4AGZE ECU issues but no fault codes.
Reposting from Toyomods to better my chances of fixing this!
Hi guys,
I'm trying to suss out an idle and hesitation/load issue with my 4AGZE. I figured I'd start with a search and have looked at all the obvious.
The idle problem is the "common" issue: Ticks over fine (first time every time), revs up to about 1800 then settles at about 14-1500.
If its warmed and left parked eventually idle comes down and settles about 900RPM, revs fine, runs fine, timing is good, the only problem is as its warming up the idle is up and down +-100rpm every couple of seconds until it finally settles.
If its driven, whether its allowed to warm up completely first or before its completely warm, the idle issues begin. The idle can be anywhere from 1400-2000rpm. Sometimes it looks like it's starting to drop then it surges back up. When its at this point, unplugging the TPS and ISC can bring the revs back to about 1000-1100 but thats it and once they're back on the RPM is back up. The only thing that drops the RPM back to the set idle is unplugging the coolant sensor but that throws a code.
The hesitation/low power is only below 2,500-3000rpm and it feels as if the engine is labouring with no load (whole car shudders), as the revs creep theres a hesitation then it surges and away she revs (feels like really bad turbo lag). Cruising anywhere around 2000-2500 and the whole car shudders at the sight of an incline and the exhaust sounds like a trombone. It also bucks a little cruising at this rpm too, nothing drastic but the worse the idle the worse the bucking. Finally, its impossible to take off from the line without massive clutch slip. If its idling at 2000rpm it does not want to drop below this, again the whole car starts shuddering and kicking like its on the verge of stalling.
The cars an AW11 4AGZE Manual running Auto ECU, with the neutral start bridged (possibly should be disconnected after start?) and the Auto computer disconnected; though, I've just found that while this doesn't throw codes it alters the throttle voltage and possibly others?
I've checked the coolant temp sensor and compared it with another.
Checked the AFM
checked the vac lines
bled the coolant
checked the ISC
timing is set to 8DTOD.
earths are good and ran extra to try to alleviate the issue.
New plugs
new diz
leads are ok
and spent hours getting the TPS perfectly within tolerance (surprisingly hard to get 0.8Ko at closed and infinite at .65mm).
All ok.
Finally I've checked the ECU and not so good.
TPS-ECU ohms VTA-E2 0.77 closed (0.2-0.8 tolerance) Open 1.77 (3.3-10 tolerance) Where did the rest of the 3.5ko I measured at the TPS get lost?
(IDLE/THA/THW-E2 all ok)
TPS-ECU Volts IDL-E2(open only) (auto comp off) 4.55V, (auto comp on) 11.55V. AT tol 10-14V MT tol 4-5V
VTA-E2 (trottle closed) 0.51V tol 0.1-1V, Open 3.05V tol 4-5V
W-E1 1.57V tol 0.5V or less.
Everything else was ok...
Another issue I've noticed is my temp gauge never stays still! I've checked the sensor and compared with another and its fine; but its bouncing around like a yo-yo (not physically bouncing, just never stays at one temp). Again if the car is left parked it climbs fans come on and everything is stable. If I drive it, the temp drops back to cold within a few mins at 40-50km/h regardless of how I drive.
I've done all the suggested quick fixes but can't seem to trouble shoot a solution. My best guess is the ECU is confused by sensors but is happy to accept the signal and just adjusts as it sees fit.
EDIT:
I've had a bit more of a play around and not much luck, tried it with the auto comp on and same deal.
The leads are all about 8Ko.
It now sounds like its pinging while free revving but the timing is staying advanced.
It really seems like its something to do with the cooling sensing side but everything there is working fine, the only thing the computer is getting wrong is the VTA-E2 and I have no idea where the resistance drop could be coming from (or how its even possible).
This is the most confusing part! How is it possible for resistance to drop between the sensor and the computer but if the sensor is unplugged increases to infinity? I'd have thought it was a leak but jumping to open when its unplugged indicates to me thats not the case.
I've attached a photo of the plugs for no reason at all.
EDIT 2:
Ok, I've isolated the leak to the E2 wire link in the AFM. Its meant to be there. I've checked it against a second loom, second AFM and second TPS and its designed that way. The back up set does exactly the same, with the AFM plugged in, TPS output reaches 2ko (under tolerance) with the AFM unplugged TPS output reaches 6.5Ko (right in the middle of tolerance). I've double check timing again and its still fine. I've triple checked the temp sensing and its all exactly within spec, yet it runs perfect when its disconnected. What am I missing?
Any help?
Thanks
Nick