MustangEater82

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So, I bought a car as a second car. 1985 Camaro z28, LG4 5-speed. Owner claims brand new quadrajet, not tuned or anything, with 300 miles on it whten I bought it. Other then idling a little low at start up car ran fine. For 5 months. Well ran fine other then a occasional idle issues on cold start up, and typical "quadrabog" hitting the acceleration.

Just recently I have been getting detonation at higher rpms(fine at low rpms and idle, almost like when the secondaries open) I am hoping its just detonation and not something more like valvetrain noise. I checked, I had to add a little oil, but I have plenty and it still makes the same noise.


Now I recently just messed with carb, idle is much better. The "cold idle solenoid" wasn't adjusted to even contact the throttle lever.

I also tweaked the secondary spring, still not right, possibly worrse, but I haven't played with it too much since I still have detonation.


I haven't touched timing, or anything else, kind of puzzled what could cause it. The closest thing is I had a quick accident and 2 stroke oil/gas spilled ont eh car so I ran it through a touchless car wash. That is when I really noticed the issue, it is possible it was happening just befroe.

I also drive the car 2-3 days a week, and when it started, I had driven it 6-7 days straight. So its not like the car sits a month at a time.

Any tips are welcomed!

MustangEater82

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Any chance a vacuum line or electrical connection could cause detonation?

bestracing

Detonation usually happens when the motor is under load like going up a hill or accelerating suddenly and it will sound like someone tapping on the motor with a hammer. Also outside air temperature will play a roll in this. The hotter the outside air the more likely you can have detonation.

Timing is the first thing I would check. 6*-8* of initial timing at idle (with vacuum advance disconnected) for a stock motor. After that it could be a number of problems from carbon build up in the cylinder to a vacuum leak. The factory cure for detonation is to retard timing through a knock sensor but this doesn't work all the time.

Watch your secondary boosters to see if fuel is flowing out in a nice cone pattern when you hit the throttle wide open. You will have to use something to hold the upper flaps open when doing this. Also do not over rev the motor, don't take past 5K if going by the dash tach.

You can also try and run a higher grade fuel as well and add a fuel system cleaner. Once you run a full tank through, change your fuel filter just to be safe.

MustangEater82

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Well air temps are dropping, around here. It didn't detonate in the summer with heat indexes of 115.

Timing, I don't have a gun(yes I know I need one, and shoudl be the first to check) I will probably order one online. Any reccomendations?

My timing hasn't been touched.

I am wondering if I have a fueling issue and it is running it lean. It will sould like detonation, just reving up to 3k or so, in neutral.

I doubt its from carbon build up, previous owner said he had the heads off in the last year or soe to have valve seats replaced and cleaned up a little. Nothing major was done, but they were cleaned.


Now when you say a vacuum leak, any specific spots to check? The way this came about suddenly, I suspect something like that.

I do have a fuel filter laying around too, I might change it just for piece of mind.

Damon

It's not detonation. Not free-revving in neutral. Detonation requires some load on the engine.

MustangEater82

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I gave it a drive and I am starting to agree...


I am thinking its topend issues, hopefully nothing serious, not ready to do the motor swap I want to do.

bestracing

get one of these to try and trace down the source of the noise

MustangEater82

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I have one have to dig it up and start digging around, as suddenly as it came about, maybe a collapsed lifter?

bestracing

Could be. I've also seen valve retainers break, locks pulled through, but the rocker kept the retainer on the spring and the rocker rubbing and hitting the retainer make a weird noise.

With drag racing and working on my cars for over 25 years I've seen a lot of things but I still come across stuff that I haven't seen before.

Damon

I'm with Bestracing on the general idea of LAYING EYES DIRECTLY ON THE VALVETRAIN.

But first see if the mechanic's stethescope gets you over in the valvecover area. If it does, take it off and look at the parts under there carefully and in detail. Look for wanything that looks different than the other ones. If you have to run it with the valve cover off to see it in action- do it. It's messy, even if you use the rocker arm clips to divert the direct spray, but it would probably be worth it if you get that far in.

AvantiHall

Pull codes, find the aldl computer connector. Under dash 12 pins, jumper between a and b with a paper clip. Turn on ignition key. Watch the check engine light and count the flashes. On - on ---on on on = 23 space again same code. Write it down.

Cheep gas, water in the fuel. Never fuel at a station where the truck is dropping fuel. If bad fuel use an additive to move thru the system.

If vacuum leak, use rubber hose to hear it or gently spray carbuartor cleaner around engine when running, have a fire extingusher near by.

