not fully off the gas. Consider a coast with light throttle. Maybe I'm merging on the freeway and after a little romp I back off a bit to go with the flow of traffic. Maybe I pass a school and ease off the throttle to slow down but keep going. A/F shows rich initially then goes lean under throttle. Engine stumbles under the 17:1 a/f. That's one of the moments I'll see the maf counts hang when rpm and load are lower. Now getting back into the throttle after this, the truck stays lean at 17-18:1. After a few seconds of sputtering, then i get full rich 10:1. If it doesn't die there, then I'm usually surprised.
The second lean condition is stepping on the gas from a stop. At idle I'd see the normal 14.8-15.1:1 a/f. Stepping into the gas, when fully warm, the a/f will go lean on me again to 17:1 and then cause the truck to run bad. More gas and richer but back off again and I get the condition I mentioned previous to this one.
Both conditions mainly show themselves when the truck is really warm. At that time, the truck is usually much more fun to drive because the turbo is spooling up, I'm hitting boost quickly, and then when trying to return to some level of sanity is when it wants to die.
So, if you think what I thought, the first thing I say was well, that lean condition from a stop must mean your maf transfer is jacked. So I've been datalogging the hell out of it. In neutral, noting a/f and short term fuel trim counts and making sure the numbers are right. OK. Still does it. So what do I do? I decide why not richen it up and make it fat with an open loop tune. But that didn't work out as I thought it would as low throttle besides idle was horrible.
The dashpot settings made this much better in addition to increasing the range of learning the computer can do. If I can keep it from doing the lean issue it might actually be a streetable ride. I should check my TPS voltage.
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Phil, can you datalog TPS and IAC?
That lean-out on tip-in is absolutely baffling...
That lean-out on tip-in is absolutely baffling...
airtroop01
Active member
I've datalogged TPS but haven't tried to datalog IAC.
Have also changed IAC unit.
Have also changed IAC unit.
skidmarkracing
My wife says i'm retarded
We had a good conversation on the phone. The lean out is actually a false reading. What is happening is this, the truck is going so rich that it is not burning the fuel and showing as a lean condition.
Here is what happens. You step on the throttle and get back off. The computer sees the amount of air that just got pulled by the MAF and dumps in fuel. This is all before you actually close the throttle. Now you have no air and a ton of fuel.
Run the dashpots up to slow the coast down. Then add more idle air to account for the fuel.
I will shoot you a base file so we can test and see what we get
Here is what happens. You step on the throttle and get back off. The computer sees the amount of air that just got pulled by the MAF and dumps in fuel. This is all before you actually close the throttle. Now you have no air and a ton of fuel.
Run the dashpots up to slow the coast down. Then add more idle air to account for the fuel.
I will shoot you a base file so we can test and see what we get
camcojb
Active member
skidmarkracing said:
Good info. Phil and I were talking and I said that it should go rich, not lean since the maf numbers are hanging up with the throttle closed. He's hopefully going to get it up here so I can do some tuning this weekend, and I appreciate any info as to where to start.
Jody
I didn't know a wideband could show a false lean.
I've actually never had a vehicle die from going rich, only from going lean, so it's going to be interesting to me to see what settles out from this.
I've actually never had a vehicle die from going rich, only from going lean, so it's going to be interesting to me to see what settles out from this.
roach4047
Member
Sounds to me that the problem is too much air into the mix at the wrong time.... During the brief periods time that the engine is trying to lower its rpm's and an attempt of the ecu to correct the issues of a temporary much higher than needed volume of air=while fuel is down/off since the engines rpms are dropping creating a leaned out condition and therefore stalling the engine..how do you fix that? I've just confused myself entirely...
Once again, I'll be interested in seeing how this plays out. I can show you vids of mine trying to stall at L-Fest 1 after the burnout. It doesn't do that anymore. And it had nothing to do with it being rich
To add to all the confusion.....you really should be watching your 02 sensors and make sure they are cycling correctly at an idle.
I know you had to put big extension on your sensors and I think you have aftermarket cams also, so it is something else that you have to watch because it will effect the idle big time.
Dale
I know you had to put big extension on your sensors and I think you have aftermarket cams also, so it is something else that you have to watch because it will effect the idle big time.
Dale