'97 L29 ---Annoying Idle

RedBurb said:

Snap on Solus Pro ----does it read CAM Retard value (please advise)?

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Of course. As did the older Snappy MT/MTG2500.

The only "scan tools" that wouldn't are the consumer-grade junk; and even some of those will.

RedBurb said:

The related Code (0345?) ... ...eventually cleared itself but I'm left wondering whether the timing might be a whisker off hence the unsettled idle...?

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Turning the distributor doesn't change timing. Ignition timing is based on the crank sensor, not the distributor position.

It does change how the rotor aligns with the terminal on the distributor cap. If that's way off, the secondary voltage could be sky-high; and it runs the risk of jumping to ground or a wrong distributor terminal.

I am using one that seem to be decent. Vident. Only issue I had was having to replace the SD card

The new distributor alignment seemed perfect when I stabbed it in ---TDC, rotor pointing right at dot on AL housing and aiming towards Cylinder #1. However Code 0345 triggered and wouldn't clear for the next 9-10 starts and approximately 200 miles. But it then went away and hasn't come back since (the good old, "shot gun effect")

What symtoms does a failing crankshaft position sensor typically display? Do these symptoms gradually become more erractic over time or is this component a pass/fail?

RedBurb said:

The new distributor alignment seemed perfect when I stabbed it in ---TDC, rotor pointing right at dot on AL housing and aiming towards Cylinder #1. However Code 0345 triggered and wouldn't clear for the next 9-10 starts and approximately 200 miles. But it then went away and hasn't come back since (the good old, "shot gun effect")

What symtoms does a failing crankshaft position sensor typically display? Do these symptoms gradually become more erractic over time or is this component a pass/fail?

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usually cutting out on mid to high acceleration like when you are almost out of gas, long crank times when starting.. when cutting out it would set a code right after. Becoming more problematic over time maybe. Mine was bad for a while ,but took a little time to figure it out it would only occasionally give a symptom. Then one day it wouldn't start. Scan tool showed no signal .That's been my experience with bad ones.. that's wild that your code fixed it's self. Must have learned on it's own or accepted the parameters after so many start cycles. You really can't adjust the timing by moving the distributor like older cars. have to lift it out and rotate the rotor or move it a tooth if you will.. the few times I've had mine out I haven't had to deal with the code. it was always on point apparently so that was nice.

I don't have any experience with the new chinesium distributors, but I distinctly recall on the OEM ones you had to aim the rotor at the 8 that was cast into the housing. It may be worth confirming if the dot on the new one and the 8 on the old one are in the same location.

spider injectors ,hated hearing that was filling my block wiyh gas ,what!.yup but that was around 200k, smooth ever since,currently 281,070miles and counting .original engine.4L60e 3Xs .any who good luck

81nascar said:

usually cutting out on mid to high acceleration like when you are almost out of gas, long crank times when starting.. when cutting out it would set a code right after. Becoming more problematic over time maybe. Mine was bad for a while ,but took a little time to figure it out it would only occasionally give a symptom. Then one day it wouldn't start. Scan tool showed no signal .That's been my experience with bad ones.. that's wild that your code fixed it's self. Must have learned on it's own or accepted the parameters after so many start cycles. You really can't adjust the timing by moving the distributor like older cars. have to lift it out and rotate the rotor or move it a tooth if you will.. the few times I've had mine out I haven't had to deal with the code. it was always on point apparently so that was nice.

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Based on your description I doubt my crank sensor is the issue (yet). The engine starts, accelerates, and cruises just fine and doesn't throw any codes. I drove it 250 flat freeway miles this weekend (@65-70 mph) averaging 13.4 mpg on 87 octane. It's the "slight missing" @idle @red lights that really, really sucks. I'm confident the new dizzy is installed correctly. Next, change the fuel filter followed by a good faith, "help me NOW Lord!" can of fuel injector cleaner---a long shot but a relatively painless effort (amen). If that doesn't work (and even if it does) I'm gearing up to replace the fuel injectors and regulator while elbowed in there. After all the engine has +180K miles and those injectors are way long in the tooth. Plus I blew past my original budget on making my "occasional tow rig" reliable a year ago so why stop the fun now? I'll post results in a few weeks for posterity sake.

Tiime to fess up. Today I finally found the main problem with the rough idle/slight miss. The #7 spark plug gap was 0.00"! When I changed the plugs and wires many months ago I set the plug gaps at 0.045" but must have accidently compressed the #7's electrodes together while reinstalling that plug back into that dam hidden black hole blocked by the steering rod and brake lines. I felt a combination of shock, exhilaration, and relief when I pulled the plug and saw the "zero gap." After resetting the gap to 0.045 and checking the others, I started the engine and drove 15 miles. What a night and day difference in smoothness at idle and general giddy-up! The stark reality of having spent 6 months and close to a $1000 in new parts chasing down this stupid problem is now sinking in. But I solved it and the dam thing runs purdier than ever. So Keep on trucking Bros!

True story of my '97 K2500 7.4L plow truck:

Between Christmas 2018 and New Years of 2019 I located a truck with V-plow at a reasonable price. Easy ~300 mile round-trip drive to view it. Owner says it leaks PS fluid. I bought a gallon of PS fluid on the trip to see the thing.

Actual Craigslist photo from his listing:


Show up. Won't start. Owner dickks with battery cables. Got truck running--very poorly. Test-drove with MTG2500 scan tool. No torque converter clutch, #8 is a dead miss. Sky-high misfire counts. Other cylinders OK.

Price dramatically reduced due to trans and engine problems.

Needed most of that gallon of PS fluid to get home.

Decided to pull #8 spark plug to test cranking compression. Figured I might be in for "real" engine problems--pull the head for valve job, or worse.

Loosen spark plug with wrench. When it turns easy, I reach down to unthread it by hand. Instantly felt broken porcelain.

Got used-but-good spark plug from the L29 heads I used to run on my boat. Tested cranking compression (adequate) and then put "used" plug in the hole. Has run fine ever since. By the way--when the computer detects misfire, it'll disable the torque converter clutch.

One used spark plug fixed my engine misfire AND the transmission.

'Course, I've been fixing other stuff on the truck ever since--PS "cooler", brakes, suspension, electrical, starter, A/C, etc. No shortage of crap to deal with. Latest crisis is totally-rotted right-rear cab mount bracket (cab floor rusted out.)

The value of a scan tool cannot be over-estimated. If you'd have connected a scan tool to begin with, the misfire counts would have told you which cylinder to investigate. You'd have fixed the problem in under an hour.

Bought an 86 4x4 Burb like that from a dealer bad miss, deeply discounted. Swapped two plug wire back in order and she ran great