Just converted my 1990 Civic back to DPFI. When I turn on the car, it runs well for about 20 seconds and then it starts sputtering and dies if I don't give it gas. When I do drive it, there is power in first and forth gears, but then it loses power in second and third. I have not gone far enough or fast enough to go in fifth. Funny thing is, there is no CEL. When i turn the car on, the CEL comes on, but turns off right away, so it is working. When I step on the gas, tons of black soot, mixed with water spews out of the exhaust. Also, there is a strong smell of exhaust and fuel. When I pulled out the spark plugs, they were covered in soot. When I did the swap, the one thing that I did not change was the intake manifold gasket. I used the same one that I had for the MPFI manifold. The reason is that I bought it new and I only had the MPFI swap for 3 months. Could the gasket be the problem? The reason i ask is that when i checked Autozone and O'Reilly's, the gasket part numbers for the 1.5 and 1.6 liter engines are the same. I checked all the engine wires and vacuum lines and they seem good. I checked the ECU wires and they look good too. I have a new distributor, new spark plugs, and new spark plug wires. Just want to get some knowledge before I go out and purchase a new gasket.

 

Gaskets should be the same. Did you reverse the wires on your TPS? I know with the MPFI swap you are supposed to reverse the two outer wires so the ECU reads the throttle position correctly. Probe your middle wire with a multimeter and make sure it is reading that the throttle is closed at idle (0.5) and not WOT (4.5-5v)

 

I believe the wires are good. I cut out the 3 ECU wire connectors from another DPFI Civic STD as reference and matched the wires all up to my current set up. Do you think the problem could be that the ECU is bad? I am not getting any CEL codes, even when the engine dies on me. The DPFI intake manifold should not have any problems since it was working fine before the MPFI swap 2 months ago. Also, I noticed that there is a dent on the ECU case on the top. Maybe it got banged up when I put it in storage?

 

The ECU wires might be fine, but there is a connector on the TPS sensor under the hood that EFvtec is describing to you.

The TPS sensor rotates opposite directions on the DPFI and MPFI. Flipping the wires around fixes this issue.

 

Aside from the TPS, do you know if it is misfiring by chance? It is a DPFI distributor, right? Not the MPFI one.

 

I am using the original DPFI distributor that was on before I swapped the car. I had if off for about 2 months, then reinstalled it after I did the swap back. I purchased a brand new distributor to see if my distributor had gone bad, but got same issues. So, I ruled out the distributor. Running out of ideas on what is causing the problems. Summary of issues:

Car turns on fine when cold, but after a minute, starts to shudder and then dies. No CEL code

Car smells really bad, running rich. Tons of black soot and water spews from muffler when I press on gas

When driving, it is extremely sluggish in 2nd and 3rd gear. Seems to perk up after switching to 4th, but haven 't driven too long on forth.

At idle, car dies.

When trying to start car after dying, it does not turn on unless I give it a lot of gas. Then it dies again in I leg it idle.

Spark plugs are covered in soot.

Hopefully it is there ECU since there are many DPFI Civics at the local junkyards. Anyone have any ideas?

 

Just saw the message re: the TPS sensor. I'll see if I can find it and switch the wires. That is one thing that I did not look at. Did not know about it since I did not originally do the MPFI swap. Anyone have a pic of the wires? I'll look if up too. Thanks for all your help, I really appreciate it!

 

Just checked the TPS on the Intake Manifold and realized, I installed a new engine wiring harness, so the wires shouldn't be switched. Since the original DPFI harness was cut into and modified for the MPFI swap, I decided that it would probably be better to get an engine wire harness from another 1990 Civic STD just to make sure that everything would be compatible and that I would not miss anything. Luckily there was one at the junkyard, which was in great condition. So, back to the original question, could it be the ECU?

 

You can always give that a shot. I'm not sure. It sounds like you are misfiring to me. Maybe your DPFI injectors have gone bad or something. Are you running an injector resister box? Is the O2 hooked up?

 

No Injector Resistor box, removed that after the DPFI swap back. I believe that everything is hooked up, I checked all connections and there is nothing on the harness that is left unconnected. One thing, though, is that there was a wire that looked like a ground that I had no idea where to connect it to. It was toward the back of the starter, but not the starter ground, since I had already connected it. The only place to bolt it to was on the back of the transmission, where there were 2 bolts that looks like they had no function. I took out one of the bolts and connected it there. Funny thing is, when I had taken out the converted MPFI harness, if the ground wire went there, I would have had it unscrewed. I looked all over the engine and there was not an area that I had left unscrewed. Before I had connected that ground, the engine would not turn over. After I connected it, it turned over. I don't think that that would cause the problem, but at this point I am open to anything. I still have to connect the TPS wires to a multimeter to see if it is messed up and causing the problems. Will have to do that on the weekend.

