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Discussion Starter #1 (Edited)
This one is a bit puzzling for me. I was at a track day at VIR, I would get a check engine p1302 after going over the bumpy curbing. I checked the coil pack plugs and it seems #3 or #1 came slightly unplugged. I fixed this, reset the engine light and go back out and the car was 100% fine. Then if I hit those curbs shortly after the light one come on. I did this a few times.

The last lap out it happened again, but this time the car lost power after downshifting from 5,4,3 at the end of the big straight. I shut it off coasted in, waited 30min and it started right back up. It seemed normal so I figured I was lucky and time for new coil packs. I turned it off and loaded it up to leave.

When I inspected the coil packs, you could see arc marks on the tube section. I had applied the dielectric on the coil tube years ago. I figured it was time for new coil packs/ more grease.

I figured I haven't checked the compression in a few years. Why not check it. Now things get weird.

The engine was cold. Unplugged injectors, but forgot do full throttle.
I started at #1 and went to #2 next.

Front of engine
#4 #3 #2 #1
First test
205,150,210,120
Second test
210,155,215,70



So I add oil to #1 and it goes to 90.

Tried again with full throttle and #1 is still at 90.

On to the leak down test with compressed air. Checkout the video.

 

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Sounds like your exhaust valve(s) on hole #1 are leaking. How did the plugs look? How are your valve lashes?

Do you have leakdown percentages for each hole?
 

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Discussion Starter #5
I don't have leak down percentages, i just ran compressed air about 80psi and turned the cams with all spark plugs removed.

Spark plugs looked fine they all more or less looked the same.

I didn't check valve lashes. There were two different methods to do it cam to rocker and rocker to shim. What is the easiest way to measure this?

I found this site, looks like rocker to cam
https://www.eliseworks.com/engine-works/fix-wiped-cams-on-the-2zz-ge-engine/
 

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I admit I'm confused. Sorry.

You rotated the crank to TDC for each cylinder, right? Can't do leak down unless both its valves are closed.
 

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Are you sure you at full closed valves on cylinder closest to timing chain? (1) unsure of exact valve timing but may be a little before TDC (top dead center) you should rotate crank shaft with pressure until assured all valves are closed. If you get leakage the air is going to crankcase which would indicate a piston ring problem. When this happens the air will go to the next open valve if another piston ring is bad. If you close both valves and open your PCV inlet and hear air escaping then it is most likely ring land damage. Must do each cylinder separately. As it it is I may have a similar issue but will check this weekend. Idles erratically for 10 seconds then fine. new coil packs, plugs, injectors. No lose of power though. 7.5 psi boost VF1. Did you check your oil filter for bright metal fragments or dust? Also I would not rotate assembly via cam shaft. Hope you find out. Tommy
 

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Discussion Starter #8
Short version, cylinder #1 read 120psi then 70psi on back to back cold compression tests. I removed all spark plugs and rotated cams a little to close the valves. I now realize now I wasn't at TDC on cylinder #1.

Next I used compressed air to find the leak, no air came out of the oil fill tube, and no air showed up in the coolant. It only came out of the exhaust and other cylinder with partially open exhaust valve.

I will retest with #1 at TDC per this.
https://www.boefab.com/blogs/tech/50212675-2zz-ge-cam-timing

Thanks for the tip, I will rotate with the crank and check the oil.
 

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finger in spark plug hole will tell you that cylinder is a tdc.

Engine s/b warm iirc.
 

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120 is still pretty low as is 155.

I'd buy a leak down gauge kit for the sake of science and do the test with each piston at TDC. Engine doesn't need to be hot.

For the sake of speculation and wild ass guessing, let's assume your air test was performed with #1 at TDC: Although I have not experienced this myself, having too tight of an exhaust valve lash can burn exhaust valves. Valves cool themselves by transferring heat to the the seats/head by touching them. If the lash is too tight, the valve won't spend adequate time on the seat and will get so hot the valve melts to a degree. Mildly burnt exhaust valves would exhibit the exact same sort of air passage as your youtube video demonstrates. The air is leaking around the exhaust valves and into the open exhaust system which includes cylinder #3 because those exhaust valves are partially open. That's why I recommend checking the lash.
 

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Discussion Starter #11 (Edited)
I didn't buy a leak down tester, but I did follow the BOE procedure to find TDC on #1

Here are the videos
Cylinder#1
Cylinder#2
Cylinder#3
Cylinder#4

Followed the valve lash measurements between the cam and roller from a toyota manual. Also while having #1 on TDC then rotating.

In inches, I tried to fit a 0.011 on exhaust and it wouldn't fit.

C1-Exhuast 0.010+ a little tighter than the others.
C1-Intake 0.005
C2-Exhuast 0.010
C2-Intake 0.006
C3-Exhuast 0.010
C3-Intake 0.005
C4-Exhuast 0.010
C4-Intake 0.004

Something to note, on cylinder #2 significantly more air is coming out of that "breather tube" However this originally tested with 210PSI
 

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Wait here.

Perhaps I'm confused. Did you not rotate each cylinder to TDC for each test?

That is not a skippable step.



We pressurize each cylinder when valves are fully closed, so no air s/b escaping. If it is, we listen at intake and exhaust to determine if valves and/or rings aren't sealing properly.

Is this what you did?

Borrow a tester from a local or pay a shop to run the test.

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I don't know why ppl here don't list their locations, so someone could say "I can help you with that."
 

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Discussion Starter #14
I did a poor job of explaining the original problem. When the car lost power it made a sound that wasn't mechanical, but electrical. Flat brappp sounding... When throttle was applied.

After talking with someone more skilled than me. He said to check oil level which was fine.

I rechecked compression with a different gauge and the previously bad cylinders were reading 210+ on a cold engine.

I think my leaking problem was an issue with me not being 100% on TDC.
 
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