Warm start leaning out for a short period

R4ND0M_AX3 · 03-15-2006, 06:40 PM

I'm in the middle of fine tuning my PE850 injectors. The biggest problem I see so far is about 10-15 seconds of very lean idle after starting the car when it is already warmed up. The long term trim (AF learned) doesn't give any clue as to what is happening. The short term trim (AF immediate) however is almost pegged trying to add fuel to counter the lean condition. My wideband shows the engine hunting between about 16:1 and 18:1. Then after 10-15 seconds of terrible running everything clears up and runs fine.

I suspect it's the product of some table I don't have access to in StreetTUNER.

Anyone else experience this?
Anyone have PE850's with a reflashed factory ECU and not get this?

jays05 · 03-16-2006, 04:32 AM

Does it happen if you wait a few seconds after turning the ignition key to the on position, before you actually start it?

R4ND0M_AX3 · 03-16-2006, 07:06 AM

Quote:

Originally Posted by jaygoesfast

Does it happen if you wait a few seconds after turning the ignition key to the on position, before you actually start it?

Yes.

Actually I just made a closer observation. when it starts it is near 14-15:1. Then it leans out gradualy to 16-18:1. This takes about 10 seconds. I see the same type of taper during cold start except it's running richer and at a higher RPM so it's not really a problem.

I think it's some sort of startup enrichment that is supposed to start rich and lean out to a normal AFR. But my new injector scale may have moved things in a weird direction.

WolfPlayer · 03-16-2006, 07:19 AM

When I get a chance I will test this.

t

R4ND0M_AX3 · 03-18-2006, 07:39 AM

I noticed that there is a sound I can here during this event. When it stops the AFR goes normal. I suspect something to do with the fuel pump. I thought about logging the FP DC to see if that's it. I still have the stock pump on right now. I'm gonna change to the walbro today.

R4ND0M_AX3 · 03-18-2006, 09:09 PM

The 'noise' appears to be the fuel pump at 100% duty cycle during start. As soon as it goes to 33% the problem goes away.

I replaced the stock fuel pump today with a Walbro. I'm not sure if it's because of the new pump or the fact that I had the battery disconnected but I had to play with my latencies again. Now there are some times where the car doesn't restart. I are confused. If I can't shake this bug soon I will need to go back to the stock injectors.

R4ND0M_AX3 · 03-19-2006, 05:10 PM

I put the stock injectors back in. Same issue as before so it's not injector related. Against my own good judgement I installed the injectors, APS TGV deletes and APS turbo inlet at the same time. Now I think it's a botched install (missing vacuum line or problem with relocated FPR) or the TGV deletes themselves. More likely the first.

R4ND0M_AX3 · 03-19-2006, 07:12 PM

Let's throw the Fram Air Hog oiled panel filter into the list of suspects too.

I took off the intercooler to get a better look at things. Didn't see anything special. I hooked the top section of the stock airbox (has MAF on it) directly to the throttle body to try to eliminate the turbo inlet tube and connections to it. Car behaved the same.

My two symptons right now are the warm start goofiness and extremely rich running (low 9's) under load or higher rpms with a near OTS Stage 2 basemap that worked fine before all of this.

Next chance I get I'm putting the stock fuel pump in. I'm done for tonight.

STirish · 03-19-2006, 08:21 PM

Sounds like a vacuum leak somewhere given the weird idle and running rich. Metered air is being lost somewhere.

R4ND0M_AX3 · 03-20-2006, 08:59 AM

Quote:

Originally Posted by STirish

Sounds like a vacuum leak somewhere given the weird idle and running rich. Metered air is being lost somewhere.

Makes sense. I guess this thread should moved to a more appropriate forum.

If it's metered air that is leaving the system then it should be a post turbo leak right? If so then that leaves me with the following possible places to check:

turbo to IC to throttle body (not likely)
throttle body to manifold
Misc Manifold ports (maybe)
Manifold to TGV
Fuel rail to TGV (maybe)
TGV to cylinder head

R4ND0M_AX3 · 03-24-2006, 08:18 PM

OK, so I got all hard core about this and used an ultrasonic leak detector to probe around the engine bay with the car at idle.

BINGO!

I found a leak. Very easy to hear with the detector headphones but very small otherwise. I duplicated a similar sized leak using the BPV vacuum hose and wouldn't have been able to tell it was there without the detector.

The leak appears to be where the fuel rail seals against the TGV tower.

When I was doing the 'big install' and had the intake manifold off I put the injectors in the rails and then lined the injector outlets so they were centered in the TGV holes. I guess something was off because after that the bolt holes on the front sides of the TGV towers didn't line up (faces front of car). I'm hoping that fixing this will fox both problems I have. If so I'm going to use the theory that the fuel rail distorts a little when the fuel pump is running a 100%. Not sure how realistic that is though. Otheriwse I can't explain the warmstart part of this problem.

R4ND0M_AX3 · 04-05-2006, 01:24 PM

APS finally got their install instructions for the side feed fuel rails posted. I also just got some new seals. The manifold is coming off again this weekend. The only thing that is gonna stay stock is the fuel pressure regulator.

The new rails are way overkill but throwing parts at a problem is fun.

R4ND0M_AX3 · 04-10-2006, 11:52 AM

Problem solved. It was the seal between the TGV and the Fuel rail. When the fuel pump would run at 100% the factory rail would tweak enough that the ripped seal would leak.

***wdb*** · 04-10-2006, 01:25 PM

Good find. Thanks for keeping us updated.

soggynoodles · 04-10-2006, 01:40 PM

Awesome.
thanks for the update. Have you had time to tune it?

