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bill k
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Feb 16, 2009, 3:22 PM
Post #1 of 49
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93 Sentra 1.6 misfire it suddenly started to run rough, pulled the distributer cap, it is all clean and no pitting, pulled each plug and none are wet and they all look good, what can it be?????
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Tom Greenleaf
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Feb 16, 2009, 3:44 PM
Post #2 of 49
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Re: Sentrta misfire
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Open to lots of possibilities: Cap, rotor, wires, etc., can look ok and not be. If it just started it could be low fuel pressure (check) or valve timing - when was last timing belt change?
Sometimes secondary ign like cap, wires etc., will react or make visable arcing if they are the trouble when misted with water,
T
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bill k
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Feb 16, 2009, 3:53 PM
Post #3 of 49
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Re: Sentrta misfire
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My wife said it did this about three weeks ago and it cleared up after she got on the turnpike and it just started again yesterday.
If the plugs are not firing won't they be all wet????
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Tom Greenleaf
Ultimate Carjunky
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Feb 16, 2009, 4:01 PM
Post #4 of 49
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Re: Sentrta misfire
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>>If the plugs are not firing won't they be all wet???? <<
Not necessarily. If it's misfiring due to lack of fuel especially. Also - misfiring is still firing so may not show. Eventually it would show something and soon if not already will damage o2 sensors and cat converter(s) if not chased down and fixed.
If you want to do some things right away a new fuel filter wouldn't hurt and new plugs if not recent or any other tune-up items not done recently.
Fuel pressure problems can be the cause also,
T
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bill k
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Feb 16, 2009, 4:46 PM
Post #5 of 49
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Re: Sentrta misfire
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OK I swapped all the plugs around, nothing, pulled each plug in turn and started the motor with the plug on the engine, each plug is sparking real good, found an old leaky compression testor and ran the motor for a few revs with it screwed into each hole I started with number 4 next to the distributer, it wobbled the gauge up to 50-60, moved to the next plug and the engine immediatly ran worse and it moved the gauge up to 90-100 so did the other two holes, I know the problem is in number 4. Here is what I did. I am an outboard mech so I fugured the rings are sticking or a valve is stuck and not closing properly, I had a little seafoam deep creep left and I sprayed it in the hole, cranked it a few times and sprayed some more in put the plug back in and now it is sitting, will let it sit overnight and see what happens in the morning, waddyathink?????
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Tom Greenleaf
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Feb 17, 2009, 12:49 AM
Post #6 of 49
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Re: Sentrta misfire
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When was the last timing belt change OR have you checked basic valve timing?
I understand the "outboard" motor problems as in "seasonal" use items and deep creep, seafoam and things help with stuff like that but this is a car that you didn't mention just came out of storage or something??
What's with the valve timing - checked or not?
T
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Anonymous Poster
Feb 17, 2009, 5:56 AM
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Re: Sentrta misfire
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The timing belt was changed 3 or 4 years ago. The car sat unused for for the recent three day weekend.
The overnight soak did not work, I will pull the valve cover this evening to check the timing and to see if the valves are being moved by the rockers.
In airplanes we would pressurize the cylinder with 80 psi of air at tdc and listen to see where the air was leaking, the exhaust, the intake, or the dipstick to find where it was leaking from , But this car has the plugs buried way down inside the valve cover sorta like a hemi.
I have always been able to fix a misfire but has me really stumped.
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Tom Greenleaf
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Feb 17, 2009, 6:56 AM
Post #8 of 49
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Re: Sentrta misfire
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3-4 years?? How many miles?
Pressure test: Use a compression tester with gauge removed and a rubber hose rigged in if needed,
T
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Anonymous Poster
Feb 17, 2009, 7:17 AM
Post #9 of 49
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Re: Sentrta misfire
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OOps. let me clarify, we replaced all the belts 3 or 4 years ago, this engine has a timing chain, not a timing belt. she puts around 5 to 6K a year on the car, darn thing is like new, everything works and we have replaced just about everything that wears out.
