Cold start brief random misfire and I'm running out of stuff to try!

Stick Figure

Stick Figure

New member
So sometime towards the end of last year my truck developed an occasional random misfire on cold start. Usually last for about 3 seconds or less, every 50th time or so would be bad enough to throw a random misfire code, but always only that. As it started to happen more frequently I was hoping it would just fail a component and make my life easy, but no luck. With 264k on it I decided to start throwing some parts at it rather than waste too much time trying to diagnose a short not repeatable problem. So here's where we are now:

New OEM Toyota Plug wires:
New NGK plugs (iridium--not the right ones) Replacing the ones that lasted 2 years prior.
Used OEM Toyota Coils from a JDM Engine.
Used OEM Toyota Injectors from the same JDM Engine
New OEM Toyota Injector Seals

I have also tried a used Igniter but it didn't seem to effect the issue. Valve lash was checked when I was swapping injectors last time and while they were on the loose side of specs, they were within spec.

I have my original injectors back from Witch Hunter after a cleaning (and by the before vs after specs they didn't really need it). So they will go back in soon.

I think I may need to finally move the 4Runner up in the project list and do some diagnostics. Right now I am thinking leak down when cold, and maybe keep an eye on fuel pressure on these cold start. Anyone else want to throw their 2 cents in as to what it might be?
 
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Stick Figure said:
So sometime towards the end of last year my truck developed an occasional random misfire on cold start. Usually last for about 3 seconds or less, every 50th time or so would be bad enough to throw a random misfire code, but always only that. As it started to happen more frequently I was hoping it would just fail a component and make my life easy, but no luck. With 264k on it I decided to start throwing some parts at it rather than waste too much time trying to diagnose a short not repeatable problem. So here's where we are now:

New OEM Toyota Plug wires:
New NGK plugs (iridium--not the right ones) Replacing the ones that lasted 2 years prior.
Used OEM Toyota Coils from a JDM Engine.
Used OEM Toyota Injectors from the same JDM Engine
New OEM Toyota Injector Seals

I have also tried a used Igniter but it didn't seem to effect the issue. Valve lash was checked when I was swapping injectors last time and while they were on the loose side of specs, they were within spec.

I have my original injectors back from Witch Hunter after a cleaning (and by the before vs after specs they didn't really need it). So they will go back in soon.

I think I may need to finally move the 4Runner up in the project list and do some diagnostics. Right now I am thinking leak down when cold, and maybe keep an eye on fuel pressure on these cold start. Anyone else want to throw their 2 cents in as to what it might be?
Click to expand...

This is - without exaggeration - EXACTLY what I have been dealing with. In addition to your problems I was having quite a bit of smoke out of the exhaust on cold start. Do you not have this?

New plugs, new wires, cleaned and flow matched injectors, fixed every little tiny vacuum leak, everything. Nothing helped.

I THOUGHT I was losing coolant (lost a bunch when removing the throttle body hoses and I guess didn't replace enough) so I thought it was time for a compression check.

My results were...
5- 185 // 6- 150

3- 175 // 4- 180

1- 190 // 2- 190

So I feared the worst, and without doing a wet check (stupid) I tested my coolant for exhaust gases. Thankfully there were none. Headgasket was fine.

I THEN did a wet check on that cylinder and it was over 200 which apparently points at an issue with the rings.

So then I used a non-conventional treatment recommended by a very intelligent friend of mine...

I put 2 tablespoons of Marvel Mystery Oil into cylinder 6 and let it sit for 2 hours. After 2 hours I cranked the engine by hand 1 full rotation and let it sit 2 more hours. After 2 hours I crannked it again 1 full rotation (by hand) and added 2 more tablespoons to the cylinder and went to bed, letting it sit overnight.

When I woke up I put a towel over the spark plug tube and cranked the engine a few times with the key to try and get as much of the mystery oil out as possible. It took quite a little bit of patience to get enough out to feel comfortable starting it.

Re-installed the plug, and started the engine and let it warm up to burn off any remaining mystery oil.

After that I checked the compression again and... drum roll... 175 psi!

The cold start issue has not happened since.
 
In addition to Alex's input about his piston soak I would also think about the ECU. Fellow member Brian SD has been chasing a ghost misfire for some time as well. I have seen 6 ECUs replaced on Civics and Accords for misfires due to bad capacitors. Without having seen a 3rd gen ECU for myself I won't say much more.

I hope your are still taking some great pics and have the zeal for tool buying......
 
A.Wilson013 said:
This is - without exaggeration - EXACTLY what I have been dealing with. In addition to your problems I was having quite a bit of smoke out of the exhaust on cold start. Do you not have this?

New plugs, new wires, cleaned and flow matched injectors, fixed every little tiny vacuum leak, everything. Nothing helped.

I THOUGHT I was losing coolant (lost a bunch when removing the throttle body hoses and I guess didn't replace enough) so I thought it was time for a compression check.

