I thought I would post this if anybody wants to share my pain while I practice my novel writing skills.
I have one of those (2-volume) big ol' stinkin' official GM Service Manuals (about 2000+ pages), one of which is just the "...Driveability & Emissions" volume for the 93 Bonneville.
DTC code 42 (Ignition Control Ckt)
DTC code 18 (Cam/Crank Error) (less frequently)
Code 42 doesn't quite fit the standard of the diagnostics, since it SHOULD come on at idle. I have to race the engine. It may be running in limp home (or module) mode. It goes to running like it has a rev limiter, but only above about 2000 rpm.
Code 18: If I let it get up to op. temp and nail it while driving, that'* when it will also throw a code 18 (cam/crank sensor error) when I "gas it." But there'* more to the story.
Past related history:
1. Have had two TPS (throttle pos. sensor) go bad. 2nd one was an Autozone part and only lasted 2 years. This was to fix the problem of the engine rpm up and down at idle as high as 1500 - 2500, really fun in rush hour traffic.
BTW, good to know, both of them passed the voltage test, but ohming pins B to C (unplugged) would display multiple K-ohms of resistance at idle position. This should usually be real low, almost a short. Replacing TPS fixed both times.
2. Also have had an erratic no start problem that would rear its head every few months. Would, for no reason come out of it after any where from a few minutes to a few hours.
3. Noticed the exhaust smelling rich & mileage getting worse
3. Last week I headed out on a 25 mile trip to work (which would also acid test it for my wife since her trips are slow and short) and that'* when I saw the true picture
a. It did okay at 40 mph or less (low revs), but I had to nail it for a yellow/"pink" traffic light and it acted like it was hitting a rev limiter, running really crappy, but only at 2000+ RPM, shaking and vibrating with throttle. Now I am thinking it was in limp home or module mode.
b. It was GUZZLING fuel, like nearly a quarter tank in 8 miles!
b. Checked and found the code 18 and code 42.
c. After clearing the codes, the code 42 pops up first, once you have hit a little RPM. The code 18 comes in the same way, it seems, but only after warming up with a few laps around the block.
Work and findings so far:
1. I cleaned the ICM connector plug with carb cleaner and have also attempted to tighten the female pins' grips.
2. Ensured ICM was providing a ground out to cam and crank sensors.
3. Ensured I had continuity from ICM to PCM white wire (ckt 423) (resistance check from ICM pin to PCM pin w/long test leads!)
4. Wasted $130 on an unnecessary ICM. Same problem after replacing, maybe worse.
Suspect either a cam or crank sensor. A mechanic friend replaced one or the other several months ago (for the no start problem) in his home shop. But he cannot remember which and it was a cash transaction, so no paperwork on it. I cannot tell from "cleanliness" aspect either. Both connectors look dirty from the months of use. I read here where somebody had a similar code 18 that threw at warm up and revs & he found it to be the crank sensor.
I have been avoiding the crank sensor because of what I have read about the puller required for the HB pulley. I finally found some M6-1.0 x 90mm bolts as somebody suggested and will dive in this weekend. Anybody have any strong feelings regarding cam sensor vs. crank sensor?
I welcome any feedback or suggestions beforehand; and will update this post with another, hopefully shorter, chapter after. Hoping for " ... we have liftoff" soon.