Weird hot start idle problem...
12-09-2006, 05:50 PM
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Weird hot start idle problem... Im in OLSD, the VE table is perfect. The motor has a very small cam (LPEGT2-3) and a BR-FPR and 60# injectors.
When the car is warmed up and have been driving. Ill turn it off and come back about 30 minutes later and start it up, it starts fine, but sometimes will start to idle real funny. ill look at the WB and its pegged at 20:1 and the RPMs drop to ~400 (M6). Ill give it gas and itll rev just fine and the a/f comes back in line, but as soon as I let it drop to an idle, it does it again. If I hold it at ~1500 rpms for about 30 seconds, it clears up and idle just fine at 14.7. I never touched any idle tables since the cam is sooo small (just barely over a Z06 cam), but it idle fine once it gets over its temper tantrum...
Any idea?
When the car is warmed up and have been driving. Ill turn it off and come back about 30 minutes later and start it up, it starts fine, but sometimes will start to idle real funny. ill look at the WB and its pegged at 20:1 and the RPMs drop to ~400 (M6). Ill give it gas and itll rev just fine and the a/f comes back in line, but as soon as I let it drop to an idle, it does it again. If I hold it at ~1500 rpms for about 30 seconds, it clears up and idle just fine at 14.7. I never touched any idle tables since the cam is sooo small (just barely over a Z06 cam), but it idle fine once it gets over its temper tantrum...
Any idea?
12-09-2006, 08:27 PM
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Originally Posted by Country Boy
Im in OLSD, the VE table is perfect. The motor has a very small cam (LPEGT2-3) and a BR-FPR and 60# injectors.
When the car is warmed up and have been driving. Ill turn it off and come back about 30 minutes later and start it up, it starts fine, but sometimes will start to idle real funny. ill look at the WB and its pegged at 20:1 and the RPMs drop to ~400 (M6). Ill give it gas and itll rev just fine and the a/f comes back in line, but as soon as I let it drop to an idle, it does it again. If I hold it at ~1500 rpms for about 30 seconds, it clears up and idle just fine at 14.7. I never touched any idle tables since the cam is sooo small (just barely over a Z06 cam), but it idle fine once it gets over its temper tantrum...
Any idea?
When the car is warmed up and have been driving. Ill turn it off and come back about 30 minutes later and start it up, it starts fine, but sometimes will start to idle real funny. ill look at the WB and its pegged at 20:1 and the RPMs drop to ~400 (M6). Ill give it gas and itll rev just fine and the a/f comes back in line, but as soon as I let it drop to an idle, it does it again. If I hold it at ~1500 rpms for about 30 seconds, it clears up and idle just fine at 14.7. I never touched any idle tables since the cam is sooo small (just barely over a Z06 cam), but it idle fine once it gets over its temper tantrum...
Any idea?
12-10-2006, 03:13 PM
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Originally Posted by Sean Collins
Can you post up your open Loop Af vs temp and MAP table ?????
The table is all 1.00 from 140*s on at all MAP levels for my OLSD tuning.
It doesnt do this everytime, but its very intermentin (sp?)
12-10-2006, 07:24 PM
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Is the commanded AFR when it's doing this, in line with the
delivered (WB) or not?
The speed density side has some sort of calculation it does
for air temp to get the density (MAP, absolute temp) and
if the ECT and IAT are both heat-soaked then this may be
giving a bent air mass value. The SD guys play with some
thing that controls how much the ECT and IAT are used
(proportions) to calculate air temp. I forget the name of it
but some think it's helped their air mass accuracy.
Maybe running it at 1500RPM just gets these sensors out
of the hot-parked soak condition and into normal range.
Intermittent
delivered (WB) or not?
The speed density side has some sort of calculation it does
for air temp to get the density (MAP, absolute temp) and
if the ECT and IAT are both heat-soaked then this may be
giving a bent air mass value. The SD guys play with some
thing that controls how much the ECT and IAT are used
(proportions) to calculate air temp. I forget the name of it
but some think it's helped their air mass accuracy.
