'98 Civic: misfire issues after swap

[IlxMindFul]

I drive a 98 civic Lx D16y7, the transmission was changed over to a standard, the engine was taken apart for cleaning. After everything went back together, she worked great for three days until I was driving to work the other day, it is 100+ miles there and back. About halfway to work the car starts misfiring horribly, almost bad enough to kill the engine, pushing the throttle a little and letting off of it helped the car not miss out. I made it to work, at this time with the clutch in the engine dies, just drops off and never tries to idle. After working a full shift, I got to the car, thinking timing was an issue I turned the distributor a bit, got in the car fired it up, ran decent, but again halfway home the car died, leaving me stranded. After pulling plugs can confirm three out of four misfires. It seemed like a fuel problem (little gas seemed to work while full throttle kills the engine), changed the fuel pump, no progress. We learned that clamping down on the fuel return out of the regulator makes the car run fine, as soon as the clamp is removed, s**t again. We are getting a readings of about 35 psi before fuel filter, with return clamped its well over 90 psi we are not running it like this. So we replaced the regulator, still no change. We replaced the fuel filter, no change. We pulled the fuel rail off, everything is working/spraying fine. We have a donor car, pulled the ecu out of the car that doesn't run, put it in the good car (to avoid killing two ecu's if that was the case) the donor car ran without missing a beat. The car is in time. I'm starting to run out of options and don't know where else to go.

 

[xxBLOOD88SHOTxx]

Is the distributor OEM? Have you looked it over to make sure it's in top shape?

 

[IlxMindFul]

Is the distributor OEM? Have you looked it over to make sure it's in top shape?

Yes dist is oem, swapped with one on donor car, same results, the one from the bad car makes the donor car run fine as well.

 

[HeX]

Have you opened up and inspected your ECU? Have you inspected all the wiring to ensure there are no cuts or loose connections from the swap process?

I'm tweaking your title from "I need help - Can't figure it out". to something more specific. Vague titles deter helpful attention.

 

[IlxMindFul]

Have you opened up and inspected your ECU? Have you inspected all the wiring to ensure there are no cuts or loose connections from the swap process?

I'm tweaking your title from "I need help - Can't figure it out". to something more specific. Vague titles deter helpful attention.

Have been inspecting harness for a good 2 hours no cuts, lose wires ect. Like I said before the ecu out of the bad car makes the donor car run fine, donor ecu makes no change to bad car.

 

[HeX]

I figured but had to ask being that the car ran fine until extended driving, which could suggest a wiring or resistor issue once components heat up from extended use. Perhaps theres a poor grounding issue to fuel delivery components. I'm just throwing out theories hoping something clicks for you in the thought process.

 

[IlxMindFul]

I figured but had to ask being that the car ran fine until extended driving, which could suggest a wiring or resistor issue once components heat up from extended use. Perhaps theres a poor grounding issue to fuel delivery components. I'm just throwing out theories hoping something clicks for you in the thought process.

Is it possible that the cam gear sheared the key? It's in time from what I can see, we just found out that if the dist is unbolted, and turned past the bolt points the car runs alot better, what else can cause this? Crank pos sens?

 

[IlxMindFul]

Just took the timing cover off, the car is time sadly. I have no idea what could be causing this. Clamping the fuel return line still works to make the car run, at the risk of burning up the fuel pump.

 

[thendi]

On page 11-231 on the Honda service manual states what a normal fuel pressure is suppose to be. With the fuel pressure gauge installed and the fuel pressure regulator vacuum line disconnected the spec is 38 - 46 psi. With the fuel pressure regulator reconnected to vacuum the spec is 28 -36 psi. If the fuel pump is pumping at a low pressure than I see your car misfiring a lot and running like s**t. I suggest you perform the test to see what the pressure is exactly the way Honda wants it done then figure it out from there. I am suggesting test it because you said the car runs better with the fuel return line pinched so maybe there is a pressure problem.

 

[XpL0d3r]

We learned that clamping down on the fuel return out of the regulator makes the car run fine, as soon as the clamp is removed, s**t again.

This is a major clue. FPR works by using a spring. The spring is set to a specific pressure. Fuel pump pushes gas through the regulator, pressure is maintained using the spring, and any extra fuel gets sent back using the return line. If you pinch the line, everything works properly.. which leads me to believe that you are losing pressure somewhere within that return line. When you clamp down the line, pressure is maintained and everything works as it should.

I would inspect the fuel return line past the regulator, inspect for leaks, etc.

 

[IlxMindFul]

On page 11-231 on the Honda service manual states what a normal fuel pressure is suppose to be...

Fuel pressure is normal.

This is a major clue. FPR works by using a spring...

Will inspect after work tonight.

 

[thendi]

I agree with XpLO3dr, if the fuel pressure is lower than normal than it would be a fault with fuel pressure regulator, a fuel line leak, clogged fuel filter, or clogged fuel pump filter screen. I know you stated the fuel pressure is normal but it is really is odd that the car is running fine when the return line is pinched, just saying. Did you connect the fuel pressure gauge into the top of the fuel filter like the Honda service manual show it? I am not trying to start anything but I am just asking because in the first post you said you connected the gauge before the fuel filter so you're just checking the fuel pump pressure I think (not really sure my experience is with GM). If you do it like it shown in the service manual then you can test everything at one. Also, if you suspect the fuel pressure regulator you leave the gauge in the same position and run a different test with different psi range (that is also in the service manual).

 

[IlxMindFul]

I did not test per the service manual, I used what I had on hand, Went before filter simply to avoid fuel banjo bolt. Where can I get the special gauge? Also it's pouring rain where I live, will scavenge some cardboard and resume working before I have to be at work. Do you have a link to the Honda pressure tests??

... because in the first post you said you connected the gauge before the fuel filter so you're just checking the fuel pump pressure I think...

There isn't really a good check point on the fuel system, before or after the filter is basically the same, aside from filter resistance, have tried changing the filter as well.

 

[thendi]

I did not test per the service manual, I used what I had on hand, Went before filter simply to avoid fuel banjo bolt. Where can I get the special gauge? Also it's pouring rain where I live, will scavenge some cardboard and resume working before I have to be at work. Do you have a link to the Honda pressure tests??


There isn't really a good check point on the fuel system, before or after the filter is basically the same, aside from filter resistance, have tried changing the filter as well.

You can download the PDF Honda service manual and it's page 504 on the adobe part.
http://www.clubcivic.com/forum/threads/96-00-service-manual-free-to-anyone.176563/

I don't know where you can buy the tool but there may be an adapter for it in your fuel pressure gauge kit. If it's not in your kit the company that makes your gauge might make an adapter for it. Also, you already replaced the fuel filter and the fuel pressure regulator so you might have leak. It would be hard for you to find the leak if it raining though. My experience is mostly GM and on 2008-20010 Cadillac CTS the 90 degree elbow on the fuel pump return line would sometimes crack and cause a small leak that left residue on the side of the tank. If the elbow was broken it didn't leak all the time but my guess it only leak when the line flexed.