2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

hesitation problem

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Old May 19, 2014 | 09:10 PM
  #1  
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From: painesville oh
hesitation problem

car is a vert w. s4 t2 swap s5 turbo, emissions deleted, rev t2 exhaust, etc.

the problem: car starts, idles and free revs fine, driving like a grandma: 1st gear is fine, 2nd gear off/on will break up/hesitate at 2/2500 if feathered will break through and rev up to 5k (high as I go), 3rd around 2/2500 hits the wall and will not power or feather out of the "hesitation", 4th gear cruising at 40 if you give it gas breaks up and doesn't wanna go. Driving it a little bit harder: 1st fine, 2nd gear usually ok up to 5/6k, but sometimes hits the wall but can power through it, 3rd gear 2/2500 will hesitate and not power through it.

through all of this afrs stay good except when it hesitates goes full lean than when you let out or it breaks through it'll go to 11.5ish, battery gauge stays at 14 range entire time. I'm not going into boost at all Maybe 1-2psi Tops.... idle will sometimes bounce too? but that's happened twice out of like 20 2-3 mile trips I take.

things I have done/tried

cleaned all grounds added larger rear ground to firewall, new ground from starter to chassis, added 3 grounds at ECU, and new battery ground (relocated battery), checked the 2 vacuum lines that are new, checked for boost leaks, checked wiring, checked maf/boost sensor, checked timing, 3 different Ecus, tps, etc. basically anything that was recommended to check.


sorry it's a long story but I have read a 100 threads and tried everything I could find with no improvements.
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Old May 19, 2014 | 10:44 PM
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w0ppe's Avatar
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Hmm, quite interesting. Have any cats or restrictions in the exhaust? Probably doesn't but sounds like the turbo is trying to spool up but isn't able to due to open wastegate maybe? Another thing to check while you have the exhaust off. I'd start there.
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Old May 20, 2014 | 04:24 AM
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I read that cleaning the injectors sometimes does the job. Have you tried that?
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Old May 20, 2014 | 09:18 AM
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From: painesville oh
no cats, injectors were already cleaned/flow tested
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Old May 20, 2014 | 09:19 AM
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The primary injectors are used for starting, idling and cruising when not under load. The secondaries are used when the car is under load and the rpm at 3800 or higher. Load is determined by the TPS, the AFM, and the Boost Sensor (make sure you have the restrictor pill in this hose). Also, a clogged exhaust could cause these issues. Additionally, the wiring to the injectors may be suspect. And are you using the proper impedance injectors in your set up.
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Old May 20, 2014 | 11:38 AM
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the restrictor pill!!!! I completely forgot about that little bugger, I'll have to stop by autozone n get one

wiring for injectors I went through, put new injector plugs on, they are firing I believe, when it gets high in rpm it will get get rich.

exhaust was just off just put new gaskets on, it is clear.
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Old May 20, 2014 | 02:40 PM
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From: painesville oh
with restrictor on it, it runs lean as hell. did not change the problem
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Old May 26, 2014 | 11:39 AM
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did you fix this???
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Old May 26, 2014 | 08:22 PM
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I added 2 more grounds, and went through all the positive cables 1 was semi loose. the problem is still there, but not nearly as bad. cars back on stands though due to suspension problems

the restrictor is still off. ran much better without.
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Old May 26, 2014 | 09:31 PM
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From: tulsa,ok.
Do you have the Boost sensor plumbed to the factory spot or somewhere else.
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Old May 27, 2014 | 07:40 AM
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From: painesville oh
Originally Posted by satch
Do you have the Boost sensor plumbed to the factory spot or somewhere else.
it's going to the nipple on the pass side of intake manifold right where lim and UIM meet.
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