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Discussion Starter #1
Hello all,

I recently found a DOHC ZC locally for $250. I picked it up after the urging of members over at the CRX Community. I am confused on which generation it is though. I have read lots of stuff on the ZCR and here, and over at the Community. I was thinking it was a third generation (OBD0) engine, but now think it is a fourth generation (OBD1). I need some input. The intake manifold along with the block are both stamped PM7. A PM7 stamped intake manifold should mean it is OBD0. But, there is a rubber plug on the exhaust cam where the cam angle sensor should be which would mean this is an OBD1 fourth generation engine. So, does it matter which intake manifold is on the car? There should be a MAP sensor on the throttle body for a generation 4 as well. That is off the motor and sitting on my work bench. Been cold lately so I haven't really looked any more closely than what is pictured. I suppose I need to look at what distributor is on the engine too. If this is OBD1, do I go with a P29 ECU or can I just chip my PM6 that is currently in the car? I should mention, my CRX is a 1991 Si. I also got some exhaust manifold with the car. Not sure about that either. I would be more than happy to take more pictures and look for more info/stampings on the engine if somebody with more knowledge just points me in the right direction.

Second part of this post is this: what should I replace? I don't terribly want to dive too deep into the engine. I am planning more on things like timing belt, tensioner, water pump, alternator belt (probably take the alternator to auto zone just to have it tested), oil pan gasket. Is there anything else I should look in to replacing? And do any of these parts change from generation 3 and generation 4?


Been in to CRXs for years, but this is my first swap and don't really want to mess this up.

Thanks in advance.








 

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The engine harness is obd1. The distributor might be an obd2 as I only see one plug for it,I think it's a y8 distributor.

Look at the head right behind the dip stick there's numbers there. One of the numbers is the year.

Since your putting it in a crx you either keep it obd1 and get an ecu jumper or convert the motor to obd0.
 

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Discussion Starter #3
I would guess that buying the jumper would be easier, no? The head sure looks like it says 90 on it. What kind of hodge podge motor did I buy?
 

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90 crx si/96 accord
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You bought a great motor!!!! Not some "Hodge podge "bahaha
If the head says ninety its more than likely obd0 and someone "converted" it to obd1

Judging by the fuel rail i'd say the intake is also obd0 the manifold bolt patterns are the same...however the throttle body pattern is different
 

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Discussion Starter #5
So, should I convert back to OBD0 or just get a jumper harness and run OBD1? Which would be cheaper/easier?
 

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Discussion Starter #7
Okay, here is an update with a couple pictures. This is what I think they did. OBD0 block, intake manifold, head. Removed the cam position sensor. Changed out the distributor for an OBD1 unit. Stuck a throttle body on the PM7 IM from an OBD1 car with a MAP sensor on the actual throttle body. Sound about right? Also, don't you have to change injectors to convert a DOHC ZC from OBD0 to OBD1?

At this point, a jumper harness sounds cheaper and easier than tracking down the parts and converting back to OBD0. Or am I wrong on this one?

Thanks.

 

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91 CRX Si
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"Sound about right?" Yes, pretty close. No you do not have to change the injectors when converting from obd0 to obd1. I'd stay obd1, I also converted mine from obd0 to obd1.
 

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Discussion Starter #10
The guy I bought this from took it in a trade with an Integra. He said it was mounted in the car but had not been run. He said the previous owner never got it going. I am doubting this now. Somebody played with this engine. I am sure it didn't come over from Japan like this. I think I might do a little more internal snooping than I had planned before dropping this in.
 

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93 Legend L Coupe.
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OBD1+ Injectors are high impedance and do not require and should NOT be run with an injector resistor pack. So, if you eliminate the injector resistor then you don't need to change the injectors. Well, first you should actually measure the resistance across the terminals of the injectors to determine if they are high or low impedance.

If it's already converted to OBD1, then it will be easier to run it OBD1.
 

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97 honda HX-07 STI
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Looks like a pretty clean engine anyways for the price. Hopefully no gremlins.
 
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