 

Is it a loop? If it is a couple wires ran to a metal ring towards the back of the block, connect it to the thermostat housing. It could be part of that ground. It should be between the starter and the back of the block, location of the wire that is. That's the area it should be in if it isn't connected.

 

Yes, it is a loop. I think there is only 1 wire, but not sure. When I get home from work , I'll check it out. Do you think this could be contributing to my problem ?

 

Can't say it will solve the problem, but it will cause issues if it isnt' fixed.

 

Thanks for all your help! I really appreciate it a lot!

 

Got an ECU from the junkyard and still the same issue, so probably not ECU. I think the next thing may be to check the injectors....

 

Ok, update...I changed the charcoal canister, changed the spark plug wires (had an extra set) and seafoamed the car. It ran better and there is no more black junk coming out of the muffler. Still bogged down while in second and third, and took a little while longer to die at idle. Still no CEL light either. Then, yesterday afternoon, I decided to change the fuel filter. After the install, I went to start the car and it won't turn over now. It will very weakly turn and then just start clicking. I have no idea what I did. I have a slight leak at the top of the filter, even after tightening the bolts at the top. No CEL either. Any ideas? I read that some people used starting fluid to get it to start up after the fuel filter was changed...Does this work for the long term, or is this a short term fix? Any help is appreciated.

Thanks!

 

You drained your battery. You also have fouled plugs. Remove them, clean them off, reinstall.

This thread is confusing... All the swap writ-ups I've read state that you MUST use a mpfi distributor when you swap - you have/had a dpfi dizzy? I don't think you confirmed that you've ever addressed the tps wiring... but then you mention about swapping back? Are you saying the car is back to dpfi now? It would help a great deal if you could clarify what modifications have been done... or undone.

 

It was DPFI. He converted to MPFI and now he is converting back. That is what I gathered so far. The thread is hard to follow, I will give you that much.

OP probably has fouled some things along the way. I filled my fuel filter with gas when I installed it. Not sure if that is the proper way, but it's what I do. Also heard you should turn the key, let the fuel pump prime, turn it off and repeat that a couple times. To build fuel pressure.

I think it is the O2 sensor.

 

HI All,

Yeah, this thread has been hard to follow. Here is what I did:

1) Had a friend convert to MPFI
2) After 2 months, decided to switch back to DPFI due to idle issues and CEL lights
- Got "new" wiring harness from a 1990 STD Civic from the junkyard
- Got a new distributor (for 1.5L engine)
- New spark plugs
- New Spark plug wires
- New Fuel Filter
- New ECU
- New Charcoal Canister
- Seafoamed car via vacuum lines (car ran a lot better)

Got the car to start yesterday, turned out it was the battery. It was pretty much dead and could not be charged at O'Reilly's. After I put in the new battery, the car started up just fine. Not as many problems as before, the ones that persist are: I noticed that when I am in second gear, the car bogs down and it has no power. It continues into third, but picks up in forth. When I stop, the car's idle will start dropping and will die if I do not give it gas. Also, there is no more black soot coming out of the muffler and the strong smell of exhaust is not coming out anymore, after I used Seafoam. Hopefully I am getting closer to solving the problem. Maybe the problem is with timing?

 

Just thought of something, when I was doing the intake manifold swap, the manifold gasket tore about 2 centimeters at the top of the right hand side. I figured it wouldn't matter since it was a small tear, at the side, not close to any holes. Could this be causing my stalling problems and rough running problems?

 

Yeah, it could. It could cause an air leak which would cause lean conditions, misfires, rough idle since the ECU can't compensate for the air after the MAP sensor very well. Plus it would be on a single cylinder, which would definitely throw the ECU for a loop.

 

Changed the gasket this weekend and also noticed that the small tube that connects from the air intake tube to the valve cover was crimped. I changed that as well. The car started and ran great. I have been driving it for the last couple of days and it is smooth. Idle is a little bumpy when I idle for awhile, but it does not die on me. Thanks for all the advice!