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Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660337 08/19/14 10:59 PM 08/19/14 10:59 PM
Joined: Aug 2003 Posts: 1,145 ontario calif N ns1aar super stock
ns1aar super stock N Joined: Aug 2003 Posts: 1,145 ontario calif	Had a SVO Mustang, ya I know it was wrong b ut it was a fun car. I had this problem and it was the PVC it would go into boost and blow everything thu the crankcase very abrupt loss of power NS1AAR

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: ns1aar] #1660338 08/19/14 11:54 PM 08/19/14 11:54 PM
Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada That AMC Guy OP master
That AMC Guy OP master Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada	That is something I can check into. Thanks. Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660339 08/20/14 11:19 AM 08/20/14 11:19 AM
Joined: Jan 2003 Posts: 28,114 Irving, TX feets Senior Management
feets Senior Management Joined: Jan 2003 Posts: 28,114 Irving, TX	Quote: The only thing that's even close to suspect was the short length of rubber tube to the wastegate. It was pretty crumbly and looked like it had taken some heat. If the vacuum line to the wastegate is bad it will cause your problems. That line pushes manifold pressure to the wastegate. If you were to pull it off, the wastegate would never open. That means the turbo would not stop making boost until the computer shut down the fuel or the pistons melted. The wastegate has a spring pushing on a diaphragm. That's what holds it closed and makes the exhaust go through the turbo. That vacuum line sends manifold pressure to the other side of the diaphragm. It pushes against the spring. When the turbo spools up it will send boost pressure to fight that spring. Once the boost is stronger than the spring it forces the wastegate open and exhaust take a shortcut around the turbo. Boost pressures drop. Wastegate closes. More boost is made. Vicious cycle. Under load, the boost pressure in that "vacuum" line and the spring come to a bit of an agreement. They balance one another and hold the boost steady. Very simple and rather ingenious. Self regulating. An old trick to sneak more boost was to bleed a wee tiny bit of air out of the wastegate vacuum line. Doing this dropped the pressure on the back side of the WG. That means the turbo had to make more boost to overcome the WG spring. Other guys cut the WG rod, threaded the two pieces, and slipped them together with a long nut. That let them adjust it like a tie rod. Both of those things will upset the computer. It is programmed to shut down the fuel when the boost gets higher than allowed. We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: feets] #1660340 09/01/14 01:57 AM 09/01/14 01:57 AM
Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada That AMC Guy OP master
That AMC Guy OP master Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada	Well, I replaced all my vacuum lines and installed a vacuum distribution block on the inner fender. Now I have a 3/8" vacuum line running from the intake to the block, and then just short 5/16" lines to the necessary solenoids. The upside is the car idles infinitely better. However the problem under boost still persists. I've got a week off starting Tuesday. Going to set up my A/F meter and fuel pressure gauge so I can monitor things while I'm driving. I'm starting to think I popped an intake gasket. I swear I can hear a whistling noise coming from the intake. Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660341 09/01/14 07:04 AM 09/01/14 07:04 AM
Joined: Jun 2008 Posts: 10,958 Oakdale CT gdonovan I Live Here
gdonovan I Live Here Joined: Jun 2008 Posts: 10,958 Oakdale CT	The wastegate can could have gone bad, and you can check with a vacuum pump. The arm could also be frozen on the wastegate. Try hooking a intake vacuum line directly to the wastegate. This will open the wastegate ASAP giving you 7 psi or so and will prove if the can and valve is working or not and eliminate the solenoid. Whistle in the intake isn't odd. Overboost will flash the check engine light but you have to be paying attention for it when it happens. "I think its got a hemi"

