VG30ET troubles (long)
mtcookson
11-11-2003, 12:16 AM
Some info before I go on: This engine is the JDM VG30ET out of the 87-91 Cedric (from what I can tell). It has the intake manifold design that was on the 89-94 Maxima with the VG30E. I swapped it into my 1990 Maxima. The engine is supposed to have the euro cams which add around 10 horsepower due to a change in the duration, lift is the same as the USDM engines. The only thing that is not stock on the engine is the Maxima oil pan and pickup (the little thing that sits in the oil pan with the metal net on it) and the turbo was replaced with an 85-86 300ZX turbocharger. I relocated the turbo to the crossover pipe by having one custom made and had the stock turbo flange on the driver's side manifold welded over with a steel plate to seal it off. I did this due to fitment problems in the Maxima's engine since its front wheel drive.
Ok, I think I'm getting closer to getting my dang engine running. I believe the problem goes all of the way back to when I was having trouble with air coming out of the intake during the compression stroke. I had the heads cleaned, milled, and had a full valve job done on it. I thought it had fixed the problem until I went to do a compression test and heard air coming out.
At some point during the compression stroke the valve is open and air is coming out of the whole front bank or for you guys the left bank (driver's side/cylinders 2, 4, and 6). The timing is perfectly lined up how it is supposed to be i.e. all marks are lined up correctly and I have the cam gears on the correct cams. The cam gear with R3 on it goes on the back/passenger's side for you guys and the cam gear with L3 on it goes on the front/driver's side. The real kicker, that seems to stump everyone, is that I still have perfect compression, being around 175-180 psi, on all 6 cylinders.
When trying to run the engine it ran like crap. It wouldn't idle, it would just die if I tried letting it idle. It also wouldn't rev very fast like my VG30E normally would. This engine revs to about 4500-5000 rpm somewhat well, not as fast as it could/should, then it would just pretty much stop revving from there. Vacuum was only at 10 inHg at an idle rpm which I believe is directly due to half of the engine creating vacuum and the other half blowing air out
At first I thought the valves weren't sealing properly so I took the rockers off and cranked the engine and there was no leaking at all. So... there has to be something wrong with the rockers, lifters, cam, or cam gear. I was thinking that possibly the valves are sticking... but what are the chances of that since I just had them cleaned a few months ago?
Any of you guys ever experience or heard of anything like this? I think this is my final step into getting my car running.
Any and all help would be much appreciated. Thanks in advance!!
Ok, I think I'm getting closer to getting my dang engine running. I believe the problem goes all of the way back to when I was having trouble with air coming out of the intake during the compression stroke. I had the heads cleaned, milled, and had a full valve job done on it. I thought it had fixed the problem until I went to do a compression test and heard air coming out.
At some point during the compression stroke the valve is open and air is coming out of the whole front bank or for you guys the left bank (driver's side/cylinders 2, 4, and 6). The timing is perfectly lined up how it is supposed to be i.e. all marks are lined up correctly and I have the cam gears on the correct cams. The cam gear with R3 on it goes on the back/passenger's side for you guys and the cam gear with L3 on it goes on the front/driver's side. The real kicker, that seems to stump everyone, is that I still have perfect compression, being around 175-180 psi, on all 6 cylinders.
When trying to run the engine it ran like crap. It wouldn't idle, it would just die if I tried letting it idle. It also wouldn't rev very fast like my VG30E normally would. This engine revs to about 4500-5000 rpm somewhat well, not as fast as it could/should, then it would just pretty much stop revving from there. Vacuum was only at 10 inHg at an idle rpm which I believe is directly due to half of the engine creating vacuum and the other half blowing air out
At first I thought the valves weren't sealing properly so I took the rockers off and cranked the engine and there was no leaking at all. So... there has to be something wrong with the rockers, lifters, cam, or cam gear. I was thinking that possibly the valves are sticking... but what are the chances of that since I just had them cleaned a few months ago?
Any of you guys ever experience or heard of anything like this? I think this is my final step into getting my car running.
Any and all help would be much appreciated. Thanks in advance!!
rizzspeed
11-27-2003, 06:50 PM
Did you swap the ECU as well? I would hope so, seeing as the maxima's stock ECU isn't designed to run your VG30ET engine.
Have you seen this engine in normal condition? Have you driven a vehicle equipped with this engine so as to compare with the stock engine and to know it's characteristics? What ratio of compression is the engine running? Some more info might help.
Have you seen this engine in normal condition? Have you driven a vehicle equipped with this engine so as to compare with the stock engine and to know it's characteristics? What ratio of compression is the engine running? Some more info might help.
mtcookson
11-28-2003, 10:31 AM
I have a different eprom burnt for my ecu but, I actually found problem.
It turned out to be the exhaust manifold. It was designed differently than I had thought and when I had it sealed off at where the turbo bolted to it completely blocked off any path for the exhaust to exit. I thouth when I had the flange blocked it would just flow freely to the crossover pipe then to the turbo but I was very wrong.
So, my dad took it and start cutting the inside of it with a cutting torch and eventually got to a point where it would flow really well. We took it to a guy to have a really thick steel plate welded on. Once that was finished I put the manifold on and everything back together and it started right up. Drives very well and is quite fast. The turbo that is on it (from the 84-86 300zx) is pretty small so it spools really fast. I actually want a bit more lag than it has so I'm hoping to upgrade to a bigger one pretty soon.
It turned out to be the exhaust manifold. It was designed differently than I had thought and when I had it sealed off at where the turbo bolted to it completely blocked off any path for the exhaust to exit. I thouth when I had the flange blocked it would just flow freely to the crossover pipe then to the turbo but I was very wrong.
So, my dad took it and start cutting the inside of it with a cutting torch and eventually got to a point where it would flow really well. We took it to a guy to have a really thick steel plate welded on. Once that was finished I put the manifold on and everything back together and it started right up. Drives very well and is quite fast. The turbo that is on it (from the 84-86 300zx) is pretty small so it spools really fast. I actually want a bit more lag than it has so I'm hoping to upgrade to a bigger one pretty soon.
rizzspeed
11-28-2003, 01:44 PM
Don't you hate it when the thing that you thought you had right turns out to be the problem. lol
mtcookson
11-28-2003, 04:09 PM
I think what I hate worse is that this was the problem for about 3 or 4 months... that's what really bites lol.
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