Hi, hoping for some help. Customer told us he had a 2002 Accord non-vtec so we ordered him the engine for that which was the F23A5. Had a new tech install the engine and he didn't realize the customer actually had a vtec F23A4 engine. After it was installed customer keeps getting PO1259 vtec code and rough running at times. We looked a little into it and realized that the cam and rockers are different in the head. Thinking that was the only difference we took the cam and lifters from the F23A4 head and installed it into the F23A5 head and engine in the vehicle. After driving for a while the same code PO1259 still comes back. Tried a new vtec solenoid and oil switch and it doesn't make a difference.
Can anyone tell us what else can be different from the non-vtec to vtec engines that may cause this code. What are we missing and can this be modified somehow? Thank you very much.

 

The entire cylinder head is different. Looks like you guys are buying the proper engine and swapping again. I wouldnt blame your tech for the install. I would be on the *** of the tech would didnt look up the VIN properly.

 

Thanks for your reply but what is different on the head casting? Once your swap the cam and rocker assemblies It appears the same. It has the three holes for the vtec solenoid that go all the way through. Are we missing something?

 

Im not 100% sure the F series non-vtec head has the proper oil passages as the VTEC head. On B series engines you always have to add an external oil pressure line. This is achieved by installing a sandwich plate at the oil filter. There are several other steps for this but I cant tell you with 100% confidence the difference between the different F series heads.

I am quite certain you can find VTEC conversion threads for the F22 engine on this forum. I have seen it done in the past on this forum and ClubCivic.com

Generally folks who complete this conversion, swap the entire cylinder head from a VTEC F series engine.

 

Someone had mentioned to run the old motors vtec head on that non vtec block, there's just a orifice between the cylinders that needs to be removed. Could be wrong but if you were to try to swap the heads to make it work, you would probably see something that needs to be done.

 

Check for oil pressure at the VTEC pressure switch/cylinder head. The F22B2 and F23A4 Non VTEC SOHC blocks have an oil control orifice (plug) between the block and the cylinder head. This port supplies the VTEC passages with the appropriate amount of oil. If you do not have proper oil pressure at the VTEC solenoid/switch @ the head, this is more than likely the reason why.

This is an image of an F22B2 non VTEC block, should be the same as the Non VTEC F23A block, orifice plug circled in red.

by GhostAccord, on Flickr

 

That makes sense! Thanks so much. Do you know if this plug is removable so it will be open like the F23A4 Vtec engine block has?

 

Yes it can be removed. It's a brass plug with a rubber o-ring, if you look closely at the picture I posted you can see that it has a threaded hole in the top to insert a screw to allow you to pull it out. I do not recall the thread size right off hand. I know that it is a regular Honda metric bolt though.

 

Perfect! Thank you so much this seems to be exactly what we needed to find out. Much appreciated!

 

I know Ghost already offered the solution to the OPs problem, but just to clarify... F22Bx would have a different head casting between VTEC and non-VTEC engines. But, the F23Ax are all the same head casting. for the most part only the cam and rocker assembly differentiate them mechanically. of course the VTEC head has the solenoid mounted where the non-VTEC head has a factory block-off plate.