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: gdonovan] #1660342 09/01/14 10:14 PM 09/01/14 10:14 PM
Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada That AMC Guy OP master
That AMC Guy OP master Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada	Quote: The wastegate can could have gone bad, and you can check with a vacuum pump. The arm could also be frozen on the wastegate. Try hooking a intake vacuum line directly to the wastegate. This will open the wastegate ASAP giving you 7 psi or so and will prove if the can and valve is working or not and eliminate the solenoid. I will give that a try! Thanks! Quote: Overboost will flash the check engine light but you have to be paying attention for it when it happens. I was watching for that. Not once did the light even flicker. Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660343 09/02/14 12:10 AM 09/02/14 12:10 AM
Joined: Apr 2007 Posts: 905 SD Z zrxkawboy super stock
zrxkawboy super stock Z Joined: Apr 2007 Posts: 905 SD	I had an 89 Spirit 2.5 Turbo I that had a wastegate issue, and so was over-boosting. Instead of bucking, though, it simply felt like I'd let off the gas pedal, even if I kept it floored. Once the RPMs dropped to a certain point, it would pick back up again. I never had a CEL. I know this is 89 TI vs 87 TII, so there may be some differences, but thought I'd throw it out there. Wish I could remember more specifics, but it's been several years. It's Swifty! Swifty, you toad sucker!

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: zrxkawboy] #1660344 09/02/14 02:14 AM 09/02/14 02:14 AM
Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada That AMC Guy OP master
That AMC Guy OP master Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada	Mine will still keep trying to accelerate if I keep my foot in it. However, out of fear of damaging something, I back off. I suppose if my wastegate actuator (vacuum pod) isn't working properly, that could cause the issue too, right? I still have a Garret Turbo kicking around from my old Turbo Lebaron. I converted my Lebaron to TII, however I used the smaller Mitsubishi Turbo, packed this Garret up and put it aside. Worst case scenario, I can grab some parts off it. Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660345 09/02/14 04:33 AM 09/02/14 04:33 AM
Joined: Jun 2008 Posts: 10,958 Oakdale CT gdonovan I Live Here
gdonovan I Live Here Joined: Jun 2008 Posts: 10,958 Oakdale CT	Quote: Mine will still keep trying to accelerate if I keep my foot in it. However, out of fear of damaging something, I back off. I suppose if my wastegate actuator (vacuum pod) isn't working properly, that could cause the issue too, right? Yes "I think its got a hemi"

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: gdonovan] #1660346 09/05/14 08:41 PM 09/05/14 08:41 PM
Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada That AMC Guy OP master
That AMC Guy OP master Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada	Well, I think I've ruled out both the Wastegate Solenoid and the Wastegate vacuum pod. Earlier today, I tried running straight manifold vacuum to the wastegate pod. The bucking persisted. Reconnected to the solenoid, and the bucking persisted. Then later, a friend stopped by to help and we connected a fuel pressure gauge to the fuel rail and went for a short drive. The first time I rolled into about 7 psi of boost, fuel pressure rose accordingly to 65psi and it was boosting smooth like before. However, the rest of our drive we could not replicate that. Every time we rolled into boost fuel pressure brickwalled at 60psi and the bucking returned. I'm thinking fuel filter at this point and failing that, pump. Once I replace the fuel filter, I will also try to 'deadhead' the pump to see what it's maximum fuel output is. That should give a better indication as to the condition of the pump. Does this sound like a good plan? Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660347 09/05/14 09:06 PM 09/05/14 09:06 PM
Joined: Jun 2008 Posts: 10,958 Oakdale CT gdonovan I Live Here
gdonovan I Live Here Joined: Jun 2008 Posts: 10,958 Oakdale CT	Quote: Well, I think I've ruled out both the Wastegate Solenoid and the Wastegate vacuum pod. You have ruled out the solenoid only, the wastegate still can be bad. Quote: Every time we rolled into boost fuel pressure brickwalled at 60psi and the bucking returned. Remember base pressure is 55 psi- 10 pounds of boost will = 65 psi of fuel pressure. You need to verify what you have for boost pressure. With the wastegate hooked to the intake you should in theory have 7 psi of boost or so about 60 psi of fuel pressure would be very close to correct. Any pressure gauge hooked up to the intake will do, even an old carb fuel pressure gauge. Quote: I'm thinking fuel filter at this point and failing that, pump. I would have done fuel filter on general principle long ago, they are cheap and people ignore them since the are located out back out of sight. Quote: Once I replace the fuel filter, I will also try to 'deadhead' the pump to see what it's maximum fuel output is. If you are going to do this be VERY VERY careful and do not do it longer than a second or two. The early cars used a Bosch pump that would exceed 100 psi in a heartbeat. Squeeze off the return line at the regulator while watching the gauge, if it heads north of 70 psi stop instantly. Fuel spraying around at high pressure is a bad thing. This will also only test the pumps pressure output, volume not so much. "I think its got a hemi"

