Engine Ticking

[Dmod81]

All - need your help. My engine has developed a tick. I drove it on Sunday - embarrassingly I did hit the rev limiter. There were no issues when I parked it. Today, when I started the car, I heard the tick. Video is here: https://youtu.be/jiUyyVhvMvk

It does increase with engine rpm, although there gets to be a point where I can't hear it due to exhaust noise. The car does seem to shake a bit. Oil is good and oil pressure is good. I attached my timing light to all of the plug wires, and got only very intermittent flashing on cylinder #6. I plugged in my Tech one, and the R Int is 146 with the L Int at 132. BLM is at 133 for both. Also, the O2 voltages were jumping around a lot.

Is the ticking/knocking noise likely the flywheel, and the overall problem likely the coil?

Thanks for all of your help.

[mike100]

put a metal tube (like an old brake line) on a stethoscope or to a rubber hose you can stick in one ear and run it along the exhaust flange and any welds that might be leaking on the exhaust system.

[XfireZ51]

A little more information would be helpful like, what year car, miles, mods, what side is the tick on, etc.

[Dmod81]

92, 56000 miles, headers w/ cats/3" exhaust/Haibeck chip. Coils and injectors were replaced (Accels) in about 08, about 7,000 miles ago. I can't hear it very well from the top of the car, but can hear it better from under. Seems louder on the drivers side, but that may just be the garage wall echoing.

I'll also use a stethoscope to see if there is an exhaust leak or if there is any discernable noise under the can cover today.

So is the no light from the timing light on the #6 cylinder not really a smoking gun then? It just seemed weird that it worked on all 7 of the other wires.

[XfireZ51]

The motor shake would suggest a miss. Which would be consistent with a cylinder not firing as indicated by the timing light. I'd swap the plugs between 4 and 6 and see if that changes at all. Also compare the color of the plugs to see if they look similar. And see what u get using the stethoscope as mike suggested.

[Dmod81]

OK, I'll do all of that after work. Thanks

[Dmod81]

Here's a picture of the plugs, 6 on top, 4 on bottom. # 6 did smell slightly of fuel. I switched the plugs, still no fire on cylinder 6. Nothing discernable/ conclusive heard with stethoscope.

I'm trying to look at this as an opportunity to port the top end!

http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2832

[RussMcB]

I'm trying to look at this as an opportunity to port the top end!Not a bad idea but make sure you identify your current problem first! :-)

I might have missed this earlier - Do you see a spark arching if you hold the spark plug boot near a grounding plug? That will be a huge clue to point you in the right direction.

[Dmod81]

No, I don't see anything. So possibly either wire or coil. I'm going to replace both, I already have a set of wires and a set of gaskets.

I figured as long as I'm taking off the plenum, I might as well port since I've been wanting to. I'm also thinking about blocking the coolant as well so it will be easier to pull the plenum again.

[Z51JEFF]

Keep in mind that one coil fires 2 plugs so if the coils dead you should have 2 dead plugs.

[XfireZ51]

You may want to run the motor in total darkness. See if there is arching somewhere.

[Dmod81]

And that's the weird part- only one is dead.

I'll take a look in the dark tonight.

[Paul Workman]

You may want to run the motor in total darkness. See if there is arching somewhere.

I TOTALLY agree.^

Mice had nested on top of my coils, AND munched on a couple of the plug wires too. One wire was arching (as seen in total darkness), giving reason why only ONE plug was not firing in a "waste spark" situation. (Too bad too. The damaged wires were original with the roll-stamped with the LT5 lettering. I ended up selling or giving the rest away to someone needing a spare original (or two) for their NCRS car: same rodent issue.)

[A26B]

Although the LT5 is a paired cylinder/waste spark ignition, bad spark on a single cylinder can and has occurred on more than one instance, and resolved by a coil replacement. That being said, the problem is probably related to a coil terminal, bad coil internal connection to the terminal or corrosion since a winding breakdown would affect both cylinders.

I have not experienced the "dry plug wire boot misfire to ground" that Marc Haibeck has diagnosed and resolved. Several others here on the forum have had the problem and fixed it using Marc's recommendation, liberal application of silicone di-electric grease in the boot.

In that same vein of thought, I heartily recommend and use silicone dielectric grease on all electrical terminals and the weather seals in the connectors whenever the opportunity presents.

So, as previously stated; (1) check the spark to ground. orange = weak, blue with 3/4" gap jump = good coil & wire, (2) good spark & good plug with misfire may = need to grease the plug boot (3) if still missing after (1) & (2) check ok, replace the coil. I always save the most difficult and costly possibility until last.

