Need help solving an intermittent miss

[bk7794]

I posted this in another forum but the one answer I got really made me lose hope in it..

So I made a thread a few months back of my car getting a feeling of it missing. I hit a bump a few months back, last year, and since then I have been feeling this engine miss feeling. This feeling used to only happen when I hit 3 or 4k rpm in third gear, but now I am getting it in all gears and while accelerating and occasionally at highway speeds.

the problem is that its only intermittent. So I was thinking that it was the Gas. I filled up with some good gas, like a gas station that I always got good MPG from and was off the highway so I knew it would be fresh. Plus it wasn't the cheapest in the whole area by an absurd amount like the stations that I have been getting it at previously. So after I did that it seemed to have worked. From what I observed I didn't get any hiccups or engine miss feeling whatsoever.

So I was wondering, would a bad fuel filter cause this feeling. Maybe there is crap in the gas and the filter is plugged so the filter is just being bypassed? The whole electrical system is New. With less then 15k on everything.

http://honda-tech.com/showthread.php?t=3048622 thats the original.

[AHTOXA]

I don't believe there is bypass in fuel filter. Crap gas is a possibility. I used to have a misfire in my old xterra. Ran seafom through and all was fine. My misfire was severe enough to throw a check engine light. Cause was plugged injectors as shown on flowbench.

[bk7794]

I don't believe there is bypass in fuel filter. Crap gas is a possibility. I used to have a misfire in my old xterra. Ran seafom through and all was fine. My misfire was severe enough to throw a check engine light. Cause was plugged injectors as shown on flowbench.

These aren't too severe, I am running this redline synthetic fuel cleaner...I got it at the Honda dealer and heard some pretty decent stuff from them. I just wish I used it on a better tank of gas...

So I wonder if the valero gas is bad, I mean my friend has a problem with it on their minivan.

I wonder if I should replace the filter anyways

[AHTOXA]

Valero is not top tier gas. Who knows what detergent mix they use.

Mg xterra had the issue described above after a couple years using citgo almost exclusively. They aren't top tier and since then I've used top tier gas unless unavoidable.

[theholycow]

In the US, Valero uses the detergent mix specified by US regulations. It is quite sufficient and wouldn't be to blame for driveability symptoms. In bk7794's car it also uses Redline synthetic fuel system cleaner. However, if a particular Valero station has contamination in their supply (say, a leaky tank letting water in), that could do it.

The fuel filter would have to be really awful to cause it and I would expect other symptoms first. When was it last changed? I would expect the fuel pump before the fuel filter, although the filter is certainly cheaper and probably easier to replace first (and a good idea if it hasn't been replaced in a while).

The new electrical system: Does that include the entire ignition system? Coil(s), distributor cap (and potentially the entire distributor assembly since you have a bazillion miles), spark plug wires, plugs, etc? Especially the coil(s). Has the timing been adjusted lately?

Got a check engine light? If not, you could still be looking at a control system issue anyway. A flaky connection due to a rotted wire or corroded connector would fit your mention of the first occurrence being after a bump. A lazy sensor could do it.

[Shadow]

Go back to basics. You need three things to support combustion: Air/fuel mixture, spark, and compression. Air/fuel issues can be caused by a malfunctioning fuel injector or fuel pump, for example. Of there could be a vacuum leak that allows unmetered air into the engine causing the ratio to be too lean. Another possibility (that was mentioned already) is a clogged fuel filter....or even a bad fuel pressure regulator.

Spark issues are usually pretty straightforward to check. Look at the coil(s), wires, cap/rotor, plugs for any signs of damage and/or fouling. If you have access to an oscilloscope, you can get a really good graphic representation of the firing pattern. Any issues will be usually be completely evident.

Compression issues can be from a bad exhaust valve or even a bad head gasket. Or even severely worn piston rings. Anything that causes the combustion chamber to "leak" will obviously cause loss of compression.

Intermittent misfires are a pain in the ass because their cause comes and goes. But you still have to go back to basics and do some detective work to determine which of the three (air/fuel, spark, compression) is causing the problem. Try to determine exactly when you feel the misfire and see if it happens under the same conditions all the time. For example, does it only happen when the engine is hot? cold? under load? high rpm? low rpm? Or does it come and go randomly with no apparent pattern? This will go a long way towards helping you (or your mechanic) determine the true cause of the problem. Also, have you checked the car for codes? Even if your MIL (check engine light) isn't illuminated, you can still have pending codes that are recorded and saved.

[AHTOXA]

There has been debate whether govt spec detergents are sufficient. My personal experience doesn't prove anything but it does sway my opinion. Citgo wasn't quality gas in regards to needed detergents.

[bk7794]

Valero is not top tier gas. Who knows what detergent mix they use.

Mg xterra had the issue described above after a couple years using citgo almost exclusively. They aren't top tier and since then I've used top tier gas unless unavoidable.