03-15-2006, 06:40 PM	#1
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	Warm start leaning out for a short period I'm in the middle of fine tuning my PE850 injectors. The biggest problem I see so far is about 10-15 seconds of very lean idle after starting the car when it is already warmed up. The long term trim (AF learned) doesn't give any clue as to what is happening. The short term trim (AF immediate) however is almost pegged trying to add fuel to counter the lean condition. My wideband shows the engine hunting between about 16:1 and 18:1. Then after 10-15 seconds of terrible running everything clears up and runs fine. I suspect it's the product of some table I don't have access to in StreetTUNER. Anyone else experience this? Anyone have PE850's with a reflashed factory ECU and not get this? This ad is not endorsed by this member. Please register or login to hide this ad.

04-10-2006, 01:40 PM	#15
soggynoodles Amateur STI Driver Car: Blue Car. Very loud. Fav Mod: ZZ Top's Greatest Hits Location: Bananaville Posts: 26 Join Date: Apr 2005 Trader Rating: (0)	Awesome. thanks for the update. Have you had time to tune it? This ad is not endorsed by this member. Please register or login to hide this ad.

03-16-2006, 04:32 AM	#2
jays05 Spec C Club Fav Mod: when it's not blown up Location: Upstate NY Posts: 1,556 Join Date: Nov 2004 Trader Rating: (0)	Does it happen if you wait a few seconds after turning the ignition key to the on position, before you actually start it?

03-16-2006, 07:19 AM	#4
WolfPlayer Moderator & ECU Tech Car: 05 CGM STI Fav Mod: mo boostaz Location: Fredneck, MD Posts: 3,620 Join Date: Jun 2004 Trader Rating: (6)	When I get a chance I will test this. t

03-18-2006, 07:39 AM	#5
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	I noticed that there is a sound I can here during this event. When it stops the AFR goes normal. I suspect something to do with the fuel pump. I thought about logging the FP DC to see if that's it. I still have the stock pump on right now. I'm gonna change to the walbro today.

03-18-2006, 09:09 PM	#6
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	The 'noise' appears to be the fuel pump at 100% duty cycle during start. As soon as it goes to 33% the problem goes away. I replaced the stock fuel pump today with a Walbro. I'm not sure if it's because of the new pump or the fact that I had the battery disconnected but I had to play with my latencies again. Now there are some times where the car doesn't restart. I are confused. If I can't shake this bug soon I will need to go back to the stock injectors.

03-19-2006, 05:10 PM	#7
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	I put the stock injectors back in. Same issue as before so it's not injector related. Against my own good judgement I installed the injectors, APS TGV deletes and APS turbo inlet at the same time. Now I think it's a botched install (missing vacuum line or problem with relocated FPR) or the TGV deletes themselves. More likely the first.

03-19-2006, 07:12 PM	#8
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	Let's throw the Fram Air Hog oiled panel filter into the list of suspects too. I took off the intercooler to get a better look at things. Didn't see anything special. I hooked the top section of the stock airbox (has MAF on it) directly to the throttle body to try to eliminate the turbo inlet tube and connections to it. Car behaved the same. My two symptons right now are the warm start goofiness and extremely rich running (low 9's) under load or higher rpms with a near OTS Stage 2 basemap that worked fine before all of this. Next chance I get I'm putting the stock fuel pump in. I'm done for tonight.

03-19-2006, 08:21 PM	#9
STirish Spec C Club Car: '99 M3/'03 WRX Avant Fav Mod: Modification is wrong! Location: SLC, UT Posts: 1,026 Join Date: Sep 2004 Trader Rating: (6)	Sounds like a vacuum leak somewhere given the weird idle and running rich. Metered air is being lost somewhere.

03-24-2006, 08:18 PM	#11
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	OK, so I got all hard core about this and used an ultrasonic leak detector to probe around the engine bay with the car at idle. BINGO! I found a leak. Very easy to hear with the detector headphones but very small otherwise. I duplicated a similar sized leak using the BPV vacuum hose and wouldn't have been able to tell it was there without the detector. The leak appears to be where the fuel rail seals against the TGV tower. When I was doing the 'big install' and had the intake manifold off I put the injectors in the rails and then lined the injector outlets so they were centered in the TGV holes. I guess something was off because after that the bolt holes on the front sides of the TGV towers didn't line up (faces front of car). I'm hoping that fixing this will fox both problems I have. If so I'm going to use the theory that the fuel rail distorts a little when the fuel pump is running a 100%. Not sure how realistic that is though. Otheriwse I can't explain the warmstart part of this problem.

04-05-2006, 01:24 PM	#12
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	APS finally got their install instructions for the side feed fuel rails posted. I also just got some new seals. The manifold is coming off again this weekend. The only thing that is gonna stay stock is the fuel pressure regulator. The new rails are way overkill but throwing parts at a problem is fun.

04-10-2006, 11:52 AM	#13
R4ND0M_AX3 Grassroots STI Racer Car: 05 Subaru WRX STi Fav Mod: Cobb StreetTUNER Location: Elk Grove, CA USA Posts: 592 Join Date: Jul 2004 Trader Rating: (0)	Problem solved. It was the seal between the TGV and the Fuel rail. When the fuel pump would run at 100% the factory rail would tweak enough that the ripped seal would leak.

04-10-2006, 01:25 PM	#14
*wdb* dances with roads Posts: 4,972 Join Date: Apr 2005 Trader Rating: (8)	Good find. Thanks for keeping us updated.