The ticking goes away when engine is rev'ed as the frequency goes above our hearing; but it is still there.

Take valve covers off and compare rocker motion across all cylinders to find which one it is.

Taking the intake off is actually pretty easy. Just take pictures of how hoses and electrical harnesses are routed.

 

Actually, that is a very good point! Thanks for that!

I have done some reading in my factory shop manual set and on the Internet. I found that there is no camshaft sensor "relearn procedure" - the CMP Retard Offset Procedure is only a scan tool check of the cam sensor's relationship to the crank sensor - and since the cam sensor position in the distributor is non-adjustable and the coil is triggered off the crank sensor, being off would only affect the rotor position when firing a cylinder (and not ignition timing). Probably why it has to get >25+ or so degrees out before setting the code and also why a misfire could occur without setting the cam sensor code.

But if timing chain or distributor gears have worn, that would cause the CMP Retard Offset to be off - even if the distributor housing position has not changed since the vehicle was manufactured.

Now I have completely flip flopped and want to check it twice - first time as a diagnostic for the timing chain/distributor gears and possible arcing in the distributor before tearing apart - then second time after the distributor has been out to pull the intake. If I end up going through the bottom end at a later date, I will need to do it a third time. Looks like I'm going to need a different scan tool if I'm going to avoid paying the dealership $$$$$.

Anyone know of a $200-$500 scan tool that will read the CMP retard offset as well as do the crank sensor relearn? Or is that a pie-in-the-sky wish? Nevermind - ordered ScanXLPro software with GM Enhanced PID package for my old netbook. At least it will read the CMP Retard Offset and has some future write possibilities.

Thanks to all who have replied.

Les

 

The camshaft position sensor itself is not adjustable. However, it is mounted to the distributor, and rotating the distributor is how CMP retard is adjusted. You are repositioning the sensor and accurately aligning it with the camshaft. At the same time, the distributor cap is positioned correctly for a minimum amount of crossfire inside the cap. BTW, if the camshaft position sensor is totally disconnected, the engine will still start and run. However, a CMP sensor DTC will be set, and cylinder misfire will not be detected.


Exactly correct. The PCM uses camshaft position sensor data, along with the crankshaft position sensor data, to detect and accurately identify cylinder misifre. If CMP retard is out of spec, cylinder misfire identification will not be accurate. This can lead you on a wild goose chase for sure The distributor drive gear has 13 teeth. Each revolution is 360 degrees. Each tooth accounts for approximately 27.692 degrees of rotation. The PCM is programmed to set P1345 in memory and illuminate the SES light if CMP retard exceeds ~27 degrees (positive or negative).

Absolutely correct. Excessive stretch in the timing chain, worn timing gears, or a worn distributor drive gear can all cause P1345 to set. The big clue here is if P1345 was not present before the distributor was removed, and it shows up immediately after installing it, it's a dead give away that the distributor was not installed correctly.

Bottom line: If P1345 is not present, the distributor gear is meshed properly with the camshaft, and CMP retard is less than ~27 degrees. Is that close enough? You decide. It means the rotor could be as much as 26 degrees past the terminal on the cap when the coil fires... crossfire up the ying yang! Spec is zero degrees plus or minus 2 degrees.

 

Got the ScanXL Pro software up and running on my old Asus netbook with the OBDLinkSX USB tool.

CMP retard average was -3.7 degrees and varied from -2.5 to -4.7 when going from idle to about 2200 rpm and back. Any big indications of a problem there? Looks like just a little timing chain slop and wear to me. What do you think? I've never checked this stuff before so I don't know what is normal. I do know it is supposed to be set to 0 +/- 2 when adjusting it.

Thanks,

Les

 

I think you're probably right about timing chain slack. You can check it very easily without removing the timing cover. Remove the dist cap so you have a clear view of the rotor. Using a socket & ratchet on the crankshaft bolt, rotate the crankshaft clockwise until one of the marks on the dampener lines up with with the index mark on the timing cover. The object here is to put all chain slack on the passenger side. So, if you pass the index mark, don't turn the crank backwards, rotate it clockwise another revolution and stop on the mark. Next, have an assistant hold, or watch the rotor closely while you slowly rotate the crank counter clockwise. The instant that the rotor starts to move, stop rotating the crank. You have now transferred the chain slack to the driver side. Measure the distance the crank moved to calculate how many degrees it moved. Anything more than ~12 degrees, you can literally lift the chain off the sprockets... far too much slack.

