So I have a JDM b20b swap with about 43k miles with a p75 ECU(OBD1) in a 93 hatch. Just bought the car and I drove it here an hour down and it made it without any major problems. Owner says its in "limp mode" until all the sensors it needs are fixed and the CEL reset.

I don't know what that means and i'll be honest with you I don't know much about the ECU or about cars in general so i'd appreciate some in-detail help



Problems with the car:

Throwing out the following CEL codes (OBD1)

- Throttle Position Sensor (verfied, checked resistance, no good)
- Map Sensor,
- Engine Coolant Temp.
- Intake air temperature sensor

So far I ordered a new TPS, new spark plugs and wires (current plugs are burnt and no good)

Major problems that i've seen so far:

- Car takes a few tries to start, loud "whirring noise", sometimes cranks a little then shuts off, then after a few tries starts up fine and will continue to start up with no problems after its warmed up.

- Sometimes idle is high on cold start (2k RPM) and sometimes its a little low (500-700 rpm) and jumpy. Lately it's been low and jumpy.

- Exhaust smells rich in gas (I don't know if its running more rich or lean), 2 1/4 straight pipe, no cat (flexpipe) but it smells alot and unbearable to drive, thought I was going to pass out from the carbon monoxide driving it down to my house. Don't know if something is leaking into the cabin or if it's just the straight pipe is supposed to be like that, never had one installed.

- Car jerks ALOT in 1st gear as I try to take off, rest of the gears are fine (third grinds a tiny bit going into it SOMETIMES, doesn't grind downshifting into 3rd)
- and also the shifter is stiff and hard to put into gear (B&M short shifter)

- Car doesn't run well in general. Doesn't have the power a b20 should have. Accelerates slow, throttle response is not great, overall running like ****.

- When I turn on the car it makes a loud squeaking noise like its one of the belts (noise comes from around or under the cam gears and goes away after it warms up)



If I find anything more I will post. I just want to narrow down what could be causing my car to run shittier then it's supposed to. Might it be jumper harness or could it just be all the sensors that need to be replaced which are making it run bad?

Engine doesn't knock, tick or smoke. Seems like its good just not running correctly. Want to narrow it down so I don't spend money on things that DON'T need to be fixed because i'm on a tight budget now.

 

Sounds like someone who really didnt know what the were doing just slapped it in there and now its running like ****. The best thing for you to do is to find someone in your area that knows hondas well that can just go over everything and see what is actually wrong with it. To me it sounds like its just a bunch of little things adding up, but for someone who doesnt really know a whole lot, you might not have the experience to find them all and correct them

 

Pretty much exactly what I thought. But I just wanted to narrow down as many problems as I could by myself then have the rest looked at locally. Problem is it's not registered. And even if it was I don't think it would be healthy for the motor to drive 20 minutes and back to my local honda tuner. So i'm kind of stuck weeding out the easy problems and leaving the more complicated ones for a mechanic when I get the chance.

 

Try and swap the tps and map sensor and swap the other two, same plugs then reset ecu and see if that fixes problem. Sorry I mean wire plugs, tps and map, ect and iat same plugs

Let me know results

 

So swap all that and change wire plugs for TPS and MAP sensor only? Also do any of these sensors need to be calibrated a certain way? If so how do I do it?

 

Swap the tps and map wire plugs then swap the iat and ect wire plugs. The only sensor that needs calibration is the tps. Assuming all the wires are still in the same spot in the plugs they came in stock, follow these steps for calibrating tps

https://honda-tech.com/tech-misc-15/diy-calibrating-voltage-tps-2947986/

 

Buying all the pieces this weekend and replacing those, as well as an oil change and new spark plugs + wires. Will make a video to show you how it's running afterwards, thanks man.

 

Oh I forgot to mention my car is getting HORRIBLE mpg. I don't know if it has to do with the TPS or another problem?

 

The one thing I wasn't clear on was that the tps and map have the same shape plugs. The ect and iat have the same plugs

It's easy to get them mixed up

Since the b20 and b18 use the same size injectors. With a b18 fuel map on a b20, the fuel needs will be different

 

Have you once looked at the wiring diagram? All those sensors get a 5volt reference from the same place!!!! Have you looked into that ? Also I dont know wtf you are doing checking the tps sensor for resistance. Thats not how it works!!!! Unplug the freaking sensor with the ignition on and check for the 5 volt reference!!! Make sure there is a ground. If you dont know how to do that stop touching the car. And for your information, to properly test the tps you will need to graph it. You will need to backprobe the plug for the sensor return signal to the ecu and verify that at closed its 0.5 and open 4.5v and has a smooth transition from open to close on the graph. I wish I lived closer so I could make some money

 

Actually the tps dpes work on resistance. It has a conductive arm that goes across a resisitance trace inside. As you sweep the tps it increases resistance. Thats how you get the 5v reference to drop to .5v-4.5v
Any damage to the internal contact pad will result in erratic resistance values.

If you dont have a battery for the car pr its not hooked up, you can check the resistance between the middle pin amd the outer pin (either one, one goes low to high, the other goes high to low)

As long as it has a smooth resistance sweep then the tps itself isnt broken. It still needs to be calibrated based off the voltage though

 

Ok so UPDATE....

Switched spark plugs, wires, oil change, definitely ran better.

Throttle body is for an AUTOMATIC LS, realized (from what i've gathered, will need conformation) that it is an OBD1 LS head on a OBD2 JDM b20b block.

