7mgte stumble HELP

ccguy · 05-27-2013, 06:04 PM

here is the updated (clearer) explanation:
1987 7mgte rebuilt motor, head milled, oe hg, arp studs torqued to 80 ft lbs and were retorqued after heat sequences, 440 injectors, stock 7mgte afm housing and meter, 3" doenpipe/full exhaust, water to air intercooler, ign timing at 10 deg. wiring to the tps, afm, ect, hac have all been rewired with new wire and to speck on the tsrm for a 1987 7mgte ( http://www.turboninjas.com/mk3supra/...7_Mk3_TEWD.pdf )( i thought the original wiring was to blame), cps is installed correctly and triple checked.
~6300 ft elevation
engine swapped into 1980 toyota 4x4

-engine starts and idles great at ~800ish rpms. fuel pressure at 32psi at idle and fuel up vsv line hooked up to the FPR and fuel pressure changes to 40 psi when throttle applied.
-ign timing with jumper in place it is 10 deg btdc at idle and at operating temp.
-at idle -17 vacuum
-PROBLEM: with light throttle (very slowly applying throttle) revs smoothly up to 2800 rpm. once 2800 rpm has been reached if throttle is applied over that the motor will not go past the 2800 rpm and bog down to 2000rpm and act like/sound if you were to exhale all of the air out of your lungs and continued to blow more out but cant. while doing this it will make a stumbling noise and some popping noises, also you can hear the turbo spooling through the exhaust and occasionally a backfire pop through the air filter if the throttle is WOT.
this hesitation stays from the 2800 rpm amount of throttle through WOT. up to 2800 rpm the vacuum is -15 or so and when hesitating at WOT it will go to 0. once the hesitation starts it continues through WOT and when it is hesitating the more throttle from the begining at 2800rpm to WOT the vacuum gauge acts as if it is operating from -15 to 0 on a cable attached to the throttle.

if the throttle is revved up like vroom vroom vroom vroom sometimes it will overcome the problem and rev up to redline like a normal motor.

this happens at idle and even worse during driving.
when the hesitation starts at while driving it bucks violently and fells like some suspension is going to break a ring gear, u joint, tranny etc...
during driving if you get past the hesitation and are at cruising speed (under 2800 rpm) if you hold the throttle steady and the speed catches up to how far the throttle is open it will feel like a switch, it is off power and will accel back up to where the throttle is depressed (the off power feels like when you would hit the cancel switch while on cruise control).
if i open the throttle enough to get over the 2800 rpm hesitation the truck will act like i am flooring it (WOT) even if the throttle is barely cracked and accelerate like crazy until it catches up with the speed and then "power off".

here is the link to my youtube with the videos
http://www.youtube.com/user/cctool/v...ew=0&flow=grid

what i have found through testing.
***with the tps (only) unplugged:
-no dash cel light on.
-with jumper in and engine off and key on cel code 51 illuminates.
-slightly higher idle
-i can rev it up over the stumble by working the throttle open closed open closed etc...to redline
-can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway.

-reset ecu and no cel stored
***with afm (only) unplugged:
-dash cel light as soon as motor is started
-key on engine off cel 24 and 31
- i can NOT rev it up over the stumble by working the throttle open closed open closed etc...
-will not rev past the 2800 rpm at all.
-can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway.

-reset ecu and no cel stored
***tps and afm unpluged:
-dash cel light as soon as motor is started
-key on engine off cel 24, 31, 51 codes
- i can NOT rev it up over the stumble by working the throttle open closed open closed etc...
-will not rev past the 2800 rpm at all.
-can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway.

-reset ecu and no cel stored
***unplugged hac (only):
-no dash cel light
-key on engine off cel 32
- i can rev it up over the stumble by just giving it more throttle
-will rev past the 2800 rpm. and seems to rev up past the hesitation a lot easier than with it plugged in.
-it does not hang up like when it I is plugged in

-reset ecu and no cel stored
***with ect (only) unplugged:
-dash cel light as soon as motor is started
-key on engine off cel 22
- i can rev it up over the stumble by working the throttle open closed open closed etc...
-can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway.
With all unplugged (afm, tps, ect, hac)
-It will not rev over 2800 rpm. And ign timing will not advance and stays at the 10 deg
***With the intercooler pipe from the turbo disconnected before the intercooler to simulate a blown hose. It
-no cel
-it Idles irratic 700-900
- -9 vacuum, and smokes like crazy,
-- i can rev it up over the stumble by working the throttle open closed open closed etc...

****with the HAC unplugged the hesitation is only a little noticeable at idle/not driving.
once it is over the hesitation Driving at 2200-2400rpm. It runs and drives fine. I can hold the petal steady in say 4th gear and about 3200 rpms and the petal stays still and the speed matches without any cut out. But if it is below 2800 to 2200 rpm while driving the throttle sucks. Will not hold speed and cuts out.

no feed voltage change to the afm, tps with the hac unplugged.

