93v6 3vz-fe spits and bogs when cold...

Sorry for the long post but I've been fighting this problem for about a year and I've replaced quite a few parts. I really would like to know if anyone here has a fix for this problem. I've modified the symptoms as it's getting worse lately.

Symptoms:
1. it starts great - hot or cold
2. it idles great cold
3. it idles a little rough when warm
4. it drives ok (but not great) when warm
3. cold startup, during the first 2 minutes of driving in open loop mode is terrible however: bogging down, some coughing or spitting, no power unless I go to W.O.T. Then it will at least go ahead and move. I believe the acis flap closes, timing is advanced, injectors are told to stay on longer, etc., under W.O.T., so I assume that’s how I am able to temporarily overcome this lean, cold running condition until the engine starts to warm up. After about 2 minutes, when the temp gauge gets off the C, then it works fine. I believe at this point the engine is in closed loop and begins using all the sensor inputs to give a better running engine than I’m getting with the cold mappings.
4. there are no C.E.L. or codes being stored on this obdc-I engine.

I've replaced:
-plugs (ngk platinum)
-wires
-distributor cap
-distributor rotor
-cold start injector switch (old one showed 75 ohms hot or cold)
-4"air intake, big black hose
-'fuel up' VSV (old one showed open)
-fuel filter
-PVC
-acis vacuum actuator


I've verified these parts are working:
-coolant temp sensor, ohms out good, hot and cold
-air intake sensor in the maf ohms out correctly closed/open/hot or cold
-o2 sensor (at least the one i can get to on the front - i pulled a vacuum with the wire disconnected to see if made it go lean .1v and it did, also revving it made it go rich .9v – doesn’t matter as it’s out of the ‘loop’ in open mode anyway)
-distributor timing is correct as i can see the mark on the flywheel with the 2 pins jumpered at the testing terminal block
-there's no fuel leaking into the vacuum portion of the fuel regulator
-pulling the vacuum tube off of the fuel regulator makes it idle up
-pinching the return hose makes the pressure increase (you can hear the fuel pump pumping harder)
-pulling a vacuum on the EGR makes the engine idle like crap (doesn’t matter as it’s out of the ‘loop’ in open mode anyway, but I believe this proves the egr is working)
-cleaned the intake
-checked the egr valve, but it wasn't gunked up
-cleaned the IAC and ACIS flap side too.
-clear air filter
-ran seafoam through it: half through the brake booster and smoked up the neighborhood and the other half in the tank of premium gas.
-checked out the distributor pickup coils for proper resistances. it's dry, no oil/water inside.
-checked out the ignition coil for proper resistances.
-had a 3-stage fuel injection cleaning performed by local shop.
-pulled the front 3 injectors to check them myelf and they were fine, but I can’t get to the back 3 as I stripped one of the 2 - 8mm hex head intake plenum bolts and can’t remove the intake now.

What I haven't done:
-put a fuel pressure gauge on the rail to verify actual fuel pressure numbers but the flow rate at the rail is about 1.5 qts / minute
-replaced or checked main computer/ecu/ecm
-had the timing belt replaced as it’s only got 50k on it. The last one I had replaced at 60k was like brand new so I’m dubious that the current belt could be so loose as to slip a cam tooth, but I’ll spend the $500 to get it replaced if that’s the only thing it can be.

What have I missed?
Any help is appreciated.
Tony

Welcome to the AF!

Here are some things (in no particular order) to think about and check if you can't discount them from experience:

Ignition coil (may be bad even with correct resistance at low potential of VOM)
Hot spark? (blue, not yellow)
Disconnected or leaking vacuum hose
Leak in intake manifold/cylinder head gasket(s) (torque?)
Plugged or partially plugged cold start injector (although idles cold)
Inadequate fuel pressure
IAC valve may still be partially plugged
Intermittent IGT signal from ECM
Bad Ignitor (try different one)
Air gap between distributor pick-up/inductor (0.008-0.020") or shaft wobble
plug gap (0.043", max 0.051")
TPS needs adjustment
Crankshaft Position Sensor signal (sensor or wire or connector)
Crankshaft Position Sensor inductor (scratched or dinged during timing belt replacement?)
Bad camshaft position sensor signal
Leak in injector O-ring (cracked or installed cocked)
Compression test

I think, since it runs best at WOT, then your best bet is assuming a leak into intake runner or manifold, since vacuum is lowest at WOT and leak into intake will have least effect. Also, open loop would be less able to compensate for leak than closed loop.

