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Discussion Starter #1
Hi all,

I just recently finished with building a 164 24v engine into my gtv6.

i bought the engine wihtout hearing it run, and assumed it should be ok..

So the engine starts directly everytime i start it cold and hot,
on cold start it will run for about 15 seconds, and than it will swing between low and high revs, untill the engine dies.

i have noticed when i disconnect the TPS or disconnect the AFM the engine will run but with far too much revs...
i have measured the voltage from the tps and this goes nice from .50 volts to a 4.3 volt on full open

i have diassembled the inlet runners, cleaned them and bolt them on with some silicone gasket replacer,
i have tested the car without any extra vacuum users, so only with the ICS connected to the inlet chamber.

but every thing stays the same... engine is swinging on idle till engine dies.
engine runs nice in higer revs, i do not notice antything off ... but on idle its almost if its not running on all cylinders... ecu gives me no fault codes

i am now at the point that i do not know the next thing to check ...does anyone here have ideas?
next weekend i will check also check the compression and will put in some new spark plugs .. but i don't have high hopes for that
 

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Report your findings after next weekend.
 

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Well the short answer is that you need to do a smoke test on the engine and find out if you have hidden vacuum leak which I suspect you do.

Also list you location in your profile, as that determines what kind of resources are near to you.

Finally list some details about the car/engine. I assume you are using the stock Motronic ECU and wiring harness? If not what are you using? Also what kind of intake manifold are you using?

Welcome to the AlfaBB

Bye
 

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Discussion Starter #4 (Edited)
Hi MilanoGuy,

thanks for your reaction,
its a gtv6 from 1981 (done a complete restauration on it 6 year back....)

the engine is the 3.0 24v with the stock motronic 1.7 from a alfa 164.
i adjusted the wire loom, made it a bit shorter, but before this the engine had the same problem...
put some photos of the engine as attachement
i also put on the 45mm intake runners.

i have adjusted the original manifold, and replaced all vacuum hoses with new lines, so at this point i don't think that it will be a vacuum leak..

however i will do a smoke test, to exclude this... is there a way to do some test on the ICV so i can exclude this wihtout buying a new one?
 

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Still think it's a vacuum leak

Hi
Very nice pictures, very nice car. By "smoke test" I mean a machine like this

https://redlinedetection.com/products/smoke-pro-total-tech

That's the machine I'm most familiar with but I'm sure other brands are good.

You said

"... is there a way to do some test on the ICV so i can exclude this wihtout buying a new one?...."

You can spray WD-40 or starter fluid around the ICV (Idle control valve yes?) while the car is idling. If the idle goes up, or at least the car doesn't stall there's your answer.

I still think this is a vacuum leak because a car that starts, and then dies but will keep running if you get the revs up before it dies, is the classic intake vacuum leak scenario.


Think about this . The engine starts. This means that fuel pressure is good, spark and ignition timing are good, valve timing is good. Furthermore if you rev the engine it's keeps running (yes??) this means it's not running out of fuel or anything else. An engine most needs a sealed intake tract when it is idling. When the engine is at high revs there is so much air rushing in that the leak is not enough to disturb the flow.

Hope this helps
 

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I used an unlit propane torch to successfully find an air leak in my 164LS. Worked like a champ, the idling engine reacting immediately when I waved the torch in a certain area.

The car ran fine at cruise, but sometimes the check engine light would come on at idle, and the idle was a little "floaty", so to speak. Fixing that small air leak cured everything.
 

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Discussion Starter #7
Sorry For my late response, we had to move out, and are in a temporary geast's at my parrents....

Meanwhile i did some testing:
-Tested the ignition coils, (local company tested the signal and according to them this was perfect on all 6 of them)/also swapped the ignition modules and both are giving the same signals. (The spark plugs are new)
-tested the inlet on vacuum leaks with a smoke machine, (local company has done this)
- injectors were cleaned a year a go
- put on a new idle control valve
-replaced all sensors, camshaft/crankshaft/2 x knocking/temp ecu and the throttle position sensor
-bought a fuel pressure gauge and this reads a 37psi stable at idle and 45 PSI with the vacuum line disconnected on the pressure valve.
- Done a compression test, only one cylinder did 9.5 but the rest was around the 12 bar

co wass measured, and came back to 8.6 (so far too rich...)
unfortunly my ecu is one without Lamba sensors...

i did discovered that the Bosch number on my LMM was original on a 12v ... don't know if these are exchangable....
Unfortunly I don’t have a spare lmm to test…. I hope you guy’s have some (new) ideas cause I’m totally out of them …
and thinking of putting back on the old sensors/cleaning the injectors again etc ...

Greetz Johan
 

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Discussion Starter #8
ps. also good to know ... that this is a different engine as the one where i started this topic with...

i bought a revised engine, which was not finalized ... (project went out of funds or something) i bought it cause it was almost a brand new engine, (all inners were renewed) and thaught that i couldnt get a better engine as this almost new revised engine...

so with this info, i think we can definitly say that is isn't a mechenical problem coming from the engine..
 
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