I have a 1995 Ex, 2.2L.... I'm hoping to figure out the cause of two issues which may or may not be related, that is a burnt rubber smell (seems like it might be coming from under the hood) and smoke (or extra vapor--it's 22 degrees F outside, can't be sure, it's white not black, blue or otherwise) coming out of the exhaust.

I know there are *countless* threads on various burning smells, but I'm hoping to narrow this down based on my situation: some of you may have seen my other threads--the throttle was stuck open on my car (due to mouse in throttle body being trapped in butterfly valve) while I was driving. I braked hard but steadily to a stop, smoking the brakes. There was also this burning smell after I stopped, which I thought came from the brake pads.

Here's the recent rundown, and if you can give me hints as to where to look, that would help immensely.

1) Braked hard, smoked brake pads (I mentioned it, but want it in list form of relevant things).
2) Removed & replaced air filter, removed and cleaned throttle body (replaced gasket), disconnected and reconnected vacuum lines, coolant lines, electrical connectors...
3) Removed and cleaned intake plenum, removed mouse, replaced gasket, disconnected and reconnected various electrical connectors, coolant lines, vacuum lines, the throttle valve cable and the accelerator and cruise control cables.
4) Drained coolant out of radiator (couldn't drain out of engine block where car was) to perform above tasks,
5) Filled radiator and bled coolant system after said tasks... car ran for 20 minutes or so. I revved engine a bit at first to help it along, not high rpms--THERE WAS NO SMELL.
6) May be worth mentioning that I lost my footing a little and spilled some antifreeze in the radiator area. I have no idea what it smells like if it burns....
7) I did disable the airbag before starting all this, disconnected the radio, and some other things in the way since I decided to see why the heater control would spring back--guess it's a good thing since it needs to work for bleeding the cooling system... I don't THINK the smell is electrical, but it would smell like rubber if something burned so I'm mentioning it.
8) The smell DOES seem to be coming from under the hood, but if when I stopped hard, could have I burned some boots, and the scent of that or the brakes is getting into the engine bay? Roasted the transmission (shifts fine, currently)? Damaged the engine??? <<<Very concerned about that. Or just coolant?

LASTLY, the burning smell TODAY (as opposed to the day I braked, not sure if it's the same issue!), occurred when I was trying to move my car from the icy spot in the yard to the garage (so I can replace brake pads and see what else I need to do to make this car roadworthy again).... in park, if I revved, no smell.

In DRIVE, when I revved to get my car off the icy and only the gravel that I put down in the tire path after digging snow and ice from around the wheels.... THAT's when the smell occurred, and that's also when it appeared through my rearview mirror that the car was putting out a lot of exhaust. I noticed it when the RPMS were around 3000, when I pressed just a little more on the gas after feeling the car gain traction on the ground. I keep my foot pressed down long enough--not floored, just about halfway, not close to redline---for the front tires to get onto the road (about 3-4 seconds) then eased up as the car got onto the road... pulled into the garage and parked it.

I'm concerned about particular damage that can occur when braking hard while the throttle is open. Turns out the throttle was held open about a 1/4 of the way, no more, but the mouse.

SORRY THIS IS LONG, but really want to hone in on the troubleshooting, especially hear on what to look for on more serious signs that the car isn't worth fixing. Thank you for all who read this!!

 

First, if the pads are mechanically fine(compound not cracked, backing plates still straight and flat), leave them alone. If anything you may have the best bed-in ever done on that car. The car will more than likely brake better now than before the incident. So leave the pads, if they are physically fine, alone.

When antifreeze leaks/burns it smells sweet. Just a bit more potent than the normal anti-freeze smell when pouring in fresh.

If you have electrical components unhooked verify they wiring harness is not chaffed(insulation burning smells like rubber), or an open terminal is not grounding out. Secure the loose harness/connections with quick-ties/tape/string/whatever. When you brake a wire may shunt into a grounding position and cause a high resistance short. Not enough to blow a fuse but enough to cause burning.

If during the braking/uncontrolled acceleration problem, the PCV system may have ingested more oil than usual. There may still be oil lingering in the PCV valve/hose/intake manifold port. Verify these systems including the fresh air feed on the corner off the valve/cam cover are not full of oil. This would account for the excessive burning in the exhaust.

If the engine bay is dirty, clean it with a 'green' cleaner (409/Simple Green/Green Kleen/etc), spray it on and hose off. This will help you pinpoint any possible oil leaks.