Right, citgo also gave me MPG issues. But the problem I am facing is that It worked fine before I hit this bump.

In the US, Valero uses the detergent mix specified by US regulations. It is quite sufficient and wouldn't be to blame for driveability symptoms. In bk7794's car it also uses Redline synthetic fuel system cleaner. However, if a particular Valero station has contamination in their supply (say, a leaky tank letting water in), that could do it.

The fuel filter would have to be really awful to cause it and I would expect other symptoms first. When was it last changed? I would expect the fuel pump before the fuel filter, although the filter is certainly cheaper and probably easier to replace first (and a good idea if it hasn't been replaced in a while).

The new electrical system: Does that include the entire ignition system? Coil(s), distributor cap (and potentially the entire distributor assembly since you have a bazillion miles), spark plug wires, plugs, etc? Especially the coil(s). Has the timing been adjusted lately?

Got a check engine light? If not, you could still be looking at a control system issue anyway. A flaky connection due to a rotted wire or corroded connector would fit your mention of the first occurrence being after a bump. A lazy sensor could do it.

The Redline stuff has only been in there for one tank. And this misfire isn't like a noticeable one that drags my speed down. I am able to stay up to speed usually.

Also the entire electrical system, the coil (which is in the distributor), wires, plugs, cap, everything. Now the timing...It should be in time but the problem is that its at the end of its adjustability part.

Fuel filter was replaced maybe 50k ago. But we have been getting gas there for a few years, and some of the gas we have gotten has not been top notch. (I say we meaning the previous owner and I)

Go back to basics. You need three things to support combustion: Air/fuel mixture, spark, and compression. Air/fuel issues can be caused by a malfunctioning fuel injector or fuel pump, for example. Of there could be a vacuum leak that allows unmetered air into the engine causing the ratio to be too lean. Another possibility (that was mentioned already) is a clogged fuel filter....or even a bad fuel pressure regulator.

Spark issues are usually pretty straightforward to check. Look at the coil(s), wires, cap/rotor, plugs for any signs of damage and/or fouling. If you have access to an oscilloscope, you can get a really good graphic representation of the firing pattern. Any issues will be usually be completely evident.

Compression issues can be from a bad exhaust valve or even a bad head gasket. Or even severely worn piston rings. Anything that causes the combustion chamber to "leak" will obviously cause loss of compression.

Intermittent misfires are a pain in the ass because their cause comes and goes. But you still have to go back to basics and do some detective work to determine which of the three (air/fuel, spark, compression) is causing the problem. Try to determine exactly when you feel the misfire and see if it happens under the same conditions all the time. For example, does it only happen when the engine is hot? cold? under load? high rpm? low rpm? Or does it come and go randomly with no apparent pattern? This will go a long way towards helping you (or your mechanic) determine the true cause of the problem. Also, have you checked the car for codes? Even if your MIL (check engine light) isn't illuminated, you can still have pending codes that are recorded and saved.

The problem is that this car is TB, so there is really two injectors, one for light load, and the second (backup) injector comes on for heavy load.

This misfire feeling comes on sometimes when I am accelerating, and sometimes when travelling up a mountain going only 62MPH. Like around there is where I feel it. I used to have issues with my steering wheel vibrating there and only there. I am wondering if something in the suspension is gone, the tie rod end is and maybe my alignment is out of whack. I got the part to put it on...I just have to do it now.

I am doubting it could be an electrical problem because its not a heavy misfire, like it doesn't feel like I just hit something..I had one in a family members Automatic Taurus and it was very noticeable. Now maybe I will spray water on these wires to see if I get any arcing, these aren't cheap wires either, NGK.

My big problem is that it changes with a tank of Gas. I am going to fill up at Mobil today.


Also another story I was driving home once and I was low on a tank of gas, like maybe my last 3 or 4 gallons, and whenever I would try to make it up a hill it would be hiccuping or missing. I filled up the next day in Mass, which I know good gas is served there, and it went away.

I agree with water being in the tank though.

also my car is starting to crank a lot longer to get it started. I thought that was a symptom of a dirty fuel filter, could be wrong.

[theholycow]

Now the timing...It should be in time but the problem is that its at the end of its adjustability part.

That sounds significant. Any idea why it's like that?

Fuel filter was replaced maybe 50k ago. But we have been getting gas there for a few years, and some of the gas we have gotten has not been top notch. (I say we meaning the previous owner and I)

50,000 miles is probably plenty of life for a fuel filter. Replacing it now would probably not be wasted over-maintenance.

The problem is that this car is TB, so there is really two injectors, one for light load, and the second (backup) injector comes on for heavy load.

This misfire feeling comes on sometimes when I am accelerating, and sometimes when travelling up a mountain going only 62MPH.

