[Spotlight0o1]

So I have an 89 crx with a zc Dohc swap. The problem that I’m having is that under load the car hates 3k and below. And is running really rich. I put a new o2 sensor in it, replaced distributor coil and plugs. I’m not much of a Honda guy so idk what the problem could be. It does have the ecu swapped from the car the motor came out of.

Update there was a plastic placer in the intake manifold we removed it and it idles smooth now put still runs like crap from about 1500-3500rpm

 

[Baker]

Any CEL on or is the ECU throwing any codes?
Do you know how to check that for OBD0?

 

[Spotlight0o1]

Any CEL on or is the ECU throwing any codes? Do you know how to check that for OBD0?

Has no engine light. And there is no code flashing on the ecu

 

[mossin_90]

Have you checked cams timing marks?

 

[Spotlight0o1]

Have you checked cams timing marks?

Have you checked cams timing marks?

Yes many times timing is dead on and have even taken a timing light to it.

 

[mossin_90]

You need to make sure the timing marks represent the correct value in degrees as the ecu is set for.
If the ecu you are using is paired to an engine that is set to 12BTDC and the timing marks on you engine are set for 16BTDC you will have problems.

The crank pulley timing marks will look the same on both engines. Disregard the dots.
I I I.......I

placing them one behind the other at the correct position(both crank keys aligned to 12 o Clock position) will show if they are different.
I I I.......I Vs
..I I I.....I
the single mark TDC will match both pulleys but the running timing marks may be off.
If you have the correct pulley and ecu skip to the next paragraph.

Another possibility is that the ECT is bad or failing, assuming wiring and connectors are good.
Running rich is a sign of a bad or failing ECT.

 

[Spotlight0o1]

You need to make sure the timing marks represent the correct value in degrees as the ecu is set for.
If the ecu you are using is paired to an engine that is set to 12BTDC and the timing marks on you engine are set for 16BTDC you will have problems.

The crank pulley timing marks will look the same on both engines. Disregard the dots.
I I I.......I

placing them one behind the other at the correct position(both crank keys aligned to 12 o Clock position) will show if they are different.
I I I.......I Vs
..I I I.....I
the single mark TDC will match both pulleys but the running timing marks may be off.
If you have the correct pulley and ecu skip to the next paragraph.

Another possibility is that the ECT is bad or failing, assuming wiring and connectors are good.
Running rich is a sign of a bad or failing ECT.

Alright so we checked all that and everything is right for that motor, we found out today that it’s running rich at idle and and lean in the upper rpms the o2 code pops up on the ecu when the car has been idling for awhile. But what is weird is it ran perfectly fine after it warmed up a bit in my state.

 

[mossin_90]

Ohh wow!
Diagnose sensors one at a time to rule out any other possibilities.

 

[Cam67]

Any update on the zc swap crx? I just bought a 91 si crx with a DOHC zc swap and it sounds like it's having the same exact problem, where it runs terribly at low rpms.