2nd best guess is MFI sensor problem. May still be ignition or ignition timing-related sensor.

I don't see how it can be the timing belt.

Brian has some good suggestions, but I'm going to comment on some of the ideas:

1. I doubt it has anything to do with the cold start injector if the car starts ok. That only works at startup.

2. If it runs ok after warming up, I doubt it is the ignition system.

3. if the car is ok going up a steep hill after warming up, it is probably not fuel pressure related.

This happened to my wife's 93 XLE a year ago. It turned out to be cracks in the 3" rubber intake hose, so it was getting too much air and running lean. So I would suspect you have a similar issue of either too much air or too little fuel. So I would focus on the following:

1. fuel injectors. Make sure they are all firing on a cold start. Make sure the ECU is sending signal to them all.

2. Look for vacuum and intake leaks on all hoses as Brian suggests. Re-inspect everything. Pinch off the vacuum lines going to the VSV's right near their attach point at the engine manifold. Inspect the IAC hose that comes off the side of the 4" hose. Remove the IAC valve and clean it, replace the gasket that attaches it to the TB. Inspect the throttle plate and make sure it is fully closed when cold starting, and it moves freely. Check the throttle cable to make sure it moves freely and does not snag. Inspect the connectors and wires to the IAC and TPS.

3. If nothing pans out in 2. above, then start focusing on the intake manifold. Check if there are broken or loose studs attaching it to the heads. When it is running rough while warming up, try spraying carb or brake cleaner around the manifold gasket area and see if you get a change in the idle. Spray around the TB to intake manifold gasket area too to check for leaks.

4. As Brian suggests, you may want to do a compression test if you have not done one yet. There is a possibility that you have a bad head gasket that is leaking coolant into one of the cylinders after it sits for awhile.

good luck

dave mc

1. I doubt it has anything to do with the cold start injector if the car starts ok. That only works at startup.

2. If it runs ok after warming up, I doubt it is the ignition system.

1. I guess a leaking cold start injector would be more likely.

2. Ignition is low priority, but stranger things show up as ignition problems. I wouldn't discount them. Particularly a wobbly distributor shaft (inducter gap) that tightens up when warm, or a coil that has a cold crack in the insulation that seals when warm. Dave is probably right, but keep your options open. You may have more than one fault.

well, this is true. you never know. If it is a leaking cold start injector, you would think it would just run rich rather than rough. Maybe he can try to pinch off the cold start injector fuel supply hose and see next time?

cheers

dave mc

okay, thanks for all the replies so far.
here's some stuff I didn't put in my first post.
1. i've sprayed TB all over the place hot and cold with no difference in idle speed.
2. i've checked all hoses i can see and they don't have cracks.

i checked resistances on the distributor when it was cold and they were within tolerances. i guess the gap could be bad in the distributor. i can check that or replace the pickup coil(s). my vom is rated @ 1megohm/volt so i believe it to be accurate. i couldn't make the distributor shaft wobble with my hands. how much pressure would i need to apply to make it wobble?

i can't check the back 3 injectors cause i screwed up the 8mm hex head allen bolt that goes into the intake plenum, so I can't remove the intake and can't access the injectors. can i assume they are firing cold if they're firing fine hot or is that faulty logic? note that i did replace the 4 o-rings per injector on the front 3 injectors that i could get to though.

the cold start injector isn't leaking. it sprays fine - i removed it to be sure. I'm pretty sure that'd make it run rich but the plugs show white, so i'm pretty sure it's a lean condition i'm fighting.

i haven't done a compression test, but it doesn't use excessive amounts of oil it should be close enough tolerance for an old engine. also, no loss of coolant or bubbling on the dipstick or white smoke or sweet smell on startup.

tps is adjusted to .021mm for the break point per the manual.