I think the MSD distributor, throttle body, intake mani, fuel rail and injection system are all from OBD1 LS, with an OBD1 p75 ECU, and a hackjob of a wiring harness.

After I took the throttle body off and replaced the gasket (it was broken) now the car idles even worse and stalls out after a few seconds of turning it on. Seems like my main problem is coming from the throttle body because that's where the MAP sensor and TPS are and where my idle problems are most likely originating. I'm not getting the power I should be during acceleration as well.

this is how it looks like, i can get better pictures tomorrow

 

Update:

I looked into my swap some more since I just got the car and I came up with some conclusions, maybe this will help those who are trying to help me because to me it looks like theres a bunch of mixing between obd1 and obd2 parts.

The swap is comprised of:

- OBD1 LS p75 ECU

- b20b JDM block (don't know what year), and unconfirmed whether an LS or b20 head (casting number p75-6, made December 1999)

- What I BELIEVE to be an obd1 distributor (2 wires coming out) but it's an MSD distributor with some sort of external component, looks like a power supply, and i'm not sure about the wiring harness or how to check.

- Not sure about the intake mani/throttle body but it's an AUTOMATIC throttle body, not a 5-speed one (has the extra plug piece at the bottom)


Basically the car is running like crap. It's idling VERY low (almost at 0) and it wants to stall out after I give it gas and it drops. Car drove to my house fine and now the problem seems to be getting worse. It burps and throws white smoke when I hold it at 2,000 RPM all of a sudden, but this is right after I added coolant/water in the radiator and a whole bunch of coolant spilled down into the block and tranny/exhaust area because my boy let the coolant line going to the throttle body hang loose.

 

Youre going to need to do a lot of research online to see what is involved doing that engine type swap into your style Civic.

Its going to be a steep learning curve if you have no type of automotive diagnostic experience trying to solve these issues. Hopefully you didnt bite off more than you can chew.

I was in the same boat with my B18B1 swapped EJ6 but thankfully i was able to diagnose wnd fix my primary issues.

Good luck and keep us posted.

 

So TPS has been switched. Problem still occurs.

IDLES low like at 200-300 and stalls when I come to a stop. I have to give it gas to keep it going. Hesitates without any power in first and second gear lower in the power band.

Same CEL codes still on. Map sensor, TPS, Intake air tempature, Engine coolant tempature

I'm stumped. I have a OBD1 LS ecu, OBD1 d-series engine harness and obd1 injectors and distributor with obd2 intake manifold and obd1 head and block (JDM b20b)

does that sound like it shouldn't be together? What parts should I switch out to see if it works? I was thinking of buying an LS obd1 harness and a new distributor to see if that fixes any issues but I Don't know.

 

parts switched out? You still trying to shotgun this? Get a meter. Get a wiring diagram. Did you check to see if the map, tps, intake air temp, and etc are getting their 5volts? Since they all share the 5volts I would assume that would of been the first thing you would have checked. Just tow it to somebody who knows how to work on cars. Or just keep spending money on swapping parts, then give up and put it up for sale on craigslist

 

Sorry for the long response I've been busy at work and I have not had time to work on the car.

I did a few things today.

-Thoroughly cleaned IACV valve and entire throttle body

- Checked voltage coming from ECU off the TPS and MAP sensor plugs, which showed 0 voltage for each sensor plug. I did this because I already switched both the TPS and MAP sensors to new, working sensors and it didnt fix the problem.

I put my red probe into the yellow wire with red trim (first prong) on map sensor plug and grounded to metal in my engine bay. 0 voltage coming out with ignition ON.

Red probe into red wire on TPS sensor plug and grounded to metal on engine bay. 0 voltage with ignition ON.


So what seems to be the problem? Bad ECU? Maybe I performed the tests wrong? I stuck the probe into the front of the plugs to each corresponding wire, and performed the SAME tests using a paperclip in the BACK of each plug and corresponding wire. 0 voltage all around. Nothing is coming up on my multimeter.

Both TPS and MAP sensor check engine lights remain on.

 

bump

 

Cool. Now you are on your way to fixing this issue. Now you have to test for continuity from the yellow/white the reference voltage pin on the tps (I don't know your specific model) to the ecu plug d20. Do this with the plug disconnected and key in the off position.

 

Thanks, will post back with results

 

From what I tested it seems like there is continuity on each plug. Kind of stumped now.

 

what do you mean continuity from each plug? you tested them from their respective spots on the ecu ? They all dont go to the same place. did you also do a voltage drop on the ground side. And do you know how to use a dmm?

 

Sorry for the late response once again. I managed to fix most of the problems above. Turns out after further inspection the engine harness was only partially plugged in on left side. Intake air temp sensor was melted, switched it.

All problems are fixed and its running good now. One problem still persists though, the TPS. Car still idles alittle too low for comfort, maintains idle doesn't jump now only sometimes after I release the gas it'll dip

Still throwing TPS code. Checked voltage now and its giving me about 0.27 - 0.30 depending on how I move it. It won't go any higher or any lower..even when I open the throttle it doesn't change voltage and go up to 4.5 like it is supposed to..

It is an after market TPS I got online for real cheap so maybe that's why?

 

Get a new TPS, that one is bad (or the wiring is bad...)

Once you get that working properly, set the idle using the procedure outlined in the FSM.

 

It's a brand new TPS and the wiring seems to have low voltage like I said so I just don't know where to go from here. Splicing the wire going to TPS and replacing or what?