I have a d16 that will not run right. I have changed distributor, wires, plugs, fuel pump, fuel filter and still this engine doesn't want to run right. The timing is set correctly. I have ran just about every type of fuel you can imagine through it...Non-ethanol 87, 93 and ethanol 87, 93 nothing will make it run smoothly. It has an AEM cold air intake, 4 into 1 header and full exhaust. I am about ready to pull it out and run a K swap if I can't fix this issue. When I put it under a load it acts like it wants to spit and sputter unless I hold it wide open. Hell that is the only time it runs right is when I hold it wide open. I just want it to run smoothly again. What would you do?

 

Post the CEL codes.

What specific car and engine?

 

Check for a loose ground, especially on the thermostat.

 

MAP sensor issue ???

 

The car is a 96 Honda Civic Dx with a JDM Non-Vtec ZC or D16a. It starts right up runs nice until it gets some temp into it. That is when the stutter starts. Usually when I am cruising at highway speeds at a steady throttle. It doesn't like it when I am maintaining a steady throttle or speed. It bucks until I give it more gas which is usually full throttle.

 

CEL codes?

Does the problem go away if you unplug the O2 sensor.

 

No codes. I will unplug the 02 sensor and see what happens. Let me go and try that.
Still dealing with it. I have 2 O2 sensors on the car when I unplug one it idles really rough. Should I unplug them both and run it down the highway or just one at a time?

 

Could a MAP sensor cause a sputter like this?

 

Unplug the primary O2 sensor (the one closer to the header). Then drive the car under a load. Does problem remain?

 

I unplugged the 02 sensor plug that was nearest the header and the sputter stopped. It ran like a top. Idle was a little rough, but it ran down the highway without the sputter. Does that mean my 02 sensor has gone out?

 

Replace the primary O2 sensor.

 

Could I put an AEM Wideband O2 sensor in it with gauge? I will eventually need a Wideband if I plan on running a AEM ECU in the future so why not do it now?

 

Unplugging the sensor causes the ECU to stay in "open loop" mode where it runs the engine richer than normal. Apparently when the mixture is leaned out it runs badly. The O2 sensor could be giving bad readings so do try that first. It could be a MAP sensor that is out of calibration or getting bad readings due to an air leak near the sensor. Also check the TPS with a voltmeter.

A good general rule about modifying cars is to have it running properly stock first, then modify. Don't change multiple things at once.

 

^Overkill at this point.

And read mk's comments carefully as his suggestions are almost always dead on solid advice.

 

I want to thank you both. I will get it running correctly for sure. I am going to go ahead and buy the correct 02 sensor and see how that goes. I also need to see why my stock fan doesn't want to come on from time to time. Thank you both for everything. I will keep you all updated with my progress.

 

Overheating problem?

 

The fan just doesn't want to come on when it is supposed to. Anytime it gets over normal operating temperature the fan is supposed to come on and it doesn't.

 

Start by bleeding the cooling system.

 

My Engine cooling switch is bad. I warmed car up and shorted the plug out with a paper clip and the fan ran like a champ. I then plugged it into the switch on the thermostat and nothing. The temperature gauge was over the normal operating temperature so it should have been on. Now I need a new switch and a new set of o2 sensors and I should be good to go. Thank you for the help. The forums are the way to go.

 

FYI - The result of your test could be due either to air in the cooling system or a bad fan switch.

 

I went ahead and ordered the fan switch and will be draining and refilling my coolant when I put the new switch in. I am outside right now installing the o2 sensors.