Need help figuring this out; lean spot at ~3k rpm
08-24-2011, 07:16 PM
#91
Three Wheelin'
Not to encroach on techno ducks post, but I modified my fuel rail to eliminate the risk of fuel leaks and engine fires that have occurred on other 951's. I cut off the stock fpr, welded on a AN fitting then ran steel braided fuel line on the fire wall instead of directly over the exhaust to my afpr. Also the afpr allows for additional tuning capabilities over a fixed 3 bar regulator.
08-24-2011, 07:19 PM
#92
Three Wheelin'
Have you tried using the after market rail without the damper? IF that is a fuel damper on it? I don't see the point in dropping the tank if it seems to work fine with the stock parts?
08-24-2011, 08:20 PM
#93
Nordschleife Master
Thread Starter
Ive said it a few times but to reiterate; i am beginning to doubt the problem 'went away' when i had the stock rail back on. I am thinking perhaps i did not get the car hot enough to bring out the lean spot issue. The stock rail will be going on yet again tomorrow if find nothing out of the ordinary when i replace the screen in the fuel tank.
To answer schip43's question, the damper is integral to the aftermarket rail, it cannot be removed.
Ronin, i will try zip tying the ignition wire bundles out of the way. Anything is worth a shot at this point.
I made a longer jumper line so i have the fuel pressure gauge routed into the cabin where i can watch it now. From what i could best make out while driving the fuel pressure is doing nothing out of the ordinary when the lean spot is occurring. I am going to have a friend watch the gauge a little later tonight to be sure. The bouncing of the fuel gauge i saw in the video i took was probably just vibration picked up from the way i had the gauge mounted. When i saw nothing out of the ordinary going on with the fuel pressure i am pretty sure when i screamed 'F*CK' it was about as loud as my car was when i had the wastegate dumping to atmosphere.
If i cant figure this out by friday it will be brought somewhere. Bottom line is i have lost all motivation to continue with this car.
To answer schip43's question, the damper is integral to the aftermarket rail, it cannot be removed.
Ronin, i will try zip tying the ignition wire bundles out of the way. Anything is worth a shot at this point.
I made a longer jumper line so i have the fuel pressure gauge routed into the cabin where i can watch it now. From what i could best make out while driving the fuel pressure is doing nothing out of the ordinary when the lean spot is occurring. I am going to have a friend watch the gauge a little later tonight to be sure. The bouncing of the fuel gauge i saw in the video i took was probably just vibration picked up from the way i had the gauge mounted. When i saw nothing out of the ordinary going on with the fuel pressure i am pretty sure when i screamed 'F*CK' it was about as loud as my car was when i had the wastegate dumping to atmosphere.
If i cant figure this out by friday it will be brought somewhere. Bottom line is i have lost all motivation to continue with this car.
08-24-2011, 10:19 PM
#94
Three Wheelin'
Aww sorry man, your not alone with problems, mine has been sitting about a year..won't go into gear with the motor running! I'm gonna replace the hydraulic lines with the stainless steel kit. I just don't wanna cral under that beast!
Sooo, I'm putting AC in my Tercel(not stock, suspension wise) alot easier to work on and anything I need is at Pick and Pull!
Just don't post a for 951 for sale ad! Don't let the silly beast beat you down! But hey "adding" the Honda would be pretty sweet!
Sooo, I'm putting AC in my Tercel(not stock, suspension wise) alot easier to work on and anything I need is at Pick and Pull!
Just don't post a for 951 for sale ad! Don't let the silly beast beat you down! But hey "adding" the Honda would be pretty sweet!
08-25-2011, 12:04 AM
#97
Rennlist Member
I really don't think that this PITA of a problem has anything to do with the fuel system on your car.
It seems like textbook heat related electrical resistance in the harness somewhere.
You need to check the resistance/(or voltage drop) of the wires at the DME plug after the car is fully warmed up.
(Maybe it's your speed reference sensors; (since it always happens at the same RPM)).
Another thing: do you have ballast resistors for your injectors?
If so, try taking them out and go for a test drive.
It seems like textbook heat related electrical resistance in the harness somewhere.
You need to check the resistance/(or voltage drop) of the wires at the DME plug after the car is fully warmed up.
(Maybe it's your speed reference sensors; (since it always happens at the same RPM)).
Another thing: do you have ballast resistors for your injectors?
If so, try taking them out and go for a test drive.
08-25-2011, 02:40 PM
#98
Nordschleife Master
Thread Starter
Ballast resistors were bypassed with no effect. I replaced the injector harness a few weeks ago and last week put in two new resistors last week.
I agree the problem is probably not in the fuel system especially after last night, i put a few miles on with my buddy watching the fuel gauge and nothing was out of the ordinary as i had suspected. Still i am going to drain the tank and replace that screen.. probably not a bad idea after 126k miles plus a few of the hoses back there have seen better days. I was going to knock that out today but the rain is saying otherwise.
I thought something too could be problematic with the speed / ref sensor harness which is still original. I sort of ruled it out in my head though because the car has no starting or running issues at all. I would suspect if it were a sensor issue the car would have a very noticeable misfire or cutout of power. The car does 'bog down' slightly.. i mean a noticeable drop off in acceleration but it does not feel as if its a misfire or anything. Also i would suspect this to happen at other times, not just around the 3k rpm range? I have the LR replacement crank harness i guess i will finally install tomorrow, like ive said ill try anything at this point. The sensors are new, think i replaced them last year.
