cziemer

Have a '94 extra cab DLX, 4x4, with the 3.0 and a 5 speed, just changed the oil and knock sensor (relocated to engine hook at least for now) yesterday, and while I gained power back, I now have quite a bit of white smoke at start up. As soon as the temperature gauge approaches 1/4 it's completely gone. I have a hesitation that's almost like (and maybe) a miss until I hit 3k then it clears right up. Coolant level appears normal. I may have 5 miles and 3 cold starts since yesterday. It has not even came close to overheating, even after sitting 15 minutes running at idle then driving across town (3ish miles). Have not really checked anything else out with the truck, did I just happen to blow a head gasket, or is there something else I should look at first? Knock sensor was bad for approx. 3-4 months of daily driving before I changed it. Oil change was a little over, about 3500 miles. Just looking for insight before I tear into it.

thook

How long have you been driving a vehicle, dude? I don't mean to sound flippant, but haven't you ever noticed this time of year (especially) most everyone living in humid climates has white smoke coming out the exhaust after initial start up? It's condensation in the exhaust. Quite normal. As long as it doesn't ever smell like burning coolant, you're fine.

The rough idle could be a sluggish idle air control valve (run a forum search on that). Does it clear up at all once the engine has reached operating temps?

cziemer

I don't mean it has a little puff of smoke, I'm talking fogging for mosquitoes smoke. Solidly until the temperature gauge hits 1/4. Then it stops, it doesn't taper off just abruptly stops and the idle gets a little better. Should I have reset the ecm when I replaced the knock sensor? Could I have trashed the cat or 02 sensor from driving for so long with the motor in limp mode? It did smell vaguely of rotten eggs on the first start up. When I do a compression test, does anyone have a link to a write up if it is a head gasket? I have a haynes manual and I'm comfortable with tearing it apart that far, but more guidance is always better. Will be doing further testing tomorrow afternoon. There was a drastic drop in temperature, but at 198,000 without the head gasket recall I don't want to risk cracking or warping a head over what could be a cheaper fix, especially when I have a week off. Rough idle doesn't completely clear up at operating temperature, but the hesitation/miss goes away at 3k rpms.

93toyrunner2

IME rotten egg smell is the sign of a bad catalytic.

cziemer

Rotten egg smell was only at the first start after the oil change/knock sensor mod that may have nothing to do with whats going on, but it did start immediately after. Haven't noticed it sense.

thook

1) Well, I can't really gauge the extremity of your "fog" situation since I can't see it. But, I will say my 3vze emits more than just a puff and there's absolutely no head gasket leakage. Like I said, if it doesn't smell like coolant, you're fine. What's more, if there's no coolant in the oil or vice versa, you're fine.

On the other hand, if it's that much of a concern that won't be satisfied by our dialogue, a compression test won't hurt one bit. It's not a bad idea, anyway, to determine the health of your cylinders and valves since low compression.....for whatever....can be a factor in this type of idle issue. Not to scare you, but aside from head gasket problems, valve issues on these motors are fairly common if/when they've not been inspected/adjusted periodically. Plus, if there's heavy carbon on them.....read excessively rich from a prolonged bad KS.

Here's the link:http://personal.utulsa.edu/~nathan-b...66compress.pdf

2) It's procedural to reset the ECM whenever an electronic part is replaced and/or there's a code. Having said that, not having reset the ECM won't affect the ECM's ability to read the new KS and adjust accordingly. However, if you have a code, that will be stored until you reset.

3) Hmmm....hard to say about your CAT, but it's possible. It may be why you're getting so much white smoke, too. It's not overheating or getting red, is it? Certainly the O2 may be sluggish from soot. Running about with a bad KS means your vehicle's been running rich for an extended period. That can/does foul O2 sensors and plugs. It may not have killed the CAT, but it may be impaired. The rotten smell is usually an indicator. I'd have it looked at and the O2 inspected or replaced.

cziemer

You've eased my mind quite a bit on the head gasket situation, will probably do the compression test anyway, bought the truck about a year ago and the knock sensor went out about august to September. Will also look to replace the O2 sensor if I can get one in the next couple of days. If the cat seems to be super hot or starts glowing I'll see if I can't get a replacement locally or sub in a test pipe until an ordered one gets here. I've downloaded the FSM to the 93 pickup,so that should give me a pretty good base to start testing from. Thanks for your help, I'll report back what I find if I get the chance to mess with it tomorrow. (I hate to go back to this, but now that I'm thinking about it wouldn't a head gasket cause white smoke regardless of operating temperature?)

thook

It's a fair question, but realize the question "is my headgasket blown?!!" gets asked a lot when, more often that not, the answer is condensation.

If a head gasket leak is not too severe, it's possible for steam to appear only at start up. What's much more common, though, is that steam will always be evident. But, your not going to all of a sudden blow a head gasket during the course of a knock sensor replacement. Afterall, as you say, the symptom didn't appear until after you changed it, right? As well, you said it never overheated. Again, if the exhaust doesn't smell like coolant, it's not coolant.

As for the CAT, you said you haven't noticed the smell since. One option for you is to remove the CAT and temporarily install a straight pipe until you sort out the issues. This way you've eliminated the CAT as a suspect. Once the issues are sorted, if the CAT is actually involved, you'll know when you put it back in.

cziemer

Head gasket is toast for sure, started it up after letting it sit 12hours and it smells like it's running off straight antifreeze, and coolant is now low and oil is high. Ordered the Head Gaskets, bolts,timing belt, and water pump today.

thook

Dang, dang, dang. That's a bummer. I'm really sorry to hear it for ya, dude.

cziemer

Both head gaskets are officially replaced with only a few small hiccups. The biggest one is my oil cooler is no longer hooked up because I got the wrong water pump in a box that was labeled as a bypass style. The right pump is three days out at all the part stores in town, so I got to keep the wrong pump and got my money back and just eliminated the coolant portion of the oil cooler. Will be getting an oil temp gauge and if I have any issues I'll get an aftermarket cooler. Broke my fan shroud into 3 when I tried to put it back, so I'm running without one (it's 20 degrees without the wind chill) until I find a junkyard one. When I got the truck running again I thought I screwed up the timing, couldn't get it rev over 2.5k and it was missing like crazy, couldn't find any vacuum leaks and the tps was within range when I had TB off. I went to pull the distributor to see if I was a tooth off and the coil wire literally fell apart when I touched it. Replaced the plug wires and now she's running better than ever, with no codes and plenty of power.

TNRabbit

Congrats! Feels good, huh?

fork

glad to see you repaired it instead of tossing it out

thook

That's great news, dude. Cold weather's not any fun for wrenching, either.