[Dmod81]

I TOTALLY agree.^

After mice had nested on top of my coils, AND munched on a couple of the plug wires too. One wire was arching (as seen in total darkeness), giving reason why only ONE plug was not firing in a "waste spark" situation. (Too bad too. The damaged wires were original with the roll-stamped with the LT5 lettering. I ended up selling or giving the rest away to someone needing a spare original (or two) for their NCRS car: same rodent issue.)

Painful to lose nice wires like that.

Funny you mention rodents - I found signs of rodents in my garage last year. Never caught one, and haven't seen anything since. I checked the cars and bike, but didn't see any obvious issues. Maybe it did get the Z...

[Paul Workman]

Painful to lose nice wires like that.

Funny you mention rodents - I found signs of rodents in my garage last year. Never caught one, and haven't seen anything since. I checked the cars and bike, but didn't see any obvious issues. Maybe it did get the Z...

Yeah, apparently the word got out to all of mousedome that LT5s have a nifty spot for nesting, judging by the frequency of times folks have found evidence of them nesting there...da sunzabitches!

[USAFPILOT]

mouse got in mine once, caught with a sticky trap

[Dmod81]

Just ran the car in the dark, nothing seen. Last time I changed the plugs, I filled the boots with dielectric grease, but I don't know what's on the coil ends. I'm going to start the plenum removal tomorrow.

[RICHARD TILL]

I replaced my coils with MSD`S last year due to no spark on #3 cylinder only. A month later i was pulling the plenum again. I`ll never pull it again without cleaning the contacts inside the starter solenoid.

[Dynomite]

I`ll never pull it again without cleaning the contacts inside the starter solenoid.

Great suggestion :thumbsup:
Starter Rebuild (http://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-10.html#post1588695490)

......and I might add........Never pull the Plenum without blocking TB Coolant at the Injector Housing :p

To accomplish that without removing the Injector Housings would require the removal of the Injector Housing Coolant Manifolds (use heat on those stubborn Coolant Manifold Bolts heating the Coolant Manifolds/Injector Housing in the area of each bolt). The Coolant Manifolds are removed to make sure you keep out aluminum shavings that may drop into each Injector Housing Coolant Port during installing of the TB Coolant Port threaded 1/8 inch pipe plug.

Injector Housing TB Coolant Blocking (http://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-10.html#post1588695506)

[Paul Workman]

*...To accomplish that without removing the Injector Housings would require the removal of the Injector Housing Coolant Manifolds...*


Hmmm..... Cliff, I'm scratchin' my head, trying to think of why drilling/tapping the TB passages would require removing the coolant tubes (mounted on each side of the motor). I don't believe I did, but I've slept since then and may have forgotten.:o I did mask off the rest of the holes in the IH, of course, and was careful of filings, but a tiny filing or two in the coolant jacket would be no big deal, no?

[Dmod81]

OK, so I checked resistance of wire pairs, no differences there, all around 20k Ohms. Tested spark on #6 and #1, no spark on 6, spark on 1- but it might be weak. I'm not quite sure. The engine didn't seem to run too much worse without #1 firing.

Good points about blocking the coolant. I'm still trying to decide on that and porting. I don't want to get to far along a path if coils and wires aren't my problem. My parts came in from Jerry's Gaskets today, so I'm starting the teardown.

[Dynomite]

Hmmm..... Cliff, I'm scratchin' my head, trying to think of why drilling/tapping the TB passages would require removing the coolant tubes (mounted on each side of the motor). I don't believe I did, but I've slept since then and may have forgotten.:o I did mask off the rest of the holes in the IH, of course, and was careful of filings, but a tiny filing or two in the coolant jacket would be no big deal, no?

Because. :D






It is just easier to stuff a paper towel in the injector housing which collects all aluminum from drilling and tapping for 1/8 NPT aluminum allen head Pipe plug.

Those coolant manifold bolts being stuck in manifolds along shank and in injectore housing threads is an issue with many LT5s as you know. So what a better time to install new coolant manifold gaskets and SS Allen Head bolts in coolant Manifolds when you remove Plenum.

[Dmod81]

Well, I've got it off. Have a few broken vacuum lines: the connectors on both the driver and passenger side plenum, and the coiled one that goes to the front underside of the plenum. Does anyone have any idea where I can get these?

The old wires all seem to read about 5k ohms, whereas the new ones are all between .4 and .9 k ohms. The old coils are about 7.5k ohms and the new are about 5.2k ohms. Nothing really points to #6 being any different than the other cylinders.
http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2836

[mike100]

I broke one of my hard lines, but I spliced it with some German style vacuum hose. This is the thick hose with the exterior braid layer- it is way more durable than parts store vacuum hose. You can get various similar hard tubes and rubber elbows from the junkyard and fit them into place as needed. the big curly one is probably better off replaced with a genuine LT5 part, or get creative with the repair.