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Anonymous Poster
Feb 17, 2009, 7:30 AM
Post #10 of 49
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Re: Sentrta misfire
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Just checked my compression tester. the hose is attached to the gauge with a standard air hose fitting, So I took the hose out back to my small 10gal compressor and it hooks right up, Tonight when she brings it home I can pressurte test it.
On piston airplanes that run on 100LL a very common problem was a stuck valve, about half the time we could free it up by straking the valve stem, driving it open with a blow from a hammer and seeing if it will pop back shut. I have never removed the valve cover on this car and I think it has dual camshafts. Can this proceedure be used with out removing a camshaft?
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Anonymous Poster
Feb 18, 2009, 12:04 PM
Post #11 of 49
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Re: Sentrta misfire
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All 4 cylinders have around 110 psi, I am real;ly stumped
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Loren Champlain Sr
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Feb 18, 2009, 5:53 PM
Post #12 of 49
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If the plugs are not wet, and you have relatively fair compression, I'd be looking at injectors. Remove, inspect, and reconnect each electrical plug at the injectors. They are a known trouble spot for corrosion. If you have an ohmmeter handy, might be a good idea to check resistance across each injector while your there.
Loren
SW Washington
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Lisa11
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Feb 19, 2009, 1:02 AM
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Re: Sentrta misfire
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The information you have provided is new to me. Thank's for it.
Lisa11
************
(Edited to remove hyperlink - Thanks for the SPAM Lisa11
TomG)
(This post was edited by Tom Greenleaf on Feb 19, 2009, 4:51 AM)
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Anonymous Poster
Feb 19, 2009, 7:12 AM
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We thought about the injectors, we listened to every one of them clicking with a stethescope. We have looked very closely at the distributer cap inside and outside and it looks almost brand new. I even ran the engine in the black of night looking for stray sparks I am just thinking that maybe the cap is sending that #4 plug wire spark at the wrong time. there might be a hairline crack I cannot see ???
I just went to change the fuel filter and discovered that the fuel lines to and from that thing are old and dry rotting on the outside. I an gonna buy a new cap and rotor and a couple feet on fuel line and see what happens
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Loren Champlain Sr
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Feb 19, 2009, 3:49 PM
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Re: Sentrta misfire
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That's not a bad idea; But, if it were a secondary misfire, I'd think you'd see it with the plugs. I don't by any means want to mislead you, but still could be an injector problem, as in plugged. Hope I'm wrong. btw, did you get a resistance reading on the injectors? If so, post the results if you could. Thanks.
Loren
SW Washington
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Anonymous Poster
Feb 23, 2009, 7:00 AM
Post #16 of 49
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Re: Sentrta misfire
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My ohmmeter is not working properly other then continuity.
We put on a new distributer cap and rotor and changed the fuel filter with no improvement, still number 4 cylinder is not firing .
I called the Injector warehouse and told them what we did and they said sometines a plugged injector will click but fuel will not spray out and they felt that I had a bad injector. So I ordered a set of injectors from them along with all the required gaskets and O Rings. The parts should be here on wed or thursday. They had the best price and guarantee and have been around a long time
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Loren Champlain Sr
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Feb 23, 2009, 2:28 PM
Post #17 of 49
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Re: Sentrta misfire
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It's obviously up to you, but injectors can be cleaned. If the resistance is within specs, and you can hear them clicking, electrically, I'd take a chance on cleaning them before replacing. JMO...We've brought back to life many injectors by cleaning. Admittedly, it's about $100.00 gamble, but if you haven't had the whole system cleaned.....
Most independents and dealers now have a MotorVac injection cleaning system. It is, pretty much, state of the art. It cleans the whole injection system, fuel rails, plenum, ect. Also, helps eliminate carbon deposits on/around valves and pistons. I guess what I'm suggesting is, that even if it doesn't unplug the injector, you've still done an important maintenance job. Just my personal thoughts, for what it's worth.
