1G Started running on 2 cylinders mid drive?

[Volif_]

I went for a drive yesterday on a uphill road near me. The car was driving fine and pulled great uphill. Then I went downhill (with mid/high rpm's for braking, but I was not pushing it just a normal drive), and after I almost came to the village below the car just became very loud, lost power, stalled when stationary, shook a lot and lost rpm's. I got it towed back to my place and began the inspection to see what was the problem. While the car was roughly idling I pulled the spark plugs to see if there was any change to the rpm's. If I pulled either the 4 or 1 plugs the engine would die furthermore if I pulled the 3 or 2 plug the engine would not change one bit. I saw sparks on the 3 and 2 plugs. I also tested the spark plugs which showed great spark, no issue whatsoever. I have also tested the injectors and they spray and work fine. Also switched the sparkplugs between with no different result. Compression seems good have not tested it yet, but the engine has been rebuilt about 5000 miles ago with no issues as of now... I have read on the forums that it could be the coils but I wonder why if it gets good spark on all of the spark plugs... The ECU also looks great with no leakage of the capacitors. And no smoke coming out of the exhaust when revving just the smell of unburnt gas from the 2 cylinders.

Any ideas before I go changing cables, sparkplugs (again), coil packs, CAS and so forth. Parts are pretty scarce here in Europe for these cars.

The car mentioned is my 4G63T GSX 1991 with a fully rebuilt engine, rebuilt turbo and fully stock (not consuming any oil or antifreeze)

Thanks,
Vid

 

[steve]

Any fault codes?
What are the compression numbers for all 4 cylinders?
Loosing 2 and 3 usually points at an ignition issue since those are paired. ECU, PTU, Coil.

 

[Volif_]

Any fault codes?
What are the compression numbers for all 4 cylinders?
Loosing 2 and 3 usually points at an ignition issue since those are paired. ECU, PTU, Coil.

No fault codes whatsoever on the OBD 1 connector. No check engine or other lights either.
I have not checked the PTU yet. From what I have read on the forums this module should increase the signal voltage from the ECU and then send it to the spark?

Thanks for the reply
Vid

 

[steve]

The PTU switches the voltage from the two coils to ground to cause the charging current to flow. When the ECU turns it off the coil discharges and fires the two spark plugs. The PTU also outputs a signal to the ECU (and RPM gauge) telling it that the coil fired.

Our ignition is called a wasted spark system because of the paired plugs, one fires in the cylinder with fuel and the other fires into the cylinder exhausting which does nothing (wasted). It's the coil (via the collapsing electric field) that causes the voltage to be boosted from battery voltage to the high voltage the spark plugs need. The PTU just switches a large battery voltage current on and off. (two big transistors and lots of heat).

The mounting bracket acts as a heatsink, in cause yours is loose. There should also be a spring clip on the connector that keeps it attached to the PTU.

 

[Volif_]

Sorry for the late response,

Thanks for clearing up the spark system in our engines. I am assuming that one of my coils is bad. It gets spark, and I assume that the spark on cylinder 2, 3 is not strong enough to make combustion occur. That would be the only logical thing that I can assume happened in my scenario. I will test compression during the weekend and report back with the results. I will also look at the PTU, heatsink problems, and all of the connectors leading to the PTU and ECU.


Thanks again for the fast response,
Vid

 

[Volif_]

Hey, so bad news

Tested the conpression nr. 1 and 4 compressor have 10.5 bar or 152 psi and nr. 2 and 3 are not holding compression...

Don't know what problem is causing the compression to vanish. The engine was out of the car and rebuilt around 5000 km ago and about 1.5 years ago. And the car was not under heavy load when this happned.

All I know is that I am very dissapointed.

Thanks for the help,
Vid

 

[pauleyman]

Hey, so bad news

Tested the conpression nr. 1 and 4 compressor have 10.5 bar or 152 psi and nr. 2 and 3 are not holding compression...

Don't know what problem is causing the compression to vanish. The engine was out of the car and rebuilt around 5000 km ago and about 1.5 years ago. And the car was not under heavy load when this happned.

All I know is that I am very dissapointed.

Thanks for the help,
Vid

Have you checked mechanical timing or any valvetrain components? You can pinpoint cause with a leakdiwn test also.

 

[Volif_]

Nope,

I am gonna take the head off sometime soon to see what has failed me. Hopefully it is just a headgasket.

 

[HaveBlue83]

I had the exact same thing happen to me after a long pull. Lost spark, ran on 2 cyl. Smells like raw gas out the exhaust pipe.

I towed it home, swapped out spare coil packs and it went away! Hooray!

Came back out today after work, back to 2 cyl. I swapped in all my spare out and coils, nothing.

ETA:
Anddd it was #3 inj clip popped off half way OMFGGGGG DSM PROBLEMS.

 

[Volif_]

Update time!

I have removed the cylinder head from the engine and found out that the head gasket had indeed blown between the 2. and 3. cylinder.
I have also found out that the head on my car has been resurfaced to the last mm and was cracked and fixed at some point (as of my inspection).

I have attached photos of the blown head gasket and the cylinder head if anyone has any tips on getting the head fixed somehow. Parts again are pretty scarce here and it it difficult to find a new head to put on the engine

Thanks,
Vid

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[1990TSIAWDTALON]

Was the head resurfaced before it was installed? How about the block deck? Very important steps. Just inquiring.

 

[Volif_]

I honestly don't know...

The previous owner did the matinance on it snd he said he resurfaced it all... but I am a bit sceptical