1993 Es300 Injector Pulse Problem

[mobotech]

We're running out of ideas. '93 ES300 was brought in for a blown head gasket. Repaired/replaced applicable parts... starts up and runs great for a few minutes. Found two stuck injectors... so we replaced two injectors OEM Toyota parts on cylinders 1 and 4. Now... Injectors on cylinders 1 and 4 starts pulsing faster than all the other ones after vehicle warms up... or all the other injectors except 1 and 4 pulses slows down once warmed up. Did the test mode and self diagnostics... no codes except the normal 42. Wiring harnesses are fine. Mass air flow meter cover looks like it was broken open or serviced because there is silicone around the edges... but the engines purrs when it's cold. Couldn't be the MAF could it? Any ideas would be greatly appreciated!

[Toysrme]

So to re-cap, what's the problem? It's running like crap after a few min? You better damn well make sure it's not still overheating. You better re-check the *timing* too. Both ignition & crank/cam timing. Warm it up & check compression.

Is it rich? Is it lean? Poor spark? Vacuum leaks are common in this kind of sintuation.

Change the fuel filter. Ya... I said it... There's something that I say once a blue moon.

New injectors have new springs. It takes them longer to shoot the same amount of fuel. (The old injectors stay open longer on the same pulse width.) They shouldn't have the same pulse length. If they did, they wouldn't be squirting the correct amount of fuel. (btw Damn 2 clogged injectors? It's rare enough to just hear of one!?).

Plugged cat 2win!

I wouldn't immediately think it's the AFM (MAF = hotwire, AFM = VAFM i.e. Vane Air-flow Meter) at all. They're a low failure rate part, and if someone is adjusting one, you have to adjust it a long way to make anything more than an appreciable change.

Does it look like silicon a redneck would use, or does it look like it was silicon somebody at a factory would put on with Japanese loving care?

The AFM's are fine-tuned to the engine itself, then the cog is sealed & the idle-bypass screw has an aluminum plug hammered in at the factory so most people won't play with it. Until they get online & figure out they're a dizzy & AFM cog rotation away from turning a 185bhp engine into a 195-200bhp one. (Hence, does it look like it came like that, or does it look like somebody cut the thing off, adjusted it & put it back on?)

For the AFM:

Read the voltage on the VS wire (Blue wire, yellow stripe), or cut the top of the AFM off. (Slice the silicon & pry the top off carefully) & clamp the multi meter lead to the armature itself. DO NOT pull the connector off the AFM without taking the clip off. YOU WILL rip the traces & pins off the AFM & if you're very lucky you can soldier them back on.

Keep in mind EVERY engine will be a little different... Every AFM will be set differently. As a compairison, and my engine is far from stock, but that is as good as you'll get. In park:

The key in the ON position gives around 4.1-4.3v

The engine IDLING @ 750rpm is around 2.7-2.9v

The engine @ WOT, bouncing off the fuel cut is around .2-.3v (Stock average would probably be more like .3-.35)

It's a genII Denso AFM, meaning it's a backwards scale (lower voltage = more flow).

If you still think it's fuel, you should look at the o2 output on the 2 main sensors also. Normal .45v (.4-.5) at idle. Around that cruising. You want atleast 780-800mv @ wot to be safe. 830 is a sweet spot for power/torque, anything more is factory bloated rich-ness & it's likely running a 10:1 AFR. Anything less could be lean, could be an o2 sensor that's old, & could be an o2 sensor that's not hot enough. (They're un-heated.)

Cold-start injector doesn't inject much fuel, I say bypass that idea.

You can check the TPS sensor. On other Toyota's of the type & time they're known to go out-of-adjustment. That is nearly unheard-of in the ES/Camry circles (Even tho it's the same part as models where that is a common thing.)

42 is the speed sensor. Those are easy to replace.

OBD-I Toyota is unsensative, uncaring & doesn't do anything in diagnostic mode. Good for tuning, bad for troubleshooting. The bright spot is atleast you're working with their most advanced OBD-I system. It has diagnostic mode II. If you set diag mode II, it will trip & store every single out-of-spec issue instantly.

That means you'll get the speed sensors b/c you're not moving 6mph, ignition codes b/c ya aint turned the engine on yet, etc. lol

But you can set that & drive around for 5-10 min & see what that picks up.

*Edit* Wrong idle voltage on the AFM. Eh. Can't remember everything dead on all the time.

[mobotech]

First of all... Many thanks for your input on this matter. =)

Yeah, everytime we start it up cold it's runs like a champ. It revs smooth, no smoke, absolutely perfect until 5 minutes later. It's not overheating anymore, and we have the timing set to 10* with the Diag connector jumped. Going to check the cam timing again tomorrow since you mentioned it. One of the mechanics checked the compression cold and said it was "okay" but I'll ask him what the readings were tomorrow and check it warmed up again. Right now it's running way too rich. Plugs are black with just a bit of white on the tip. Checked for vacuum leaks and it seems fine. Good point on the difference in pulse width between new and old injectors. As far as the two injectors we replaced... they were stuck open... hardly clogged. Super soaker out the spark plug hole when the compression was being checked.

