If the cam timing was off by 1 or 2 teeth on the cam gear the fuel trim would be off by 10-15%, you have a more serious problem. When you get a chance remove the upstream oxygen sensor and start the engine.
Hence why checking the camshaft is next. Iâm not checking for exhaust restriction until Iâve ruled out camshaft damage, head gasket issues, and valve damage. Timing chain issue was just first in line.
If this were a problem caused by one cylinder I would check the compression on the cylinders, then inspect cam/valve operation but your problem seems to affects all cylinders, that is why technicians are telling you to check for an exhaust restriction.
I will just reiterate what I said in an earlier post. The vacuum reading is low IMO. Youâre at 1200 feet and Iâm at 1100 and after countless checks of various types of cars in solid mechanical condition I find that roughly a steady 20"
of vacuum is the norm.
As I mentioned, gasoline diluted motor oil can chew up an engine. I personally feel that a compression check should have been done while the spark plugs were out; and especially due to the dilution comment.
Twitching of the needle at idle can mean a misfire or valve issue. I canât speak to what youâve done with the timing gears and so on but low compression can also cause this kind of problem.
It would seem to me that it would be better to make sure the gears are aligned and run a compression test. One would hate to keep flogging the horse only to find out that itâs going lame.
No duh, itâs low. I replied with an âincorrectâ as you used the term âabnormallyâ. I do not agree a 3-5 loss equates to that term. Nothing less, nothing more.
I did do a compression check. Do you rationally think I didnât do a compression check when I did a hundred other tests? I didnât poste said statistics as the original post and the info therein, has been many times skimmed or ignored. So too, many of my posts since. I was waiting to post the results when I was able to stop repeating myself on the info already clearly posted.
You too seem afflicted, as much of your post directly shows you heavily skimming, or not reading the thread at all. When you do, Iâll be happy to provide you with statistics.
If a man has a broken arm, with a part of the arm bone sticking out, you fix the bone and find out why the arm broke. Checking for an exhaust restriction before checking for cam or valve damage in a non interference engine thatâs had a very loose chain for who knows how long, is like trying to heal the wound the bone made before fixing the bone.
Plus, wildly swinging timing has what exactly to do with exhaust restriction? Sure it would starve the engine for air a bit, change the timing a small amount, but most times unless its a full on clog you only lose 2 inches of vacuum in restriction tests. Not 3-6. And its not full on clogged as the rear pipe has decent output. Not to mention you wouldnât get gieger counter level timing readings.
Even if Iâm wrong, the car is effectively dead atm. Checking other avenues, and other areas for damage does nothing bad. The timing cover is still off, and all the components covering it. The valve cover is off, and the plugs removed. Am I supposed to reassemble all of that, just to run the engine with an O2 sensor removed to check for a minor problem, instead of checking currently easily accessible areas usually far from easily accessible, that could have much more serious damage and a higher chance of actually being malfunctioning? Should I add an oil change so the diluted oil doesnât do anymore damage in the short time its ran on top? Should I do hours of reassembly, to skip or put off doing a couple tests that take half an hour tops each to complete, just to disassemble it all again in the very likely chance restriction isnât the problem?
404 logic not found.
IMHO a 96 Olds Cierra just isinât worth the time, effort or expense to save. Move on. Unless you put no value on your time and effort you have already âspentâ enough to get a decent used car.
Also I know this has absolutely nothing to do with the discussion.
The 404 error is not a logic error,
The HTTP 404, 404 Not Found and 404 (pronounced âfour oh fourâ) error message is a Hypertext Transfer Protocol (HTTP) standard response code, in computer network communications, to indicate that the client was able to communicate with a given server, but the server could not find what was requested.
A logic error is an error in a programâs source code that gives way to unanticipated and erroneous behavior. A logic error is classified as a type of runtime error that can result in a program producing an incorrect output. It can also cause the program to crash when running.
Logic errors are not always easy to recognize immediately. This is due to the fact that such errors, unlike that of syntax errors, are valid when considered in the language, but do not produce the intended behavior. These can occur in both interpreted and compiled languages.
Just my thoughts,so please donât start shooting at me.
I read back through the thread and I can find no mention of compression numbers. Could you post those?
