2.7 stick stalls when cold

Out of rope
anyone have ideas ?
98 Tacoma 4x4 2.7 stick 201,000
starts fine but stalls at stops only at stone cold start until temp guage reaches norm operating level
it will not stall if I keep it revved with my foot
if I let it stall it turns over a long time , about a minute before it re-starts
idle only goes up to about 1,000 at cold start and drops to 750 within 5 seconds

things replaced/ tested so far to try and cure this within the last two weeks
idles smoother but with no change at cold stalling

replaced :
ECT sensor (autozone)
IAC control (OEM)
MAF sensor (OEM)
TPS (OEM)
inline fuel filter
air filter
spark plugs/wires OEM
valve cover gasket/ plug seals

thouroghly checked out/cleaned:

battery cold crank charge/voltage
cleaned ground to body/motor wire end
checked fuel pressure with snapon guage at cold start condition holds perfect 44 psi at idle, 39 at stop , no leakdown
throttle body removed and cleaned, replaced gaskets
ran down tank to last gallon and ran a can of seafoam though
checked for vacuum leaks/intake leaks
EGR compared operation with new unit , working perfect opens with small vac and snaps back tight
removed and checked operation of EGR VSV valve works perfect
removed and checked temp opening and cold shut of thermostat
removed and checked cat for flow , ran Nox probe and it is catalyzing
wiggled plugs to ECM
rechecked aftermarket engine control temp sensor for OHMs output cold and hot

no change after all that to cold stall , just runs better and idles smoother
bad items found :
removed valve cover and found some tight valves
compression weak #1-140, #2-150, #3-180, #4,190
runs good up the mountain where I live and runs idles good enough for me, never stalls once it is warmed up for the day even after sitting at work all day
just want to cure cold stall, dont want to rebuild engine as the dealer tech suggests
I gave up after doing all that and took it to local mechanic and they were stumped said rebuild motor
took it to dealer for the $100 diagnosis and they suggested replace $300 IAC valve (after I cleaned mine), it resulted in no change waste of $400 , then they suggested engine teardown to replace valves
both said valve job on old motor is a gamble and dont adjust the tight valves now or they could fail

after at least three weeks of this ( I drive it 200 miles a day LA stop&go/4000ft climb up mountain ) I finally got a code at cold start while keeping it revved during the cold run in to the first stop sign
PO104 "excess EGR flow detected"
EGR shuts at idle and opens at higher RPM , I noticed the EGR opens when cold , manual says EGR should not open when motor cold if I am not mistaken ?
rechecked EGR and it seems to operate perfect, rechecked EGR Vacuum Switching Valve and Vacuum modulator work perfect
cleared the code with the OBDII and it has not come back in the last 500 miles
Idle does not go above 1000 at cold sart manual says it should be 1250 to 1500 until it warms up
if I am not mistaken ?
all the diagnostic trees I have chased seem to dead end at the ECM computer ?

possible related/unrelated recent events :
about 4 weeks ago the AC compressor clutch melted so I disconnected the belt , IIRC the cold stall started before this but not 100% sure , I know there is an idle-up circuit for the AC but havent investigated it yet

also 3 weeks ago had a condition where the starter would just click loud and not engage , at random after several attempts it would engage , I bought a reman starter to install and found a loose connection at the starter battery cable lug tightened it and it has not happened since , took the reman starter back

 

I simulated the cold stall this morning pulled out the driveway and back in and let it stall . After stall it will sound funny turning over like there is no spark or no compression , weak but easy spin turn over sound like it doesnt even want to try to fire
after cranking for about a minute with the weak sounding crank it will start

this time I just let it stall, then cranked it for 5 seconds to confirm it was making the funny weak & easy crank sound and then opened the fuel line to check for fuel it ran out so I tightened the line back and removed #1 plug wire and checked for spark with a spark tester and it had a fat blue spark

replaced the plug wire and it started right up with no funny crank sound , just started first kick
now it will run normal for the rest of the day

