by sergei » Tue Aug 28, 2007 10:08 pm
From my experience (with lots of AE101/cars fitted with silver/black tops) basically almost all pre 1993 suffer from bad injectors, it is design flaw, if you compare prefacelift injectors to facelift or black top there is difference between gaps in the injector cap (spacing is different) this messes up the spray pattern thus no spraying properly it just pours fuel in. The symptoms are (usually very severe when thermostat jams open):
Running rough on idle, random stalls. Random miss fires.
black smoke under medium high load, nailing it results in smoke screen. chronic sooty bumper.
No torque in midrange.
Poor performance.
Black spark plug tips.
Oxygen sensor dead, new one dies after short while.
Only Levins/Trueno/Corollas pre 1993 suffer from this, and preface lift manifold. This flaw gives bad name to 20v. Most of the owners/mechanics are not aware with the problem. I personally rebuilt an engine because of that (bore wash) and did not know it was injectors that cause the bore wash in first place ruined that engine. When I got new engine, it was out of face lift car. When I swapped engines over I used my old manifold + injectors, which again resulted in symptoms above, to try and fix that problem I swapped many things (resulted in 2 dead oxygen sensors, which I revived later), I installed adjustable pressure regulator, when the obvious hit me:
if I increase fuel pressure by 30% it would smoke like a chimney!!! if I decrease pressure by 30% it would stop smoking but run very funny.
Then my friend which had also 20v, which recently spent over $1000 on trying to fix his bad miss fire and smoking problem hinted me that at the end he swapped a few injector sets until it rectified problem (all other ones were pre-facelift).
Since I had facelift manifold with injectors, I decided to swap them (just injectors at that stage) and see if it makes the difference... After I swapped injectors, even if I would increase the fuel pressure by 50% it would not smoke! When I took it to test drive, the car actually had torque where it never had before and it actually was more responsive. Please note I was not aware at that stage between facelift and pre-facelift difference in injectors or manifolds. I also had another manifold with injectors (facelift) and 2 sets of pre-facelift injectors (junk yard missions) again at that stage I was not aware of the difference. So I have tried all other sets and what I noticed that only 2 sets would work fine. So I pulled them out and looked at them, first thing that I have noticed is the spacing between sprayer holes was significantly different (about 1mm).
So I made mental note about that (I did not concluded that the good ones were facelift injectors - again I was not aware of the difference at that time). Then my other mate buys AE101 (this was in 2000 when 20v was cool) and he has exactly same problem, while my mate on marino doesn't.
I would concluded that Marino injectors are good ones, if not for my good set coming from a Levin. So after I did research and found that there is a difference in manifold design I concluded that there was also difference in injectors (which Warwick can confirm, unless toyota covered it up). Every single smoking one happened to be a pre-facelift 20v (AE101), so far I have swapped injectors on about 7-10 cars. To be sure I order /tell people to get black top ones, as if you don't have a sample of a dud one, there is really no way to tell unless measure gap between holes and no wrecker would do that. If I tell mechanics that it is injectors fault, (which I did for my mates levin) they laught, then when they swap every single bit of EFI (AFM, TPS, sensors, fuel pump regulator, ECU) then they order injectors, guess what injectors? OUT OF SAME YEAR!!! so they are back to square one. At that point I told my mate - I can fix this for under $200 all up (black top injectors are about $150 from wreckers, and rest for O-rings). After swapping injectors, the car runs perfectly.