If/when a timing chain stretches, (or jumps a tooth) valve timing will retard.** This causes hard starting, (long crank times) and will cause a lack of power at low RPM. As RPM increases, so will power.

None of this stuff relates to a P0304 though. You're looking for something specific to cylinder #4 only, ie plug, wire, injector, valvetrain, etc. Performing cylinder contribution and injector balance tests might tell you more, but probably not any more than you already know. It doesn't explain the the ticking noise either. May need to do some "exploratory surgery"

**On engines that have a pickup coil in the distributor, (or points) ignition timing will also retard. On this 4.3L, ignition timing is not affected when valve timing changes.

 

Thanks, at least now I feel I can put my new cap/rotor/wires/plugs on without worrying about spark jumping to the wrong terminal and creating a bad path in the cap.

Would like to approach this one area at a time, so I know in the end what really fixes the P0304 - ignition, injectors, or valve train.

I suppose I should cause a miss on a specific cylinder to make sure the system is capable of accurately detecting it. If so I should be able to trust it is cyl#4 that has the problem.

Then I'll put the ignition parts in (checking compression on all while plugs are out) and recheck for the miss. If miss is still there I'll shut off hot when ticking loudly and pull valve covers to check valve train out (focus on #4) and also try to determine which valve is making the ticking. After that I'll pull the intake for inspection, any valve train repairs needed and finally do the injector replacement/upgrade.

 

If the ignition & injector parts don't help, a cylinder leakage test will tell you more than a compression test. A compression test is great for detecting bad piston rings. So is looking at the tailpipe while the engine is running If it smokes like a big dog, and you've got an oil fouled spark plug, chances are you've got a bad piston ring Doing a dry & wet compression test will confirm or deny it. A cylinder leakage test does a far better job of checking for leakage. Pressurize each cylinder with compressed air. The pressure will force the piston to BDC, (bottom dead center) and both valves will close. Listen for air rushing from the throttle body, (leaky intake valve) PCV grommet in the rocker arm cover, (leaky piston ring) and the tail pipe, (leaky exhaust valve). If you hear air rushing from any of those places, you know exactly where to focus your attention.

Just a thought

 

I hear you, and I have the hose to pressurize the cylinders left over from installing the inner valve springs after cam break-in on my little V8 2WD S10. Also have a very nice Comp Cams on-car valve spring compressor tool ($$$$$$) that should work on this V-6, in case I have to remove or replace a valve spring for some reason. Only problem is having to borrow my buddy's air compressor - I have never invested in one. He is 30 miles away and just visited last weekend so he's not going to volunteer to bring it this weekend and drink beer while I work. The only cylinder leak down test I've ever seen done had a special tool to measure the air flow being put into the cylinder. Yours sounds like a down and dirty, but valid test.

Guess l'll keep the pressurize cylinders in my back pocket of diagnostics and go ahead with the compression test, since I want to verify ability to detect misfire on a different cylinder, install the electrical parts including spark plugs this weekend, and see if the CMP retard will set to zero. This would either fix the P0304, or rule these things out as the problem. Maybe the tick will be related to the P0304, or maybe not. Will have to see about the tick and any further diagnosis when I get the intake off/replace injectors/inspect valvetrain around Thanksgiving time. I can probably get the air compressor by then.

Thanks again,

Les

 

Here's the latest update on my pretty POS.

Checked compression and all cylinders were OK. #3 plug sure is not fun, but it is do-able with the right tools. I eventually found that taking the rubber insert out of my swivel spark plug socket allowed it to go onto the plug when going past the steering shaft. Replaced spark plugs with AC/Delco Irridiums. Installed the the AC/Delco cap, rotor, and plug wires. Adjusted CMP Offset as much as possible - was able to get from around -4.0 degrees down to around to -0.9 degrees. Also rented the fuel pressure gauge from Autozone, and verified pressure/no leak down (always starts first turn of the engine, in any case) so no problem found there.

