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l28et swapped 240 extremely high idle at startup


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Okay,so my car is frankensteined very much.it has a f54 block,p90a head,83 na dizzy,83 na ecu/wiring,83 turbo injectors,75 intake manifold.

 

I made sure it ran good before I went and put the turbo stuff on it since I was running that block and head with my su's for awhile.after alot of messing around I finally got it to run right and idle smooth around 800rmps.

 

So after it was running right,I put all of my turbo stuff on it which includes: turbo exhaust manifold,turbo,and intercooler.and of course the piping as well.i ran it through the 83 na afm since the turbo afm doesnt go with that harness.

 

After I got everything set up, I went to fire it up and the rpms kept climbing very fast.i had to shut it off asap...

 

What would cause that problem when it was running fine without the turbo,I bolted the turbo on and the idle climed very very fast and wouldnt stop...and there is no throttle problems.i put all of the na stuff back on temporarily and it runs fine again...

Any help is greatly appreciated.thank you

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That was a lot of work to swap over and then swap back. :icon9:  I did your swap exactly but to my 260Z.

 

Did you lock up the mechanical advance in the stock distributor?. If not, you need to do that. Either rtv it, jb-weld it or have it welded.

 

Did you move the pcv valve location foreward, under the intake manifold??... If you didn't its almost impossible to get the pcv hose on the valve, so you may have a huge vacuum leak at the valve. You then just install a threaded plug in the pcv valves original location.

 

Make sure you didn;t catch one of the fuel line brackets, inbetween the intake manifold and the cylinder head. Again a huge vacuum leak.

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Let us know if you forgot to install that pcv valve in the manifold, You didn't say if you did or you didn't.

 

Yes a large vacuum leak will cause a very high idle, sometimes over 2500 rpm.

 

You lock the mechanical advance up in the dist so your timing doesn't advance and you blow the headgasket, due to Detonation.

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Ok good,

 

What may help is after you swap the turbo parts back on your engine, post some pics of the intake setup so we can see what you have going on, with the hose routing. :icon56:  Feel free to PM Me also.

 

Like my earlier post said, i did the swap the same exact way you are and didn't have any problems with it running. I even found an intake hose that connects from the n/a air flow meter to the front of the stock turbo. It puts the air flow meter position almost exactly where it was when it was n/a.

 

My engine flew through emissions for 3 years, then i registered the car as a collector car and no more emissions for me in AZ. Emissions guys always said, i didn't know they turboed these cars in 1974. Lol

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Haha.well I asked my inspection guy if I have a newer motor in it that does require emmisions,if it would need it and he said no.they only go by the date of the car.i still need an emissions exempt sticker though.-_-...and when I do get it plummed back up,dont laugh at my ic piping...its temporarily pvc piping due to a lack of money.but regarding that,there is no air leaks,they are sealed very well.also,I am not sure if my problem would lie somewhere in the wiring harness...it may.i will explain how my ecu is hooked up,and you might have a better idea of what it may be.but before I describe how it is hooked up, just know that it runs and idles very well(after I tweaked the afm a bit)

...let me rephrase that...it starts when it wants to.there is no pattern at all.but when it does start,it runs and drives great...

..so here goes...

 

First ill name all of the parts that are attached to the wiring harness.see if maybe im missing anything huge.

 

Starting at the ecu I have the fuel pump relay, the efi relay, the head temp sensor, the tps sensor, the afm, all injectors.and I believe that is all that is connected off the harness.other than the fuel pump itself.

I do not have a coolant temp switch/sensor.just the head temp switch.

I believe the harness/ecu is grounded very well in 3 or 4 spots,with one going directly to the battery.

For power to the ecu,I have the ignition and my electric fan powered to a toggle switch(just because I havent dug into my fuse box yet to get a good ign lead...the switch is only temporary). The power to the battery is straight to the battery.but there is the confusion that I dont understand.when I flip the toggle switch,the ecu does not come on...for the ecu to turn on I put power to each pin until the ecu finally kicked on.when it turned on the fuel pump primed for 5 sec like it should and the relays clicked...now the pin that I had to put directly to the battery was for one of the afm wires.so basically there is always power going to the afm for no reason.i still left that wire hooked up to the afm,but its also spliced off to the + of the battery...I apoligize in advance if that was jjmbled and confusing,but hopefully you can get the jist of it.my biggest problem with the efi swap was getting the ecu to turn on.i went over every diagram imaginable to no avail...just had to test every pin until it turned on.im sure that has a big part in the turbo problem...

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Ok, Well i'm not sure if your supposed to have power to the ecu from the battery like that, might be to much voltage.

 

You don't need an intercooler if your not running ig boost numbers. So maybe eliminate that pcv piping.

 

Did you post in another thread about your put together wiring harness, and me saying your missing relays ??.

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Yeah,at.fist I didnt have the efi.and to relays.I had to go back to get them.

And I don't have a boost controller yet,so I just plan to run wastegate pressure for now...does that make sense?I was told that the boost pressure shouldn't be too high while just using the wastegate.so if that is true,I can temp use the j-pipe for now for less chance of leaks

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