Misfire, Shuddering/shaking, lopey idle... (1 Viewer)

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BlueCruiser84

BlueCruiser84

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I have noticed a slight miss in my 80 over the past week or so. Start it up, little miss at normal idle that got progressively worse over the last week, but still drove fine.

Started it the other day and it had a really low idle, big miss, and threatened to die on me. Take off down the road and the thing is shuddering. It feels like I would imagine and unevenly placed load of towels would feel like in the spin cycle of a washing machine. Gets less noticeable with higher speed/less load on the engine. Basically the thing is missing/misfiring to the point where it is scary to drive.

Pulled the plugs and they look good/the same with the exception of 4 and 6 (pictured below). These plugs probably have 6,000 miles on them.

The only thing out of the ordinary that I have done recently is to put a can of seafoam in the tank. That was right before it got really bad. Maybe it freed up some junk that is now clogging and injector or two.

Thoughts on these plugs? I am hoping that is not the "steam cleaned" look on the number 6 plug.

***UPDATE ON THINGS I HAVE REPLACED*** All Toyota OEM parts. Same problem exists.

-New Sparkplugs, wires, cap, rotor
-New Valve cover gasket and spark plug gaskets
-New PCV valve and hose
-Repaired wiring harness at EGR and rewrapped
-Repaired wiring at glovebox
-New EFI main relay
-New (used) AFM
-New (used) Igniter
-Cleaned/rebuilt injectors
-New Fuel pressure regulator
-New fuel pump relay
-New fuel pump sock
-New fuel filter
-New ECT Sensor
-New intake manifold gasket
-New fusible links
number4_2.jpg
Number6_1.jpg
 
Last edited:
and one more of number 6.
Number6_2.jpg
 
Sooo pulled plug wires with engine running and found the number 6 cylinder is the one not firing. It is getting spark at the distributor, the wire checked ok (installed circa 2001 according to the date on the wire), and the plug didn't smell fuel fouled, but was wet... I am becoming more and more leary of the headgasket.

I have not put that many miles on this ole girl since I bought her. I think the PO put some bars stop leak in the radiator as a temp fix, but I can't confirm that. The radiator leaked and so did myriad other hoses. I fixed the hoses and drained and refilled the coolant. The coolant level dropped for a while which I attributed to air in the system and the leaking radiator, but I kept and eye on it and never let the overflow go dry.

I have not had any signs of a bad head gasket. No condensation in the oil, no white smoke, no exhaust smell. What other things should I be checking before I check further into the headgasket?
 
gabepari said:
Pressure test the cooling system. Compression and leak down test. Should help to confirm or rule out HG?

Gabe
Click to expand...


I know I need to do one or both of those to verify the headgasket, but what other obvious things should I check for the misfire?

Someone, I guess a PO has already rewrapped the wiring harness by the EGR with heat shield tape, so I am guessing that issue has been addressed. Could a clogged injector cause something like this?
 
Did you put in a new spark plug in #6 after pulling it? Cracked plug? # 6 wire is hard to get a hold of and someone else may have worked over the wire boot, causing a wire problem before you got the truck. Ten year old wires on a cruiser is not that bad, but they are ten years old. I would bite the bullet and get a set of Toyota wires anyway along with cap and rotor to be sure it is up to date.

Pull the cap and look at the under side of it. If a cap has cracked and the spark is shorting out in there, you will see a black line from the post down the inside of the plastic to the edge where the cap meets the edge of the distributer body. It will look like a very small termite trail of black carbon.

To me, the #6 only looks like it is not firing. It does not look at all like a steam cleaned plug. Also, it doesn't have black carbon oily goop all around the base of the electrode indicating oil leakage in the cylinder.

A clogged injector would have to have a really big piece of crap stuck in the top of the injector itself. There is a screen on the injector where the gas comes into the body of it. A piece of crap would first have to get by the fuel filter, then completely cover up the intake on the injector body.

I would start easy with the maintenance stuff first, then move on from there.
 
elhombre said:
Did you put in a new spark plug in #6 after pulling it? Cracked plug? # 6 wire is hard to get a hold of and someone else may have worked over the wire boot, causing a wire problem before you got the truck. Ten year old wires on a cruiser is not that bad, but they are ten years old. I would bite the bullet and get a set of Toyota wires anyway along with cap and rotor to be sure it is up to date.

