Ok, I got my 87 turbo rebuild back a little while ago and finally got it into the car and felt comfortable enough to start it and see how it ran. The car starts right up, occasionally I have to use the gas pedal to get it to start, but it generally starts up pretty quick. So anyways, the car will not hold an idle at all. I basically have no bypass air of any sort, as the vast majority of my emissions and related equipment has been removed (Yes, BAC valve included: I have no p/s nor a/c installed on the car, and I know the con's of removing the valve). So I have the idle set screw out as far as it will go, and it will not even touch the lever for the throttle plates, such that it seems like they are not even effected by its position. I'm not sure if there is a way to actually tighten the lever that the throttle cables connect to, or if this is normal, but it seems to have at least a few centimeters of play in it, which might possibly be the cause of the set screw not being able to come into contact with it. I should mention that I have done the throttle body mod, including removed thermowax. I have let the car warm up completely, and it still experiences the same problems. I've checked pretty thoroughly for vaccuum leaks, but really aside from the fpr, oil injector vac spider and pressure sensor/bov I have no vaccuum lines, which includes a hard pipe in place of the stock TID. If anyone has any thoughts on that, I'd like the input so I can get an idle set and start breaking the motor in.

Another problem I have been having with the car is that even while I am inside keeping it alive with the pedal, it seems to rev relatively slow. Bear in mind I am only talking like blipping it from 1500 to 2000 rpms. It just seems to climb relatively slow. Also, as the rpms do climb, the car seems to shake more than I would think is normal. I replaced the stock motor mounts with the solid mounts available from mazdatrix due to my stock mounts being broken. I am not sure how much of the shaking could be attributed to the mounts - I hope that mostly this is me worrying more than I should be.

Sorry for the long, wordy post - just trying to get thoughts across in a legible manner =)

 

You know there are at least 5 vac lines on the LIM alone right? Double check for leaks, make sure the MAP sensor is connected. You used new intake gaskets? You used a good egr block off? You have good gaskets or a good amount of rtv on the Block off plates?

Sounds like a vacuum leak.

New o-ring on the throttle body elbow?

 

Yes I am aware of all of the nipples on the LIM. I stated that much of the emissions equipment was blocked off - this includes caps on all of the nipples. I also said that I have a vac line going to the pressure sensor. All new intake gaskets were used, and egr as well as acv have been blocked off for quite some time, and were not causing problems prior to the rebuild, so I have kind of ruled them out as causes of a vaccuum leak.

 

check all of your clamps and boost hoses then, do you still use the TMIC? See if it got damaged or if the rubber plugm (Im pretty sure there is a rebbuer plug in it) hasnt come out or hasnt been damaged. This sounds exactly like my car when the TB elbow was loose letting a huge vacuum leak happen. If the car is actually shaking make sure you have the ignition wires routed properly and all of the spark plugs are snugh, make sure you are getting spark period as well.

 

I don't mean to discount a vaccuum leak - it seems likely that I could have one still. But even with a vaccuum leak, shouldn't the idle screw on the TB be able to adjust the idle higher to make it not die? As mine is now, the screw does essentially nothing. I'm relatively inclined to think that that is the cause of the dying. Kind of like if I just put more tension into the throttle cable, it could idle that way, but that seems like a hack fix.

As far as the shaking, I suppose it could be timing or spark related, but the car basically starts up really easily, and when the RPMs remain constant, it really doesn't shake more than I would consider acceptable - only when the RPMs are changing.

 

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Is your idle air mixture set properly? Check and see if it is overly lean or rich. The idle screw also does not touch the throttle plates, it is an orifice in the TB that allows air to pass through, if you are adjusting a screw on the tb that looks like it should be adjusting the throttle plate it is the wrong screw.

 

I think I am thinking of the correct screw, just I think I was completely wrong about how it was supposed to work to up the idle. Which way should I try turning the screw to increase the idle?

Edit: Just for clarification, I am talking about the screw with the 8mm jam nut on it. It almost seems like if it was just a teeny bit longer it could sort of prop the lever a bit, which would make the neutral position of the throttle plates slightly more open.

 

Unscrew it to increase idle. Left, or counterclockwise.

 

I'll definitely give that a shot tomorrow, thanks for help thus far =)

 

Fresh rebuild is not going to like to idle or run nicely under 3kRPM.
Just be patient.
Once you get a couple hundred miles on the engine, things will start to run a lot more smoothly.
It sounds like the rebuild was a success - if you can get the engine to crank over and fire, that's a very good start!


-Ted

 

This is only on NA engines NOT turbo. His idle adjustment screw is on the side of the throttle body and DOES directly move the linkage.

 

Hrmm... I suppose I'll go with what reted says and be happy it is running at least decently. I'll put some miles on it just keeping it alive myself. However, even after a break in, if the screw at its full extension is unable to touch the throttle linkage to prop it open, chances are it will be the same after break-in, possibly leading to the inability to idle then too?

 

Tightening the throttle cable will work also to prop up the idle speed.


-Ted