05-27-2013, 06:04 PM	#46
ccguy 3" Exhaust Join Date: Jun 2012 Location: az Posts: 50	here is the updated (clearer) explanation: 1987 7mgte rebuilt motor, head milled, oe hg, arp studs torqued to 80 ft lbs and were retorqued after heat sequences, 440 injectors, stock 7mgte afm housing and meter, 3" doenpipe/full exhaust, water to air intercooler, ign timing at 10 deg. wiring to the tps, afm, ect, hac have all been rewired with new wire and to speck on the tsrm for a 1987 7mgte ( http://www.turboninjas.com/mk3supra/...7_Mk3_TEWD.pdf )( i thought the original wiring was to blame), cps is installed correctly and triple checked. ~6300 ft elevation engine swapped into 1980 toyota 4x4 -engine starts and idles great at ~800ish rpms. fuel pressure at 32psi at idle and fuel up vsv line hooked up to the FPR and fuel pressure changes to 40 psi when throttle applied. -ign timing with jumper in place it is 10 deg btdc at idle and at operating temp. -at idle -17 vacuum -PROBLEM: with light throttle (very slowly applying throttle) revs smoothly up to 2800 rpm. once 2800 rpm has been reached if throttle is applied over that the motor will not go past the 2800 rpm and bog down to 2000rpm and act like/sound if you were to exhale all of the air out of your lungs and continued to blow more out but cant. while doing this it will make a stumbling noise and some popping noises, also you can hear the turbo spooling through the exhaust and occasionally a backfire pop through the air filter if the throttle is WOT. this hesitation stays from the 2800 rpm amount of throttle through WOT. up to 2800 rpm the vacuum is -15 or so and when hesitating at WOT it will go to 0. once the hesitation starts it continues through WOT and when it is hesitating the more throttle from the begining at 2800rpm to WOT the vacuum gauge acts as if it is operating from -15 to 0 on a cable attached to the throttle. if the throttle is revved up like vroom vroom vroom vroom sometimes it will overcome the problem and rev up to redline like a normal motor. this happens at idle and even worse during driving. when the hesitation starts at while driving it bucks violently and fells like some suspension is going to break a ring gear, u joint, tranny etc... during driving if you get past the hesitation and are at cruising speed (under 2800 rpm) if you hold the throttle steady and the speed catches up to how far the throttle is open it will feel like a switch, it is off power and will accel back up to where the throttle is depressed (the off power feels like when you would hit the cancel switch while on cruise control). if i open the throttle enough to get over the 2800 rpm hesitation the truck will act like i am flooring it (WOT) even if the throttle is barely cracked and accelerate like crazy until it catches up with the speed and then "power off". here is the link to my youtube with the videos http://www.youtube.com/user/cctool/v...ew=0&flow=grid what i have found through testing. *with the tps (only) unplugged: -no dash cel light on. -with jumper in and engine off and key on cel code 51 illuminates. -slightly higher idle -i can rev it up over the stumble by working the throttle open closed open closed etc...to redline -can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway. -reset ecu and no cel stored with afm (only) unplugged: -dash cel light as soon as motor is started -key on engine off cel 24 and 31 - i can NOT rev it up over the stumble by working the throttle open closed open closed etc... -will not rev past the 2800 rpm at all. -can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway. -reset ecu and no cel stored tps and afm unpluged: -dash cel light as soon as motor is started -key on engine off cel 24, 31, 51 codes - i can NOT rev it up over the stumble by working the throttle open closed open closed etc... -will not rev past the 2800 rpm at all. -can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway. -reset ecu and no cel stored unplugged hac (only): -no dash cel light -key on engine off cel 32 - i can rev it up over the stumble by just giving it more throttle -will rev past the 2800 rpm. and seems to rev up past the hesitation a lot easier than with it plugged in. -it does not hang up like when it I is plugged in -reset ecu and no cel stored with ect (only) unplugged: -dash cel light as soon as motor is started -key on engine off cel 22 - i can rev it up over the stumble by working the throttle open closed open closed etc... -can rev slowly up to 2800 rpm then above that to WOT it will bog down and drop to 2000 rpm while doing this it will make a stumbling noise and some popping noises and occasionally a backfire pop through the air filter if the throttle is WOT while not under load in driveway. With all unplugged (afm, tps, ect, hac) -It will not rev over 2800 rpm. And ign timing will not advance and stays at the 10 deg With the intercooler pipe from the turbo disconnected before the intercooler to simulate a blown hose. It -no cel -it Idles irratic 700-900 - -9 vacuum, and smokes like crazy, -- i can rev it up over the stumble by working the throttle open closed open closed etc... ***with the HAC unplugged the hesitation is only a little noticeable at idle/not driving. once it is over the hesitation Driving at 2200-2400rpm. It runs and drives fine. I can hold the petal steady in say 4th gear and about 3200 rpms and the petal stays still and the speed matches without any cut out. But if it is below 2800 to 2200 rpm while driving the throttle sucks. Will not hold speed and cuts out. no feed voltage change to the afm, tps with the hac unplugged. __________________ 1980 toyota 4x4 truck 1987 7mgte motor, 3" exhaust, water to air intercooler. 4.88s locked, dual cases, lift.....