[Dmod81]

Thanks, I'll look for that. I found the curly line, and I decided to pull the secondaries as I found the passenger side was binding, so I don't need that drivers side line. I'll just try to find a fitting that looks close to stock for the passenger side plenum and replace the line with what you suggested.

[Dmod81]

I just wanted to post a follow up. The car is all back together and runs great. Actually it runs better than it ever has- a lot faster too. The secondaries are eliminated as well as the TB coolant.

Big thanks to Locobob, he did an awesome job with the porting and refinishing. Also thanks to Jerry and Marc for their support to the community, I couldn't have done this without them. Last, thanks to the rest of you, I spent a lot of time in the threads making sure I did things right.

http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2889

[Dynomite]

Very nice top end :thumbsup:
........so.......what was the engine ticking? ;)

I just wanted to post a follow up. The car is all back together and runs great. Actually it runs better than it ever has- a lot faster too. The secondaries are eliminated as well as the TB coolant.

Big thanks to Locobob, he did an awesome job with the porting and refinishing. Also thanks to Jerry and Marc for their support to the community, I couldn't have done this without them. Last, thanks to the rest of you, I spent a lot of time in the threads making sure I did things right.

http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2889

[Dmod81]

Ahh yes, it was a coil causing the misfire, which was causing the flywheel to rattle.

[cvette98pacecar]

And that's the weird part- only one is dead.

I'll take a look in the dark tonight.

Just to give you a heads up, There was a group of us that did a lot of work last year on a Dark Green 95 in Michigan. New GM coil packs, wires and plugs were installed, Cylinder 3 was dead, Cylinder 2 was firing.
I know it is a pain in the can, I would start with the coil packs.

Does your car have the rev limiter set at 7200 RPM?

[Dmod81]

Thanks, good to know that it has happened before.

Yes, the limiter is now set at 7200.

On a side note, the throttle sticks slightly coming down to idle now. A slight tap will bring it back down from 900 to 750. So I think I'll go ahead and have the throttle body rebuilt after all (and ported to 63 mm).

[Dmod81]

Looks like I have spoken too soon about it running great.

Symptoms (other than the slightly high idle that will go back down after a small tap on the throttle):

Miss every few seconds at idle (rpms will drop about 20 on tech 1)
Every once in a while it will stumble and almost die at idle
After coasting, when I get back on the gas, it will stumble and buck until it clear out and runs normally again
Smooth operation in normal driving and heavy throttle

KOEO pressure is 0 psi, slightly over 40 at idle
Both pumps run when tested
Car starts normally

It looks like the book points me to the hoses in the tank (entire new pump assembly was installed in April 2013) or the fuel filter (new installed April 2013), but I wonder if I might have a bad injector (s) too? They're accells that were installed at the same time as my failed coil (Sometime in late 2008 I believe)

[lfalzarano]

Save time and call Mark Hailbbeck at 630-458-8427 with your symptoms. Don't take it to a Chevy dealer...

[FU]

Dmod81 where are you located ?

[Dmod81]

Currently Central Coast California, near Santa Maria

[Dmod81]

Just a little update:

I ran through the fuel pressure test procedure and was getting almost instant leakdown, so I replaced both pumps. Now I get 52 psi when the pumps are running, which drops to about 43 when the pumps stop and holds there with very slight leakdown. Pressure at idle is about 42. I also replaced the fuel filter. Rough running/miss at idle still there.

Finally I replaced the injectors. There was some crud in the rails that I cleaned out. I also checked my plug wire routing/reseated the wires, replaced plugs, O2s, and checked all other connections/vacuum lines. All seemed good. Rough/miss at idle is still there, but it might be very slightly better. However, the stumble with throttle after coasting is MUCH better. Almost non-existent.

As a kicker- I now have a very large screw in a rear tire. Must be a gift for driving the car only 40 miles over the last 4 months trying to fix it. I think something is trying to tell me it's time to throw in the towel.

[XfireZ51]

You're sure you don't have a vacuum leak like at the PCV valves?

[Dmod81]

All of the pcv parts are new and attached snugly, but there could be a leak somewhere. I'll see if I can find a leak with a homebuilt smoke machine or something.