Maybe running it at 1500RPM just gets these sensors out
of the hot-parked soak condition and into normal range.
Intermittent
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12-10-2006, 07:33 PM
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Originally Posted by Country Boy
The table is all 1.00 from 140*s on at all MAP levels for my OLSD tuning.
It doesnt do this everytime, but its very intermentin (sp?)
It doesnt do this everytime, but its very intermentin (sp?)
Got a fuel pressure gauge ??? Sounds like a fualty fuel pump check valve in alot of ways. tape a fuel gauge to the windsheild and watch the pressure when it does this. Is the pressure low after pump priming ?? if so you have a bad fuel pump.
12-11-2006, 09:58 AM
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One other thing that occurs to me is vapor lock,
or its EFI equivalent. You could have full pressure
but a rail-pair full of vapor (esp. with high underhood
temps and a non-return fuel system). Then you will
deliver a shot of vapor rather than liquid and short-
fuel it big time. Maybe your time-at-RPM is purging
the fuel line. Even with a return style system if pressure
is below crack-point you will not blow the rails clear
right away and the "bubble" may be back in the feed
a good ways from expansion.
or its EFI equivalent. You could have full pressure
but a rail-pair full of vapor (esp. with high underhood
temps and a non-return fuel system). Then you will
deliver a shot of vapor rather than liquid and short-
fuel it big time. Maybe your time-at-RPM is purging
the fuel line. Even with a return style system if pressure
is below crack-point you will not blow the rails clear
right away and the "bubble" may be back in the feed
a good ways from expansion.
12-11-2006, 11:19 AM
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No vapor lock, Had that before. I have a totally aftermarket big dog fuel system. Big external pump, regulator, lines, etc... The FP is rock steady at 50 psi (due to vacuume on my FPR). Whouldnt any kind of bubble register on my FP guage? It stays rock steady.
12-11-2006, 11:22 AM
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Originally Posted by jimmyblue
Is the commanded AFR when it's doing this, in line with the
delivered (WB) or not?
The speed density side has some sort of calculation it does
for air temp to get the density (MAP, absolute temp) and
if the ECT and IAT are both heat-soaked then this may be
giving a bent air mass value. The SD guys play with some
thing that controls how much the ECT and IAT are used
(proportions) to calculate air temp. I forget the name of it
but some think it's helped their air mass accuracy.
Maybe running it at 1500RPM just gets these sensors out
of the hot-parked soak condition and into normal range.
Intermittent
delivered (WB) or not?
The speed density side has some sort of calculation it does
for air temp to get the density (MAP, absolute temp) and
if the ECT and IAT are both heat-soaked then this may be
giving a bent air mass value. The SD guys play with some
thing that controls how much the ECT and IAT are used
(proportions) to calculate air temp. I forget the name of it
but some think it's helped their air mass accuracy.
Maybe running it at 1500RPM just gets these sensors out
of the hot-parked soak condition and into normal range.
Intermittent
No, the WB is reading at 20:1 and thats just where it stops. The idle gets choppy and drops. The IAT isnt hot with ambiet being in the 50* range and Im not hard on it before I park it because of the turbo. Theyre about 70-80*s.
IS there any tables I should post? I could post my tune file if needed, but Id rather PM it since I spent so much time getting it setup right.
12-11-2006, 12:18 PM
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Originally Posted by white2001s10
sorry this makes me laugh uncontrollably.I am sorry you're having troubles. Seek the help of another tuner experienced with OLSD operation.
I didnt see whats so funny. This isnt rocket science. I was asking for advice. Anytime you ask a question, Im going to laugh at you and tell you to take it to an experienced mechanic.
12-11-2006, 12:34 PM
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Originally Posted by Country Boy
I didnt see whats so funny. This isnt rocket science. I was asking for advice. Anytime you ask a question, Im going to laugh at you and tell you to take it to an experienced mechanic.
I would've told you the solution to the problem, but I've put in lot of work and don't want to share.
Really, an experienced OLSD guy should be able to fix you up. It was sound advice.