I agree with you on the IACV and you should probably check the intake air temperature sensor, too. For the IACV, you can clean it out (I used throttle body cleaner, but eventually replaced with one I pulled at a junkyard). You can also check/adjust the resistance on the pins of the throttle position sensor, if needed. I ended replacing the TPS with one I pulled from the junkyard, too. I have the service manuals for the 94, so this is all documented in there.

You probably want to check for vacuum leaks, too. I replaced all the hoses around the intake recently and I also found a big split on the underside of the main intake hose from the air filter to the throttle body. Good luck and I hope you find something that's a clear issue!

 

Thanks for the reply, Zuno.

Done more troubleshooting.

Tested and re-tested CTS and IAT sensors and circuits. Resistance tests, though unreliable, showed both sensors working properly. Power feeds and grounds good for both - solid 5 V to, and solid 12 V back.

Pulled off IAC, and, while grimy, both valves opened and closed correctly. Still, I cleaned the thing 'til it was sparkling silver before reinstalling. Power feed and grounds to IAC good, too, though I gotta re-test again when freezing out.

Checked vacuum lines - all looked solid but one, and I replaced that one. Even then, it was cracking around the barb, so I doubt much air, if any, was leaking out.

Fuel supply ain't a problem - I flooded the engine twice while troubleshooting. I feel confident that it's either an air-supply or air-to-fuel-ratio problem, but, aside from testing IAC power/grounds when freezing outside again, I'm a bit miffed as to where to go next...

 

I know you've stated that you replaced most of the ignition components, but you should still verify you have spark.
Unless your injectors are just pouring fuel like a busted water main it should be pretty difficult to flood the motor if there's spark.

 

Also, if you replaced the ignition components with aftermarket they are a hit or miss in terms of working as designed. We have several examples of defective parts new out of the box when aftermarket, and some success stories where people got cheap aftermarket ignition parts that worked fine. Seems to be a roll of the dice and frequent failures. Take a look at the distributor sticky at the top of this forum.

So.... unless you got Toyota or Denso ignition parts I wouldn't rule out ignition issues (and even with Toyota/Denso you should still perform some level of diagnostics like the aforementioned spark check).

 

Update.

Yeah, distributor is aftermarket, though it's already got ~1000 miles on it, including freezing conditions. Still, y'all right in that it's best to double-check just to rule out ignition 100%. So - just did. Frigid outside right now, and she's throwing beautiful, strong lightning arcs at the wires' plug ends.

The IAC might've provided a clue. IAC is sound itself, as the tests showed when I pulled it off. Have solid 12 V at power feed coming from ECU, and I've a solid 12 V going out to ground at top pin, but nothing on bottom pin. So I jumped that bottom pin on the IAC direct from battery, and she fired right up but idled too high (~2000 RPM). I don't quite understand how the ECU manages the IAC, so I'm unsure how this fits into all the evidence...but I think it does.

Possibly a worthwhile piece of info - the coolant hose from top of radiator to thermostat housing blew out real good just before she started having these problems, and that IAC connection took a solid shot of it.

 

Hey y'all,

Anyone got a link for the female plug for the coolant temperature sensor (I'm lazy and don't wanna go digging for it myself!)? Am thinking that plug might be my problem (and yeah, same problem persists - a pro mechanic I threw $140 was miffed, too) since I re-tested that plug and I gotta play with the probe on the ground side to get voltage. Can see that being a voltage pinch that would then reduce resistance going back to the ECU and therefore cause the ECU to think it's warmer than it is. (That connection took a direct hit from the blown coolant hose, just like the IAC connection did.) In contrast, my '95 Civic's CTS power feed/ground both have very strong, very solid voltage (that car's bangin' great...and man parts on it are so much easier to access).

 

Never mind, found a connector with pigtail.

Sturdy 12 V on ground back to ECM on wire downstream of connector by ~1", but, still, touchy getting that solid 12 V on the connector pin. Will give update when I get the part and swap.

 

Hey y'all,

Okay, I've an update...and yeah, nearly two years later. But I figured what I learned should be helpful to some others out there and minimize throwing parts at problems.

Did replace the CTS connector, and current in/out of it has been solid. Also learned that the voltage the Denso coils throw out reaches a higher maximum than the aftermarket ones (can't recall where I found that info, however), and the aftermarket rotor's contact was notably thinner than the Denso, so I bought the Denso coil and rotor and threw those into the distributor. Those changes helped very, very mildly.

An issue I'd had troubleshooting was that where I lived when I first posted, it rarely got to freezing, and so I had just a tiny window when it'd fail so I could test. I've since moved to a much colder place where it freezes all the time, and so more time to troubleshoot. First morning when it got real cold (~20 F), I got bundled up, ran out to the car to troubleshoot, turned the ignition, and - it fired up just fine. I was shocked. Warmed up fine for a while, too, but then, at a warmer engine temp than in the warmer area I lived before, it died again. After a half-dozen kinda starts (it'd catch for a few revolutions then die), it fired right up with no problems. I then tried starting it at various temperatures, and it became obvious that the problem wasn't related to engine temperature but the temperature of the engine bay.

And I got lucky - one time it failed just enough to throw back a CEL code: 14, no IGF signal.

The only thing that made sense to me at that point was that the igniter was faulty. Checked out new OEM igniters, and nearly had a heart attack at their cost ($500?!?!). Scoured through many junkyard 7A-FEs, and last week I finally, finally found one with the OEM distributor, including the igniter (albeit with 230K on it). I pulled the igniter from the distributor in my car (which I was able to do with the dist in the car, though getting to the igniter's retaining screws was brutal), and dig what I found - the aftermarket igniter's cover had detached and was just flopping around on top of the igniter (see attached photo). Put the OEM igniter in, and - problem solved. No more no starts at all, and I've fired it up in a bunch of conditions now.

So I guess this thread should go onto the distributor sticky.

Two questions for y'all. Man, I'm not sure what I'm looking at in the guts of the igniter - any of you savvy electrical guys see any problems with it? Second, would it make sense that it was just that cover flopping around causing the problems, and somehow at that narrow temperature range in the dist, some current was robbed from the igniter so it couldn't deliver the current to keep the car running? Given that my car is otherwise in very good condition, the insane cost of an igniter from Toyota, the age of the OEM igniter I got in there now, and how hard it's been to find one at the junkyard, it'd be relieving if that loose cover was the only problem with the aftermarket igniter.

Thanks for any help y'all got - and sorry for the long post!

 

Good to hear you figured it out!

I'm looking at in the guts of the igniter - any of you savvy electrical guys see any problems with it?

I'd have to see a good one to compare it with, but nothing stands out to me. Looks like everything has conformal coating except that resistor which I would assume to be a current limiting resistor on the transistor under/next to it. I should look up the schematic for the igniter, but maybe someone else has the knowledge already.

...would it make sense that it was just that cover flopping around causing the problems

Potentially, I could see an issue there in that the guts of the igniter are now exposed to the ambient temp of the engine bay more directly than if that cover was on. I would think that the components used inside would be extended temp parts, but...

 

Zuno - thanks for the response.

Hey, got a recommendation for an adhesive to reattach that cover?

 

Probably just a 2-part epoxy would do the job.