Pull the cap and look at the under side of it. If a cap has cracked and the spark is shorting out in there, you will see a black line from the post down the inside of the plastic to the edge where the cap meets the edge of the distributer body. It will look like a very small termite trail of black carbon.

To me, the #6 only looks like it is not firing. It does not look at all like a steam cleaned plug. Also, it doesn't have black carbon oily goop all around the base of the electrode indicating oil leakage in the cylinder.

A clogged injector would have to have a really big piece of crap stuck in the top of the injector itself. There is a screen on the injector where the gas comes into the body of it. A piece of crap would first have to get by the fuel filter, then completely cover up the intake on the injector body.

I would start easy with the maintenance stuff first, then move on from there.
Click to expand...


Wires were going to be my first purchase. Come to think of it I don't think I tested the whether the plug was firing. I could see a good spark arcing out of the distributor to the wire when I pulled the wire off to check whether or not that cylinder was the one firing, but I never looked at the plug itself. Worth a check when I get home.


I didn't think the plug looked steam cleaned either, but it also didn't reak of fuel and it was a bit wet, which got me nervous.

I need to pull the plenum and get to testing/cleaning the injectors to rule them out.

Thanks for the input. i'll post up later with feedback.
 
Check the plug closely where the porcelain insulator meets the metal base. I had one with a nearly invisible hairline crack which was causing an intermittent misfire.
 
I will check the plug again, but this is not an intermittent misfire. It is a very noticeable very repetitive misfire. I will also swap a different plug to that cylinder.
 
Update:

I put a new plug in the #6 boot and laid it across the rubber air intake hose. When I started her up it was throwing an arc fom the bottom of the spark plug boot to the rubber hose. Is this normal? In my head I am picturing that same arc going to the sparkplug tube when the boot is in its proper position.

I pulled another wire, off the number two cylinder, and stuck a new spark plug in and it was not throwing an arc to anything until the spark plug body touched it.

I feel like I might be on to something...
 
GOOD! haha. Better than a new headgasket. I've never pulled a spark plug and tested it that way so I wasn't sure. Thanks.
 
Hopefully the new wires will get you straight
Sounds like the wire insulation and the boot have been compromised
 
I'll report back when I get the new wires on and she purrs like a kitten.
 
Welp I put in new Toyota wires, cap, rotor, PCV valve, and plugs. NO CHANGE!

It runs ok at WOT, but it still has the low end and midrange miss. I drove it around last night with lots of skinny pedal and it never got hot, I never smelled anything except for a rich exhaust, and never saw any white smoke. I saw lots of grey/dark smoke....

I'm starting to suspect injectors. Looks like the Throttle body will be coming off. I'll report back.

Any other ideas?
 
It may be worth taking a closer look at the wiring harness, even though you said the PO re-wrapped it, there still could be damage that is causing you mysterious misfire.
 
94SRUNNER said:
It may be worth taking a closer look at the wiring harness, even though you said the PO re-wrapped it, there still could be damage that is causing you mysterious misfire.
Click to expand...

x2. Check the entire loom that travels in parallel with egr; to/from both directions (firewall and injectors' wires/connectors).
 
Re: all

I actually mistook the original factory wrapping for a rewrap of the harness. I wasn't aware that it came wrapped in that silvery heat wrap from the factory.

I dug into the harness behind the glove box and if I am reading the wiring diagram right, I THINK I found one injector wire that was severed and one that was close. I have no idea how that would just happen or how the vehicle would run at all, but that is what I found. Both wires were in the large plug in the ECU. The severed one was white with a red stripe and the close to severed one was white with a blue stripe. I repaired both wires and it seems to idle a bit smoother, but still has a very noticeable miss.

I put a long screwdriver on the number 6 injector and I was not getting a crisp "click, click, click" out of it like the 1 and 2 injectors.

I'm thinking the next step is to look into the wiring harness behind the EGR. It is still factory wrapped but it is laying up against the EGR pipe.
 
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