Areas that may be hard to see/find oil leaks.
Under the distributor, oil from the O-ring seal of the distributor housing, or the internal oil seal may leak, this will drain down ontop of the wire harness or bellhousing, which can then blow back onto the exhaust/catalyst and cause stink/smoke from the engine bay.
VTEC solenoid/switch. I had a leak that was pretty sneaky to located. O-ring gasket on the VTEC oil pressure switch would leak, but only leak at higher rpms. Wash off, idle the car, nothing. Go for a drive, oil all over the place, but not much on the switch itself.
Valve/cam cover gasket. This usually only leaks at the 'corners' where the cover arcs over, gasket is usually reusable and just need sealant at the 'corners' where the cover goes over the cam. Make sure the surface is clean, put a dap at the corners and reinstall cover. These can be hard to see as the leak usually drizzles back and down, either under the distributor/onto the VTEC solenoid, or back behind the timing belt cover, usually can tell on that side by looking at the step above the WP, if it is covered in oil usually the cover is leaking.
PCV valve/grommets/hoses.
Pull the spark plug wires out of the spark plug tubes, look for oil. This would cause a minor internal oil leak, oil burning smell, and slightly smokey exhaust. Blue smoke is usually only seen with heavy oil consumption due to combustion. Bad oil control rings(pistons/cylinder) or wasted valve seals.

 

I started the car up with the hood open--sounds fine, no smells, though the car seems to be idling fast. Maybe I changed something when removing the plenum... wondering if the fast idle is waiting for the ECU to reset, but come to think of it, it was idling a little fast before (1000-1200rpm), but more so now (@1500rpm)

The valve cover gasket DOES need to be replaced--oil around the seam and above where the 3rd spark plug is... ALSO noticed oil around the seam of the alternator and seemed to be a faint burnt rubber smell coming from that area. Just read that oil on alternator can be from valve cover gasket leak? But doesn't look like it's flung up there... just seems to because around the seam of it. The oil was changed less than 1000 miles ago and the level is full. The color is translucent amber--darker than brand new but not cloudy or cruddy.

Mad-Mike: I find that VTEC Oil Valve o-ring leak interesting because I noticed the smell only at higher rpms trying to pull onto road. Sounds like a pain to check. From what I understand, the PCV valve is easy to check and replace, so I'll do that first

Not sure if this is relevant: when I drained the coolant out of the radiator, it looked normal. But when I was bleeding the coolant system, when the coolant was bubbling in the funnel, there was a slight cloudiness to what was bubbling up but it looked perfectly fine when I shut the car off. Hoping this isn't an early sign of headgasket failure (how can one be sure? just take it to the dealer?) and is just caused by the cold and swirling of maybe two antifreeze solutions mixing. I wasn't concerned about it when I saw it... but reading online today of people with smoky exhaust and burnt rubber odors really causes me concern.

 

There should only be the fast idle from the FITV there isnt any learning to do for the idle. If the idle, when warm, is still high and everything else is working fine(FITV/IAC) check for vacuum leaks. Use throttle body cleaner around all major joints and vacuum lines. Hopefully you will be able to locate a leak.
Jumper the diagnostic connector(two wire blue connector under the glove box door) and verify base timing is correct. Verify that the throttle body has not been tampered with. There are two ways that the idle speed is adjusted the incorrect way(throttle blade screw, it should have paint on it, if the paint is missing or broken it has most likely been tampered) and the correct way(attach test tach to test tach port(blue with white speckles with a rubber cover located by the fuse box) disconnect IACV warm engine up til fan comes on(may need to help hold throttle open) idle should be 550 in Neutral(Park) +/- 50rpm with no assistance, adjust idle speed at the horizontal screw above the intake tube
)
That may be power steering fluid. On Hondas it is clear when new, it does become brown/amber in color when older. Common leakage comes from the shaft oil seal. It dribbles down from under the PS pump and onto the ALT. If you find the underside of the PS pump gunked up then it is most likely the PS pump seal. PS fluid can smell like burnt rubber when it gets hot.

I would recommend just replacing all the seals for the VTEC solenoid and switch. Not too hard to do, I found using an offset brake bleeder wrench(10mm) made removal of the VTEC solenoid base from the head pretty easy. Switch is a bit tricky, I used a deep impact socket to remove it on my '95.