My results were...
5- 185 // 6- 150

3- 175 // 4- 180

1- 190 // 2- 190

So I feared the worst, and without doing a wet check (stupid) I tested my coolant for exhaust gases. Thankfully there were none. Headgasket was fine.

I THEN did a wet check on that cylinder and it was over 200 which apparently points at an issue with the rings.

So then I used a non-conventional treatment recommended by a very intelligent friend of mine...

I put 2 tablespoons of Marvel Mystery Oil into cylinder 6 and let it sit for 2 hours. After 2 hours I cranked the engine by hand 1 full rotation and let it sit 2 more hours. After 2 hours I crannked it again 1 full rotation (by hand) and added 2 more tablespoons to the cylinder and went to bed, letting it sit overnight.

When I woke up I put a towel over the spark plug tube and cranked the engine a few times with the key to try and get as much of the mystery oil out as possible. It took quite a little bit of patience to get enough out to feel comfortable starting it.

Re-installed the plug, and started the engine and let it warm up to burn off any remaining mystery oil.

After that I checked the compression again and... drum roll... 175 psi!

The cold start issue has not happened since.
Click to expand...

Absolutely not what I wanted to hear, but thanks for chiming in with your experience. I guess I will find out sooner or later. I'm going to try and find some time in near future to do a leak down, and compression test. The "good news" is that my spare injectors and coils came from the JDM engine I picked up (just in case) so if it does turn out to be ring related I should only be a weekend away from a fix one way or another.
 
LittleCaesar said:
In addition to Alex's input about his piston soak I would also think about the ECU. Fellow member Brian SD has been chasing a ghost misfire for some time as well. I have seen 6 ECUs replaced on Civics and Accords for misfires due to bad capacitors. Without having seen a 3rd gen ECU for myself I won't say much more.

I hope your are still taking some great pics and have the zeal for tool buying......
Click to expand...

I used to see this a lot with the Mitsubishi cars. Caps would leak and take out the ECU. It is certainly worth a look although I have/had a lot of older Toyota's and never seen the issue on the ECU. My experience is that the ECU also has a quicker death than my occasional random issue that I have had. Still worth a look though if the bottom end checks out.

Still snapping a lot of pics, but I've been doing more on the car front recently. I sold my MR2 Spyder and was picking up an engine for my Supra when I decided to buy a 3SGTE for my AW11 MR2 while I was there with the trailer. I then decided rather than just simply sell off the engine out of my my MR2 that it made sense to buy a car to flip. This turned into a MUCH longer process than I thought since the new MR2 had been sitting for years. As if this wasn't enough I took a chance to pick up a mostly restored AE86 Corolla. Oh yeah and I still have the GS430 as well. Its been crazy around the shop recently!
 
Yep. I'm still getting ghost idle CELs that hit once, usually doesn't flash and have no other symptoms.

Here is my latest. All happened at a stop light, usually once per day. Injector #2 maybe? I've changed out almost everything spark related with replacement OEM. I haven't touched the injectors.

I just went on a multi state trip and 99.99999% of time the truck ran fine.


03/20/16, 8am
CEL Was flashing
300,302, 303
Had been running less than 10 mins
Shut off truck, started up again, not flashing
Scan gauge was blank, like not connecting at this time.

3/26, 4pm
CEL
300, 301, 302, 303
Not flashing

3/31 Friday
CEL
302, single code

4/2 Saturday
CEL
239,435
302, single code

4/4 Monday
CEL solid
239,566
300, 301, 302

4/6 Wednesday
CEL solid
239,605
300, 301, 302, 303

4/8 Friday
CEL solid
239,863
302 single code
Click to expand...
 
Last edited:
BrianSD_42 said:
Yep. I'm still getting ghost idle CELs that hit once, usually doesn't flash and have no other symptoms.

Here is my latest. All happened at a stop light, usually once per day. Injector #2 maybe? I've changed out almost everything spark related with replacement OEM. I haven't touched the injectors.

I just went on a multi state trip and 99.99999% of time the truck ran fine.
Click to expand...


mine has only happened at first start, never once it starts to warm. And same with us on our X-Mas trip. I actually thought the plug wires fixed it since it didn't happen again on the entire trip (about 5000 miles).
 
Had some time to do a compression test today. Stone cold hasn't been driven in a couple days numbers:

1) 200psi
2) 200psi
3) 170, 180psi
4) 190psi
5) 183psi
6)190psi

Funny thing is that it was the #4 plug that showed signs of fouling. Since I've seen much worse cold engine results on engines that had no signs of misfire I think my next step is going to be to tear down the front and swap out/inspect the cam and crank pick ups. Either that or I need to borrow a scope from work and start doing some testing. Maybe the ECU has a chance of being the culprit after all.
 
Those are healthy numbers even for a cold engine.

How bad was fouled? Like lawnmower soot crusted? It sounds like a small leak from the injector.

I had a coil failing on me earlier this year, tested numbers good but still managed to put a hole in my spark plug boot causing a misfire on #4.

