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1990 pathfinder has no power and wasting gas
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dskee
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Sep 29, 2011, 3:31 PM
Post #1 of 26
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1990 pathfinder has no power and wasting gas
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I have a 1990 6 cyl 4x4 automatic pathfinder with the vg30e and i am having a really hard time trying to figure out whats going on..ALl of a sudden one day it felt like it was missing. So I changed the basics (plugs,wires ,fuel/air filters) . and it changed norhing. So I read some stuff regarding a glowing cat, since i had noticed mine was glowing red .Ithought the glowing red meant it was glogged but acyually its a fuel/air mixture problem from what ive learned.But before learning this info I had unclogged the car to the point that it all ended up in the muffler that has since been replaced. The truck has no power at all and it constantly smells of gas and it is burning gas ar a rate of 5 mi a gallon. It shows no codes on the on board ecu and i took it to a shop and they said it had to do with the mass air flow system, So I went to junk yard replaced the sensor and it still is the same. Any help or suggestions would be awesome and greatly appreciated. Thanks
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Discretesignals
Ultimate Carjunky
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Sep 29, 2011, 3:38 PM
Post #2 of 26
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Re: 1990 pathfinder has no power and wasting gas
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Which cylinders are missing?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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dskee
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Sep 29, 2011, 3:45 PM
Post #3 of 26
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Re: 1990 pathfinder has no power and wasting gas
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all cylinders have good compression.
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Discretesignals
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Sep 29, 2011, 3:47 PM
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Re: 1990 pathfinder has no power and wasting gas
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Thats good, but which cylinders are misfiring?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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dskee
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Sep 29, 2011, 4:00 PM
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Re: 1990 pathfinder has no power and wasting gas
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Im not sure how to check which ones. Would the ecu display a code if any were misfiring? Please excuse my inexperience for not knowing how to check.
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Discretesignals
Ultimate Carjunky
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Sep 29, 2011, 4:12 PM
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Re: 1990 pathfinder has no power and wasting gas
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I don't think the ECU back then had the capability of determining misfires. If the engine is running bad and you have no power, you have misfiring going on. Misfiring is causing from a cylinder that doesn't go through the combustion process. It will make the engine vibrate/buck and not have power on acceleration.
If the engine is skipping at idle or vibrating, you need to figure out which cylinders are missing. You can do this by disabling spark or fuel to the cylinder. The cylinder(s) that doesn't make a change in the running of the engine is the one(s) that are missing. Once you determine which cylinders are missing, you can figure out why.
If a cylinder is missing because of a mechanical or spark related problem, the injector is going to still spray fuel. The unburnt fuel ends up in the exhaust causing the catalyst to overheat or in your case turn the outer case cherry red.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Discretesignals
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Sep 29, 2011, 4:25 PM
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Re: 1990 pathfinder has no power and wasting gas
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The preferred way to disable a cylinder is by unplugging the electrical connector from that cylinder's fuel injector.
Sometimes you can't get to injector connector because they are underneath the intake. In that case you have to disable the spark on that cylinder. Most people would pull a spark plug wire for that cylinder off the plug or distributor. Most of the time you get shocked if the voltage finds a way to ground though you. The other bad thing about pulling wires is that when you open the spark plug circuit the ignition coil is going to go full tilt looking for ground. Doing that too a weak coil can finish it off. This is why they tell you never to leave a plug wire not grounded to something.
I've had some luck disabling cylinders with a 12 test lamp connected to battery ground. I just slide the probe in between the wire and the boot to ground the wire at the distributor. Just be careful. You don't want to pierce the boot and create a place for spark to leak out.
You disable one cylinder at a time with the engine running. The cylinder that doesn't change the running of the engine is your culprit.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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dskee
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Sep 29, 2011, 4:26 PM
Post #8 of 26
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Re: 1990 pathfinder has no power and wasting gas
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ok thanks i will go check which one is. I appreciate your help.
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dskee
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Sep 29, 2011, 4:59 PM
Post #9 of 26
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Re: 1990 pathfinder has no power and wasting gas
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ok like you said some injectors are not eay to get to but 1,3,and 5 i can get to. 3 and 5 are missing since when i removed the injector harness it didnt change the performance. Is it likely to have more than 2 miss? If so ill have to check 2,4 and 6? Thanks again for all your help
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dskee
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Sep 29, 2011, 5:21 PM
Post #10 of 26
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Re: 1990 pathfinder has no power and wasting gas
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ok i have checked the rest and 1,2,4,6 seem to be ok. All cylinders have spark and I had recently changed all plugs, and wires so we can eliminate those possibilities. 1 thing to mention , like most or all pathfinders I had a broken manifold stud and have been messing with it for some time now , could that be the reason for the cylinder issues?
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dskee
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Sep 30, 2011, 4:44 PM
Post #11 of 26
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Re: 1990 pathfinder has no power and wasting gas
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Anyone have any suggestions on what my next move should be, since i've changed most things that would cause a missfire.