Still SES light on with P0304 before 1/2 mile. Nothing seems changed and I really didn't expect what I did to change anything. So common ignition parts or misfire in the cap due to excessive CMP offset or fuel supply is not the problem. They have been ruled out.

So I induced misses to see if computer could correctly recognize them and identify the cylinder. Took one of my old plug wires with old spark plug and clamped spark plug to a piece of metal on the engine with vice grips. Then disconnected each plug wire one at a time from the distributor and replaced with the test wire/plug. I watched the 6 miss counters I added to Torque Program display while holding about 1500 rpm for each cylinder. Even though engine obviously had a dead miss on each cylinder that you could feel with each plug disconnected, the counters did not register much of anything (except for #4), and #4 continued to be detected as a problem all of the time. So it appears the computer is not capable of recognizing misses correctly and is setting a false P0304. Silly me. I thought it was correctly detecting a weak cylinder as I knew #4 wasn't a dead miss.

So I went back to reading on the Internet, this time for false P030x codes. Turns out I think there is a scenario that could account for everything.... Tick, low oil pressure, false P0304. Unfortunately this scenario is excessive clearance in the bearings, including thrust bearing. I think this extra clearance could be allowing the crank to move excessively - raising hell with the crank sensor and causing the P0304 as a false detection.

As for the tick. Next time I drove the vehicle and got it completely warmed up, I noticed it didn't give the loud tick when in gear - but immediately ticked when put into neutral. Thought it might just be a RPM difference thing, so I tried both when held at 1500RPM. Back and forth between in-gear and in-neutral several times. Loud tick immediately went away when put in gear and then would immediately return when put in neutral. I really don't see how this can be a lifter collapsed from lack of oil and I have always said this does not sound like your typical valve train noise or lifter tick. It's not on a particular side and seems deep and in the front of the engine.

So what is the deal with the tick going away when in gear, even at the same RPM??? We know that driving the torque converter with the trans in gear pushes the crankshaft forward. I submit that the crankshaft walking back and forth is causing the loud ticking noise somehow - from something hitting that is attached to the crank/cam in the timing area - maybe even the crank sensor itself. When I put it in gear the crank stops walking back and forth?? That seems to be the evidence.

Next I am going to inspect the crank sensor for damage (hitting anything) and try to see if I can get a dial indicator set up to get an idea of thrust bearing clearance with the engine installed in the car. I am not relishing the idea of future engine removal in this vehicle.

Still proceding with intake gasket and injector replacement with check of valve train and leak down testing in next two weeks, just to complete things I have planned to do. Don't really expect these to change anything, but I want to know exactly what I am working with and I will be doing these things at some point anyways. So I waste some gaskets and put them in again if I tear the engine down later.... big deal!

Les

Comments anyone? I wonder if doing a crank relearn on a vehicle with a sensor issue could make it fail to recognize all true misses?

 

Sounds like youre on to something, ive read many posts on P0304 codes with these blazers, there must be some reason that its always #4? I had a #4 code on mine i was putting a cap and rotor in it at the time and found a plug wire with higher resistance than the rest so i swapped it out with a known good one i had on the shelf and put a new plug in that cylinder to see if it would cure #4 and nope it didnt, i think an overlooked part in these ignitions is the coil, if you can run the engine in a closed garage at night in true darkeness you can watch the coil glow and see arcing from the center winding to the outer part of the iron core. I used to get a miss on my wifes astro occasionally and i put an msd coil on it and havent problems ever since, I got the coil on ebay from jegs for like $35 or $45 bucks. I would give that a shot.
My blazer is a 5 speed and i always notice it because being locked from engine to wheels through the clutch causes it to buck at highway speed, i usually get the code when its raining or humid which leads me to it being a high voltage issue, im goind to get a coil and keep it in the glovebox til it does it again and change it on the spot and see if the bucking stops, i like definite conclusions to annoying problems so i can forget about them!
On the crank sensor issue though, i think i remember something about shimming these sensors, i worked a gm dealership in the early 2000s, i cant remember for sure but that worth a shot in the dark, maybe #4 is the reference signal for engine position and the reluctur wheel gets too close after a few thousandths of bearing wear, try finding a thin shim to put in between the sensor and its mounting face on the timing cover.