Well it all started on the way to my gf's house for a M day cook out. Had a short straight stretch before I got there and decided to open it up. It acted like the ICM was going back, run go then try to die or just die. Well managed to get to her house and tried to start it the next day. Started but really ran rough, sounded like a funny car, very distinct miss or misses, running very rich. After warmed up it smoothed out on excelleration but missed bad at cruise or less. I changed the ICM no change, wondering if it's the MSD box. Really acts like a loose wire somewhere. Any suggestions ? Thanks Rick
85 GT 3.4 14.9 @ 90 1.9 60' Old TH125/3.06 Unknown New 4T60/3.42
This last week end my son's 3800sc new install was running on 5, most of the time. He changed a lot of things over the 3 days trying to fix it. in the end it was a cracked plug. not a broke plug, just cracked. He was safer when it was on 5.
Did some more checking today. Not the MDS box. I did notice the rotor seems to fit losely. How would you check the distributor ? Fuel pressure holds at 42 psi when running but does leak down rather quickly when turn off 2-3 minutes to 0. Should not have any dead cylinders only 20K miles on the engine plus it runs smooth under light /medium acceleration. I did check for arcing at night time and moved the wires around but no change.
Can a leaky cold start injecter cause a miss and rich running condition ? I don't know much about the cold start injector system. I changed the rotor today, fits alittle tighter, still no change. I'll try pulling the plugs tomorrow to look for a rich condition, maybe narrow it down some.
I had a very similar situation to you. Try unplugging the 02 sensor and see if it smoothes out.
I had a very similar driveability issue, did a complete tune up on my own to no avail: plugs/wires/coil/cap/rotor/fuel filter/etc.... Turns out it was a combination of too-far advanced timing from the previous owner and a bad O2 sensor. My O2 was giving the ecm a false lean condition causing it to run pig rich.
Didn't get any testing done today because of the rain. But did let it run to normal temperature at which time it kind of went into a hunt idle mode. Would idle to 2500 rpms load up with gas and when about die. Doing this constently. Any ideas ? Haven't tried the O2 sensor yet.
Hope to get it to one of my mechanics to put on his scanner. It has developed a new problem, Idles to 3k+ and won"t come down. I disconnected the map/fuel pressure vacuum from the intake (blocked it off) and went back to the original problem. Any ideas?