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660348 09/05/14 09:11 PM 09/05/14 09:11 PM
Joined: Dec 2004 Posts: 2,703 Mohnton, Pa DodgeCharger master
DodgeCharger master Joined: Dec 2004 Posts: 2,703 Mohnton, Pa	Did you check all of the vacuum lines under the dash for a leak. My son has a charger and there was a connector with a bunch of vacuum lines connected to hit that basically fell apart from age. The plastic became brittle. Good luck.

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: DodgeCharger] #1660349 09/05/14 09:36 PM 09/05/14 09:36 PM
Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada That AMC Guy OP master
That AMC Guy OP master Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada	I will totally feel like an idiot if it turns out to be the fuel filter - you are right - that is something I should have changed a year ago when I bought the car. It ran good so I just assumed and that there was my mistake. That one time we had 65psi of fuel, my boost gauge was showing over 5psi boost. But the other times it was stopping at 60psi and the boost gauge tried climbing, but couldn't with the bucking. So, I'm very much thinking now it's been fuel related all along. DodgeCharger: All vacuum lines under the hood have been replaced along with the line to the boost gauge. The one from the brake booster to the heater control is still the factory one, but it checked out good and rather than changing a bunch of fittings, I simply re-used it. This car is a Shelby, so I don't have cruise control or anything else (thankfully) I think I'm getting closer and narrowing down all the possibilities. Couldn't do it without your guys' direction though - and I think you for your help! Hopefully I'll have some good news to report soon! Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660350 09/05/14 10:07 PM 09/05/14 10:07 PM
Joined: Jun 2008 Posts: 10,958 Oakdale CT gdonovan I Live Here
gdonovan I Live Here Joined: Jun 2008 Posts: 10,958 Oakdale CT	Quote: I will totally feel like an idiot if it turns out to be the fuel filter - you are right - that is something I should have changed a year ago when I bought the car. Filters were a common problem, awful hard on the pumps too. Its happened to me as well, its out of sight and out of mind. I had one plug up on my Caravan on a trip home from Detroit. I was on my back at 2AM in a dark dirt parking lot on 80 East in Pennsylvania and I swear I could hear banjo's in the distance as I was trying to blow out the filter. I never seen a truck stop with a dirt parking lot before. After that I changed fuel filters on a regular basis, usually when I do spark plugs even though I think filters were rated for 75k or 85k "I think its got a hemi"

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: gdonovan] #1660351 09/05/14 11:20 PM 09/05/14 11:20 PM
Joined: Sep 2006 Posts: 1,680 Raleighwood 2Bad360sfromNC top fuel
2Bad360sfromNC top fuel Joined: Sep 2006 Posts: 1,680 Raleighwood	The filter may very well fix it. If you have enough hose to tape your fuel pressure gauge to the windshield, drive the car around for a good while to make sure the pump gets as hot as it's going to get (not sure how long you drove it to do your test). My old pump would go for 20 minutes or so fine, then drop down to 30 or so p.s.i. and barely even run. I was used to pumps dying instantly if they were bad, so it took me a bit to figure that out. (Edit: re-read and saw you'd already taken care of the FPR) Once you get it sorted out, I highly recommend a 3-bar setup and more boost (and a wideband)--it's tons of fun. Here's a pic of what I've been up to this week for inspiration. 8262379-motor.jpg (286 downloads) Last edited by 2Bad360sfromNC; 09/05/14 11:31 PM. 1968 Charger project. I don't have a fender tag or a buildsheet, so it's getting a 440. Help me decide on a color--most everything looks great! (NOT white. My Challenger is white. Need some variety :D) 1974 Challenger 360 2012 Challenger R/T 1991 Dakota 5.2