[LGAFF]

Will apologize if its been discussed as I did not read the thread, but sounds like a MAP sensor issue;either a rotten hose on the primary or under the ECM

[Dmod81]

No worries - I don't believe it has been discussed, although the map and the hose (plastic) are relatively new. The MAP seems to be reacting correctly on the tech 1. The sensor under the ecm is open to atmosphere, as I've eliminated the secondaries (That is correct, right?)

[XfireZ51]

All of the pcv parts are new and attached snugly, but there could be a leak somewhere. I'll see if I can find a leak with a homebuilt smoke machine or something.

I bought my first ZR-1 and it ran fine but had a bit of an annoying idle hunt. Not bad and could easily have been ignored but I'm a bit finicky on that.
At a Haibeck BBQ, Marc told me it was likely the PCV F connector. He was right.
Look to zip tie those and see.

[Dmod81]

Just tried that out- no change. I had the old connector zip tied, but this new Jerry's one is really tight. Checked the pressure regulator vacuum line, that was good. I also took a look at the inside of the grey ecm connector. I couldn't really tell if those were spread out too far. I haven't backprobbed them, but the previous owner might have. But then again, if it was that why would it act up now?

Seriously, with respect to the engine when I was fixing the first miss,the only changes I've made is new starter, new alternator, new coils, new wires, new purge vacuum lines, new passenger vacuum line to the plenum, ported intake, remove secondaries and new chip. Seems there shouldn't have been any issues after this.

Then as I had a rough idle after the fix, I've replaced pumps, filter, injectors as tests indicated these were questionable. I've also replaced the IAC and cleaned its bore, and TPS and O2s. I'm at a loss. My wife is really pushing me to drop the car off at the Oxnard Carmax.

[XfireZ51]

Looks like I have spoken too soon about it running great.

Symptoms (other than the slightly high idle that will go back down after a small tap on the throttle):

Miss every few seconds at idle (rpms will drop about 20 on tech 1)
Every once in a while it will stumble and almost die at idle
After coasting, when I get back on the gas, it will stumble and buck until it clear out and runs normally again
Smooth operation in normal driving and heavy throttle

KOEO pressure is 0 psi, slightly over 40 at idle
Both pumps run when tested
Car starts normally



It looks like the book points me to the hoses in the tank (entire new pump assembly was installed in April 2013) or the fuel filter (new installed April 2013), but I wonder if I might have a bad injector (s) too? They're accells that were installed at the same time as my failed coil (Sometime in late 2008 I believe)

OK. So you had the top end ported. Do you have a scantool? What are your IAC counts? At idle, what is the TPS V?
Whenever you change the airflow in the motor, the Min Air throttle opening needs to be re-set which in turn affects the TPS voltage. And if the TPS volts are not below .59v at idle, the ECM does not invoke the Idle routine which includes timing. Or it could be on the edge of in/out idle. If its dying at idle, the IAC may not be able to keep it alive if throttle isn't open enough.
The basic settings on the motor need to be within spec before anything else.

[Dynomite]

I bought my first ZR-1 and it ran fine but had a bit of an annoying idle hunt. Not bad and could easily have been ignored but I'm a bit finicky on that.
At a Haibeck BBQ, Marc told me it was likely the PCV F connector. He was right.
Look to zip tie those and see.

If you want to do it "right" get rid of the old PCV hardened rubber connectors and install new soft rubber connectors without using hose clamps or nylon ties of any kind Jerry has them all (http://www.jerrysgaskets.com/search.php?search_query=PCV+Connectors&x=23&y=10) :thumbsup:

PCV Upgrades (http://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-8.html#post1587653786)

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite11/6c6a8c6d-3bd7-48e8-ae28-7fa48835bce4.jpghttp://i287.photobucket.com/albums/ll142/dynomite007/Dynomite11/cc07ee5b-a4cc-4a63-b7e0-491cd951b2e6.jpg
http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite11/b53f6b19-43c1-427e-8d91-794769bcd3e7.jpg

[Dmod81]

The IAC counts at idle are 25, cold open loop. The TPS voltage was at .50, which is weird because I set it at .54. With the engine off and pressing and releasing the throttle it settles at .52 or .54. The last time I drove it on sunday, I noticed the IAC counts were 3 at hot closed loop idle. This was after restarting after it stalled on me when turning a corner.

How do you set minimum air? I don't think I've done that.

Dynomite- I've got all of Jerry's parts for the PCV system- they are great. The old parts just kind of stretched/fell apart in my hands.

[XfireZ51]

The IAC counts at idle are 25, cold open loop. The TPS voltage was at .50, which is weird because I set it at .54. With the engine off and pressing and releasing the throttle it settles at .52 or .54. The last time I drove it on sunday, I noticed the IAC counts were 3 at hot closed loop idle. This was after restarting after it stalled on me when turning a corner.

