[mastacox]

*UPDATE: Problem discovered, described below*

 

So I've been having a very annoying problem the past couple of weeks that I want to get tracked down with my 4Runner.  It's a 1998 Toyota 4Runner SR5 V-6 Supercharged w/ URD fuel kit for those that don't know.  Have been running premium gas with cheapo-octane booster every tank for about 2 months, and haven't gotten any kind of check engine lights since I started using the octane booster (which is quite rare for a supercharged/URD'd 3.4l).  I figure my tune is pretty well dialed in for the summer temps I've been seeing.

About a month ago, my engine started to display an intermittent power surging, where when I went into boost the engine would have good power, and then stumble/lose power for about half a second, and then regain it.  The "stumbles" were approximately equally spaced, and similar in length.  From what I could tell, it would only happen in boost, starting at about 1psi on the gauge.  This problem got progressively worse, until about 2 weeks ago going into boost the engine would just bog and make less power than in vacuum. 

Strange thing is, this cannot be attributed to a fuel delivery problem because the AFR stays completely normal at or around 14.7 in low boost, and 11.5-12.0 in the higher boost range when the oxygen sensor calibrator kicks in (but before open-loop, for those of you that know what I'm talking about).  Changing from 14.7:1 AFR to 12.0:1 AFR by pushing more boost did not make any difference in power or "hesitating."  I have a permanently-installed AFR gauge on my a-pillar, so I have been monitoring AFR ratios in my engine ever since I installed the URD kit almost a year ago now.  When the engine would "hesitate/bog" there was NO change in AFR reading.  So, I'm thinking it's ignition or timing related, maybe my spark plugs are fouled/over-gapped/something.

So I took the spark plugs out, and they were all uniformly dry, and all had a light red coating on them.  It was kind of like the dry white/gray coating you see on a normally used spark plug, except these had a slight red hue to them.  I'm thinking this may be due to the cheap octane booster I have been using for the last 1.5-2 months, which comes in a bright red plastic bottle.  They also had some carbon build-up which I attribute to my tuning the engine early on, when I would end up running too rich for extended periods of time.  The red coloration isn't from leaking coolant/anti-freeze (IMO) because I'm using Prestone Dex-Cool which is bright orange in color, and all of the spark plugs look exactly the same.

Anyway I cleaned all of the plugs with a brass wire brush, and re-gapped then to .034".  Yes, I am aware that .034" is lower than stock, but it is generally recommended from what I have heard to run .032"-.035" in forced induction applications of our engines.  After cleaning the plugs, I put them back in, and have run a can of Seafoam in the tank for the last 2 tanks; this seems to have significantly helped the problem, but not eliminated it.  On cold start-ups the engine will bog/hesitate under boost, and once warmed up the problem is "better" but not gone, I can feel some jumping/hesitating under boost and WOT doesn't seem to have the power it used to.

I'm thinking that my spark plugs are "fouled" and need to be replaced, and I need to do an agressive seafoam treatment to help get rid of any carbon build-up in my cylinders from the rich tuning process.  It sucks though, because I just changed my oil about 2 months ago (Amsoil W2000 0-W30).  At about $70 a pop, I don't want to change my oil again if I don't have to (the oil should be good for 1 year/15,000 miles)  I would also like to avoid fouling my oxygen sensor, since it has been working fine (I have confirmed that with my AFR gauge as well).

Anyway, this post has gotten way too long, but I'd like to hear a few more opinions to make sure I "seem" to be on the right track.  Lemme know. 

EDIT: Spark plugs are Denso Iridium IK-22's, which is why I tried "cleaning" them first.  Have to order them, they're not cheap, and they're less than a year old.

[mastacox]

I haven't used my scan tool to look at timing advance on the engine when the "problem" occurs, but I don't think it will show anything out of the ordinary... 

[oly884]

Well, I'd first off ditch the octane booster. In an 18.5 gallon tank with premium costing ~$0.30 per gallon more you're looking at $5.55 more per tank if empty. Small price to pay for the right octane.

As for the stumbling, what's the weather been like?

I say this because mornings my truck has noticeable difference in response. Afternoon, it bogs down quite a bit more.

[mastacox]

Well, I'd first off ditch the octane booster. In an 18.5 gallon tank with premium costing ~$0.30 per gallon more you're looking at $5.55 more per tank if empty. Small price to pay for the right octane.

As for the stumbling, what's the weather been like?

I say this because mornings my truck has noticeable difference in response. Afternoon, it bogs down quite a bit more.

You misunderstand, I run the octane booster WITH Premium gas (91 octane), giving me a "super-octane" tank.  It has seemsed to help with the check engine lights, but I think I need to dump it for a while and see if my stumbling symptoms subside.

