Help with Engine knock - rod bearing/hydaulic lifter/fuel injector, which one?

[abhusa]

I think you are barking up the wrong tree with the lifter additive. Defective lifters usually get lose, not tighter. A slightly burned valve will cause your symptoms. You need a compression and preferably a leak down test to rule out mechanical issues.

I'm not super familiar with the Barra engines except that they have a very good reputation in general. Is 2007 one of the years where some of them had valve spring breakage?

Hi, I agree it most likely is a valve issue. But like I mentioned d earlier manually cranking the engine seems impossible for now until I figure out how , for the leak test. I have the 190 Barra 4l, they are considered bullet proof. Car will likely break apart before the engine. Another engine would probably have conked off or puttered if it were a burnt valve. This one drives like it doesn't care. I have a boroscope , wondering if I can glean any info thru the spark well with it. Not high resolution, but should be good enough. There are plenty of anecdotes online that state their lifter noise went away with an additive. I added it to see if it might be a stuck lifter, not thinking it to be a permanent solution. I will give it a couple hundred KMs and let you know. If it does quieten a fair bit, then about 8 months down the line I will add rislone which claims to clean the valves and lifters. By then I should have figured out how to do the leak down. In any case my fuel trims have sorted themselves out and are balancing to +-10, combined. Only a problem at idle which reads -12.5 LTFt, which I think is livable.

 

[abhusa]

I think you are barking up the wrong tree with the lifter additive. Defective lifters usually get lose, not tighter. A slightly burned valve will cause your symptoms. You need a compression and preferably a leak down test to rule out mechanical issues.

I'm not super familiar with the Barra engines except that they have a very good reputation in general. Is 2007 one of the years where some of them had valve spring breakage?

Hi,
one thing puzzling me is if it were a burnt valve, I would imagine the rough idle would not go away when engine is hot. But am absolutely sure the rough idling often times reduces quite a bit to being of not much concern, when engine temp is past the quarter mark. If it were a burnt valve, i can only imagine the valve face is expanding due to thermal expansion to close the tiny hole/trimmed edge that might exist to reduce the rough idle.

 

[kschachn]

How’s the leak down test coming?

 

[abhusa]

How’s the leak down test coming?

I cant get to the crankbolt to get the cylinder head to TDC. Its placed inline towards the front, and between it and the radiator fan, there is no place to barely fit my hand leave aside a wrench. I am going to see if can get my hands on a vacuum gauge. Should give me the same overall end result i am after, which is to see if i have a sticky or burnt valve and much easier.

 

[kschachn]

I cant get to the crankbolt to get the cylinder head to TDC. Its placed inline towards the front, and between it and the radiator fan, there is no place to barely fit my hand leave aside a wrench. I am going to see if can get my hands on a vacuum gauge. Should give me the same overall end result i am after, which is to see if i have a sticky or burnt valve and much easier.

A vacuum gauge is not a substitute for a properly performed leak down test.

You're continuing to shoot at everything but the target.

 

[abhusa]

Incase anyone is interested I have figured out what happened. Leak test is a long wayz away as not in the mood to remove any parts for something I am pretty sure off. Will post results of a vacuum test when I do it and it is a valid test to know if one has a burnt valve somewhere in the engine. I got the car cheap (so I thought) and it was shuddering at idle, but i just thought it would need new plugs and coils at most. Subsequently, when I did the smoke test, discovered the oring leak in injector 1, head side, and changed O-rings, then changed the injector , issue continued. Nothing seemed to fix the issue and it didnt feel like a lifter tick or rod bearing, hence came on this site. What I believe has happened is the previous owner neglected the bad oring which was causing a super lean STFT LTFT ~~16%. Probably more in actuality. After fixing the Oring the shudder didnt go away, by then damage had occured and a valve had burnt off (before I bought the car). A super lean mixture can burn off valves. And am pretty sure that is the case. Now the car is old and I am cheap, so I am gonna let it run till it dies and just do the usual maintenance on it. If I can get 30k kms out of it, got my money's worth. Let us see.

 

[Barkleymut]

Any chance it is an exhaust manifold leak? Does the noise go away after the engine is hot?