What really gets me is the car boosts fine once you get past 3k rpm. I did a few WOT pulls last night and it felt great with a steady AFR.
And regarding the S2k, i drove my friends '06 yesterday (AP2 with the 2.2L) for an hour or so and gotta say its a fantastic car.. i really want one now! The torque thing i think is a little blown out of proportion probably from people who only drove the AP1 with the 2L. I can cruise in 6th on the highway (it was turning about 3k at 70mph) and you can overtake without having to shift out of 6th. Its a bit buzzy on the highway but for an engine that redlines at 8500rpm what can you expect. The engine is awesome, loves to be spun high and very responsive. The interior is very spartan but its not something that concerns me. Great gearbox, handles great and is uber reliable.. valve adjustment every 80k or so, change the oil, diff and trans fluid at regular intervals and just drive.
I agree the problem is probably not in the fuel system especially after last night, i put a few miles on with my buddy watching the fuel gauge and nothing was out of the ordinary as i had suspected. Still i am going to drain the tank and replace that screen.. probably not a bad idea after 126k miles plus a few of the hoses back there have seen better days. I was going to knock that out today but the rain is saying otherwise.
I thought something too could be problematic with the speed / ref sensor harness which is still original. I sort of ruled it out in my head though because the car has no starting or running issues at all. I would suspect if it were a sensor issue the car would have a very noticeable misfire or cutout of power. The car does 'bog down' slightly.. i mean a noticeable drop off in acceleration but it does not feel as if its a misfire or anything. Also i would suspect this to happen at other times, not just around the 3k rpm range? I have the LR replacement crank harness i guess i will finally install tomorrow, like ive said ill try anything at this point. The sensors are new, think i replaced them last year.
What really gets me is the car boosts fine once you get past 3k rpm. I did a few WOT pulls last night and it felt great with a steady AFR.
And regarding the S2k, i drove my friends '06 yesterday (AP2 with the 2.2L) for an hour or so and gotta say its a fantastic car.. i really want one now! The torque thing i think is a little blown out of proportion probably from people who only drove the AP1 with the 2L. I can cruise in 6th on the highway (it was turning about 3k at 70mph) and you can overtake without having to shift out of 6th. Its a bit buzzy on the highway but for an engine that redlines at 8500rpm what can you expect. The engine is awesome, loves to be spun high and very responsive. The interior is very spartan but its not something that concerns me. Great gearbox, handles great and is uber reliable.. valve adjustment every 80k or so, change the oil, diff and trans fluid at regular intervals and just drive.
08-25-2011, 03:50 PM
#99
Rennlist Member
You know, the more I read, the more this reminds me of a problem I had once.... car would just fall on its face at about 3k... but otherwise it was fine...after fiddling with a bunch if stuff, I noticed that the vacuum line that connects to the underside of the TB was pinched between the hard pipe coupler and the j-pipe and the hose clamp on the hose from the ISV to the intake manifold was loose... I tightened it up and moved the vacuum line so it wouldn't get pinched and the problem went away.... I don't know if either of those were actually the problem, or if I bumped something else in the process, but that's my story, FWIW
08-25-2011, 06:51 PM
#100
Rennlist Member
Are you going to reinstall the stock rail to check
your earlier finding? Seems like that was the most promising avenue to date. Could be some odd harmonic in the new rail unique to your set up.
your earlier finding? Seems like that was the most promising avenue to date. Could be some odd harmonic in the new rail unique to your set up.
09-01-2011, 02:15 AM
#101
Nordschleife Master
Thread Starter
Anyone ever take apart a damper like this? Ive never seen the internals but pretty sure the rubber diaphragm should be flush inside the recessed portion of the end cap. I asked Dave about it but i know he is busy so not sure when he will be able to get back to me.
Put the stock rail back on this morning, lean spot has not happened once yet. My guess is the firing pulse of the injectors at about 3k rpm combined with the damper not functioning right was causing the lean spot. Just a guess, but its the only conclusion i can draw from this.
Put the stock rail back on this morning, lean spot has not happened once yet. My guess is the firing pulse of the injectors at about 3k rpm combined with the damper not functioning right was causing the lean spot. Just a guess, but its the only conclusion i can draw from this.
Last edited by Techno Duck; 09-07-2011 at 09:21 PM.
09-01-2011, 02:25 AM
#103
Nordschleife Master
Thread Starter
And as usual, the last damn thing you check.. well more like the second to last thing, i was going to replace the crank harness tomorrow.
Seriously though, i cant believe how much time i spent chasing this down. I think i started screwing around with it like 2 or 3 weeks prior to the original posting date.. so a solid 3 months.
Seriously though, i cant believe how much time i spent chasing this down. I think i started screwing around with it like 2 or 3 weeks prior to the original posting date.. so a solid 3 months.
09-01-2011, 02:38 AM
#105
Nordschleife Master
Thread Starter
Me apparently! I should have taken the damn damper apart like 3 weeks ago when i swapped the rails in the first place. I just assumed it was the regulator that was the problem!
Anyway when i get this damper situation figured out, this rail back on the car and it still running right, then i will be 100% convinced.. as of now i am just 98% convinced..
.
Anyway when i get this damper situation figured out, this rail back on the car and it still running right, then i will be 100% convinced.. as of now i am just 98% convinced..
.