Hey Guys,

I just replaced the coolant temp sensor in my B16 1st gen in my 91 Civic Si Hatch with the old SOHC Si one. But it is having a really tough time starting up. I have to turn the car over and hold it for anywhere from 5-10 seconds. Sometimes I have to try it twice.

I replaced the distributor cap and rotor, spark plugs and it still does that. When I hit the throttle it drops the rpm's and then slowly kicks up. When I'm driving I can't get any response. It feels REALLY sluggish and I have to give it light throttle to SLOWLY accelerate or else the car just bogs.

What can be the cause of this? Lack of fuel from the Fuel pump? Bad injectors? Fuel filter clogged?

It now throws a CEL code for Heated O2 sensor (1 quick flash), and another (2 quick flashes) that I don't know.

All the VTEC wiring has been hooked up. I've heard that something about switching the 02 wires or something of that nature. If it is a bad 02 sensor, which year/model do I use to replace it with?

All help is greatly appreciated. Thanks fellas!!

Joe

 

How does it sound when it's running? Very rough? If so check your cam timing; sounds to me like a cam skipped a tooth... if not that then check how rich it's running and what your ignition timing is.

 

Some Important Items to check

VACCUUM Lines make sure they are all tight with no leaks. This is a problem I ran into a few weeks ago.

I would suspect the code 1 and 2 (o2 sensors in manifold) are a result of the car running rich and the sensors checking out. Once you solve the stumble problem, they should be fine.

Check in the dist to be sure that the little screw holding the rotor in place is there. I have had one come loose and it some interesting things.

Also check the throttle position sensor. Although it might not throw a code, it could have a range where it freaks out.

 

The car idles pretty smooth. It's only when I give it throttle that it bogs out on me. I will check timing because my friend's car did the same thing when the cam gear slipped. Since this car doesn't have an adjustable one, it could have jumped a tooth. I will keep you updated but in the meanwhile any more info would be appreciated.

Joe

 

I've got a similar problem with hard starting and bogging when giving it throttle, but I'm getting a code 6 (Engine Coolant Temp Sensor).

Are you sure you replace the coolant temp sensor on the B16 with the old SOHC one? I'm asking because I tried doing the same thing, but its a completely different design and didn't look like it would work. Or did you swap out the thermosensor? A lot of people seem to get them confused (which made researching my problem somewhat more difficult). The thermosensor is located on the back of the block near the oil filter, while the coolant temp sensor is located on the head near the distributor.

The explanation I found about the coolant temp sensor said that if its bad, the ECU doesn't know how much gas to inject which results in flooding while the engine is cold. Once it gets warmed up it isn't as much of a problem.

 

My dx had the same stumble/hesitation problem and it was a jumped tooth. It also took a while to start. And my zc used to take a while to start too when it had the code 6, after fixing that it started after 1 turn.

 

What was your fix for the code 6? I just replaced the ECT sensor, and that didn't fix my problem. My wiring should be fine, since I didn't touch any of that when modifying my wiring harness, and I don't have a spare PW0 ECU sitting around to swap out...

 

When I swapped I used my old a6 harness and one of the 2 wires going to the sensor had broke, so I took the connector from the zc and just connected the wires and problem fixed. I also swapped the sensor first and it didnt fix it and I went to clean the connector bc it was gunked up and thats when I noticed the broken wire.

 

I had replaced the Coolant sensor that's located on the passenger side of the head. It's a green two prong/wire sensor. I didn't replace the one on the back of the block.

During my search I also ran into problems with people getting confused with the two sensors. I will check the timing and see if the cam gear had skipped a tooth. I'll post back tomorrow. In the meanwhile, keep the suggestions coming and thanks for all of you that have!

Joe

 

I checked my timing and it was off a little. But timing wasn't the problem because it still hesitates.

I replaced the fuel filter and installed a manual fuel pressure gauge onto the fuel filter and it only read 18-20 psi of fuel pressure at idle. When throttle is given, it doesn't raise or lower at all. I know that at idle it should be around 36 psi. So is it the fuel pump then? How can I check?

In my 97 Civic when I turn my ignition to the #2 position it will show about 30+ psi of fuel pressure and when I turn it over it idles at about 38 psi. But on the 91 B16 Hatch it shows 0 psi!!! It's only when the motor is being cranked over for about 5-10 seconds that it slowly builds fuel pressure.

Joe

 

My son is having this same issue with his '90 Civic B16a swap. The car idles fine but bogs when accelerating. I've been advised to check the exhaust for blockages, check the timing, check the tps and even the control module. The plug wires and dizzy cap were replaced to no avail. Does anyone have an idea how to eliminate the issue in a methodical order?

 

Our issue is fixed, it turns out it was at least one fouled spark plug. My suggestion would be to start there.