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: 2Bad360sfromNC] #1660352 09/06/14 02:50 AM 09/06/14 02:50 AM
Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada That AMC Guy OP master
That AMC Guy OP master Joined: Feb 2003 Posts: 4,837 Castlegar, BC, Canada	2Bad360: Your engine looks like the one I did up for my Lebaron coupe a few years ago. I just want this ol' gal to be running and reliable again before I got putting any more mods to her. I think my next big purchase will be a bobble-strut replacement so the engine will quit flopping around! I don't have a pic but I did a similar vacuum block setup to mine recently. Except I ran a 3/8" vacuum line from the intake down to the inner fender, and then from the block ran 5/16" rubber to all the necessary solenoids and for the gauge. Much cleaner setup if'n you ask me. Funny thing was, upon inspection all my plastic vacuum lines were in good shape and still very pliable. Oh well. Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: That AMC Guy] #1660353 09/06/14 11:37 AM 09/06/14 11:37 AM
Joined: Sep 2006 Posts: 1,680 Raleighwood 2Bad360sfromNC top fuel
2Bad360sfromNC top fuel Joined: Sep 2006 Posts: 1,680 Raleighwood	It would look better somewhere else, but shorter vacuum lines seem to allow the turbo to spool faster. 1968 Charger project. I don't have a fender tag or a buildsheet, so it's getting a 440. Help me decide on a color--most everything looks great! (NOT white. My Challenger is white. Need some variety :D) 1974 Challenger 360 2012 Challenger R/T 1991 Dakota 5.2

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: 2Bad360sfromNC] #1660354 09/06/14 12:33 PM 09/06/14 12:33 PM
Joined: Jun 2008 Posts: 10,958 Oakdale CT gdonovan I Live Here
gdonovan I Live Here Joined: Jun 2008 Posts: 10,958 Oakdale CT	Quote: It would look better somewhere else, but shorter vacuum lines seem to allow the turbo to spool faster. Err, false at least on these cars. The wastegate default is closed position which will already maximize spoolup. "I think its got a hemi"

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: gdonovan] #1660355 09/06/14 02:11 PM 09/06/14 02:11 PM
Joined: Sep 2006 Posts: 1,680 Raleighwood 2Bad360sfromNC top fuel
2Bad360sfromNC top fuel Joined: Sep 2006 Posts: 1,680 Raleighwood	Quote: Quote: It would look better somewhere else, but shorter vacuum lines seem to allow the turbo to spool faster. Err, false at least on these cars. The wastegate default is closed position which will already maximize spoolup. It is closed in the absence of vacuum, when the engine is off or at WOT, but what about when the car is running, it's under vacuum and open, right? (Stick car, no brake-boosting) I'm not arguing, just trying to learn more. I feel pretty confident tinkering with the car, but I know you have way more experience with them than I do. I went from very long lines to much shorter ones, and it sure felt quicker. I have no hard data for it, unless the old "butt dyno" matters. 1968 Charger project. I don't have a fender tag or a buildsheet, so it's getting a 440. Help me decide on a color--most everything looks great! (NOT white. My Challenger is white. Need some variety :D) 1974 Challenger 360 2012 Challenger R/T 1991 Dakota 5.2

Re: '87 Shelby Daytona: Cutting Out/Bucking when Boosting [Re: 2Bad360sfromNC] #1660356 09/06/14 03:47 PM 09/06/14 03:47 PM
Joined: Jun 2008 Posts: 10,958 Oakdale CT gdonovan I Live Here
gdonovan I Live Here Joined: Jun 2008 Posts: 10,958 Oakdale CT	Quote: It is closed in the absence of vacuum, when the engine is off or at WOT, but what about when the car is running, it's under vacuum and open, right? (Stick car, no brake-boosting) I'm not arguing, just trying to learn more. : The wastegate is spring loaded in the closed position, the only thing at all that will open it is boost pressure supplied by the wastegate solinoid when the engine is under boost of course. "I think its got a hemi"

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