mikegbuff

93 Toyota Pickup Dlx 22RE 2.4 L
I have battled an intermittent engine miss for the last year on my truck - happens both at full throttle and when starting from a stop. It has gotten more frequent lately and actually resulted to cutting off on idle and being very hard to crank back up at times (happened at stop lights/signs a few times). No issue when cranking after truck has been sitting a while. Over the past year, I tried several fuel injector/system cleaners, changed plugs/wires, new fuel filter and even tried a mass air flow meter based on the advice of a mechanic who said it is going into a "flood state". The new air flow meter/sensor that didn't fix the issue either. Check engine light has never come on and I've tried to get trouble codes a few times via the jumper method and got nothing. I finally got some trouble codes today when I tried the jumper method. Does anyone know what the problem could be with this one: "31 - Air Flow Meter signal (Vacuum Sensor signal)" ? Could this be related to my issue?
At this point, my next step is going to be a new ECU unless I get other advice. Two mechanics didn't think my fuel pump is the issue, but they didn't actually test it. One other thought is the cold start injector switch could be causing it to flood, but I've always heard a bad one of these will kill your gas mileage and I haven't noticed any effect there.

I'm also showing these codes. I got them with both the engine cold and when it was at normal operating temperature. I assume these are unrelated to my issue?
22 - Engine Coolant Temperature Sensor signal
24 - Intake Air Temperature Sensor signal

Thanks for any insight.

scope103

That's interesting; there was a long thread on just this issue recently https://www.yotatech.com/forums/f116...cement-309022/

Oh, that's you! You got a lot of advice in that thread; did you follow any of it?

Whenever you get code 31 (open or short to ground on VC) and code 24 (open or short in intake temp sensor) together, a light should immediately come on. They are BOTH in the VAF, and their wires are in the same bundle. You could have a bad VAF, but those are two independent functions in one box, so they won't necessarily go bad together. But you've got an open or short in a circuit, and wires can easily go bad together when they're next to each other. That's where I would look.

The wiring for the ECT isn't THAT close to the VAF wiring, but two bad wires in a harness sure hints at more bad wires. I would check for the ECT signal back at the ECU. Easy to do.

I'm not sure where you're getting your definitions of codes, but tread carefully. You don't have a "Vacuum sensor" to give a signal. (You seem to be getting a fair amount of demonstrably wrong advice.) Here's the FSM section with the codes. http://web.archive.org/web/201211190...85diagnosi.pdf

You can replace the ECU if you want (they're expensive, unless you get a junked one ...) But it doesn't seem too likely that would explain your problems.

mikegbuff

scope103:
Thanks for the info - very helpful.
Here is the link I was using for trouble codes: https://www.troublecodes.net/toyota/ Your link is better, I haven't seen that one while searching.
My biggest issue has been no one (dealer included) wants to try anything since I haven't been getting any codes and the issue is so intermittent, it can't be easily replicated. I'd love to go forward myself, but don't have a lot of electrical knowledge, so I'm thinking I'll take the truck somewhere again hoping these trouble codes and your thoughts gets someone to actually check things on it. It's been frustrating, not being able to trust driving my truck the last year as I love it as a second vehicle. I talked to the manager at Autozone and they have a rebuilt ECU for $220 that they said I can get to try. If it doesn't fix the issue, I can return it as long as it doesn't have any scratches on it. I know theirs won't be the best quality, but it would quickly eliminate/confirm that potential issue for sure. That was my next step before I got the info from you. So now I'm debating, try the ECU or take it to someone with the info I now have on the codes. I've never been one to take my vehicles to the dealer, but wandering if that may be the quickest resolution at this point. I just don't want to mess up anything electrical through trial and error.
I did start a new thread since I now have something to go on (trouble codes and more frequent issues) and I had originally titled the thread around the mass air flow sensor since I thought that was the issue. I tried to summarize the previous thread so it would be more concise for people to read through since I was shooting at a black hole previously and thought it was the VAF before I tried another one on it and that didn't help (works fine on the '92 truck it is on now and shows as same part # as mine) . I tried everything suggested there that I was able to and suggested the other things to people who have looked at my vehicle.
Once again, appreciate the response and best regards.

Aaron Borhegyi

I replaced my MAF twice before the code 24 for air flow had finally been removed. Maybe same with you. Defective on Arrival, it happens :/
I would replace your coolant temp sensor too its screwed into the water block behind the upper plenum and fuel rails. Junkyard cheap.