The engine does not need to be on when bleeding the system and best it should not be. Heater core valve open, open the bleeder valve and fill the system. When a steady stream of coolant comes out of the bleeder close it and you should be done. Bleeder valve is there because the air in the system would become trapped behind the thermostat. Air would not heat up the thermostat enough to open it and purge, by the time it did the engine would overheat/warp the head.

 

Thanks for the tip, Mad-Mike--given that I just disconnected all these hoses, that seems like the place to start. I recall seeing yellow paint on the screw on the TB and wondering why it was painted.

BTW... I was thinking I should change the spark plugs (given I have to replace the valve cover gasket and the possibility of oil being on them) and looked up iridium vs platinum--the only spark plugs I've ever changed were for the lawn mower, so I didn't know there were all these options. I found a post you made inquiring about this in 2008 on Bob id the Oil Guy (unless there's another Mike who is Mad out there!) and a response in this forum you made in 2014. I'm not ready to drop $50+ on plugs right now... money's a bit tight (which is my usual reason/excuse for DIY car repair), but wanted to know if today, years later, you think the NKG Iridium IX is a decent choice to go with.

I'm going to place the order for the valve cover gasket set, engine paint & primer (the original paint is flaking off--so might as well), spark plugs, PCV (it's cheap, so I'll just replace it), and the seals you mentioned when I get up.

Oh, I should order that o-ring for the IACV as well and clean it out also (which I would have liked to have done when the throttle body and plenum were off, but I didn't have the gasket and needed to move the car out of the yard), but if it's clogged, it would idle slower, not faster, wouldn't it?

I want to thank you for being so detailed in your explanations, because I like to see the logic behind what I must do.

 

Yup, if the hoses are really old or not factory they ends can become gnarly and simply clipping off that first 1/4-1/2" will clean up the end for a better seal if they are deformed/cracked. Set from the factory and the throttle blade screw should never be touched. Adjust idle speed at the air bypass screw to change idle speed.
I am an iridium fan boi, but I prefer Denso Iridium TT plugs. Our cars don't use a waste spark system so the Plats are not really worth it IMO. Go to Rockauto, the plugs should cost less than $30 shipped.
Dunno who the other Mackeral could be, plenty who want to be like Mike.
If it was merely the filter of the IACV that was clogged, yes. But if the IACV, or FITV, had been removed and reinstalled with the old gasket/filter then there could be a an air leak(false air) which would then allow the engine to rev higher. As for cleaning the IACV, only clean the filter. If the internal part of the IACV looks sooty/carbon fouled be VERY careful when using a TB cleaner to clean it out. Keep the motor side up to prevent any cleaner from going to the motor side of the IACV. Cleaner is designed to remove carbon, soot, gunk and varnish buildup. Motor windings are coated in varnish, no varnish will create a dead short and effectively kill the stepper motor of the IACV. This is why you will see 'I cleaned my IACV and now it doesn't work' on forums.

 

Ah, well, I ended up getting the ngk ones this morning; the denso's were in stock, too, just $1 more per plug, just had to make a decision.

Wow, I hope I didn't also damage the IACV...I didn't remove it to clean it but could have TB cleaner gotten into the thing when I was cleaning the plenum? However, there was an metal bracket attached to the IACV and I removed the bolt to it to detach the harness from the IACV. I don't think I separated the IACV from plenum in removing the bolt, but if I find a vacuum leak there, then I know now to change the gasket! I didn't have a chance to work on the car today, but tomorrow's supposed to be much "warmer" and I'm devoting the day to doing whatever I can get done, and also find out if the burnt rubber scent persists or not.

Silly question: is the engine considered "under load" if you rev in park? I don't get burnt rubber smell or white exhaust in that case, but see references here and there to problems that occur when an engine is "under load" so I just want to be sure I know what it means.