ECT original?
 
LittleCaesar said:
Those are healthy numbers even for a cold engine.

How bad was fouled? Like lawnmower soot crusted? It sounds like a small leak from the injector.

I had a coil failing on me earlier this year, tested numbers good but still managed to put a hole in my spark plug boot causing a misfire on #4.

ECT original?
Click to expand...

I'd go so far as to say those are very VERY good numbers for a cold engine.

Aren't compression levels typically lower when cold?

As for leaking capacitors... I had to replace the ECU on my LS400 due to this issue. It's VERY common on those cars. The failing ECU was weird. The car would run just fine without the MAF plugged in. Would rev to red line, but if you put it in drive it'd sputter and die. In reverse it ran like nothing was wrong.
 
Andddddd mine is back.

I'm rooting for you to figure it out [MENTION=28064]Stick Figure[/MENTION] . I tried what I was able, but I am out of skill/ideas.

For what it's worth I have thrown the random misfire code twice while it was happening. Once about 2 months ago, and once about an hour ago.
 
Maybe the ECU has a chance of being the culprit after all
Click to expand...

I put in a new used ECU two weeks ago. It made no difference.

Cost: $50 on EBAY. You will want to call the dealer and give them your VIN so they can tell you the two possible ECU part numbers for your exact 4Runner. Then use those numbers for the part on ebay. I believe the parts sellers listing a "H number" are the most legitimate. I paid local mechanic $40 to swap it out but you can do it yourself I'm sure.
 
Kinda left this thread hanging.

I swapped out the CAM and CRANK sensors with no change.

I re-installed the OEM injectors freshly cleaned and tested by Which Hunter. I finally removed my Teflon intake gasket in favor of factory Toyota and it seemed like it was fixed for a while. but nope it came back.

I've just been living with it and not driving it as much.

The most recent update is I have now started to notice the gurgling water behind the dash when its cold (heater control is set to hot). I haven't confirmed with a leak down, but I'm not seeing any external leaking either. Guessing I have a head gasket issue. Obviously I need to confirm before making any decisions.

At 266k it wouldn't be worth just doing the gaskets, so do I swap in the spare 5VZFE I have here, or do I go big and swap in the drive train out of the GS430 my g/f recently totaled?

I was also thinking that 3UZ would go well in a 60 series Land Cruiser, so we'll see.
 
If you have a leak down tester I would take some readings and go from there. Do you lose coolant?

I'd vote for the 430 swap just for the more HP and the nice pics that would follow the swap.

Keep the thread rolling.
 
LittleCaesar said:
If you have a leak down tester I would take some readings and go from there. Do you lose coolant?

I'd vote for the 430 swap just for the more HP and the nice pics that would follow the swap.

Keep the thread rolling.
Click to expand...


I do have a leak down tester but I don't think there is a need. Coolant was low and over the course of about 20 minutes it continued to have those tiny little bubbles that makes me reminiscent of the 7M in my Supra back in the day. lol

After doing some reading on others V8 Swaps, I don't think its going to happen. While I have a complete donor car, the wiring would be a nightmare, and I don't want to down the truck long enough to make it all work. I sold my GS430 to the g/f when she wrecked hers, so my only running cars are the AW11 MR2 that I've spent that last few months resurrecting from dead in a field for 7 years status and my Corolla. The AE86 is just too clean to risk out on a daily basis. So basically the truck sits there as a back up right now until I prep the spare 3.4 to be ready to go in over a weekend.
 
I noticed you indicated that you had replaced "almost" everything electrical/spark related.

We chased a random misfire for a while and it finally turned out to the the plug boots connected to the coil packs. We had replaced plugs and wires but those 3 boots did not come with the wire kit. We finally noticed some carbon tracking on the insulator of the plug and replaced those boots as well.

Thought I would pass along.
 
The only two things that I have ever known to cause bubbles in the coolant is a bad cap or the head gasket.

I guess you don't have a coolant pressure tester or a block tester kit then.

Good luck with installing the new engine.
 
mmendelscfi said:
I noticed you indicated that you had replaced "almost" everything electrical/spark related.

We chased a random misfire for a while and it finally turned out to the the plug boots connected to the coil packs. We had replaced plugs and wires but those 3 boots did not come with the wire kit. We finally noticed some carbon tracking on the insulator of the plug and replaced those boots as well.

Thought I would pass along.
Click to expand...

I actually tried this on the original coils. They were super dried and cracked. I ended up just grabbing a set from a local auto parts store since I was in a hurry when I did it. Good thing to mention in the thread though for anyone searching for answers in the future.
 
LittleCaesar said:
The only two things that I have ever known to cause bubbles in the coolant is a bad cap or the head gasket.

I guess you don't have a coolant pressure tester or a block tester kit then.

Good luck with installing the new engine.
Click to expand...

Thanks, I've got a few parts to source first so I'm thinking Memorial weekend will be the weekend. YAY more parts from Lithia lol
 
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