| Re: '92 LT1 idle issues (long post) |
Subject: Re: '92 LT1 idle issues (long post) by screamin_conure on 2010/3/16 20:25:44 I have a little update on progress here... Last week, my mechanic replaced both 02 sensors and the inline fuel filter. Got the car back and it ran slightly better than before (idle was slightly smoother). I had the scanner hooked up directly from the mechanic's shop, and with the new 02 sensors, both BLMs were in the 110-115 range at idle and 120-125 under acceleration/driving. I could actually see both 02 sensors neatly flipping between lean/rich whereas before the sensors would go in one direction (typically rich) and stay there for a long moment, and do a lot of really fast flipping around. I immediately took it for an emissions test and it passed with flying colors. Always a good thing! As I had mentioned in my original post, the actual RPMs at idle and the "Desired Idle" as asked for by the ECM were very close and consistent. Now, this past Saturday, I installed a set of Bosch III injectors from FIC. Easy enough job, and it went off without a hitch. I was VERY careful to check for leaks (none found). Fuel rail bolts torqued down to spec. Everything looked good. The car took a bit of cranking to fire, as expected. Here's were things are getting confusing though. The idle, though noticeably smoother with the new injectors, no longer wants to stay at a consistent RPM. In other words, once up to operating temp and in closed loop, the desired idle and actual RPMs are almost always off. Most of the time the actual RPMs are much higher, but sometimes lower. Driving the car like this results in a different idle experience at almost every stoplight. Sometimes, as I'm applying the brakes approaching a light, I can really feel the transmission laboring against the motor as it is downshifting, and sure enough when I get to a stop, I need extra pressure on the brake pedal to keep the car still. Other times, I'll come to a stop and the tach needle will drop slightly below the 500 mark and whole car will vibrate. Yet, other times, it will come to a stop and idle just fine. It's no fun at all driving the car in this state, and I also know that when it's idling high, I'm putting a LOT of additional wear and tear on my trans and brakes. Now, last fall, before storing the car for the winter, I had installed a new PCV valve. I bought one of the $1.65 cheapy valves from the major auto parts chain near my house. From everything that I've read about PCVs, my symptoms really sound like they COULD be PCV related, and I have a suspicion that my el-cheapo PCV might be the source of my grief. Thoughts? This coming weekend, my brother and I are planning to check over all the vacuum lines, pull the TB off and thoroughly clean it, focusing on the IAC passage way and put it back on with new gaskets. We're also putting in a fresh set of plugs, and I also have a new ACDelco PCV valve on order as well. Fingers crossed. |