Weather has been fairly normal, but more precipitation lately.  Don't think higher humidity would casue tehese symptoms...

[mastacox]

So I ended up hunting down the problem, but have not yet decided on a solution...

The spark plugs I use, Denso Iridium IK-22's, have a very annoying feature- a threaded on connection for the plug wires.  This little guy loves to come loose, and play hell with your ignition system.  I popped in some Toyota OEM plugs for a quick temporary fix, and the symptoms immediately disappeared; great power under boost and no misfires.  Have not yet had any problems with increased spark knock even though the OEM plugs are not "cooler."

So, I ordered some new IK-22's from URD, and I have to figure out a way to prevent the thread-on caps from coming loose before I install them.  Cranking it down with pliers does not work, since I have tried twice now and I'm more likely to damage the plug than get a reliable preload on the threads.  I'm not sure solder will work, because spark plugs get pretty hot (how hot is undefined however).  What I really need is a high-temperture electrically conductive Loctite compound, anyone have any ideas? 

[MTL_4runner]

Try using some high temp loctite, but only use it by the base of the stud at the top of the spark plug (ie screw the cap onto the stud and only put loctite on the last 3-4 threads down by the base and give it a good preload to make contact well).  Loctite makes several high temp, permanent threadlocker types (Loctite 272 is a good choice).  You don't need to worry so much about it being conductive because the threadlocker will just fill the gaps between where the metal threads touch.  The critical part will be the high temp aspect which keeps it from backing off the preload under high operating temps.

[mastacox]

I'm thinking I may try using a conductive silver-filled epoxy compound, which is used as a "cold solder."  The question that remains is how hot do spark plugs get?  There are silver filled epoxies rated at 257*F, or "metal-filled" rated up to 500*F.

JB Weld is a metal filled epoxy; but is it electrically conductive?

[MTL_4runner]

JB Weld is a metal filled epoxy; but is it electrically conductive?

No it is not but some JB weld would would also work well if applied similarly to how I explained above.

[mastacox]

Well I think I may try the high-temp JB weld route and ohm-meter the plugs before putting them in.

[MTL_4runner]

Well I think I may try the high-temp JB weld route and ohm-meter the plugs before putting them in.

Try one and do a before and after resistance reading on them with a DMM.  If you didn't add much resistance,  then go ahead and do the rest.  I'd also pull a plug after a few heat cycles and take another ohm reading just to be sure the heat isn't changing anything.  The 500F limit on the JB weld should be enough (the electrode tip on a plug is VERY hot, but the body shouldn't be above 500F).

I'll be curious to see how you make out on this fix and what kind of reading you get on them before and after with heat cycles involved.

[mt_goat]

So what did you end up doing Brian?

[mastacox]

Well, I JB Welded the plug caps.  I measured the electrical resistance before and after the JB weld and found no difference, so I put them in and haven't had any major problems again.  I still get a little misfire here and there that I attribute to either poor fuel atomization at higher flow rates, or possibly plug problems.

Denso Copper plugs are by far the best option to avoid all of this IMO; I'm just lazy and haven't gotten them yet.  Been too busy paying for rebuilding the ENTIRE rear axle and the supercharger.

[mt_goat]

Rebuilding the SCer already?  How many miles on it?  Did you just dab a little JB on the threads and screw the cap on?  I still haven't taken mine out to check them.

[mastacox]

Rebuilding the SCer already?  How many miles on it? 

Yeah, that was its own little adventure, basically the nose drive was leaking behind the pulley and you can't replace that seal yourself.  So I sent the SC in to Magnuson and had it rebuilt.  They ended up not having to replace the rotors, so it only cost about $350 for all new bearings, seals, and bypass valve which was a nice suprise.

Here's the thread on that little adventure-
Time to get the supercharger rebuilt...

And my problems with my rear axle I've been getting fixed for the last month or so:
Rear Axle Seal Finally Went Bad...
Rear Differential Whining

I really want my 4Runner back, it's been down with problems on and off for 2 out of the last 3 months I would say.  And now my '92 4runner's throwout bearing has seized and is sqeals like hell...    When it rains it pours 

Did you just dab a little JB on the threads and screw the cap on?  I still haven't taken mine out to check them.

Yup, just a little dap of JB weld, tightened the caps down, and let the JB weld set overnight before putting the plugs back in.  Seems to have worked as well as can be expected for a ghetto-fab solution.  It's a good idea to ohm your plugs before and after the JB weld, just to make sure you've still got a good electrical connection.

[mt_goat]

I may see if I can't crimp them a little bit.