98 Civic with 95 Z6 vtec swap - misfires

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Mike Coday

New Member
We have 98 Civic EX with a 95 D16Z6 vtec engine swapped in and haven't gotten it running right yet. (manual tranny, td-42U dizzy, cold air intake mod) Runs good cold, but sputters under load at low rpm when warm. Here's what we have done so far:

Switched the P75 for a P2P ecu. That got the vtec kicking in at abt 4500 rpm which is kind of fun. Then we jumped the crank angle sensor at the ecu per this: .:FFS TechNet : CKF Bypass Trick :.. Needed to do that because the 95 Z6 engine did not have the crank sensor on the oil pump. Jumping the crank angle sensor reduced the misfire, but it's still there at times.

We went to Autozone, they read the error codes and it said knock sensor and transmission sensor problems. We bought plugs, rotor, dizzy cap, and installed these ignition parts. Misfire was less noticeable, but still there so we are on to the knock and tranny sensor issues.

Where is the knock sensor on the Z6? I am thinking there may not even be a knock sensor on the 95 engine, then I guess we get to find one and mount it somewhere. We knew about the tranny sensor, but have been avoiding fixing it because it's kind of spendy to fix. We are also thinking about switching to external coil to improve spark, but we don't think we should bother til we get these error codes addresses.

Thanks in advance for any suggestions.

Mike, Josh, and Zoe
 
Your engine should have a knock sensor, it is located on the back of the block. I wouldnt be surprised if that was responsible for all of your driveability problems. You have to clear all your codes before you can track down any other problems that could be affecting performance. You should have gotten a jumper harness to convert from obd2 to obd1 and bought a obd1 p28 ecu that would have been a good idea. No secondary o2 or crank angle sensor to worry about either.
 
Thanks

We will get the car up on jackstands later this week and look around for the knock sensor. I assume it's mounted on the block, under intake manifold. Impossible to spot from above, but maybe we will spot it easily from below.

Will clean up the contacts, make sure the sensor is nice and tight, but I guess if everything is good and we are still throwing the knock sensor code, we will need to replace the knock sensor. Whoopee. I think that one's a little spendy.

We got the P2P ecu for a really good price. We would have preferred the P28, but couldn't pass up the P2P at the price we paid. We may end up getting a P28 eventually, but swapping in the P2P for the P75 that was there earlier did allow the vtec to kick in and also allowed us to avoid buying the obd2-obd2 harness adapter for the time being. Still trying to decide if it makes more sense to switch to P28 and obd1 engine harness or use P28 and obd2 engine harness and the harness adapter.

I think we are going to have to replace the speedo sensor also because the pin read out on the ecu indicates the ecu reads this sensor, so maybe it's not just a speedometer sensor, but also a sensor for the computer. Will look around and see if we can spot that one from underneath. Not sure where it is exactly, but I am guessing somewhere on the transmission.

It would be great if fixing the knock sensor would fix the misfire, we are chasing that one and nipping at its heels.

Thanks again.

Mike
 
We were able to clean up contacts on the tranny sensor and get the speedo reading, so I think when we put the computer on it, the tranny sensor code will be gone. We worked on the knock sensor problem, but the engine does not appear to have a knock sensor. It's a hard place to reach and be sure because some of the bones in the arm just refuse to bend very much, but there just does not appear to be a knock sensor. Can't see one from below. Can't feel it by groping around from above or below, so I am thinking we will be getting one, drilling and threading a place to mount it.

When we put the computer on the car, we also got a "possible misfire" code in addition to the tranny sensor and knock sensor codes. :confused:
 
We fixed it!!!

Man, did that feel good to post.

So, we jumpered the P2P ecu to get rid of the ckf - crank fluctuation sensor was not on the 95 engine that was swapped in. The jumpers did the trick, got rid of the ckf code. Then we cleaned contacts and managed to fix the tranny-speedo sensor - that got the speedo working and also got rid of the VSS speed sensor code that was coming up. Then we installed the radio shack piezo transducer to the plug for the knock sensor - engine had no knock sensor. That got rid of the knock sensor code.

Along the way we replaced the distributor cap, rotor and spark plugs. With all that done the engine still had a pretty steady misfire and the scantool at Autozone said ignition misfire - yeah, we knew that. So we moved on to spark plug wires and bang, that fixed the misfire. We were getting misfire on the spark wires down near the spark plugs themselves. Engine is running smooth and even. Great acceleration, vtec kicks in at around 4500.

We are jazzed. Thanks to everyboy who helped along the way, especially boostin4fun.
 
I have a question about the piezo transducer? how did u exactly conect the sensor to it. Im doing the same exact swap but my v tec wont kick in. Im thinking its the ckf and the knock sensor.:confused::(
 
piezo transducer

We just stuck the wires off the transducer into the plug for the sensor and taped it off with electrical tape. I was planning to go back and do something more permanent, but you know how that goes, when the car runs good, you leave things alone.

Have you run the codes on your engine? What computer are you running? The standard computer - P75 - on our car would not kick the vtec in. Even when it was running like crap, the vtec kicked in once we switched the computer out. If you have a vtec computer and it's not kicking in, I would wonder about your transmission sensor. Is the tach/speedo working?
 
well i have not ran the engine codes yet but i know what it is. I was having a lot of trouble with the head swap of my old y8 head into the z6 block some how the cam froz because it wasnt receiving oil from an oil line so im currently fixing that and hopefully it will work that tranducer do you know the name of it because i went to radio shack and they had no clue what i was talking about
 
Here is the knock sensor bypass info pasted from elsewhere. The radio shack part you want is #273-073.



So if anyone ever needs to bypass their knock sensor without tripping a CEL, here is what you need to know.
First of all, you can't ground it out or replace it with a resistor. The knock sensor is not an electrical load, it actually produces it's own voltage. Your ECU is looking for a variable voltage from the sensor.
So what you want to do is mimic the voltage output. Here is a guide of what to do:
1. First, go to Radioshack and buy a piezo transducer, part #273-073. You will find it will all the buzzers because that it's intended for. It costs $1.99.
2. Flip to the back of your haynes and look at the chassis electrical pages. Find which wire going into your ECU is for the knock sensor. If you have a 96-00 civic, it is the Red wire with a blue stripe. MAKE SURE YOU DON'T MISTAKE IT FOR THE BLUE WIRE WITH A RED STRIPE. That's for your AC system. Cut the wire about 6" from the ECU.
3. Tape the transducer to your fuel rail.
3. Weave a single wire from your fuel rail back to your ECU.
4. Connect the speaker wire to the (+) wire on the transducer.
5. Connect the other end of the wire to the Red/blue wire on your ECU.
6. Connect the (-) wire on the transducer to a good ground.

So basically, the positive wire of the transducer goes to the ECU and the negative wire goes to ground. I taped the transducer to the fuel rail because that's where I found it made the most voltage (most vibration).
The transducer only makes about a half a volt at 4k rpms and the ECU usually sees about 1.5 volts. So if you try this and it doesn't work, you will have to find a better location to tape the transducer or you will have to add a second transducer to bump up the voltage.
 
oh man thats a big help alright hmm im done with the y8 head so that is going to be bolted on tomorrow morning hopefuly and see if i starts up fine i hope its going to be my 4th time trying it out.
 
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