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Old 07-12-2015, 11:33 AM   #1
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Hesitating while driving

Have an 88 now, and completely new to the EFI motor so im stumped on what it could be but when I give it gas I feel it hesitating as I'm accelerating or cruising at one speed. I did some research I'm getting tps sensor, vacuum leak, egr valve, and distributor cap. I do hav a vacuum leak though coming from my upper intake manifold looks like the gasket is worn so I will be pulling that today and adding rtv.


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Old 07-12-2015, 05:08 PM   #2
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Gotta run your codes first then move onto other free things.

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Old 07-12-2015, 09:47 PM   #3
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A vacuum leak can definitely cause hesitation,so fix it first to see if the problem disappears.Check tps voltage with key on/engine off & make sure it registers .70-1.0volts...If the issue exists after doing the things above,run the koeo koer test that SmurfStang mentioned.
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XE276HR .544" .544"
Flowtech 1 3/4"
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Old 07-12-2015, 11:15 PM   #4
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Ok so I pulled manifold. Won't fit right it seems like without the correct gasket itself so I'll get one tomorrow and test it out. While I was at it I pulled my all my plugs and cleaned my grounds, connectors etc. looks a lil better I figured it would give me something to do to kill more time.


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Old 07-13-2015, 07:00 AM   #5
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You can go ahead & do it now or wait til you get the intake back on to see if the hesitation still exists or not,but do the maintenance routine on the salt & pepper connecters(10 pins)located behind the upper intake.White/black connecters.The pins get corroded and they also loosen up between the male & female pins..Driveability issues,erroneous trouble codes & weird EEC conditions can occur when there's an issue with the connecters.Dont ignore the simple stuff either like a dirty fuel filter,dirty throttle body or air filter,dirty egr valve,etc.Check the egr valve diaphragm for movement at idle.It should not move(open)at idle or wot.Check your pcv valve and its hose while you've got the intake off since its easier to get to with the intake off.You can get a small handheld propane torch with a piece of vacuum hose attached or a can of carb cleaner and use it to check for vacuum leaks.Spray cleaner on or run the vacuum hose (that's attached to the propane torch)alongside every gasket,vacuum hose and vacuum operated component on the engine.Areas like the breather hose fitting on the throttle body,evp sensor & egr valve gaskets,injector bosses,tab/tad solenoids(on rear side of pass strut tower)evr solenoid, etc are good places for a vacuum leak to exist.The links below will help with the 10 pin maintenance & tps testing.

http://web.archive.org/web/201312291...tion.com/?p=85

http://sbftech.com/index.php/topic,29736.0.html
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Old 07-13-2015, 12:33 PM   #6
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One way to help rule the egr valve out as a possible cause for the hesitation is to disable it.When the egr valve is operating,the ecm advances timing & leans the fuel mixture.If the valve is opening when its not supposed to be,its affect on timing & fuel mixtures can cause hesitation, rough idle or surging.To disable the egr valve,remove the vacuum hose from it and plug the hose.The ecm will see no vacuum to the egr valve then turn its function off in the logic.Timing advance & fuel mixtures will go back to normal.
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TFS track heat
XE276HR .544" .544"
Flowtech 1 3/4"
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Old 07-13-2015, 01:14 PM   #7
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Ok. I'll will do all that soon as I get off work. I'll post a pic of my intake also to show where I think the leak is coming from.


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Old 07-14-2015, 11:58 AM   #8
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Sry guys had to pull a double shift yesterday got off late but here's pics of the manifold its the side piece and where the gasket is completely gone is where the whistling noise was coming from.


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Old 07-14-2015, 12:46 PM   #9
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I got the gasket cleaned off...but before I put some rtv down is that oil in the manifold normal or am I looking at another issue?


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Old 07-14-2015, 02:45 PM   #10
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I decided to try it out, put rtv down, started it up, it's idling fine but I noticed my intake pipe is too short. The maf and intake pipe are barely clamped together. But anyways I drove it around the block no more hesitating..I'm going to pull my salt n pepper connectors and check the connections jus in case.


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Old 07-14-2015, 02:51 PM   #11
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Quote:
Originally Posted by wbrockstar View Post
One way to help rule the egr valve out as a possible cause for the hesitation is to disable it.When the egr valve is operating,the ecm advances timing & leans the fuel mixture.If the valve is opening when its not supposed to be,its affect on timing & fuel mixtures can cause hesitation, rough idle or surging.To disable the egr valve,remove the vacuum hose from it and plug the hose.The ecm will see no vacuum to the egr valve then turn its function off in the logic.Timing advance & fuel mixtures will go back to normal.




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This is my vacuum hose to the egr correct?


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Old 07-15-2015, 09:50 AM   #12
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I would also replace your PCV valve and mesh as that helps control the oil vapor going into your intake manifold. This is something that gets overlooked regularly.
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Old 07-16-2015, 05:33 PM   #13
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Quote:
Originally Posted by Foxbody91 View Post
Attachment 187080

This is my vacuum hose to the egr correct?


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Yeah that's the egr valve vacuum hose.Its connected to the evr solenoid or another hose that comes off the evr solenoid.
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91 LX 342ci(10.5:1)
TFS 190cc(stage ll)
TFS track heat
XE276HR .544" .544"
Flowtech 1 3/4"
Prochamber w FM
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Old 07-16-2015, 05:44 PM   #14
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Attachment 187075
I got the gasket cleaned off...but before I put some rtv down is that oil in the manifold normal or am I looking at another issue?

Yeah it is kinda normal,but you can install an oil separater between the pcv valve hose & intake & it will stop that from happening.You can buy one of those inexpensive air compressor filters and use it instead of paying $75+ for a Steeds,etc separater.If your car is a daily driver,you'll have to drain it every few days or once a week,depending on how much oil your intake sees.A catch can with a screen/filter element also works for this.The pic below is a filter from Home Depot.


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91 LX 342ci(10.5:1)
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TFS track heat
XE276HR .544" .544"
Flowtech 1 3/4"
Prochamber w FM
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