 

theory 1 ?. because the valve condition is causing weak compression at cold start, the Electronic Control system on this model cannot compensate enough to keep it from stalling , evn though it is operating properly?
the weak turnover sound is weak compression and a lean condition that would be sufficient with fresh compression ?
theory 2 ? . the ECM electronic control module is not sending voltage signals to compensate for cold start conditions ?. Fuel injector pulse, Idle Air Contorl and EGR may not be getting the voltage commands necessary to compensate fuel trim at cold start ?
the weak turnover sound is weak compression and lean condition caused by the IAC not closing and EGR opening because the ECM is not telling the VSV and/or IAC what to do but the injectors are still dumping extra fuel or not enough ? ?
as the engine comes back down to idle stone cold with tight valves the added suction at valve overlap through the intake with the EGR open drains the fuel rail as the engine stalls from bad fuel/air ratio , and therefore it takes a while of turning over to get the fuel mixture high enough to let it combust

 

I'm new here and was searching for another topic and ran across yours.

There is an idle control valve which on my 2003 2.7 Tacoma is under the throttle body and very hard to see and reach. Sometimes rough idling is caused by the air passage to that valve getting clogged by carbon buildup in the throttle body. I use fuel injector cleaner in a spray can (not to be confused with carb cleaner). I loosen the plastic intake duct at the throttle body, run the motor on high rpms and spray all around the throttle body intake. By doing so, some of the cleaner will get into the idle control valve and clean out that passage. Make sure you're in a well ventilated area as it may smoke a little.

I noticed that your compression readings are quite far apart. Maybe a fouled plug in contributing to the problem.

Good luck.

 

removed the throttle body, removed the IAC and cleaned it all

replaced it with a new toyota IAC after the "expert" toyota diagnosis

the long post is a list of everything I have tried so far

I have checkedOK or replaced everything but the ECM and the engine

 

Probably won't help but when I changed my plugs, I was experiencing the same thing the first morning after. I thought that I didn't put something back right and wiggled the vacuum hoses and wire cables that were disconnected during the replacement. The issue went away after that. I am guessing the problem may have been anti seize on the plug end or new plugs burning in or similar.

If not already stated in the OP, try checking for vacuum leaks and loose cables around the ignition system.

 

Saugus made a good point about the vacuum issue. Maybe a mounting bolt, clamp or hose is just slightly loose or cracked. Maybe a vacuum gauge would be of help. There are websites that show various vacuum readings and what the probable causes are.

Good luck.

 

all that is on the first post that is too long to read

Had local mechanic run vaccuum test and backpressure test
I have checked removed replaced every vacuum line and VSV valve at least once including blocking off the brake booster

I ran it to make it cold stall and checked for spark , lots of spark when it cold stalls


runs better after changing plugs and wires but no change to the cold stalling

when I changed the plugs found the #4 plug cap was soaked in oil so I replaced the plug tube seals and no more oil

plugs tend to cause misfire
this is stalling at stops when stone cold after sitting all night
after warming up for the day it runs fine

 

If keeping the rpms up helps, it really sounds like a small vacuum leak. Once the motor develops enough heat, the leak is sealed.

I had a similar problem (on a carb) which was at the base where the throttle linkage opened the the butterflies for the primary bores. There was a kit to replace the bushings that the linkage runs through but it cost just a little less than a new carb! Even spraying carb cleaner at that point didn't show a vacuum leak and the vacuum gauge still showed a good reading at idle. I learned of this potential problem area from others on another hot rod forum.

Those compression numbers don't look good.

Good luck.

 

makes sense i had that on a chevy throttle body with 250,000 but it wasnt this extreme

but this thing starts right up
if I let it idle up to warm it will be good for the day
if I drive 100 feet, pull over and let it stall
it will not restart for 1 minute
I can set a watch to it 1 minute

I can just wait one minute and it will start right up

or I can hit the starter for one minute doesnt matter
after it restarts it will still want to stall , until the temp is up all the way

then it is good for the day

 

Wonder if the fuel pump is acting up while driving. I remember reading about others with stalling and then delay and then restart like you describe about a month ago here.