Could the fuel filter cause this kind of excess fuel problem? Wishing I have a clogged one!

The AFM (thanks for the correction)... redneck application. Haha... it actually broke loose from resting our elbows on it so we had to reattach the cover again with some black silicone. I'll do those checks you mentioned in the morning too.

The o2 sensors could be bad since the guy ran the car with the blown head (minor at first and progressed) for a while. But could they cause such a big problem to make the system dump so much fuel? At this point I'm open to any and all possibilities. Will post the results tomorrow.

Thank you again!

[Toysrme]

Well it's good to know we've got too much fuel! :) Now we can concentrate on spark/fuel.

NGK 6779's if you want to start with new plugs. $1-2 a pop. No big deal. So the obvious problem, is we have too much fuel dumping into the cylinders. (Or a case of really weak spark.)

Test that AFM real quick tomorrow morning, If you want, get hands on with the damn thing. You can manipulate it by hand to open (more fuel) close (less fuel). Either stick your hand in the pipe, or just turn it via the arm. (Make sure it will open all the way smoothely. The ONLY AFM "failure" I have seen myself in real life was because the flap door was sticking).

If you look VERY carefully at the cog, you can see that there will likely be scrape marks on it *if* it has been moved.

Ya if they broke the AFM loose & actually hit it enough to bend the swing arm in there (You'd have to like.. nearly destroy that black plastic piece, so I doubt it). Ya, that'll throw the entire fuel curve of the engine so ungodly far off it won't be funny.

Looks like that.

I'll tell you like I tell everyone else. Mark the starting position on the cog, else you're asking for loads of trouble... Only re-tune it after exhausting any else under the sun & verrifying the fact that the AFM is the problem.... Because the AFM cog changes the *entire* fuel curve. Top to bottom.

More tension = leaner, Less tension = richer. Don't expect to top the AFM out around 0.03v. That's a boost-only affair. Vacuum can't do it.

Concentrate on getting the AFM output on a multi-meter & checking idle, cruise rpm, transitions & WOT.

I have to appologize too, I was watching a video of my AFM output. I idle at 2.9-2.7v (Normally 2.85-2.89v)

If the AFM output is OK. I would probably check the TPS sensor (Since you have the multi-meter out already). That's the VTA signal. If that's OK, I would jump down into the nitty-gritty of pulling spark plug leads & injector leads & testing the cat / backpressure. (It's easier to me to drop the cat out & run exhaustless than it is drill & bung & weld back together.)

Bits of randomness.

Fuel filter excess fuel. Nope. I was thinking massively lean / rich. They hardly ever clog (lean).

Cold compression values are junk. They'll let you know if it's blown, or not blown, but nothing much relivant past that. (People are just too lazy to take the intake manifold off a second time.) It's freshly rebuild, that !Removed! oughta be over normal spec in the 180's. (psi)

o2 sensors wouldn't cause that big of a problem. You spend the first few min in open-loop mode. If you want to test them without pulling out a multi-meter, just disconnect them. That will force open-loop.

[Toysrme]

Thinking about it more. I doubt yall moved the arm. If you guys hit it hard enough, you could have made the spring that holds the cog in place move. At which point the cog is under spring tension - it woulda spun like a top.

If you look in the closeup of my cog you can see scoring from where it was adjusted at the factory. Why don't you see if there isn't more than 1 scoring mark on your cog.

[mobotech]

Here's an update to the AFM test. With the test lead connected to the blue/yel these were the readings we got:

Key On: 3.91

Idle: 1.9 - 2.0

WOT: 0.425

Way off! I tried to turn the arm manually to match the specs but the engine starts to die out. We're gonna try adjusting that cog to 4.1-4.3 with the key on and see what happens. What do you think? =)

[Toysrme]

Sounds OK to me.

As bad as I'm sure you want to get that thing out of your shop. I would strongly suggest watching the o2 output & drive that car around making some hard, long accelleration runs in 2nd gear. You give a car back to someone that's running lean & you'll kiss that headgasket goodbye all over again. Just shoot for around 830mv (.83v) the o2 sensors at wide open throttle all the way through the redline.

You can just plug into the engine bay DTC & run the wires inside the window.

[mobotech]

We adjusted the AFM to match the specs as close as possible and it smoothed out the idle. Turned it a few clicks clockwise and rechecked the timing. When the plug on the AFM is jiggled the voltage reads as high as 4.98v with key on, from the previous 3.91 reading. What's causing that??? Anyways... we decided to take it for a test drive (40 miles to be exact) and the smoke cleared up and idle was still smooth. Rechecked the voltage reading from the AFM while idling and it was a steady 2.84. So far so good. Would've never figured that the AFM would be causing all this commotion! Hopefully after a cooling system flush and a oil change it'll be ready for delivery! Thanks to the valuable information you've provided us. :)

[Toysrme]

No problem. Good luck with it. I bet yall just knocked the little spring off that holds the cog in place & it went spinning around abit. No big deal.