I don’t know if ya’ll followed my GVR4 purchase thread http://pittspeed.com/forums/showthread.php?t=45584&highlight=gvr4 , but I have a '91 now. All stock, one owner, etc. However, it ran shitty (high idle, then low/miss idle, miss under load, etc). So we finally got around to working on it, and sure enough the cam timing was off (prev owner had just had a t-belt done).
After fixing the cam timing, we ran a compression test, 3 holes were at 160psi, one at 165. Seams good to me… thoughts?
-TJ
Check voltage, they can run quite shitty without having trouble starting if the alternator output is low.
Did you check for boost leaks?
read. the. thread.
I forget exact numbers but your’e way above service limit. Only a 5 psi difference between the cylinders is fine as well. looks like you got a good one!
I believe what he meant was read this thread. The link to the other thread was just for reference, for those that cared to read it. The real question is how do those compression numbers look. The general consensus is they’re solid and I’m good to go.
I’m going to button it back up today or tomorrow afternoon and see how it runs now. Again, if you read this thread you’d see that I found both cam gears were off a tooth or two. It’s very likely that was causing the idle issues, I figure I might as well get it back together and check and see before moving on to other tests.
Thanks.
-TJ
As Steve said, great numbers, nothing to worry about.
i appreciate your snide use of italics. :bowdown:
dude, your screwed. just sell it now b4 it causes anymore headaches
wat
Hahaha, I know it’s true, but I’ve always wanted one, and I don’t know, I’m dumb.
So it runs much better now (obviously) but still a bit rough at ~750rpm, and is super duper rich. Thoughts?
Haha.
-TJ
6 bolt motors brand new compression is supposed to be around 170 so your good
Bewst leak.
my car leaks boost on purpose because it cant handle all that powA
Do you agree that a b0000000eeeeewwwWst leak could be my problem?
-TJ
has the MAS ever been messed with? could be causing your richness at idle
burn it?
My 90gsx ran shit rich, ecu was f’d. Kurt fixed me up.
No but really, burn it.
yes siri had a few boost leaks and ran rich as fuck
Okay… so how the F do I effectively check for boost leaks?
-TJ
Basic idea - Build a boost leak tester for your to4e | DSMtuners.com
Disable your mbc.
Turn your motor to 30* ATDC to avoid valve overlap.
Start your test at the TB elbow and focus on area behind the TB first.
Spray soapy water at TB gasket, BISS, TB shaft on both sides, IM gasket, injector insulators, brake booster, afpr and all vacuum lines/connections.
Open your oil cap and listen for leaks. (PCV, valve seals/guide, rings)
Listen to your tailpipe for leaks. (EGR, valve overlap, jumped timing, bent/unseated valves)
Once all leaks are fixed, move the tester back to the turbo inlet.
Spray down the compressor cover (known leak), BOV return/flange (DO NOT TAP YOUR BOV LINE FOR YOUR MBC!!!), IC end tank/fins and all connections. Re- test.
Note that you will leak air into the crankcase through the turbo seal but do not panic, this is normal during a static pressure test as long as there are no shaft play.
The desired test result from the begining of the LICP (bypassing turbo) is around 20psi (on boost gauge) with the compressor set at 30psi, while taking no less than 30 seconds to bleed down to 0.
As a reference, my last test on my 500 mile new engine, I was able to pressurize the system to 25psi, bled down to about 16psi (my 1G bov) in about 30seconds, then took about 3 mins to 6psi and just kinda lingered there for a while. It’s not easy to do but the point is it’s possible. My next goal is 30psi After motor break in and Dodge modding my BOV. A boost leak test is one of most pita but important regular maintenace task, the key is patience and endurance
Pretty elaborate, but you get the idea. Steps 2 & 3 aren’t really necessary unless you’re bleeding out a shit ton of air. If you can’t get the system to build pressure, move the tester to the TB elbow to isolate the engine.
Realistically, 1 PSI/second or two is acceptable.
Jesse