low compression
06-11-2003, 07:43 AM
#1
Senior Member
Thread Starter
Join Date: May 2003
Posts: 535
low compression
I did a compression test on my 92 Max SE last night. Five of the cylinders were all about 170, but the last one I checked was about 120. What can I do to fix this low compression problem? Thanks
......maybe it might be a gasket or something?
06-11-2003, 08:10 AM
#6
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Join Date: Jan 2001
Posts: 2,105
i had that problem, except my front 3 were 165-175psi and my rear 3 were 120-130psi. did you do a wet compression test? is there oil in your coolant? coolant in your oil?it could be valve seals..it could be a head gasket...more likely than not its rings though.
06-11-2003, 08:23 AM
#7
Senior Member
Join Date: Nov 2000
Posts: 387
Originally posted by PCGuRu2K
You can't really fix the compression problem. Only thing yuu can do is get another motor... 120 is not too bad. When you get down to like the 90's then you can begin to worry..
You can't really fix the compression problem. Only thing yuu can do is get another motor... 120 is not too bad. When you get down to like the 90's then you can begin to worry..
Compression can be fixed but you definately have to get into the internals. Usually your service manual will tell you what the variance that is okay ex 14 psi +/- is okay. EX, if they're ALL at 150 and stock is 170, except one is 135, that's almost w/in spec.
You DON"T need to get a new motor.
06-11-2003, 08:45 AM
#9
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Posts: n/a
Try doing the compression test again. This time, put a little oil in the actual spark plug hole. Then, rig up the compression tester again. Test the compression. If it does get better, than that means you have a bad piston ring. If you can, go to www.sprintmax.com and look at his FSM online. If you don't have a password/user name, just email him.....Good luck.
06-11-2003, 08:13 PM
#11
Low compression in one cylinder usually means either rings or a valve. If you have a broken manifold stud and an exhaust leak that can eventually lead to a bad exhaust valve. You can try using a air compressor (WELL filtered please) and inject air pressure into the suspect cylinder. Then listen to where the air is leaking from. If you hear it from the dipstick tube it's rings. Exhaust pipe is an exhaust valve. Throttle body is an intake valve.
BTW, a blown HG would be the LEAST amount of work possible to fix the problem. To fix ANY of the above problems you will have to replace the HG as well.
BTW, a blown HG would be the LEAST amount of work possible to fix the problem. To fix ANY of the above problems you will have to replace the HG as well.
06-12-2003, 07:02 AM
#12
I have a nightmare story about low compression on my old maxima (90 GXE). It’s kinda long but bear with me. It all started when my car started to run a little rough like it was missing, but the problem was intermittent. I took my car into a independent garage and they couldn’t duplicate the problem, so they changed the distributor (They decided to change that without letting me know other wise I would have done it myself). Shortly after I got it back it started to intermittently run rough again.
So I ohmed out my injectors. I found that the injector on the # 1 cylinder read infinite (open) when the car ran rough and 125 ohms (normal is 10-14 ohms) when the car ran normal. So I changed the injector, but I thought that the car still ran a little rough (I could feel a little vibration in the steering wheel), most people thought it was normal and nothing to worry about.
Well a few weeks later in my high school auto tech class I did a compression test and found all cylinders to be in spec except the #1 cylinder which was around 100(I think). So I did a wet test and the compression stayed the same, so that indicated to me that a valve or valve stem seal were worn or bad. So I pulled the head and noticed that the exhaust valve on the #1 cylinder was discolored (I think it was white). So I changed the valve and did a complete valve job (with the equipment at the school). I also did a vacuum leak test on the cylinder head after it was all finished and all the combustion chambers held steady with no leaks. So I put the rear head back on the engine and I still thought that the car ran a little rough.
So a few weeks later I finally took my car into a nissan dealer. They told me that the distributor cap was bad and that the #1 cylinder wasn’t getting a steady spark. I told them that the distributor had been changed less then a year ago. They then told me it was an Italian made part (not OEM nissan part) and that they had seen problems with those before. So they put a nissan OEM distributor on it and called it good. I still thought the car ran a little rough (most people wouldn’t notice but I had felt the engine run real smooth before and it wasn’t the same).