Loren
SW Washington
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Anonymous Poster
Mar 2, 2009, 6:34 AM
Post #18 of 49
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Re: Sentrta misfire
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Well the new injectors are in and it is still misfiring on number 4, for the heck of it we installed all new plug wires too.
This is really frustrating
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Loren Champlain Sr
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Mar 2, 2009, 3:25 PM
Post #19 of 49
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Re: Sentrta misfire
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Pull #4 spark plug and take a look. If it is not firing electrically, it should be wet with fuel. If it is dry, and nice and white, I'm still suspecting an injector problem. I think it's time to get a noid light on that injector to see if it is pulsing. I remember you said that you could hear it clicking, but.....If you are getting spark, and fuel, and the compression is okay, what about a vacuum leak on that particular intake runner? The cylinder would still fire, but be very lean.
Loren
SW Washington
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bill k
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Mar 5, 2009, 10:50 AM
Post #20 of 49
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Re: Sentrta misfire compression test results
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First we put a timing light on each plug wire, they are all getting fire.
Pulled all plugs, cylinder 1 and 2 got 90psi first burst and built up to 155 psi
number 3 initially got 90 and built up to 120
number 4 got 60 and built up to 120
went back and rechecked number 3 and now it read 60 and built up to 120
As engine was running we pulled the plug wires one at a time and it appears to be running on number 1 and 2 only
I unplugged the maf and then plugged it back in and the engine ran a little faster when unplugged and when back in it then slowed again to where it was
What is wrong
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Tom Greenleaf
Ultimate Carjunky
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Mar 5, 2009, 11:16 AM
Post #21 of 49
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Re: Sentrta misfire compression test results
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Just compression test results: Two cylinders next to each other showing low would suggest they share the problem - usually a head gasket or flaw they share like that.
Did they respond a lot differently with a "wet" test? That meaning with a squirt of oil in there?
T
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bill k
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Mar 5, 2009, 11:33 AM
Post #22 of 49
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Re: Sentrta misfire compression test results
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Have not tried the wet test but will when My neighbor gets back in a little while,
Going back over the last week or so something happened that was unusual, perhaps we messed something up. When all the injectors were out we were cleaning the holes with WD-40 and Boeshield T-9 to make sure there was no dirt and we got a good seal. When we put it all back together and went to start the car we got a Hydrualic lock and it would not crank, I pulled all the plugs and told my wife to crank it over and we got a big geyser shot of fluids coming out of all the plug holes but mostly from 3 and 4. After that we put the plugs back in and fired it up only to have it do what it was doing before we did anything that is Misfiring on number 4 and now today we discovered that both 3 AND 4 ARE NOT FIRING. PULLING THE PLUG WIRE ON THOSE TWO AND NOTHING CHANGES BUT PULL A 1 OR 2 WIRE AND THE MOTOR ALMOST QUITS.
Is there any was to fix a blown head gasket now a days with out pulling the head...???
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Tom Greenleaf
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Mar 5, 2009, 11:44 AM
Post #23 of 49
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Re: Sentra misfire compression test results
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>>Is there any was to fix a blown head gasket now a days with out pulling the head...???<<
NO - nothing I know of would last if truly a head gasket. It can get worse - it could be the head or block!
What's with the hydraulic lock with the WD-40 thing? What the heck were you doing?
T
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Mar 5, 2009, 12:09 PM
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Re: Sentra misfire compression test results
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that lock up was an accident, we were spaying wd-40 in the injector holes and cleaning any dirt out, had no idea that it was puddling on top of a cylinder. One of those things you just do not want to admitt to.
when we wet check the compression with oil and there is no increase am I correct in assuming that is an indication of a blown head gasket.
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Tom Greenleaf
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Mar 5, 2009, 12:39 PM
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Re: Sentra misfire compression test results
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Hope lock up didn't cause problems of its own either
So - if again the two side by side are substantially low with oil (wet) test then you do guess head gasket or whatever you may find when you get there AND send the head out to machine shop.
Perhaps there's more that you could do while intact to be certain like a pressure test the spark plug hole (at TDC) and see if you can get a flow out of the other plug hole and vice versa,
T
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