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97 Accord Ex 2.2L VTEC 5 Speed
I thought I had an exhaust leak before. The problem started when my car would stumble when letting off the gas on the highway or shifting and after checking my fuel trim it showed a high short term. At idle the fuel trim would slowly climb up to almost +50%. I would monitor my car all the time and the long term fuel trim should be -5.5% with a short term floating around that area. I did a seafoam exhaust leak test and saw smoke coming from where I had stripped the exhaust bolt. So I fixed it. And the problem still happened. So after tightening the nuts, changing the gasket and eventually getting a new manifold (thinking it was cracked) I still am having problems.
There’s no cel yet but the car is now switching in and out of closed loop. Torque (app) says its due to insufficient temperature. My coolant reads as low as 188 on the highway and the manifold is insulated to the cat so the o2 sensor heats up well. So my car isn’t getting cool enough to switch back to open loop and nothing really has changed. The o2 sensor is properly heated up by the exhaust gases. But Im not sure about the heater wire.
Both sensors will read normal and then go to opposite voltages (#1 at .1v and #2 at .8v), stay almost dead (moving maybe .3 volts back and forth) and then it’ll go to open loop. This happens repeatedly. When I get the sensor readings the fuel trim reads a lean exhaust.
Any idea what it could be if its not an exhaust leak?
I’ve calibrated the TPS before, it fine. Timing advance readings at idle would be abnormal if it werent right?
I notice that my fuel injectors are ticking much louder (no its not valve ticking, its the injectors), but thats been going on for about two months.
Most of the sensors on the car are either new (within the past year and a half) or have been taken care of and monitored
Heres my biggest question though:
Im wondering about a bad upstream sensor- but could that cause funny readings from both o2 sensors?
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[quote=”sjrobinson” post=66315]Specifically for 90’s hondas (and Mitsubishis) they were used to allow low impedance (peak and hold) injectors to be used since they do better at high speeds but the resistor was needed as to not burn out the ecu or the injector themselves. [/quote]
I am familiar with low impedance injectors and “peak and hold” driver circuitry. All of the circuits I have seen switched the driver transistor into analog mode, dissipating energy inside the module. Never heard of an external set of resistor being switched in.Learn something new everyday.
Yeah, they’re relatively new to me as well. I always saw the box on my car and decided to look it up one day. Its interesting because its not a part you can really buy off too many third parties or the store. I need to go to the junkyard this morning to get one actually.
Well its not the resistor box. The resistance I read was slightly wrong. The FSM was actually wrong is why. The terminals I read from were supposed to be #2 with all the rest. But it wasn’t. So back to square one.
I tried replacing the main relay. I think what is happening is that it may be overheating. Or at least something is. The car is fine until I drive it a while and there after when above 2500 rpm
It was the upstream o2 sensor.
My theory:
The rich fuel mix from the initial exhaust leak caused damage to the upstream and downstream sensor heaters. So when I fixed the leak I still had the same, if not worse, symptoms. Both sensors were acting funny but weren’t damaged enough to throw an o2 sensor code.
So I replaced the upstream, since the downstream is only used for cat efficiency reference on my car, and all is better. I will eventually replace the downstream once I get an 0420.
Guess it turns out o2 sensors can cause weird problems and make you think its something else completely.
Thanks for your help guys.
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