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Discussion Starter · #1 ·
Alright we i have had this 89 daytona shelby for a wile now and since i got it, there has been a cutoff issue. when i go to WOT it pulls hard up to ~4800RPM than just dies, like a revlimiter. If i keep it at WOT its like the mottor shuts off and the RPMs fall than when it drops to ~4500 it picks back up again and than dies again when it hits 4800 again. though if i go to part throttle it will rev past 4800 no problem.

I have checked all my ignition (its all good) and did not change the issue at all, swapped injectors last night no change. there is no vacuum leaks, and it gets ~18" of vac at idle. I am confident that it is not Fuel related, since i have been running the car like this for about 4-5 months now, and if it was leaning out i would have cooked the motor. I have also tried another computer (a spare MP cal i had sitting around) and that computer has the same issue as this one.

I am VERY stumped on this issue, and frankly am running out of things to try, later today i had planned to check the throttlebody as maybe the throttleplate is loose, or flapping around a bit. (this is a long shot)

So any light you guys can shed on this matter will be greatly appreciated.

Thanks.
 

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Map
 

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sounds like an overboost fuel cutoff to me...

Mini-Mopar Turbo Preformance

what boost you running ? stock computer/solenoid control or MBC or ?

try running the vac line directly from intake mani to turbo WG and see what boost you run then (should be much lower) and see if problem goes away
 

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Discussion Starter · #5 ·
sounds like an overboost fuel cutoff to me...

Mini-Mopar Turbo Preformance

what boost you running ? stock computer/solenoid control or MBC or ?

try running the vac line directly from intake mani to turbo WG and see what boost you run then (should be much lower) and see if problem goes away
its 100% stock, this is why its so aggravating.

Its not the MAP sensor since i already had one fail and have since swapped in a good one.

is there someway the computer could be thinking its overboosting? Though i have had two diffrent computers in there... with two diffrent cals...
 

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I had same thing in my 89 lebaron its waste gate or vac lines. Check diagrams its overboost cuttoff. Check waste gate mine was unhook and bypassed re ran vac lines and fixed it. I was asking same thing just a day or two ago
 

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Discussion Starter · #7 ·
I had same thing in my 89 lebaron its waste gate or vac lines. Check diagrams its overboost cuttoff. Check waste gate mine was unhook and bypassed re ran vac lines and fixed it. I was asking same thing just a day or two ago
I redid all the vac lines when i got the car...

Though i will check them all again today, i had an issue in another car were it kept going to overboost (it throws a code when it does) and this one doesent seem to.

I will check though in a little bit.

Anymore ideas?
 

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How much boost does your gauge show when the cutout happens? Stock or aftermarket boost gauge? Are you getting any codes at all? If it was MAP (or vacuum) related, it would throw a 13 and the CEL would likely be on.
 

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Discussion Starter · #9 ·
How much boost does your gauge show when the cutout happens? Stock or aftermarket boost gauge? Are you getting any codes at all? If it was MAP (or vacuum) related, it would throw a 13 and the CEL would likely be on.
AHA! I think we are on to something here.

I just went out and tested, and the gague (stock) runs up to ~12, than when i hit ~4500RPM @ WOT it goes past 12 to ~14 (wich is the overboost shutoff) than by ~4800RPM it shuts down and boost falls to ~3PSI.

Tommorow i will check the vac line to the wastegate... It has that little yellow one way check valve thing in it... it is supposed to be blocked in the direction of the wastegate (from solenoide) so that it will not get boost pressure and only vac right?

Also if the vac lines all check out next step would be to check the solenoide. I think i have a spare around here somewere, and just to make sure what is the pinout on the old, and new style solenoides for vac lines?

THanks!
 

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Um, you should not have a check valve inline to your wastegate.



The orifice is a vacuum restrictor that's supposed to help prevent boost spiking. But otherwise there are no check valves between the wastegate solenoid and the wastegate itself. That could be your problem.
 

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Discussion Starter · #11 ·
Um, you should not have a check valve inline to your wastegate.



The orifice is a vacuum restrictor that's supposed to help prevent boost spiking. But otherwise there are no check valves between the wastegate solenoid and the wastegate itself. That could be your problem.
Its an orifice, not a check valve that i have in line to the wastegate, and all my vac lines are good. I swapped out the wastegate solenoide and had no change.

I than forced it to overboost, and the boost rockets to ~16/17 PSI and than i get the SHARP overboost shutdown. The overboost is VERY violent, were as my cutoff is soft it just dies softly.
 

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Try hooking vac line strait from intake or turbo its self to the wastegate and see if it overboost still thats how i figuire out my vac lines where bad something in hose or something cause it was all ran right just didn't work till i changed hose try that see if wastegate will work that and make sure the wastegate valve isn't stuck move make sure it moves
 

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Discussion Starter · #13 ·
Try hooking vac line strait from intake or turbo its self to the wastegate and see if it overboost still thats how i figuire out my vac lines where bad something in hose or something cause it was all ran right just didn't work till i changed hose try that see if wastegate will work that and make sure the wastegate valve isn't stuck move make sure it moves
Well i just affirmed it is NOT overboost shutdown.... but why not ill try that to.
 

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I than forced it to overboost, and the boost rockets to ~16/17 PSI and than i get the SHARP overboost shutdown. The overboost is VERY violent, were as my cutoff is soft it just dies softly.
OK so did you get the OBshutdown code this time ?

if you did, and you werent before (with your 'soft' shutdown) then my next suspect is fuel pressure

go to your mechanic, borrow his schraeder valve adapter and fuel gauge; tape it to your windshield, and then watch fuel P as you encounter the 'soft' shutdown

maybe its just fuel starving at WOT boost (when the fuel demand is highest)
 

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Discussion Starter · #15 ·
OK so did you get the OBshutdown code this time ?

if you did, and you werent before (with your 'soft' shutdown) then my next suspect is fuel pressure

go to your mechanic, borrow his schraeder valve adapter and fuel gauge; tape it to your windshield, and then watch fuel P as you encounter the 'soft' shutdown

maybe its just fuel starving at WOT boost (when the fuel demand is highest)
Yeah that was my initial thought, i have been trying to track down a fuelpressurge gague with the right fitting on it for a few days, i will call around a bit more. I dident think it would be fuel since if it leaned out it would be blowing up the motor... and it has been doing this for a wile now... but i will give that a shot if i can find a gague.
 

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Discussion Starter · #16 ·
Swapped in another of the older stlye waste gate solenoides, and ran a direct line to the wastegate from it. No change.
 

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Try to check your HEP (Hall Effect Pickup) In the distributor. This sensor controls ignition timing and injector firing. If they get too much oil they can start to go bad. If it goes completly out your car wont run at all.
 

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Discussion Starter · #18 ·
Try to check your HEP (Hall Effect Pickup) In the distributor. This sensor controls ignition timing and injector firing. If they get too much oil they can start to go bad. If it goes completly out your car wont run at all.
Yeah tried that first, have had 3 diffrent ones in it, still no luck :(
 
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