1 Like
Either you are the most literal person I have ever seen, or the belly laugh I got reading that was by design. I can talk some code now! I cut my teeth on Commodore64 âprogrammingâ (as it technically has its own âlanguageâ) when I was little, then moved to C++, python, and java later on. Iâm ok at HTML, but web design alone is a tad boring for me. Hello, fellow techy.
Iâll overlook your comments on worth, as you have obviously never owned an A-body olds. They are tanks. Perfect for driving in the winter when my sports cars or bikes canât or shouldnât., and are cheap on gas and usually low maintenance and easy to repair. So Iâll put your opinion on that in the bin with the old chain.
Absolutely. As I said, I didnât post them before because the initial post was being mostly skimmed. By the time it would have made sense to post the info, I was already checking the timing, posting about that, and rehashing previous info people were skimming at the same time.
The following was before the new chain was installed. As you can see the compression is a bit high and there is a slight variation in cylinder 1. Listed from left to right, cylinder 1-4.
D 180 200 200 210
W 225 215 220 210
Honestly, if anything those compression numbers look a bit high to me. Going over 200 can present a problem.
With numbers that high the vacuum readings should not be that low unless the camshaft is out of time OR there is an exhaust restriction.
The point could be made that there may be a 1/4" of carbon caked on the piston tops but that is not very likely at all.
As you can see the compression is a bit high
Mmhmm
On a serious note, very true. But you have to add worn lobe(s) to the mix as well. I have a dial indicator and base on the way to check for that. A leakdown test will rule out head gasket issues, and valve issues. Iâm not buying a tester, Iâm just going to TDC each cylinder, shoot air in it and listen to see if it comes out the throttlebody, exhaust, valve cover fill hole, or the radiator.
If there is no camshaft damage, then I have no idea why the timing is swinging as wildly as it is. Lack of vacuum and power sure, but not the Geiger counter effect.
With modern cars and computer controlled timing, it is quite easy for the timing to jump around if there are other issues.
Itâs quite common for timing to vary from cylinder to cylinder and second by second. That in turn can cause an erratic idle; all depending.
Most of the time the timing doesnât move around enough to be noticeable or cause a problem.
I donât see a problem with blowing air into each cylinder and listening for air leakage. Of course you need the valves in each cylinder closed and preferably the piston at the bottom of the cylinder bore. Placing the piston at the top of the bore can lead to compressed air rotating the engine unless the piston is just dead on TDC.
Yeah I can put it on exact TDC using the compression/vacuum gauge combo. Then just swap hoses on the compression gauge line, and add air. In my experience, anything under 90psi wont turn the engine over unless you have some major nonos going on. The dial indicator gets here tomorrow. Iâm aiming for Wednesday to start testing.
In other news, the car didnât want to start the last few times before I tore it down, so I had to always jump it off. Got the battery tested today while doing errands and what do you know? Battery is bad on top of everything.
I knew I shouldnât have built this place on top of that windigo sanctuary.
Did some testing. I used two different methods of using the dial indicator to determine probable lobe lift. In method 1, used a âdummyâ old pushrod to lift the dial indicator, and method 2 I used the rocker arm to lift the indicator. I tested cylinder one and two. Haynes and Melling list the lift at 288 or 7.315mm. On cylinder one when setting lash for method 2, one rocker wouldnât torque all the way down as the nut somewhat bottomed out. I only had time to test 2 cylinders and from cylinder one tests (has the lowest compression as seen above) the cam lobe appears worn. I couldnât find any info on how much wear is ânormalâ on a 170k camshaft, even a percentage.
Cylinder One
M1 6.70 In / 6.69 Ex
M2 6.80 In / 6.79 Ex
Cylinder Two
M1 6.84 In / 6.70 Ex
M2 6.84 In / 6.80 Ex
So anywhere from half a mil to .07 mil worn as I can currently tell. I called the previous owner and confirmed he used new lifters on the old cam when it had 126k.
A âmilâ is 0.001 inches.
1 Like
I did briefly ponder adding the extra l, but thought better of it. I didânt think anyone would be inane enough to comment on it.
I was wrong.
Now that youâve gotten that out of your system, care to make an actual contribution?
UhâŠno.
;-]
3 Likes