 

[abhusa]

Any chance it is an exhaust manifold leak? Does the noise go away after the engine is hot?

Not likely, I don't hear any hissing sounds or see any visible cracks. The O2 sensor reads correctly . Also, an exhaust leak would cause a lean condition not rich.

 

[kschachn]

How's that vacuum test coming along?

 

[notharry]

I know this is a older thread. a compression tester is a great and cheap tool. The next best thing is just a sparkplug fiting and compressed air. If you cannot get to the crank bolt easily, many times one can get to the starter ring gear and hold/turn the engine(bump turn with the starter works too) to get to the correct area on the compression stroke of the affeced cylander. Air will spill from are area of leaking. Test all the cylanders. Some will leak more than others. The points of concrn are Rings, Exhaust valve, Intake valve right. Your point of a burned valve is plausable. A compression tester normally can be modified to hook a air connector to it and sometimes its exactly the same as a regular 1/2" HF connector. Of all the testing tools I have used =, the compression tester and air forced in the cylander have yielded the best results. Yes a leakdown test is a great identifier as well. You will find the issue but its probably be expensive. Run it and when it gets worse, pull the head and buy 1 valve. lap them all in. you probably already know these things good luck

 

[abhusa]

How's that vacuum test coming along?

Hi, sorry for the late reply. I got busy with other priorities with life. Finally got round to doing the vacuum test. Engine is fine, no burnt valves. So there goes my theory. I even changed the TB and TPS, PCV. The MAP sensor reads fine as per the OBD reading. Infact the TPS reads fine too and the APP. Only thing I can think of now to check are 1 ) Fuel pressure regulator- but no schrader valve on it, so gonna be a headache 2) purge valve which again is gonna be a headache because it is designed a bit differently to the ones shown in youtube where u simply plug out the hose coming from the cannister. 3) Fuel injectors. The car actually runs fine - no acceleration problems or stalling whatsoever. It is just an issue at idle, my RPMs are double what they should be and what they were when I initially reported the issue, i.e. now 1500rpm in Park and about 900 rpm in drive. Infact the shudder at idle has gone away but I suspect that is due to the higher RPMs. I would have thought it would be a vacuum leak, but my fuel trims are negative and my MAP sensor actually gives the correct vacuum reading (4.93-5.08psi absolute) at idle (not sure how, since my RPMs are high, would have thought the vacuum created should be less) so can't be a vacuum leak. Another thing I can't understand is that my TP degree shows 1.94 deg. or 12% at idle which is spot on when compared to the desired TP at idle per my OBD (again not sure if the OBD is giving the desired TP at idle or at the high RPMs??, but in anycase 1.94deg /12% seems right for idle). Then how can I have higher RPMs?? Even if the engine is getting extra fuel say from a leaking injector, where is it getting the extra air from if my TP is at the correct position at idle? Basically what could be causing the higher RPMs if I don't have a vacuum leak??

 

[abhusa]

I know this is a older thread. a compression tester is a great and cheap tool. The next best thing is just a sparkplug fiting and compressed air. If you cannot get to the crank bolt easily, many times one can get to the starter ring gear and hold/turn the engine(bump turn with the starter works too) to get to the correct area on the compression stroke of the affeced cylander. Air will spill from are area of leaking. Test all the cylanders. Some will leak more than others. The points of concrn are Rings, Exhaust valve, Intake valve right. Your point of a burned valve is plausable. A compression tester normally can be modified to hook a air connector to it and sometimes its exactly the same as a regular 1/2" HF connector. Of all the testing tools I have used =, the compression tester and air forced in the cylander have yielded the best results. Yes a leakdown test is a great identifier as well. You will find the issue but its probably be expensive. Run it and when it gets worse, pull the head and buy 1 valve. lap them all in. you probably already know these things good luck

Hi,
Thanx for the idea. My understanding of the starter motor was that it's gear engages the engine only when cranking the engine with the key. So not sure how turning it would help with the engine off. I will look into it. I did do the vacuum test and that came out normal. Though it does not pinpoint which cylinder is bad, it is good for providing an overall health indicator for the engine, and it was in the normal range, with no drop in the needle. And proper swing of the needle when hitting the accelerator, just like in the youtube videos.