Noise in engine, use broom handle and put ear on stick, till you find your scope.

If EFE (early fuel evapration) is stuck on it will ping.

EGR stuck off, ping.

Springs on advance weight gone in distributor, will ping.

Top large butter flys on top of secondary set to open to easy, will have tip-ping and hesitition.

If the carb. float is set to low it can ping.

The new SN rated oil does not protect the cam and lifters, use high milage oil, most have more zink.

If you got engine wet, could have gotten distribitor wet, open cap look inside for mositure or carbon tracking.

GDad45

use a timing light to see if the timing changes with rpm changes. The dist may not have a vacuum advance, but controlled by advance weights and the ECM. RICH or LEAN conditions will cause the timing to be changed, but only in a short range.

bestracing

I'm pretty sure the ECM controlled distributor does not have weights either. The advance is controlled by the ECM and ICM electronically.

MustangEater82

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Sorry guys got my *** kicked with 12 days of work, with some 12 hour days, and 3 shift changes, from leaving at 6am, to starting at 6am

Thanks for the tips, I am going to look into ignition, a little, just for ease and I haven't really looked at it, and I don't like how the previous owner routed the wires.

MustangEater82

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Probably unrelated, but while this thread is going. You guys have any insite on this?

Cap/rotor look relatively new, as the car seemed to have alot of new parts.

BUT, one fot he screws holding the rotor down was almost completely loose, and I sas some "damaged" plastic on the rotor and on the cap, mainly where the coil/rotor meet. I don't really see this causing much of an issue. but just tossing it out there, I didn't really see much of an issue with carbon tracking or anything inside the cap.(uploading pics) I just tightened the screw down. I assume it came loose, or was never tightened down, and maybe interfered a little. I don't think it should screw with the operations.

The preivous owner, had ziptied the wires together, and they are ziptied to random things along the way. I want to re route, and put some wire seperators in. This "could" be an issue if I am getting crossfire, or just a short to ground on a cylinder not firing.

MustangEater82

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Pics...
IMAG0454_zps6692a980.jpg?t=1349849726
IMAG0453_zpsc42e4fd8.jpg?t=1349849765
IMAG0455_zps3442c789.jpg?t=1349849776

MustangEater82

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Also any tips on a good timing light?

86WS6

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I have seen the cap and/or rotor develop cracks so small one cannot see them easily. That will cause arching inside of the cap and problems similiar to what you are describing. Not one for throwing parts at a car, however if you have visable damage inside of the cap and rotor, those would be suspect in my book. If the rotor has been loose, it could have easily bumped the inside of the cap damaging either or both.

Charles

bestracing

When it comes to distributor caps, don't go cheap. Get a good quality like MSD, Mallory, Accel, ect.

Also if this is an internal HEI cap I'd get an MSD center bushing, the piece that contacts the rotor button. I've seen some from the parts store have really high resistance and cause a mis-fire in the upper RPM range. The MSD is very low resistance and provides for a better spark out at the plugs.

MustangEater82

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I am thinking the same too for new cap/rotors. I mean its only $50 or so. I was suspecting ignition wires, since they were zipp tied in bundles and maybe some cross arcing, I might do a set of wires too, or just try rerouting these first


Go figure just thought I would look in while I was ducking with wires.

bestracing

Just measure the wire resistance first before replacing them. Typically my longest MSD wire measures 1500 to 1800 ohms (used). They are the 8mm blue wires. MSD recommends 1500 ohms per foot max for their 8mm wire. I've seen some cheap wires measure near 8K ohms which is really bad. The MSD 8.5mm, red wires, typically measure 40 to 50 ohms per foot.

MustangEater82

iTrader: (1)

Bay!
Coili is trashed, one lead and are was really burnt up, and the wire insulation was burned off, it also fell off the coil as I pulled it out.

I

AvantiHall

When you replace the cap, be sure to transfer over the ground strap or buy a new one. To find it----When the cap is mounted on the distributor, you plug in the Bat, Tac (if used), then the three wire connector that comes from the distributor. Of that three wire connector, the center one is a ground strap for the coil housing. I see a lot of these missing, the car running with strange issues. If that ground strap is missing and you hook up test equipment ito that distributor it can damage DSO, Scopes, DVOM, etc.