1. any votes for a slipped timing belt?

2. how about any way to check the igniter without buying another one to put in my spare parts bucket.

any other ideas please? I'm open to everything at this point.

thanks much.
tony

For a wobbly distributor shaft, the air gap on the inductor will show that. There isn't alot of tolerance for that gap.

Fuel pressure

Manifold leak

I don't think timing belt is possble.

You can try e-mailing Toysrme. He is an expert on this engine.

If you have not pulled the IAC valve off totally for a cleaning, then I think that should be your next step. There appears to be two valve seating surfaces on the IAC: the one that seats inside the TB, and the internal one which controls air going directly into the intake manifold past the TB. (I'm looking at the factory manual diagram.) It's a long shot since I think this IAC is less susceptible to clogging unlike the smaller 4 cyl version.

You may want to try a bolt-out to get that allen or star head out of the intake manifold to access the rear injectors and inspect the manifold for cracks as well as its gasket, or is it too difficult to get to it? I think you are going to have to do this eventually to find this problem. You can try to rock the engine forward maybe by removing the dogbone mount at the front and using a cable puller or something to rotate it forward a bit.

Something else you can maybe try is to pull the plugs just before a cold start when you know it will run bad and inspect them. Pull the backs too.

Brian, just curious, why do you think it would not be a slipped timing belt? I'm just guessing since I don't have enough experience to say, but would the ECM be able to compensate for a slipped belt in closed loop somewhat by playing with the Distributor timing advance? I wonder if there is a way to check that without having to everything off the front of the engine? It looks like it's about 1-2 hrs worth of work to remove the timing belt cover to have a look. May be worth just going ahead and changing it if you feel confident enough to do it and it due.

dave mc

It seems that it would be extremely unlikely that the timing belt would skip one or more teeth on both cam pulleys. I think this is what would be necessary in order for the ECM to compensate the ignition timing for the slipped belt. If one cam is retarded and the other is correctly timed, then I would expect that the engine would never run well, hot or cold. At least, that has been what I've seen, but I guess there are no guarantees. Actually, I've never heard of a belt only slipping one tooth on one cam pulley. This small change may cause what he is seeing, but I have no experience with this exact problem.

I think the timing belt (valve timing) will be checked (if a significant number of teeth have been jumped) by a compression test to prevent unnecessary work in exposing the front of the engine. Bad valves or valve adjustment would also show up either cold or hot compression testing. A whole bank of cylinders being bad would indicate timing belt.

okay thanks guys for all the help. I'll work on getting that 8mm hex head bolt out so i can get the plenum off so i can remove the injectors to see if they are plugged somehow. i'll report back when i am able to do this as I just had triple bypass surgery and am not able to pull a lot of torque yet. and i suspect it will take a lot to get that bolt out. thanks again.
tony

Use a long extension on a breaker bar handle (and high-quality penetrating oil) to prevent your needing to apply alot of force and potentially injure yourself.

i'll report back when i am able to do this as I just had triple bypass surgery and am not able to pull a lot of torque yet. and i suspect it will take a lot to get that bolt out. thanks again.
tony

My god man, take it easy until you have fully recovered and don't worry about the car. We'll be here when you are ready. ;)

Best of luck with your recovery.

