I've had my '98 for several years now and have had a misfire on 3 occasions each time there was a really rough shaking from the engine. The first 2 times it was resolved with plugs or wires...no coil packs, timing, or injector work.

About 2 months ago I lost the water pump and had it replaced. I pushed it a bit to get to a shop, but kept it out of the red on the temp gauge. It seemed I lucked out, $1200 made it run like normal again.

Then last week and about 1000 miles later, my 3rd misfire. I was puttering around a neighborhood and suddenly it's shaking very rough, exactly like the other misfire events. I had a #2 misfire code.
Plug looked ok, but I swapped it with #4 anyway. I also moved the coil pack around. (And I ohm'd out the plug wire, same on all 3 wires.) The truck felt the same and initially I got a #2, #6, and random multiple misfire. I cleared the ecu and afterwards got only #2 misfire.

So I got a set of 6 injectors from Motorwest and put those in last night... I figured at 310k they're due to be replaced anyway. Still have a #2 misfire! but the strange thing is, the truck feels 90% smoother.

What's my next step? Have a shop check timing and compression?

 

Well, I've been reading around and thinking about next steps. Seems there are some thinfs I should do that have a low possibility of helping, but they're cheap:

1. Install the new fuel filter I already have (don't see how thst would be cylinder specific tho)
2. Run the seafoam I already have thru the PCV tube. I know there has to be a decent amount of carbon buildup and maybe it's just worse on that cyl.

Is it possible that a bad injector problem coupled with carbon buildup was a worse problem (rougher vibrations) and now that its just carbon buildup, I still have a misfire but it's vibrating less because that cylinder is kindof firing?

I read that the 2 plugs running on a coil pack are wired in series, methinks it's NOT the plug wire or coil pack, since I'm only getting a code on one cylinder. However, since it's easy, I should add some dielectric grease to the cable ends, also for free since I already have it.

 

Maybe take look at the crank sensor and the fragile rotor behind the crank that the crank sensor uses, make sure it has all its teeth, ohm the cam sensor aswell maybe. I'm sure you've cleaned the MAF by now, compression test numbers?.

 

Thanks!
I actually cleaned the MAF a few weeks ago, normal maintenance.
ugh, cam and especially the crankshaft sensor looks hard to get to ...worth a look tho...thanks!

 

I woke up to snow this morning. Not in a mood to drive across town to work on the truck....so I read up some more.

The last post in this thread about a #2 misfire said it was a slipped crank pulley and I started remembering that the crank pully bolt (part #s and torque specs there) is supposed to be replaced every morning when you brush your teeth...

So I looked at my receipt from the water pump replacement, they only purchased an autozone WP271K1C kit which doesn't include the bolt!

Quandry now...do I take it back to that shop? I have no other experience with them and only used them as the closest shop to where I lost the water pump. But they have 4.9 stars on google maps... so maybe they'll repair that problem for free.
Or do I take it to a shop I trust, because after all it might be a different misfire cause.
Or do I just replace the bolt and check timing alignment myself? Can I do that much without draining the radiator?

 

I wouldn't worry about the crank bolt, you don't need to replace it every time you remove in reality, good practice yes. The crank gear and harmonic balancer cannot slip unless you sheer the woodruff key, maybe take a look at it and check the 19mm crank bolt feels tight.

 

Update:
On the drive in to work I stopped by the shop that did my water pump work.
They wanted $175 for diagnostics.
The shop I prefer to do business with, says they'll do the leakdown test for an hour's labor, quite a bit less than the $175. And I'm sure they'll do a bit more as generally they throw in up to an hour's worth of dx work for free.

Hmm, intuition says the woodruff key would hold it.
The motor.com article (linked to in the previously linked post) cites experience saying the key doesn't matter:
and the preponderance of evidence from other threads says this is a likely problem especially since I just had work done on it.

So, even though they also said "we reuse crank bolts all the time and that shouldn't be a problem," I'm taking it in to the preferred shop tomorrow and if they want my money they'll find a way to replace it . And hopefully solve the misfire too.

 

Well there is 2 different types of crank bolts, 96-98 with the washer built into the bolt head 184ftlbs, and 99-02 has the washer separate 217ftlbs, again I see no reason to replace that bolt unless damaged in anyway shape or form, but good practice, the torque values should follow the bolt used if you upgrade or it's been updated to the newer style. That's why I suggested you check to see if it's tight as wrong torque will cause the bolt to loosen and take out the woodruff key, crank, and cause misfire problems that could lead to a complete engine crank replacement this is why everyone has there panties in a bunch over new bolts and torque spec, torque spec is all that matters, I'd be more worried they broke a few teeth on the crank rotor causing a missfire. Not every shop has a 250ftlb torque wrench either which has added to the occurancey of a lose crank pulley causing God knows how much damage before catching it.

 

Note to self: always check the dumb stuff.
I had ohm'd out the wires but had totally failed to INSPECT them ... and the #2 boot was cracked, arcing through the side.
Oh well, at least it was a cheap fix

 

Your findings confirm what I always thought of the 3.4....that the engine is bulletproof and largely trouble-free.. You said you recently replace the plugs and wires.....That includes the boot I imagine? Do not get aftermarket wires and boots....it will bite you. Get them online for 20~30% less than the local walk-in dealer. I did and I am so happy I stayed genuine factory.👍

ZUK

 

Yeah, the wires were replaced in 2015 at 270k, now I have only 314k on it. I'm not sure what brand went on then...but they were gray.
I didn't insist on NKG (is that OEM?) this time either, I guess I was too embarrassed at having missed that to think right. They're Import Direct...what's that, OOO'Reilly store brand?
We'll see how long these last.

 

OEM wires are Sumitomo, they are date stamped, and fit much nicer than the NGK wires. I just changed my original 1999 Sumitomo wires for new Sumitomo's and Denso plugs, no change, runs perfect still like always.

 

Thanks for the correction there on Sumitomo wires. Where'd you pick yours up?
I see , it's hard to be sure what brand you'd get but reviews are saying they got Sumitomo.

And what about the COP boots, any experience replacing those? I can't seem to find them without the coils, except

DENSO 6716248

DENSO 6716248

which...may be OE since the OE coils were Denso?

 

I went to the dealer for my wires. Denso is the OE manufacturer for the coils and coil boots.