When you pull the top cap off you will see the red, white, black wires on most coils. The red and white go on the outside, the ground strap is the center one that dogs to the left and is mounted under the coil. Put the black coil wire on the right screw. Just snug the screws that hold the coil in and only use the screws that came with the cap. Too tight and it will cause a hair line crack that the spark will follow ( miss-fire), to long of screws and it can crack, to short strips out the plastic cap. Also, look at the rotor: on the bottom, if it has a black dot below the center springie part. Miss-fire or no start, it's a hole, and the spark will go right to ground. The coil spark will blow right through the cheep rotors and caps. The spark plug gaps use to be 0.080, now there mush less, because they were blowing through the rotors, the cheep ones still will, the quality one won't.

And bestracing is correct, no weights in these, thanks for catching that

Dave

bestracing

When you have a lot of things on your mind it's easy to forget which system you're dealing with and post something that's correct for one but not for the thread topic. I've done it myself

MustangEater82

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Hopefully this is my problem. It definitely was a problem.

No grounding strap at all. I still need to buy one for tomorrow.

but my old Coil.

MustangEater82

iTrader: (1)

btw the groundstrap isn't easy to get.

MustangEater82

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well My coil didn't have a grounding strap, now it does, new coil, new module, new cap/rotor since all the old stuff looked to have had some sort of damage, was tempted to source out some new internal wires or go over them with some heatshrink.

Either way, I fired up, ran it, seemed like it went away but car has been off for a bit. It was rough at first I also had no aircleaner on, so I let it idle about 1k, a bit then gave it some gas. I took a vid, but might be hard to hear the noise inside.

ohmed out the distributor while it was open, all was good.

I may ohm out the wires and check the plugs, just to say I did pretty much the entire ignition.


I guess next step is stehoscope. I will see if I can get the vid up and if you can hear what I hear.

At least it looks prettier with new cap, and clean up coil cap

MustangEater82

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Video

http://s1304.beta.photobucket.com/us...1de6f.mp4.html


So I fixed a problem but not thee problem

Thanks for the help so far everyone. Still sounding like valve noise...

bestracing

Before you do anything else, break out the stethoscope and listen for where the noise is coming from. If you can't find your stethoscope then use a long 3/8 extension and hold one end to your ear while placing the other end on the motor/rocker cover.

MustangEater82

iTrader: (1)

Alright...

So I threw a stehoscope on the left side of the engine valve covers, I could hear the knock in there but really only on the left bank. But I can't really determine which cylinder it kind of hits the whole side.

Right side, under heavy load I can start to hear it on that side, but I think its just transfering through the block or something, as its very light.


Previous owner said the valve seats were replaced, new oil pan gasket and rear main seal. Oil Pan seal is verified new, everything the guy said appears to be truthful, lots of new parts. It never burned oil at startup.

Cold start solenoid has it up to 1-1.2k rpms idle and there was some white smoke, not alot but it was there. Car is in a garage with door open.

I might do plugs? and ohm the wires they appear to be good.

The cold start idle was misrigged for a bit, so the car had a low idle on cold startups. Maybe it fouled the plugs? and is misfiring on the left bank?


I am just trying to rule anything else out before I pull the valve cover.

I can assume a collasped lifter/bad spring/messed up rockers could be what is going on as well.

bestracing

At this point I would pull the rocker cover because you have ruled out most of what could cause it and the rest wouldn't matter. The problem seems to be internal and removal of the rocker cover is a good start. If you don't see anything obvious, then manually rotate the motor and watch the rockers to see if all are opening the valves correctly. Removing the plugs will make this much easier.



Not saying that this is your problem but it is a possibility. Now this is a flat tappet cam motor and they are prone to wiping out cam lobes if you are using regular oil that is on the market. This is due to oil the FED requiring oil manufactures to not add ZDDP due to emissions and to help with extending the life of the cat.

I have installed cams into cars since 1984 and haven't had any problems until I did one in my 86 back in 2003. I followed the instructions for adding the break in lube and they had a break in additive for the oil. I used Castrol oil which I have always used in all my motors and just during the break in period I had three lobes get wiped out. Took me quite some time to find out about the removal of Zinc from conventional oils and at that time there were a lot of people on message boards complaining about "Bad Cams" and lots of Crane Sucks, Comp Sucks etc. but know one had answers. (BTW Crane did replace my cam)

Shell Rotella-T was one oil that still had a fair amount of ZDDP in it but even that has been reduced from old standards and I don't know if they still add ZDDP now. Best bet is to get a bottle of ZDDP additive and just use your oil of choice.

MustangEater82

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You know there I do see it as a good possibility.

bestracing

I'll keep my fingers crossed for ya, that it isn't that bad