help: 93 vr4 running rough suddenly (datalogs incl.)

[Chris@Rvengeperformance]

The notch on the crank pulley should at least be close to the TDC mark on the plastic timing cover.

[stealthtuner]

hmm. Yes I know it 'should'

[anyonebutme]

Line up the upper marks, remove both the alternator and power steering belt, impact off the crank bolt, wiggle off the pulley, look at the timing mark on the oil pump Coop posted already. At that point you're choices are "it's OK", or "it's screwed". This method will answer any of the possibilities I posted.

Other options have all been posted in here, a very good one by Greg is to buy a compression tester and test a cylinder. You don't even have to get dirty for that as it's just pulling a plug out and cranking the engine. It'll either say roughly 150 psi or it won't. If it's under say 120psi, you got issues, but this method won't tell you WHAT the issue is.

As for how to's with pictures and stuff, Google a phrase like "how to remove crank pulley 3000GT", there has to be at least 400 hits on 3si alone.

[stealthtuner]

id like to do a compression and leakdown test after I find the problem. Just to make sure the engine isnt damaged. compression at least. not sure what a leakdown does but I hear its useful in determining engine health.

thanks for the input. I need to get some local help. Im trying to find it. I want to make sure I do the timing right because that is one of the areas I have no experience with.

[TurboSinceBirth]

You can have the timing jump on you with the car just sitting or driving it. I had my tensioner pulley bolt back out from too much vibration in the aftermarket crank pulley and/or the previous owner reusing the bolt to do the timing. I'm actually very surprised it didn't jump timing on me because as soon as I touched the belt it did. I swapped out the crank pulley, bought new OEM bolts, and redid the timing so it shouldn't happen again.

Definitely pull the crank pulley off and check that timing mark on the cog gear against the timing marks on the cam gears/valve covers. Hopefully everything lines up. If not you will need to fix it. Check out the engine manual: http://www.3sx.com/faq/manuals/Servi...gines-6G72.pdf. Read pages 54-61 to get a good idea on the timing belt system and how it should be lined up/set. You obviously don't have to do all of this if the timing is good but it will show you how it's supposed to be when you're in there checking it.

[Greg E]

id like to do a compression and leakdown test after I find the problem. Just to make sure the engine isnt damaged. compression at least. not sure what a leakdown does but I hear its useful in determining engine health.

They are tests which help you find the problem....

[stealthtuner]

thanks guys. Ill give you an update. Im having a mechanic come out to take a look. This issue is just a bit beyond my expertise.

[stealthtuner]

So the mechanic put cylinder 1 (if youre looking at the engine bay it was closest cylinder to the front of the car and towards the crank pulley; front right if you will) at its top position (with something in the spark plug slot) and the crank pulley mark exactly on T for TDC, and the cam gears were all off (the same amount it appeared). So the timing belt must have skipped teeth on a cold start. given that the belt is new and was just done. I am suspicious of the tensioner being the culprit. So I ordered a kit with 2 pulleys (tensioner) and a tensioner piece that Im guessing the pulley mounts onto. The mechanic offered me a very fair price on doing the timing belt.

It sucks and its a shame. But at least we found the problem and I was offered a good price. He compression tested the front 3 cylinders and they were all perfect. He said if there was damage to the engine (ex: valves bent) it would almost certainly be bent valves in all cylinders and loss of compression in each. He thinks the engine will be fine. If the timing was off the whole time it was being diagnosed and tested and there was damage it would be by the same amount across the board in all likelihood. I think ill have him check the back 3 compression too. Im definitely going to change the oil first thing and put some shell rotella t15w-45 in it.

Thanks for all your input and I'll let you know how it works out.