[AngryMallard]

Hey all, I might have a unique problem here...

A few months ago I did the knock sensor relocation and that worked great! This past Thursday I pulled a trailer from Greenville to Nashville and on the way the truck started knocking again. I'm not sure what caused it but my solution at the time was to put premium fuel in it and that SEEMED to work, until the next day when I drove from Nashville to Charleston (without the trailer) and it started knocking (on the same tank of premium fuel) when I got the truck a little over 70 mph. I pulled off near Chattanooga to get gas and while I was driving around at normal town speeds the knock went away. Got it back on the interstate again and it was back knocking.

So my next tank of fuel (near SC/GA border) the knock went away at the gas station again and when I got on the interstate I kept it at 60, no knock. Then I got up to 65, no knock. Moved up to a little under 70 and there was no knock. I lost focus for a bit (no cruise control) and it got over 70 and started knocking again. Slowing down doesn't help, I have to drive like 5 mph for a few minutes to get it to quit. But I think this is why when I was pulling the trailer (rarely get it over 65mph) it stopped knocking after I put the premium fuel in it.

I'm driving from Charleston to Nashville tomorrow and I would like to know (along with what the problem is and why it's happening) if this continues if I will be stuck somewhere in rural Georgia with a hole burned through my engine or something tragic. So far it's been OK but I'm in the dark here.

I haven't been able to run codes to see if the knock sensor went bad, but I just replaced it and it hadn't thrown codes in about two months. Seems weird to only be doing it over 70mph though...

 

[TwoBills]

I'm guessing that you're talking about spark knock and not a bearing knock. I would loosen the distributor hold down and retard the initial timing slightly. Don't move it much, just enough to knock the idle down a bit. You might have to do this a couple of times. Just listen for the knock when the truck is under load, or over 70 like you were saying.
Otherwise, I'd keep it under 70 or keep the overdrive off (or run in 4th gear if it's a stick). Better to run a little slower or use a little more gas than to burn a piston. Keep high test in it. Make sure it's not overheating.

 

[AngryMallard]

OK I attempted to retard the timing by rotating the distributor while it was knocking at idle and this did not stop the knock. I figured it couldn't hurt to leave the timing back though, so I didn't put the distributor back immediately. Any way, it started knocking in the beginning of my trip back to Tennessee so that's when I tried that. I kept it under 65 for about 200 miles and there was no knock until much later. Most of the east coast is flat though so after I got through the ATL it started knocking going up hills and then quit knocking going down them, which is a more common problem which usually means something is wrong with the fuel lines leading into the engine (it is my understanding that running lean sometimes causes knock). With about 70 miles to go I put the distributor back to where it was before and noticed no difference.

Another clue I got that it might be some sort of fuel issue is that on the way back I got almost 20 mpg (usually get maybe 18 highway) from Augusta to north of Chattanooga despite running the A/C almost the whole time and the 4x4 for a little bit during a huge storm. While the extra mileage was nice, it's not too great if the engine is knocking! So I'll go over some things this week and see how it goes.

 

[HKYStormFront]

i've found that around here (howdy neighbor, btw) that despite the stickers that say "Less than 10% Ethanol" that there's really a lot more than that. i found the only place i can get gas and not have knocking is the BP station at exit 27. my 4.0 was knocking really bad over the winter when the temps were down really low. i switched gas stations (from shell near the newer AnMed) and it went away immediately completely. i'm not saying you should drive 30 miles to get gas but i would suggest finding out if there are any stations in your area that have 0 ethanol, even if you have to pay a little bit more for it. :thumbsup:

 

[AngryMallard]

OK I changed the fuel filter this afternoon and drove it out on the interstate at around 75 mph for a couple miles and I did get it to start knocking again but it seemed to take longer. I really had to push it to get it to knock any, but the real test will be tomorrow morning on the way to work. I also tried to run it really hard getting out to the interstate just to try and get things moving and it seems to be running a little smoother but it still shouldn't be knocking any at speed on the interstate.

Tomorrow morning on the way to work I'm going to put some Lucas fuel system cleaner in to take care of any junk in the fuel lines and maybe that will fix it. Other ideas?

Also my truck is about to turn 140,000! Woo! (And to HKYStormFront, I just moved out to Nashville from Clemson. It was sad to leave the upstate but I have to go where the money is! Hopefully I'll be back in the area before too long, I miss South Carolina already.)

 

[HKYStormFront]

use seafoam, not lucas. you can find it at most parts stores. put it in then fill up the tank

 

[AngryMallard]

Any reason? I already bought the Lucas and it's sitting in the truck waiting on the fill-up tomorrow morning. A friend of mine recommended Lucas over Seafoam but said they were both good, so I'm just feeling out what all the opinions are on injector cleaner.

