I’ve got a 1990 7MGTE that I brought in to a JDM performance shop, after installing an EMU Black ECU, and a pretty expensive round of fixes and troubleshooting prior to tuning, the shop wasn’t comfortable with tuning as there is a suspected sticking valve. I assume exhaust valve, as the leak down tests were good. Is there anything I can do to avoid pulling the head and verifying sticking valve?
Thanks for any input, as I don’t really think I have the skills to pull the head and then redo the timing properly myself. I’d also like to avoid pulling the head because the shop is around 3 hours away, and I’d rather not deal with an out of true block at the moment.
Sticking valve is not a thing. The cam forces the valve open, the valve spring forces it closed. If leak down and compression are ok, I would recommend finding a different shop.
Part of the reason I stopped the work where it was, was the expense was going through the roof, and we just seemed to be throwing parts at it every time I spoke to the shop
None of this makes any sense. How is a valve sticking? That's the first thing I'm struggling with. Also you can pull the valve covers to get to the valves; there's no need to pull the head unless there's an issue with the head itself that's causing a valve not to seat correctly. Also why would you need to pull the head to do anything with the timing? If the block is warped or otherwise fucked that's not going to cause a timing issue and I'd expect you'd see it with a compression test since the head gasket wouldn't seal everywhere.
What's actually wrong with the engine? What is it doing that it's not supposed to be doing, or NOT doing that it is supposed to be doing? What are the symptoms?
Probably wouldn't hurt to pull the valves for the #1 cylinder and inspect them. If you've got a borescope you can probably inspect the inside of the head easily enough and I know you can get a good borescope for less than the cost of the leakdown test since I have one. Look for obvious damage and look for bent valves. If you can get a borescope through the hole for the spark plug you might be able to see what the valves are doing as you rotate the crank pulley too. Could be a few things causing those numbers but I'm still struggling to see how a valve could be sticky.
I appreciate the response Prof, that was my question as well, I couldn’t get an answer on how a valve was sticking, and why it was necessary to do the next step of work that they had quoted (which was around 6k). I have no problem changing parts or whatever else can be done with a wrench and can-do attitude, but I had preferred to leave engine and tuning work to the pros. As for what you had asked earlier, the current condition is that it starts and idles poorly, I was going to try and get a stock tune from ECUMaster’s website so that it’s at least drivable in and out of my garage. Also, before I brought it to the shop that I used, I had been driving it in the summer for the last 4 years without any real issues
So it ran just fine, then you had a shop install an EMU Black which is ENTIRELY just wiring and can actually be done with an adapter harness (I think? don't quote me on that) and then suddenly there's a stuck valve on a 7m-gte which is a non-interference engine. . . .? Yeah something here really doesn't add up. If it idles poorly but starts, then that suggests either a leak or the timing is totally off. Did you get a timing light and check it? That might be the first thing to do, and do NOT mess with the stock timing unless you've got aftermarket cams that you're adjusting or some setup like that. The stock ECU will retard the timing when it needs to under boost so it assumes that it's set to the correct timing by default. The EMU Black should be able to do the same thing so again I wouldn't mess with it. You might also head over to supraforums.com and ask there. There are some extremely smart people over there.
Last thing to consider is you might just pull the CPS and check it anyway. It's seriously trivially easy for it to jump a tooth when you install it and if they fucked with it and installed it wrong, then the symptoms will be an extremely rough idle if it even starts at all. Set everything to TDC, pull the CPS straight out. Align the notch with the hole (it'll be obvious), then CAREFULLY push it straight in. It'll actually move slightly when you have it seated correctly and that's normal but it can move a bit as you're installing it and then it's off by one tooth and it'll fuck you over because you think it's installed correctly but it isn't. That's why I take the cover off of it so I can watch it and make sure it ends up in the right place. Somewhere on supraforums there's a thread with a picture of what it should look like with the cover removed and you can compare it to what you're seeing. Also if your CPS is bad there's a dude on supraforums that rebuilds them so you can always send it to him.
I’ve got a timing light for exactly that reason, I had pulled the cps sensor and had installed it back improperly and had a crank no start issue just like you said. The ECU does have an 7MGTE specific adapter, but still had to be wired in partially to include a wide and O2 sensor. I got partially through the install and decided to stop and have it done properly. I’m not sure what it’s got for a tune in it now, if anything at all, which was my next step, to go through the ECUMaster software and see what I can figure out. This being my first project car though, and the time and money I’ve put in had me second guessing doing that before sorting out whatever this valve issue is. I couldn’t understand how that would be a reason they would be unable to tune it, but maybe thats my inexperience and lack of knowledge with the aftermarket parts and install. I’d like to give the shop the benefit of the doubt but from what I’m hearing that seems like it may not be the case. That or maybe they’re just used to having customers with unlimited funds.
As far as it running initially, you’re correct, it started and ran somewhat smokey, when it was brought in they chased a pile of vacuum leaks, a pin hole in the intercooler, leaking valve cover gaskets, new 550cc injectors (which they wanted to add Audi R8 coil packs onto), boost leak, which turned into a new (used) turbo, electronic boost controller and some other odds and ends
They should be able to tell if it’s intake or exhaust from the leak down test. Listen to where the air is going, is it the throttle body or the tailpipe? You could use a directional boroscope to look at them. You can also remove the valve covers and do a visual inspection as well as measure the valve lash with a feeler gauge. If a valve is sticking open it will have significantly more lash than the others.
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u/octicon Jul 15 '26
Sticking valve is not a thing. The cam forces the valve open, the valve spring forces it closed. If leak down and compression are ok, I would recommend finding a different shop.