Also another story I was driving home once and I was low on a tank of gas, like maybe my last 3 or 4 gallons, and whenever I would try to make it up a hill it would be hiccuping or missing.

also my car is starting to crank a lot longer to get it started. I thought that was a symptom of a dirty fuel filter, could be wrong.

These are symptoms of fuel supply issues.

Long-cranking before starting contraindicates the fuel filter as the problem. A clogged fuel filter doesn't reduce primed fuel pressure; it reduces flow volume (and therefore pressure under high-volume conditions). Therefore, fuel pressure regulator and fuel pump are likely suspects if it's a fuel supply issue. A fuel pressure gauge can help diagnose it.

Diagnostically or as a workaround for the starting issue you can try to prime the fuel system before cranking; turn the key to On (not turning it to Start) and listen for the fuel pump to run then stop. Turn it off and repeat a couple more times; you may hear the pitch of the fuel pump change, then you know there's at least some pressure. At that point it should fire with much less cranking. Some cars prime when you open the drivers door instead of when you key-on so it won't work for them. None of the driveability symptoms will be improved with this.

[bk7794]

Now the timing...It should be in time but the problem is that its at the end of its adjustability part.

That sounds significant. Any idea why it's like that?[/quote]
No, was assuming because its an aftermarket distributor, I just looked at it again and saw that its not bottomed out. I must have forgotten that I adjusted it just a bit after.

These are symptoms of fuel supply issues.

Long-cranking before starting contraindicates the fuel filter as the problem. A clogged fuel filter doesn't reduce primed fuel pressure; it reduces flow volume (and therefore pressure under high-volume conditions). Therefore, fuel pressure regulator and fuel pump are likely suspects if it's a fuel supply issue. A fuel pressure gauge can help diagnose it.

Diagnostically or as a workaround for the starting issue you can try to prime the fuel system before cranking; turn the key to On (not turning it to Start) and listen for the fuel pump to run then stop. Turn it off and repeat a couple more times; you may hear the pitch of the fuel pump change, then you know there's at least some pressure. At that point it should fire with much less cranking. Some cars prime when you open the drivers door instead of when you key-on so it won't work for them. None of the driveability symptoms will be improved with this.

The big issue is that it improves with a better tank of fuel. So its either that water is getting into the fuel somehow, and I do NOT doubt that it is happening because a relative of mine had replaced a fuel filter because it burst in the middle of winter. The starting is not extremely long, its like 2 or 3 seconds. But I started my car up next to a friends nissan versa, 07 and mine fired about a second after theirs. I mean I mentioned it because it just seems longer then before.

I am going to start by getting better gas for a few weeks, even if I have to pay 1 or 2 bucks more per tank...Wow..

[bk7794]

Okay, so I just got gas at sunoco. They both are delivered with the same truck...but we will see what happens. I ran it through a few gears with high rpms and I did not feel any missing. I also did NOT add any of the redline stuff to clean out the intake and all that. I basically bought that because when I changed the PCV which was located on the intake, it was black.

[theholycow]

The big issue is that it improves with a better tank of fuel. {...} I am going to start by getting better gas for a few weeks, even if I have to pay 1 or 2 bucks more per tank...Wow..

Getting better gas for a few weeks will certainly help include or exclude fuel quality as the diagnosis. What I read was that it had a symptom with the tank empty and not with the tank full, and I saw the fullness as more significant than the fuel quality in that particular symptom.

[bk7794]

The big issue is that it improves with a better tank of fuel. {...} I am going to start by getting better gas for a few weeks, even if I have to pay 1 or 2 bucks more per tank...Wow..

Getting better gas for a few weeks will certainly help include or exclude fuel quality as the diagnosis. What I read was that it had a symptom with the tank empty and not with the tank full, and I saw the fullness as more significant than the fuel quality in that particular symptom.

It does, now I am getting concerned...I will post back with results in a few weeks to see if I get a similar symptom.

Isn't water lighter then Gas, and the pump sucks from the bottom right?

[theholycow]

Water is heavier than gasoline. From wikianswers:

At a temperature of 20 degrees C or 68 degrees Fahrenheit, a (U.S.) gallon of pure water weighs about 8.34 pounds, whereas a gallon of vehicular gasoline weighs about 6.15 pounds at that temperature.

Fuel pumps do have to suck from the bottom or else you'd run out of fuel before your tank was empty.

[bk7794]

Water is heavier than gasoline. From wikianswers:

At a temperature of 20 degrees C or 68 degrees Fahrenheit, a (U.S.) gallon of pure water weighs about 8.34 pounds, whereas a gallon of vehicular gasoline weighs about 6.15 pounds at that temperature.

Fuel pumps do have to suck from the bottom or else you'd run out of fuel before your tank was empty.

Interesting, I never knew that...So now I may have more of a problem then I figured. Today I was going up the parkway in CT and everytime I hit a hill going from 53-68 I would get an engine miss feeling. Now I have no clue if it was a miss or what it is.

I am worried that its my axles aswell...