Code 1 Forever!

[NYSiRacer]

1990 Si (stock)
I've run out of things to check... Please help me; thanks in advance.
When the ECU first blinked code 1, I replaced the O2 sensor (new) and reset the ECU.
It blinked code 1 again, so I checked the connection and made sure nothing was loose, then reset ECU.
It blinked again, so I exchanged for another O2 sensor (also new) and made sure no loose connections (reset ECU again).
Damn thing won't stop blinking! I started checking other stuff such as fuel pressure regulator (ok), exhaust leak (ok), fuel injectors (ok), vacuum leak (ok), ECU (ok), and even fast idle thermo/control valve (ok).
The car just had a complete tune-up about a month ago, too...

Symptoms:
Power loss regardless wether the CEL comes on or not (especially in mid-range). Dramatic power loss when CEL is on (all range).
Unstable idle. (500 ~ 1200) Extremely unstable if the car is cold. In the morning, if I don't gas it, it stalls. (1600 ~ 300 - 0)
Motor shakes.
If throttle is open for more than 3 minutes, I get code 1.

[Hybrid1990crx]

my civic was doing this for awhile after I put a new header on it and I had to make the wiring for the 02 sensor longer. It ended up one night making me limp home doing 25 miles an hour the whole way. The next morning it was doing it still so I got out and unhooked the plug right form the harness and my car ran real good then but with the check engine light on. Then I redid the wiring again and its been fine ever since, no check engine light for a few weeks now.

[gunnmen01]

try a different ecu maybe???


gunnmen01

[NYSiRacer]

I doubt it's the ECU though. Since I can't find another ECU to test, I unplugged the fuel injectors, and it blinked code 16, which was right.

My header is stock, and I'm pretty sure that the connection is not loose nor a defective O2 (changed twice)

Can a bad alternator cause this?

[johnb16a2]

Check here:

O2 page1

and here:

O2 page2

GL

[91civicDXdude]

try unplugging the o2 sensor from the ECU and driving.

on OBD0 vehicles, there is no limp mode in the ECU, so unplugging the o2 sensor just forces the ECU to run in open loop mode, which means it ignores sensory input and just focuses on speed density to read the mapping (it only reads the map sensor)

[Hybrid1990crx]

No limp mode? When my o2 sensor was acting up my car ran like poo. But it wasn't throwing a code. But once the check engine light came on it ran good. What would that be considered?

[NYSiRacer]

Heh, I have those exact same 2 pages johnb16a2 provided; however, I got stuck on the voltmeter part because my friend's voltmeter was sent out for repair. I'll try 91civicDXdude's method tomorrow first and see how my car runs, and I'll post the result here.

[turtlecrxsi]

My car has done the same thing. I ran it with code 1 forever, then recently switched the O2 sensor and the code disappeared for almost 2 days. The code came back but the car ran great (bulb for CEL was yanked)... but my car broke down Friday evening and I couldn't get it running again. I replaced plugs and ignitor and checked all the wiring and still nothing. So I brought it to a shop. Needless to say, I'm getting tired of my POS Honda...

[johnb16a2]

Originally Posted by turtlecrxsi

Needless to say, I'm getting tired of my POS Honda...

Come on buddy, stiff upper lip. These are old cars....

[DJHyperXK2004]

i mitght have the same problem..

[NYSiRacer]

Alright, here's the test result.

1. Reset ECU.

2. Unplugged O2 sensor and started the car; didn't notice any changes.

3. Went to drive around; dramatic power loss (see first post under "symptoms").

4. CEL came on; power restored...

Does that mean that my MAP sensor is good?

[NYSiRacer]

Hrm... the CEL doesn't light up until at least 30 minutes of driving; during that 30 minutes, the car runs like poo just as Hybrid1990crx stated. Is it possible to make the CEL light up as soon as the car is started?

[Juicy05]

Yeah mine does something similar, the O2 sensor wires came apart so it was disconnected and no engine ligght, but as soon as i hooked it up after about 10-15 minutes of driving or less it comes on and runs like shit? i dont know i changed it maybe 5 or so months ago
i have no cat and i have the 1.5 liter intake manifold on a 1.6 the guy b4 did half a swap, also aftermarket headers......any clues?

[4G4D Store]

This is weird - I have a code 1, but I don't have any power loss at all. Depending on how I drive, the cel can come on from 1 minute after I start driving to 15 minutes after I start driving. This has been happening since I put my DC Sports header on. I don't know if it's a bad o2 sensor or not, but it drives great. I even got 39 miles to the gallon on a trip I took on the freeway doing 80 the whole way. 360 miles on 9.2 gallons. Not to shabby.