Dave Mc

thanks much guys for your help. i'll report back in when i find out something new. much appreciated.
tony

Well, i felt better today so i used a bolt out and got that intake plenum off. I checked the rear injectors and they seem to spray fine. also, i verified the rear plugs were still clean and seated. lastly, there were no hoses with cracks or loose fitting. it's all back together and still bogs and spits for the first 60 seconds or so when it's cold, under load. i'm not sure where to check next?
1. coil
2. igniter
3. distributor (not the cap or rotor as these are new)
4. timing belt (slipped tooth/teeth).
5. ecu
any and all suggestions welcome. thanks.
tony

well, today i took out the distributor and the shaft doesn't wobble and all 3 coil pickup clearances are within specs (.012), with no sign of arcing, etc. when i replaced the distributor and started to check the timing, i noticed something i thought odd. the timing light seems like it misses every so many cycles or cuts out. its not the timing light because it only seems to do it on some of the wires. (the wires are new). i aim the light at a dark surface and turn it on and when the clamp is on the #1 , #3, and #5 plug wires, the light flashes aren't even. they're what i'd call sporadic, with intermittent misses, especially when i rev up the engine. does sound like anything or is it normal behavior?
thanks
tony

Only one bank having trouble is strange. That sounds most like a distributor cap.

Coil or ignitor are most likely unchanged parts, but I don't see how they can only affect one bank.

ECM is possible.

brian, disto cap, rotor cap, wires, plugs are all new. distributor itself seems fine. also, have a good blue flame at the plugs so i'm assuming the coil is good. i don't understand enough about the igniter to rule it out - possibly if it's an oversized transistor/scr/switch that has gotten slow to switch after 14 years?

I'm also suspecting the ecm. i've found some on the auction site, but dont' know the numbers for mine. i could take it out to see if i can't find someone with my same car - a 93 v6 xle, 'j' vin, ca specs, 3vz-fe that knows the toyota numbers.

lastly, since it's the rear bank affected, would this point to a timing belt slip of a tooth now that I've discovered this?

thanks for any and all help.
tony

now that its dark, i can see the light from the timing light better and it seems that all of the wires show 'misses', especially when i give it some throttle. the light blinks then just goes dark for a split second, then starts blinking again. i'm assuming this isn't normal behavior, but the car doesn't sound like it's missing when it's warm. it actually runs pretty well warm. i can see where missing would mess it up when it's cold though. someone tell me if they think i'm onto something or just chasing my tail.
thanks
tony

Tony,

You better check your timing light on another known good car to be sure. If you are sure it is related to the camry, then you need to check the signal going to the coil itself from the ignitor to see what's happening there. Check the connectors there carefully. What kind of spark plugs are you using?

The only other things I can think of to try is to run it on cold startup without the oxygen sensor in there to reduce back pressure and see what happens. You may want to do a leakdown and compression test on the cylinders to see if it is a burnt valve or something. Maybe check the manifold vacuum too to see if you can detect a bad valve signature with it or by checking for intermittent suction at the exhaust pipe at idle.

dave mc

dave, it's got the ngk platinum plugs. i'll try to test the light on a known good car to see if it's the light or not. thanks for the help. i'll check back in if i can figure it out.
tony

well, i finally broke down and took it to toyota today. they ran a block test and tell me the head gasket is blown. i don't smell any coolant, and the coolant levels don't go down, but they said this is what's causing my poor running when cold and also poor idleing sometimes, hot or cold. they also said the PS pump, hoses and rack are leaking and it'd be $6,500 to fix it, assuming the block was okay when they tore it down. needless to say, i'm not going that route. i'm contemplating replacing the head gaskets myself but the most complicated thing i've attempted on this thing so far was removing and replacing the intake plenum. can someone who's replaced v6 head gaskets join in and let me know what i'm in for, share any secrets they found out the hard way, etc.? also, i'm assuming the TB & waterpump should/have to be replaced as part of this operation also?
as always, thanks for any and all assistance.
tony

The head gasket leak doesn't have to be to a cooling jacket. Did they do a compression test? What were the results? They should be on the repair order. That would tell if the head gasket leak was to a cylinder or not.

As far as the PS leak, I would first tighten (torque) the fittings to the hoses, and see if that fixes the leak. Then replace the hose that's leaking and see if that solves your problem. Hard to believe that everything in the system is leaking. They may be taking you for a ride.

I would get a second opinion from a trustworthy mechanic. Get a recommendation from a co-worker or friend.