 

[HKYStormFront]

well for one, we used seafoam in school (auto mechanic here). we used BG 44K at work (dealership i used to work at) which was almost identical from what i could tell. lucas is probably ok, didn't realize you already had it. i'd get seafoam next time tho

 

[AngryMallard]

OK I put about 80 miles on my truck today on the interstate after putting the injector cleaner in and filling up the gas tank. Still knocking and running badly, so in the event that the whole tank runs through and it's still knocking, what's the next step?

I'm thinking I might have a whole cylinder out because it's running really rough too. Not sure exactly what would cause that, but I had a 300ZX for a little bit that was running like this and apparently one of the injectors was bad and caused the cylinder to be not working. I can't get to all the injectors though without removing the intake manifold it looks like though.

I'm also not ruling out that an electrical problem is causing a problem somewhere else. So I've been trying to make sure all the wires are connected. Anything in particular I should look for?

 

[HKYStormFront]

when's the last time you changed the spark plugs?

 

[AngryMallard]

I have never done them and don't know when they were done last. I'll add it to the list though! I've had the truck for a little over a year and got no maintenance history whatsoever. Actually the guy I bought it from thought it had a timing chain and it was 30k overdue when I replaced the belt. So yeah.

 

[HKYStormFront]

might just be a burn plug, start there. wires, dist cap, and rotor while you are at it

 

[AngryMallard]

OK Apparently Nissan never wanted anyone to actually change one of the spark plugs. It's buried back in there! Any way I changed the easy 3 tonight, I will probably wait to do the other three until the weekend when I don't need my truck to get to work 35 miles away.

The ones I pulled out though didn't look too bad. They're probably not that old. I know the wires were replaced when I bought the truck, they still look almost brand new minus the mud I added to them.

 

[AngryMallard]

I ran through the whole tank with Lucas in it, still making the knocking sounds. Talked to the guy at Advance for a while and he's not convinced it's spark knock, but since I can only get it to make the noises at 60+ miles per hour we can't listen to it in the parking lot. So...

1) Doesn't the Frontier have variable valve timing at high speeds? Could this be causing the valves to make a ticking noise on the highway only? The sound now reliably goes away when I slow down.

2) If it is the valves, how could I verify it? I.e. how do you tell the difference between the valve train being noisy and spark knock? I kind of doubt now it's spark knock because the spark plugs I pulled out had been in the truck at least 21,000 miles and looked brand new.

3) It might still be spark knock. I did the knock sensor relocation a while back and I'm thinking it's just not in the most ideal spot to tell if the truck is knocking or not. Should I go up and replace it right? Also I was thinking that if I took it to get diagnosed at the dealer they'd be all "this is why, fix it right, now we need $40" so I'd like to avoid that possibly by putting the KS in the right spot.

What does everyone think?

 

[HKYStormFront]

only the newer 2nd gen frontiers have VVT. and that's only at higher engine speeds, not vehicle speeds.

 

[AngryMallard]

OK here is the solution that the Nissan mechanic came up with after he drove my truck around.

Apparently the crankshaft pulley that drives the accessory belts is composed of a cylinder, then a rubber "harmonic balancer" around it, and the pulley cylinder on top of this piece of rubber. The rubber layer has apparently started to fall apart and the pulley is slipping around it and wobbling, causing the apparent clicking sound. The mechanic started the truck up and I could see it wobbling really badly. He also said that this could be the reason I initially saw it only at higher speeds, as the rubber fails it gets worse and worse. By the time I took it in to the shop it was doing it even at idle.

So I ordered the crankshaft pulley and paid the fee for them to look at it. I will be doing the work myself as long as I can find an impact wrench to get that huge bolt off. They're keeping my truck overnight because apparently the fuel sending unit got recalled and they are replacing that for free.

I was a little concerned with this dealer though because the price they quoted me for the repair included brand new accessory belts AND new idler pulley assemblies and idler pulleys for the two drive belts that use them. All three drive belts are pretty much brand new and one of the idler pulleys is brand new, I replaced it when I did my timing belt. So I think they were trying to line their pockets a little but it seemed like replacing the crankshaft pulley is a good solution to the problem.

 

[Critterman]

Most good mechanics will replace the idler pulleys when they replace the belts. It is insurance so you don't come back when the idler fails and you destroy a belt.

 

[AngryMallard]

Replaced the crankshaft pulley, the truck runs A LOT smoother, so that part did need to be replaced... however the initial problem is still there! The truck might not be as rough at interstate speeds any more but it's still making a horrible clicking from the engine bay.

I believe the crankshaft pulley's harmonic balancer went bad after whatever's causing the clicking sounds, and made it seem like the same problem. It got worse while the original problem stayed hidden behind it's whines and jitters.

The Nissan mechanic mentioned that I could also have a cracked exhaust manifold. I have read that this is a common problem among trucks a little newer than mine. Is this a possibility?

 

[HKYStormFront]

yea a cracked manifold can make it sound different

 

[AngryMallard]

Is visual inspection of the manifold the only way to check for that? It seems like there's some sort of heat shield that needs to be removed first. I wouldn't mind an excuse to put nismo headers on it though, if they even exist for my year...