rworegon

While not specific to your engine, there is some good EGR troubleshooting info here:
http://www.toyotanation.com/forum/sh...d.php?t=357502

On the 2.7:
http://www.tacomaworld.com/forum/1st...ode-p0402.html
http://www.tacomaworld.com/forum/1st...sive-flow.html

Good luck.

dustrider

thanks !
VSV operates normal
EGR operates normal
new vacuum modulator
tested and cleaned the exhaust gas temp sensor

dustrider

Hopefully the valves wont need too much shim taken out ,
if its only a few thousandths then it might be servicable

dustrider

a buddy suggested checking the TPS,
had previously ruled it out because I changed it with a toyota OEM part in july in response to a CEL code , on this model there is no adjustment for the tps. I cleared the CEL and it hasnt come back since
Figured it's worth a try before I start on adjusting the valves
I checked the TPS and suspected the OHMs were out of spec at full closed according to a chilton manual spec ( the OEM manual I have is for a 96, mine is a 98 so the mechanical stuff is accurate, but not the tech stuff)
I was still sitting unstarted all nite , its about 40F out today so plenty cold.
Put in the new autozone TPS and started it
Ran crappy as usual and backing out the driveway it stalled Started it back up and the idle went up higher than I have ever seen it, about 1400, and stayed there for quite a while
it ran smooth unlike before,
drove out to where it always stalls and it didnt stall
pulled to a stop smotther than it did before even warmed up. I did about 5 more stop and go's with no stumble no stall.
Drove around and got it up to temp and it idles smoother than it ever has since I have had it
Drove about a mile up a steep grade and the power seems the same maybe slightly better
Pulled to a stop and immediatly noticed a difference . Before, when coming to a stop, the idle speed would dip below 500 and come back up to 750. Itb would feel a little stumbly at stops. Now it just stays steady at what looks like 800 on the tach.
again and again the idle stayed steady no more slight stumble or dip in rpm when coming to stops when warm


Hopefully that first stall was something to do with the computer needing to relearn

Even though I am real happy I am staying guardedly optimistic

its unbelievable how good its running now
Very smooth idle
the true test wont be until tomorrow morning at 415 am on the way to work because it only did the stall after sitting all nite stone cold

drkblu4runner

GOOD TO HEAR

dustrider

...except fer its still cold stalling
dont have time to jack with it
it seems crazy to pull the head
been driving it 200 miles a day 8 hrs at work 5-6 hrs driving through jam
and it will be down for a week waiting on the machine shop

dustrider

still cold stalling and now it is slow coming up the mountain hardly any power
changed the fuel pump the tank was real clean
changed the fuel pressure regulator
no dfference

pulled the head off and the valves dont look too bad
not bad at all
#1 intakes look a little dirty but they are holding liquid
I was expecting to find something obvious

what the hell
now I am confused AND pissed
?????

tore off the head on 2 mechanics diagnostic advice
and the valves dont look too bad
hard to believe valves can look this good at 202,000 but make it stall ?

Im about ready to scream if I took the head off after all this for no reason and nobody can figure out why it stalls

dustrider

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

dustrider

I have cold stalling
and lack of power

'98 2.7 stick
within the past two months
so far I have changed with new toyota parts :
IAC valve (cleaned throttle body passages )
MAF sensor
TPS sensor
ECT sensor
EGR vacuum modulator
spark plugs and wires
air filter
in tank and inline fuel filters
fuel pump
fuel pressure regulator
ECM computer (toyota remnan)

double checked and/or cleaned these parts:
EGR VSV
EGR valve
catalytic converter
muffler
triple checked for vacuum leaks (even at PSump and brake booster)

gave up and took it to toyota dealer for the $100 diagnosis said compression was 140-150-180-190, they could not find anything after 5 hours and said it needs the head tore off
took it to another local mechanic, they checked, timing, fuel pressure and IAC couldnt find anything and suggested valve job

I pulled the head today and put the cams back in and the valves dont look too bad on the bench
cam chain looks tight
first line up between valve marks and balancer marks was 5 degrees off , turned it over clockwise 360 and it came up dead zero TDC , with the cam dots together so cam timing seems good

maybe head gasket leaking between cylinders ?
cylinders look real good , no scoring doesnt use ANY oil in 10,000 miles

I shook the cam chain real hard at the links and cant find play
the adjuster was about in the middle of its range and sliding smoooth, ratchet holding

started raining (no garage)


now what !
just put it back together ?

dustrider

hot damn

GOT IT !

finally !

put the new head on and it fired right up
no more cold stall
no more "EGR type stumble"
idles higher and idles real, 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

on the upside I know every little detail under that hood now , before I started I had no idea how a TPS interacts with the ECM or what an EGR temp sensor,VSV or the IAC does
I could swap the head in 6 hours now


THANKS FOR ALL THE HELP EVERYONE

drkblu4runner

good to hear, did you have the old valves leak down tested?

dustrider

no because I wasnt burning ANY oil

visual inspection showed a possible loss of gasket bonding between cylinders
and evidence of previous gasket material as if the previous gasket was not properly cleaned down to metal in a former head removal

about .0002 warpage gap between cylinders at the block
the aluminum head surface was very flat