Ya, Brian has some good advice there. Check the rack and pump over thouroughly yourself to be sure. If you are willing to take on the head gasket, then you should be able to replace the rack yourself too. A new rack can be had for around $300 I think. I have never done one but I hear it's a pain to get the hydraulic lines off it. You would be better off cutting the lines and taking it all out including the pump and replacing it all.

I started a head gasket job on my wife's 93 V6 about 3 yrs ago. Same car as yours. I did a leakdown test first to identify which head/cylinder was affected since I did not want to do both heads if it wasn't necessary. I advise you do the same. Either buy a leakdown tester or make one. You need a compressor of course. I did not complete that job because when I removed the head, I found that the engine block mating surface had been pitted at the leak point from the combustion gases. It was probably driven too long with an overheated condition. I showed it to a few people and they did not recommend that I even bother with a new gasket because it would not hold with this block damage. There are some procedures out there recommended to repair this; one of them being to use JB-weld to fill the pits. Had I known that before deciding to replace the engine, I may have tried it.

Pulling the head on the V6 for a novice is going to be a big job; maybe 24 hrs of labor. I get the feeling though Tony that you are up to it. :) Hopefully it is the front head as it will be much easier to do. As to your questions: yes, it is recommeneded to replace the timing belt, the TB tensioner, the water pump. I would also replace the rad and rad hoses if they are not fairly new as well as the thermostat of course. You will need a full head gasket set. I would replace the exhaust and intake gaskets as well as the TB gasket. Use quality metal gaskets similar to Toyota's OEM ones. Without a head job, it will cost you maybe $300-$500 in parts (as recommended above) to do the min. job. Do get a Haynes manual as it helped me. As well, the V6 service manuals are available online under the Lexus ES300 manuals. Study the manuals and procedures for a week to familiarize yourself.

The most difficult part of this job as I recall is removing the crankshaft pulley and the overhead cams. You will need a decent impact gun for the Cs pulley or some tricks with a large socket. You just have to be real careful and keep all your parts organized and clean as you remove them. Don't mix up the camshafts or the lifters. Make a box with compartments to keep them all organized. Get the head(s) cleaned and pressure tested at a minimum, as well as inspected professionally to see if a valve job is necessary. When you re-install the heads, you must make sure the mating surface on the block and head are completely clean. I use the scotchbrite discs with an air grinder, but a lot of people don't recommend this because too much can create low spots. As well, getting the scotchbrite fibers inside the engine can cause premature wear. I don't know if I buy all these arguments, but it is wise to seal the cylinders and coolant and oil passages in the block if you do it. The final critcal part is to follow the head bolt torquing procedure to the 'T' as recommended by Toyota and/or the gasket manufacturer. It is best to ask the toyota techs or research Toyata tech bulletins for the latest head bolt torquing procedure as it can change. Not sure about the V6 head bolts being reuseable or not (ie may be TTY), but be sure.

dave mc

thanks brian, dave, and the rest for your help. sounds like head gaskets are way too much for me to tackle. that was a great description dave. i was hoping for the front bank too, and also that i might not even have to pull the crankshaft or camshaft pulleys. not knowing the guts of the engine, i thought the head might just come off by sliding the timing belt off of it and save me some work and money as this is a 14 year old car and i don't want to put a lot into it, but i don't want to junk/trade it either - because i've had it for 14 years, since it was a baby!
maybe i'll check out the garages and see if they can put a newer 4 banger in it or even a newer 6 cylinder, but i hate working on the 6 so much. living in ca, it might not be legal to put another engine in it for emissions - i don't know. just trying to figure out a way to save my baby.
as far as the ps pump, i don't believe it's leaking cause i had it rebuilt a few years ago. i assume its a hose or the rack, but the weird part is that i only lose xmission fluid when it's hot enough to kick in the hydraulic cooling fan, so i thought it might be something in that circuit, but who knows.
thanks again for everyone's help.
i might have to be another one throwing in the towel on the gen3's!
tony