7mgte stumble HELP

[ccguy]

here is a video from this am
http://www.youtube.com/watch?v=lUgZ2nKX5O8
after this video i am replacing the cps with another due to the oe one used in this video had cracked wires.
also i plan on trying a new tps again and see if it helps????
here is a link to some info i found useful.
www.autoshop101.com/forms/h23.pdf

it is almost like the ecu is cutting the spark or injecors (but the fuel consumption is pointing more towards spark). like in this link where it talks about the ecu cutting fuel when the igf signal is not back to the ecu from the ignitor from a serious misfire.
any new ideas from this info???

[ccguy]

so i am ordering a wideband. i have seen other threads where this type of symptom is caused by overfueling.
so what would cause over fueling? tps, afm/ boost leak,.....??
any suggestions on this would be nice.

[cre]

AFM, boost leak (will only cause real issues at higher loads), excessive fuel pressure, fault in the knock sensor circuit. The TPS is a less likely candidate.

[ccguy]

thanks for hanging in there cre. the weather is going to be bad for a little while so going to have to wait for a little bit.

[ccguy]

well i ran out of $ so no wideband for me yet. the thing runs almost normal with the hac unplugged. but drivability with it unplugged is crap. has a stumble between 2000 and 2500 like a deadspot.
i am going to do some more digging and see if the hac is messing with the volts to the afm, tps, ect. i am going nuts. hope to figure out soon.

[ccguy]

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.

[MA70-3.0GT]

That's really weird, just watched some of the videos & it almost sounds as if IDL and E2 are bridged on the TPS causing it to drop into fuel cut RPM test mode like shown here http://www.cygnusx1.net/Supra/Librar...ction=FI&P=125

Have you tried a substitute ECU at all? And there's definitely no chafed wiring causing IDL and E2 to short at the ECU pins? Hope you get this worked out

EDIT-: Especially this video, the revs are even hanging nearly the right range for it to be an IDL/E2 short http://www.youtube.com/watch?feature...dl693JyvI&NR=1

[ccguy]

thanks for the reply. yes i have tired another ecu. i have a spare. the tps has been rewired with new wire so i dont think it is that unfortunately.
but yea it seems like the afm is telling the ecu it is taking more air than it actually is.
or the tps is telling the ecu that it is floored. this would explain why the motor acts like it is being floored under load ( with the throttle body barely cracked and the motor continuing to rise in rpm like i am flooring it.
also while having the throttle barely cracked and rpm like 3000 the vacuum will be at like 0 but i can hear the waste gate open and the woooosh from that. but it is not boosting.
i really wish i had someone within a 4 hr drive that knew stuff about this motor or had a supra to help diagnose the problem.
but i will look back and check out what you suggested. thanks

[MA70-3.0GT]

Yeah I wish I was able to get over to have a proper look into it, chewy electrical/electronic faults are well, maybe not my forte, but I love working through them for some reason (must be sick in the head lol) & I'd have got my '89 round for some swap-tests too

I've found even new rewire jobs can cause issues sometimes, would def be worth checking for any kind of short at the ECU pins for those TPS terminals if only to rule them out 100%. Also, what sort of wire was used for the rewiring you did? I don't know how sensitive the Toyota ECU is to RF or EM interference but could be worth making the TPS wires twisted pairs &/or wrapping them in foil to eliminate any possible outside interference from other nearby circuits seeing as they deal with fairly low voltages. Obviously you know the knock sensors are very very sensitive to this sort of issue & their wiring should be decent shielded/twisted stuff too (would imagine they're OK anyhow as interference there seems to throw a code 52 and you don't have that at any time right?) Depending how much of a pain it would be, I'd say maybe try to isolate all the low voltage sensor signals from the rest of the loom or at least any sensor wiring that was re-hashed for the transplant.

Another quick check on the TPS & wiring is to block the throttle open slightly, switch on the ignition & run a diag check. Should throw a 51 for no IDL signal at power up. Maybe covering old ground here but then I didn't notice if this check was done in previous posts... Damn I wanna look at this, it's screaming fuel cut at me....

[ccguy]

thanks for the response. i used new automotive grade 16 gauge napa wire. and i have tested the tps wires at the ecu on ohms and volts.
i had a 52 code when i first got it running, i rewired the knock sensors with some shielded coax like the write up online.
yea i get the code 51 with the jumper in and opening the throttle at the beginning and the idl opens when testing the tps wires.
the factory tps wires do not have shielding on them. only the cps, o2, knock have a shielded ground around them.
i have preformed the fuel cut test like in the tsrm and the problem i have acts different in person than the test acts.
but i have never heard fuel cut in person so it is hard to compare it to it.
i am going to have a friend come over and help me in the next few weeks. he has a snap on super computer diagnosis tool, hopefully it can read frequency and maybe even o2 like a wideband?

it is getting hard to remember all of the stuff i have tried. between the wiring checks, sensor/parts checks, and troubleshooting.
i will look into the tps and the wiring again.
i hope i can check and see what the afm reads with the hac hooked up and with it unhooked and see what changes.
i originally thought it was the tps but have not been able to prove it was the tps so far.

i enjoy wiring motor swaps as well and diagnosis. but this one is killing me. it has been over a year.
i tried checking the vf signal at the diag port but i dont fully understand where to go with the results i get.
i have wired multiple motor swaps from tacoma 3.4s to chevy 4.3s to lexus v8 to ford i6s. so i am the guy people go to for wiring problems but i have not been able to figure this one out yet.......