So I took the car back to the nissan dealer and asked them to look at it again. They called and later told me that there was low compression on the #1 cylinder (they said they did a wet test and they thought it was the valve or valves). I told them I had already rebuilt the head, but told them to go ahead and dig into it. After they got the head off they saw the valves were OK and started to dig deeper. They later called and told me that the connecting rod in the #1 cylinder was bent (causing the low compression). So I had them change it. When I went to pick up my car I talked with the mechanic who worked on my car. He showed me the rod and it was bent perfectly, it didn’t scrape the cylinder walls or screw up the crank journals or do any damage, I was very surprised (I just wish I would of thought to ask to keep the rod as a souvenir). The mechanic said that a few weeks earlier he had changed several bent rods on a Pathfinder , due to off road driving down by a river and the engine sucked up water.
After thinking about all the problems I had with the #1 cylinder I came up with a theory. My theory is that the #1 cylinder wasn’t getting a steady spark (due to the bad distributor cap) and that in combination with the bad injector (possibly going haywire and shooting to much fuel into the cylinder) created a liquid lock type situation in the #1 cylinder thus leading to a bent connecting rod. I told this theory to a few different mechanics and they don’t think an injector could dump enough fuel to create a liquid lock and bend the rod.
I was told that most likely the injector wasn’t dumping enough fuel and the valve got to hot (thus leading to the discolored valve). And some time I most likely sucked water in my intake and it got into my cylinder and caused the bent rod.
That whole experience turned out to be a very expensive and educating lesson. Now when I change parts I will only put OEM nissan parts on unless I’m upgrading to higher performnce parts (due to the cheap imitation distributor). All this happened when there was around 100k-104k on the engine. I ended up selling the car a few months later and bought my current 94 SE 5spd.
So I ohmed out my injectors. I found that the injector on the # 1 cylinder read infinite (open) when the car ran rough and 125 ohms (normal is 10-14 ohms) when the car ran normal. So I changed the injector, but I thought that the car still ran a little rough (I could feel a little vibration in the steering wheel), most people thought it was normal and nothing to worry about.
Well a few weeks later in my high school auto tech class I did a compression test and found all cylinders to be in spec except the #1 cylinder which was around 100(I think). So I did a wet test and the compression stayed the same, so that indicated to me that a valve or valve stem seal were worn or bad. So I pulled the head and noticed that the exhaust valve on the #1 cylinder was discolored (I think it was white). So I changed the valve and did a complete valve job (with the equipment at the school). I also did a vacuum leak test on the cylinder head after it was all finished and all the combustion chambers held steady with no leaks. So I put the rear head back on the engine and I still thought that the car ran a little rough.
So a few weeks later I finally took my car into a nissan dealer. They told me that the distributor cap was bad and that the #1 cylinder wasn’t getting a steady spark. I told them that the distributor had been changed less then a year ago. They then told me it was an Italian made part (not OEM nissan part) and that they had seen problems with those before. So they put a nissan OEM distributor on it and called it good. I still thought the car ran a little rough (most people wouldn’t notice but I had felt the engine run real smooth before and it wasn’t the same).
So I took the car back to the nissan dealer and asked them to look at it again. They called and later told me that there was low compression on the #1 cylinder (they said they did a wet test and they thought it was the valve or valves). I told them I had already rebuilt the head, but told them to go ahead and dig into it. After they got the head off they saw the valves were OK and started to dig deeper. They later called and told me that the connecting rod in the #1 cylinder was bent (causing the low compression). So I had them change it. When I went to pick up my car I talked with the mechanic who worked on my car. He showed me the rod and it was bent perfectly, it didn’t scrape the cylinder walls or screw up the crank journals or do any damage, I was very surprised (I just wish I would of thought to ask to keep the rod as a souvenir). The mechanic said that a few weeks earlier he had changed several bent rods on a Pathfinder , due to off road driving down by a river and the engine sucked up water.
After thinking about all the problems I had with the #1 cylinder I came up with a theory. My theory is that the #1 cylinder wasn’t getting a steady spark (due to the bad distributor cap) and that in combination with the bad injector (possibly going haywire and shooting to much fuel into the cylinder) created a liquid lock type situation in the #1 cylinder thus leading to a bent connecting rod. I told this theory to a few different mechanics and they don’t think an injector could dump enough fuel to create a liquid lock and bend the rod.
I was told that most likely the injector wasn’t dumping enough fuel and the valve got to hot (thus leading to the discolored valve). And some time I most likely sucked water in my intake and it got into my cylinder and caused the bent rod.
That whole experience turned out to be a very expensive and educating lesson. Now when I change parts I will only put OEM nissan parts on unless I’m upgrading to higher performnce parts (due to the cheap imitation distributor). All this happened when there was around 100k-104k on the engine. I ended up selling the car a few months later and bought my current 94 SE 5spd.
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