 

I left it at the local mechanic shop and they checked the fuel pressure with a guage when it cold stalled and the fuel pressure checked out perfect , no leakdown either


I am ready to just try a $550 reman Toyota ECM

it is so difficult to test thr ECM without the factory toyota manual and even then it may test OK for continuity with certain functions but malfunction anyway
the only way to really test if a problem is caused by the ECM is to plug in a new one

 

I replaced the ECM with the toyota reman and it ran great after cooling for a few hours
Ooops !
wasted $550
the saga continues

I went to sleep last night optimistically thinking I had it licked
but my pragmatic side was nagging at my pessimistic side waiting for that stone cold start in the morning
sure enough cold stall came back

went to another toyletoda dealer to get a third opinion
he let me tell the whole story and concurred with the two others that it is valve condition
he agreed with my opinion why . I think that although the leaky valves would not make all motors stall, the nature of the toyodor engine control system will not compensate for it when the motor is stone cold . It will only meter out enough for a small amount of compression loss at cold valve condition

I think someone contributed earlier in the thread that the spongecake buildup on the valves will somehow absorb the fuel or something like that, not sure what the theory is
it would require more fuel at cold start and the toyoter system will not provide it
next thing to try will be valve job

the stupid motor has shim and bucket and is a PITA to adjust
a valve adjustment might help but i am not sure why the mechanics are saying it cant be done, when I ask the just shrug and say theyve never considered it but the manual tells how
maybe they know that enough shim cannot be removed to get the valves seated or some such

seems like a shame to pull the head when it runs fine

this is my third toyota and all were nothing but one major trouble after another

 

I have a thread going about a loud tapping noise upon cold start up on my 2.7L but it only happens when I put it into gear. The loud tapping goes away after a few moments. I also considered the valves, but I would have thought that valve clatter would be heard when just starting the engine.

I think in you situation, the compression readings are a major clue.

On the other hand, my GF has a 4Runner with the V6 and it never gives her any problems.

I think this 2.7L motor had many issues that Toyota never figured out. It's a shame as I'm really happy with the rest of the truck.

Good luck.

 

I should have bought a compression tester and checked it myself

I have seen bad valves before but these look good

I put the cams back in the head and turned it over on the bench and the valves dont look too bad

let them close and poured some gas on top and it just sits there in a pool
looks like I took the head off for no reason

 

hot damn

GOT IT !

finally !

put the new head on and it fired right up
no cold stall
no more "EGR type stumble"
idles higher and idles real smooth
about 25% more power too

worked out some bugs and did a 200 mile shakedown

I just refused to believe bad valves would act like that


THANKS FOR ALL THE HELP EVERYONE

 

I have about 3,000 miles on the new chinese aftermarket head and it runs like new

the toyota engine control system will not compensate for bad valves and low compression so it stalls when cold The 2.7 runs relatively hi compression

Instead of sending my head out to get a valve job which was about $500 + and you need to find a toyota specific shop that will adjust the shim and buckets ( most auto machine shops dont) , I got a complete new aftermarket head and gaskets from japanengines.com for $500 total shipped which cured it
Easiest head I have ever worked on Very easy to work on the 4 cyl Toyo I have done maybe a dozen heads in my life started wrenching on motorcycles at 15, the 2.7 is more like a motorcycle engine than a car

 

Sometimes one head is better than two.

 

My 98 2.7L just starting doing this EXACT SAME THING. Thanks for the thread guys.

 

Hello from 2021!

My 98 2.7 just started doing this exact same thing....been pulling my hair our trying to figure it out and wasting a ton of money. What exactly ended up being the fix?? The new after market chinese head? Would really appreciate any help!