 

I've used NGK Iridiums in the past and been happy, I've also used NTK O2s which worked fine as well.
After I 'discovered' the Denso Iridium TTs I have not looked back. I've placed them in some cars that had just garbage idle quality even after a tuneup, stuck in the Denso's in and am amazed at how much better the cars ran, especially ignition poor vehicles. I'm a believer in the TTs allowing the flamer kernal more exposure allowing a more complete burn, and probably better at burning off carbon deposits. IIRC Toyota used the TTs in the 3.0/3.3 V6s of the ~2000 era with a 120K mile service. Upper plenum is a bit of a ***** to remove on the Highlanders, nice of Yota to stick in durable plugs.
Unless you were soaking the begesus out if the IACV itself and let it flood with fluid, I doubt it. I was referencing those that clean their IACV with half a can of TB cleaner and then wonder why it doesn't work.
I loosened, erroneously, a bolt to the FITV years ago, tightened it back down, but do note a few drops from time to time after a hard run. I'm just a sloven and don't really want to replace the gasket, although I probably should. So it is possible the seal has a leak, could try using a little bit of chassis grease around the base where it mounts to see if that quietens it, if so you know you found your leak.
For an AT car it has to be in Drive, that will place the car under load at idle, but some leaks don't show up until a heavier load(accelerating) occurs. Not just cruising.
If in Park or Neutral the engine is just free revving and not under a load.

If it is the PS pump leaking, the highest load would be when granny steering the car. Engine on, car stopped and just cranking on the steering wheel to full lock to lock, that will place a hell of a load on the PS pump, if it is leaking you should be able to see something while you have someone else turn the wheel.
Also check the underside of the hood above the PS pump. I had a leak that would make a mess and could not figure out what/where it was coming from. Car is black so the color of the fluid was hard to tell even after wiping. Turns out the low pressure reservoir feed hose junction to the pump would squirt with the engine under load and turning the steering wheel. Gently pressing down on the hose with the engine running would net a blast of fluid from the hose/nipple junction(not a torn hose). Combination of the original hose and spring clamp would lose clamping force and make a mess. Worse was it would squirt into the under bracing window and piddle down the inside of the hood and onto the headlight.

 

Just to follow up, today is a great day!

I took the wheels off prepared to change the brake pads. Looking through the wheel when the tires were still on, I thought there was nothing left to the brake pads, but when I removed the wheels, they seemed to have nearly the same thickness as when new--not much different from the ones I just bought, no obvious warpage, cracking, anything.

For the record, I bought the car in 2014 and in June 2015, I changed the front brake pads, rotors and calipers, and for the brake pads I used the Wearever Platinum Pro ceramic brake pads, and it might have turned out to be a good choice--given that hard stop--since the ceramics are better able to withstand high heat.... I probably have fewer than 10,000 miles since the change, and I am not a hard braker.

Anyhow, Mad Mike, I trusted your judgment that the brake pads are probably OK (since I would have just assumed they were not), especially since I didn't see anything odd after taking the wheels off. I anticipated changing the brake pads, examining the rotors and if the rotors looked OK, I was just going to scour the rotors with garnet paper and install the new pads, BUT since the old pads look OK, I decided against also scouring the rotors since as you pointed out, the pads are probably well bedded now, and scouring them would change that.

Given these findings, I put the wheels back on and figured it was probably OK to drive it to the gas station 1/2 mile away (not busy road) since my car was nearly out of gas, and I didn't want to run out of gas troubleshooting the idle issue. I figured I'd try to find the point at which the burning smell occurred--that path is a bit hilly, so there might be a good change to load the engine. WELLLLL.......

I couldn't replicate it. I punched the gas going up the incline and no smoky exhaust or burning smell. I also braked hard. Braking is nice and smooth, though a little soft, but no off smells. I do intend to bleed the brakes today regardless, since heating up the brake fluid, as I understand, can compromise it. The brake fluid level is still full. I did change the brake fluid in August as well, so this also could have helped to preserve the car.

ALSO, for some reason, today, the idle is perfectly fine. 750RPM, just what the book says it should be. Not sure why the idle was high yesterday, but I didn't change anything. I am STILL going to install the new PCV valve since it is so simple to do, and wouldn't be surprised if it's never been done. Hey, maybe it was really that a little oil got up in there after the hard stop! Today was the first time I've driven the car *at all* since having it towed back, unless you count when I moved the car from yard to garage the other day--and that's the only circumstance other than the hard stopping event itself that I experienced the burnt smell/smoky exhaust (which, yeah, could have just been vapor given the cold temp). I even tried to replicate that backing out of the icy driveway onto the road.

So, from all I can see, everything looks good. Of course, I am still replacing the valve cover gasket & spark plugs, but will do so next week when my husband is off from work. The oil level is still completely full since changing it in August.

Also, I'm going to take it easy from now until next week, meaning I'm going to drive it just to very nearby places within 1 mile of my home just to see if I do identify anything else amiss from now until next week, and see if I have confidence to drive it regularly again.

Thanks for everything!!