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Volvo B234 problem

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Hello everyone.

I have an interesting problem with my engine, and i can't understand what exhactly happens.

So, the engine is stock volvo B234 , with standalone ecu, MAP instead of original MAF, Distributor ignition ... etc.

The car start without problem, gives good power but always especially on IDle you can see how the engine trembles (like a misfire).

This is cleary notisable from idle to 2500RPM

Checks I've done are:

-Primary triger scope diagram. >good

-All Injectors, in injector service >good

-compression from 9-10 Bar for all cylinders >good

-vacuum leaks > i can't find any.

-new spark plugs,cables, distributor cap ... etc.

Now I wonder if its a mechanical problem or not.

I will appreciate any opinion and help understanding what the problem is.

Thank you

P

Can you isolate it to one cylinder by unplugging an injector or spark plug? If so, try swapping injectors and see if the problem follows the injector.

Since you say it happens from idle to 2500 RPM, what ignition timing are you running in that area? Have you verified the timing is correct with a timing light?

Yes, I have verification with timing light. I try again to isolate cylinder by disconnect injector or spark plug but without result.

The engine run 18deg when idle, to around 35deg at 2500RPM. I'm sure this engine convulsion i have presents beyond 2500rpm but not that visual notisable.

Someting interesting. I lock my ign. angle on 10deg, and that's i see with the timing light. When RPM rise , i can clearly see how in some moments the ign. angle jumps after 0deg (after TDC).

OK. I try another experiment. I have 2x2 waste spark coil, and i quickly connected it. This ign. anle jump no longer presents, maybe some stable offset from -3deg (by eye)

However my engine trembles (short convusions) present anytime.

Hello , have you solved the probelm ? If not , what is the specs on the engine ? what kind of ECU ?