HELP: Car cutting out at 6,500rpm in 4th & 5th Gear

[RoofusX]

Our CA is cutting out at 6,500 rpms in 4th and 5th gear we cannot figure out for the life of us what the problem is. Here are some stats:

-Running U.S. electronic gauge cluster does not read any MPH-CA harness is for a automatic, so there are no sensors except speed sensor and that is the only one to hook up and is hooked up-ECU is for a auto transmission-When checking for power on clip connecting speedo sensor to harness we don't get any power reading-Have tried several speedo sensors with no luck-Running new plugs, and Walhbro 255lph fuel pump

Should one of the sensor wires going to the speed sensor have power?Please don't simply reply "search" we have searched and searched, and we have tried almost every suggestion we have found on the car to no avail.

Thank you for the help!

[USDM_OneVia]

-ECU is for a auto transmission

There is your problem.

Back in my Honda days a few of my buddies would swap from an automatic to a five speed and not change out the ecu for the correct transmission. This would cause all kinds of problems since the ecu is looking for the stuff for the automatic transmission and it can't find them. Is it throwing a check engine light? On the Honda's it will, not sure about Nissan's though.

Try swapping for a known 5 speed ecu and report back the details. What is the number on the ecu? Mine has a 98 on it fyi.

Joe

[Oneor1]

I believe I was talking to Sean (NeedCAfors13) about this way back before I got my Motor and he said that either ECU will work.... could be wrong.... but im quite sure either would work.....Sean???

[NeedCAforS13]

both CA ecu's will work AFAIK. that seems to be the opinion of most of the people i've talked to...

Sean

[RoofusX]

Yeah, the car runs fine, idles fine, etc. But as for the cut out, I am assuming this probably has something to do with the MAF fuel cut. I was reading on some chip tuner websites that if the MAF sensor senses too much air coming in it will cut fuel. This makes sense because alot of the VW guys 1.8t motors have this problem when they put in K&N drop ins or intakes. So we think this will get fixed when we get a chip to take away all the limiters and cuts.

HOWEVER, the big problem we have run into and are scratching our heads over is the MPH gauge. It doesn't read MPH, and we have tried so many things. We even tried to hook the speed sensor straight up to the ecu and dash and bypass the rest of the harness to no avail.

After looking at several autotranny wiring charts, I think we may be running into a problem with a plug. The chart shows the auto's having a plug right behind the ecu plug code named "F3". In the auto trannies this plugs into a harness that runs into the Automatic Transmission Control Unit. So since we are using a auto harness in a car that had a manual that plug and control box doesn't exist. Long story short, I think by bypassing that control box it doesn't allow the sensor to complete its circuit. I have no idea how to get around this.

[NeedCAforS13]

use your lower KA harness...with the transmission plugs.

Sean

[RoofusX]

Could you clarify that, we have to be using the CA harness and the speed sensor wire comes off that harness. So what would you be refering to?

[USDM_OneVia]

The lower transmission harness is a seperate harness from the main harness. It will unplug from the main harness.

Just look at your KA and you will see what I mean. You can disconnect it from the transmission.

Joe

[RoofusX]

Whoa, whoa, we might be onto something. We have a plug off the main harness attached to our speed sensor. You're saying that there should be a "transmission harness" and that should hook up to the transmission and then hook up to the main harness?

I will NEVER do a auto to manny transmission swap again, this is ridiculous.

[Nismo1182]

No, your right, the speed sensor plugs is on the main engine harness. Then it should go to the plug on the transmission. There is no "middle" harness for that one.

The lower transmission harness everyone is talking about includes: 4th and 5th gear plugs, reverse plug, neutral plug, speed sensor, alternator positive and negative plugs, starter positive and negative plugs.

This should all be in one single separate harness. 99% of the plugs on this go to the plugs by the fuse box next to the battery. The only plug that does not go to that box is the speed sensor plug. Which is on the main engine harness.

[RoofusX]

Well then we have it hooked up right. So that isn't the loose end. We don't have the 4th gear, reverse etc. hooked up but I was told this shouldn't be a problem.

You guys ever heard of anyone or a way to bypass the main harness with this and go straight from the sensor to the dash or something like that?

[Nismo1182]

Well then we have it hooked up right. So that isn't the loose end. We don't have the 4th gear, reverse etc. hooked up but I was told this shouldn't be a problem.

You guys ever heard of anyone or a way to bypass the main harness with this and go straight from the sensor to the dash or something like that?

The 4th gear plug you dont really need. The reverse plug (the whole sensor has to be replaced with the sensor from the KA, unless you are using the CA lower harness)

I didnt touch my speed sensor, i left the CA one and it reads mph just fine on my speedo.

Follow the speed sensor wire to see where it goes.

[boost_boy]

Quote »ECU is for a auto transmission[/quote] I would seriously worry about this! The engine will run rich and foul the plugs, so when you try to get in the uper RPM ranges, it starts coughing. I tried it before and it didn't work. I've tried everything with CA motors as far as computers are concerned and the automatic on 5spd engine thing just don't work well with this motor. But then again, I've totally given up on the factory stuff to gain experience in tuning as well as gaining flexibility and peace of mind.

[slw240sx]

Dee can i put a chip in his auto ECU to turn it into a manual ECU?

[RoofusX]

Good question Jon, thanks for bringing that up.

Though we will have an extra ECU in a week or two. The third guy that was helping us with this swap will start on his 180 hatch in the next week or so and he is getting a manual clip. He is buying a stand alone unit from the get go so we will be able to put his ECU into the 240 coupe.

Car got bumped up to 15psi tonight and I was told it was running really well. Was told it was still cutting out about 6K rpms, but that it was pulling so strong that he didn't need to run the motor up any higher than that.

Hopefully the ECU swap will get us through the bogging. So the big task right now is to figure out how to get this speed sensor up and running. But as I just wrote that, I'm wondering if the manny ECU might fix that as well. Since it will be wired to work like a manny and then will have a manny ECU maybe something will click. Here's hoping anyway. :crossesfingers:

[boost_boy]

There's too many possibilities of differences found in the auto ecu as opposed to the manny ecu. My suggestion is to get the right one because it will more than likely solve the headaches being experienced. Shift points are probably set that low from factory for the auto to prevent the transmission from being destroyed.