How do you set minimum air? I don't think I've done that.

Dynomite- I've got all of Jerry's parts for the PCV system- they are great. The old parts just kind of stretched/fell apart in my hands.

IAC counts for idle need to measured at 80+C, closed loop. .5v is a little low for TPS. I set mine at .53-.55v. The TPS needs to be, at minimum, re-checked and possibly re-set after each time you set throttle opening.
Min Air must be set so that the motor idles just under the point where it does not require IAC opening. You'd like to have IAC counts 10-15 at operating temps and idle. I set the throttle opening with fans running, putting an additional load on.

You can do a search on Min Air adjustment. I posted a step by step procedure for doing that. The set screw for throttle opening should be replaced by a hex bolt which would allow you to change throttle opening w the motor running.

[Dmod81]

OK, so I replaced the throttle stop with a bolt and ran through the procedure you have posted. IAC counts are now at 12, and TPS at .55 volts. The car is more responsive and seems to not have a tendency to stall going into a turn anymore.

I still have what feels like a miss randomly every 10 seconds or so. It just sounds like the car misses a beat. However, sometimes it does not do it at all. I've added techron cleaner and water remover to the tank, as I had the fuel system open for a couple of months while waiting for parts. I'll see if that does anything. Also, the gas on base is not top tier, so that could contribute, if this is some sort of bad fuel issue. Otherwise, everything checks out (as far as I can tell), injectors are firing correctly, and it doesn't look like I'm losing spark when it misses. Any thoughts?

[XfireZ51]

Have you tried Sea Foam?

[Dmod81]

I have not, but I just got a can of the stuff that you can spray into the intake. It has the long straw with the bend in it.

[XfireZ51]

I have not, but I just got a can of the stuff that you can spray into the intake. It has the long straw with the bend in it.

Yep!

[XfireZ51]

I have not, but I just got a can of the stuff that you can spray into the intake. It has the long straw with the bend in it.

Yep!

I also removed one of the oil tube hoses and sprayed it through the the airborne opening. Just need to keep motor running.

[Dmod81]

The bog after coasting is back (well, actually, when I thought it was gone, I wasn't off of the throttle enough for it to appear, still have a rough idle as well). It bogs if I let off the throttle and for more than about 3 seconds.

I finally got some time to datalog the car. What I think (because I have no clue how to really interpret the graphs) I'm seeing is that when I go off throttle, the O2s either go erratic, or low or high, and the integrators start dropping sharply. Then when I get back on throttle, the RPMs don't increase until the integrators start coming up some. Also at cruise, the O2s are cycling only about once per second (thanks to Marc for pointing that out).

(Integrators, RPM and TPS % on top, and O2 voltages and map on bottom)

Bog 1:
http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2917

Integrators dropping further the longer I'm off throttle:
http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2918

Everytime you see the throttle being depressed here, the car was bogging until the integrators got back up to normal and the O2s started cycling again:
http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2919

Cruise:
http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2920

[XfireZ51]

So you ported the top end, what changes were made to the calibration?

[Dmod81]

I have Marcs normal BPPAG4 cal with custom settings:
Add fuel for headers
Fuel for cats
Enable anti-backfire mode
Add Fuel for top end porting
Secondaries removed
750 rpm idle
7200 rpm rev limit

[Bearly Flying]

Just a shot in the dark..What brand of O2 sensors are you running?

My car, after porting it, did exactly the same thing.

There is a thread on the forum about the recommended O2 sensors, I put those in and no more problem.

[Dmod81]

They are new densos. I had the same issue with the old ones that were in there too, but I'm not sure which brand those were.

[Dmod81]

OK, so I replaced the O2 sensors with OE type AC Delcos and also tightened the header bolts. Several were slightly loose. This seemed to have helped the problems a lot, but was not a 100% fix. It stumbled only once on the test drive, and there was no ticking or missing to be heard.

Unfortunately, on the next drive, everything was back to how it was before. So I seafoamed again and noticed a small amount of smoke was coming up next to the engine on the passenger side. So I took a look and noticed the header flange at #6 is dirty and wet:
http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2957http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2958

Sorry for the poor quality, I was using a cheap snake camera hooked to my phone. For comparison, here's #4 and #1:

http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2959http://www.zr1.net/forum/picture.php?albumid=162&pictureid=2960

So its really only # 6 that is wet. Is it possible that after I tightened the bolts they loosened up again/ or the gasket is now damaged? Could a leak there cause a miss and stumble after getting on the throttle after coasting? I find it interesting that that cylinder is the one that had the original dead miss.