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dskee
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Sep 30, 2011, 5:56 PM
Post #12 of 26
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Re: 1990 pathfinder has no power and wasting gas
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ok I just did a running compression check and cylinder 5 is at 135 , cylinder 3 is 115 and the rest are between 155 and 165. What s the next step in figuring out whats wrong? Thanks again for your time and suggestions. Its the only vehicle I have and i dont want to screw it up anymore than i allready have, but being its the only wheels i have and it runs like crap im still driving it. Thanks again
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Discretesignals
Ultimate Carjunky
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Sep 30, 2011, 6:13 PM
Post #13 of 26
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Re: 1990 pathfinder has no power and wasting gas
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Sorry, just got home from work.
Good reading should be within 10-15% of the highest reading. If you have 165 psi, that means the lowest before you have a problem is 148-140 psi. Obviously 3 and 5 are having problems. Squirt some motor oil into the spark plug holes for those cylinders and retest the compression on those cylinders. If the reading comes up, you have ring issues. If it doesn't come up, valves aren't sealing.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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dskee
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Sep 30, 2011, 6:18 PM
Post #14 of 26
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Re: 1990 pathfinder has no power and wasting gas
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does the oil need to me 30wt or would say 10-30 be ok
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Discretesignals
Ultimate Carjunky
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Sep 30, 2011, 6:26 PM
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Either one will work.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Sep 30, 2011, 6:26 PM)
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Discretesignals
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Sep 30, 2011, 7:01 PM
Post #17 of 26
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Re: 1990 pathfinder has no power and wasting gas
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Your right HT. I didn't read that good enough. I thought he did a static compression test. If you do a running compression test with the valve in the gauge, you have to bump the release valve every once in a while. Yep, running compression should be around half static. It's been a long week.(bla)
To the OP- Did you do a static test or a dynamic test?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Sep 30, 2011, 7:02 PM)
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dskee
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Oct 1, 2011, 6:06 PM
Post #18 of 26
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Re: 1990 pathfinder has no power and wasting gas
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Thanks for the help but once again you have exceeded my limited knowledge of auto mechanics. I tried to search for what static testing and dynamic testing are ,I was unable to understand what they meant.
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Hammer Time
Ultimate Carjunky
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Oct 1, 2011, 6:18 PM
Post #19 of 26
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Re: 1990 pathfinder has no power and wasting gas
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You're the one that stated that you did a "running" compression test. I assumed that you knew what that meant. Static test is done with the engine off and dynamic test is done with the engine running.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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dskee
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Oct 1, 2011, 6:31 PM
Post #20 of 26
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Re: 1990 pathfinder has no power and wasting gas
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sorry for not knowing that. I first did the static and then the dynamic. When doing the dynamic am i supposed to releive the pressure while doing the test?
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Hammer Time
Ultimate Carjunky
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Oct 1, 2011, 6:33 PM
Post #21 of 26
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Re: 1990 pathfinder has no power and wasting gas
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You're supposed to remove the shraeder valve from the gauge first or it will not give you an accurate reading
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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dskee
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Oct 1, 2011, 6:37 PM
Post #22 of 26
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Re: 1990 pathfinder has no power and wasting gas
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ok im going to go do that now and will repost the results in just a few minutes.
Once again Thanks for all your help
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dskee
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Oct 1, 2011, 7:20 PM
Post #23 of 26
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Re: 1990 pathfinder has no power and wasting gas
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OK i have another roadblock. The valve is connected to the fitting that the hose connects to. I dont have any other connectors to use so ill have to get one tommorow. I did though test again this time using oil and the # 3 cylinder went up to 135 but the # 5 cylinder went down to 100. Is this the reason for removing the valve? Inconsistant readings? Or is it possible that while driving the car im messing it up more?
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Discretesignals
Ultimate Carjunky
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Oct 1, 2011, 8:07 PM
Post #24 of 26
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Re: 1990 pathfinder has no power and wasting gas
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Here's how it works.
There are two types of compression tests you can do with a gauge. One is static. That means you are cranking the engine, but it doesn't run while your testing pressure in a cylinder. You leave the valve in the gauge for that. When you feel 4-5 pumps on the hose, stop cranking and record your reading. You just have to be consistent in your readings across all cylinders.
The other test you can do with the gauge is dynamic or running compression test. When you do this test the engine has to be running. Normally, your supposed to take the valve out, but I have found that the gauge fluctuates a lot. If you burp the release every once in a while, you'll get a somewhat stable reading.
The static test checks how the cylinder is sealing. The dynamic tells you how the cylinder is breathing.
What did the spark plug look like when you pulled it out of #5? Was it wet with fuel, dry as a bone, or black as the ace of spades?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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dskee
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Oct 1, 2011, 8:41 PM
Post #25 of 26
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Re: 1990 pathfinder has no power and wasting gas
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it was kinda dry but black.
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