Hello Yotatech community. This is my first post and I apologize if I'm in the wrong Section, I have a complicated question that seemed beyond the scope of the introduction/newbie thread.

So anyways, I had been looking for a truck pretty relentlessly for 1-2 months, refreshing craigslist several times a day everyday, searching for something reliable that I would be proud to own but I also had a budget. Test drove a few trucks, didn’t find what I was looking for. Then about 2 weeks ago I came across this 1-owner 1993 Toyota Pickup Extended Cab, 4 cylinder (22RE) with a manual transmission,150k miles, and it was priced at much less than I was looking to spend.

I checked the carfax, everything was good, no accidents, lots of maintenance records. I met up with the owner 1 day after it was listed, and it was just an ideal purchasing situation. The owner had just bought a new truck and no longer had room for this in their 3 car garage. Super nice people, nice house, nice vehicles, the truck looks ridiculously clean and well-taken care of for a 1993, fresh wax, the interior and engine bay had recently been deep cleaned which I know to be wary of but the owner seemed very trustworthy and genuine, he seemed more concerned with finding a new owner who would take care of this truck than the selling price. Lots and lots of receipts for work done over the last 5 years or so, more money spent on this truck in recent years than the asking price. I test drove it, it ran great, the only things wrong was that it idles a little bit rough/low at 500RPM, sometimes you can hear a tick-tick-tick (pretty sure it's lifters making the noise, they aren't extremely loud and the sound happens intermittently). Everything worked. So really just those two small issues and the AC doesn't blow as cold as you would like for Texas summertime, but it works alright. No check engine light, no visible leaks, no rust anywhere underneath the vehicle. So, I drove away with it that night for much much less $ than I had intended on spending on getting a used truck.





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Two weeks and about 250 miles on the truck later, I can see some leaks now that weren't visible before. The owner told me that about a year ago, he had blown a head gasket, and spent a fair amount of money to have the engine put back together from the head gaskets up for which I have the receipts for (new fuel injectors, gaskets, and water pump replaced). There are a couple of minor leaks on the bolts on top of the valve cover, I can see the black grommets have a couple of cracks in them, a couple hoses need to be refit/replaced, and there is also a significant leak at the back of the engine just below the moon/half circle part of the valve cover gasket (which I've read is common, but does need to be fixed eventually).

Leaks visible after driving it two weeks. 1st picture is near back of valve cover, where one of the grounds is.

There also seems to be a significant leak below where the oil filter goes. The wrong oil filter is on it (filter is compatible with the v6 engine, not the 4 cylinder) it also looks like whoever did the last oil may have used synthetic which could be causing some of the leaks? I plan on switching to 10w40 non-synthetic and using correct oil filter Part # 90915YZZD1 and washer). I plan on doing the manual transmission oil (Redline MT-90 75W90 GL-4 GEAR OIL)and differential oil in the near future as well, I'm just waiting on the crush washers. I've also ordered a Haynes repair manual so I know the torque specs.

So the valve cover gasket, damaged grommets, and all other problems mentioned I feel I could do myself. I've never done a valve adjustment, but I've read enough about it in threads here and seen enough videos to where I'm pretty sure I could even do that myself (or fail, then pay mechanic to do it).
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Now the dilemma...
A couple of days ago I went to check the engine trouble / error codes which I was even excited to check them, I've never had an OBD-I vehicle and I found out how to check the codes from this community. So I used some speaker wires to check the codes and all my initial excitement about this truck just went down the drain.
Error codes are as follows:

• 14 - IGNITION SIGNAL--NO "IGF" SIGNAL TO ECU
• 24 - INTAKE AIR TEMPERATURE SENSOR SIGNAL--OPEN OR SHORT IN INTAKE AIR TEMP. SIGNAL
• 31 - MANIFOLD AND/OR AIRFLOW METER SENSOR SIGNAL CIRCUIT
• 41 - THROTTLE POSITION SENSOR SIGNAL-- OPEN OR SHORT IN TPS SIGNAL

After doing a fairly extensive search of these error codes on these forums, I've found people with a lot of the same error codes, (not all 4 the same, but several posts with 2 or 3 of the same codes) but not really any great solutions. So, based on what I've read, I'm thinking when rebuilding this engine about a year ago after the head gasket blew, the shop that did the work pulled the screws on the air flow sensor that you are not supposed to take out and now the electrical system has taken a huge blow. Most of the threads I've found where they've encountered this problem (pulled screws on Air Flow Sensor & damaged electrical connections/components) the problem is posted but there is no solution... just unanswered questions or failed attempts at finding solution.
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So now I need advice. I've done basic work on vehicles before, I've had my fair share of automotive repair successes and failures. I've got tools and the internet, but I am no expert by any means about anything mechanically. When it comes to car electrical systems, or really just electricity in general, I honestly have no idea what is going on and it has always been a very intimidating topic for me. I have a multi meter & soldering iron and I've done very basic stuff with them before, but really I don't even know where to start with this and the fact that I've found several threads about this problem and no solution is also extremely discouraging...

In the two weeks I've had this truck, I've loved it, but I haven't decided whether I'm willing to put in 100 hours of research to try and understand electricity and this car's electrical system so that I can maybe fix this cars electrical problems and get it running correctly/reliably. Right now, I could turn around and just resell this right away and also make a profit because I got it for so cheap. Any thoughts/comments would be appreciated.

 

Welcome!

First of all, bookmark this: http://web.archive.org/web/201208120...buchanan/93fsm

Those strip contacts in the VAFM can be re-soldered unless they're really screwed it up, depends how far the shop pulled on it after removing the screws. You can take the cover off with a blade cutter to see the damage & solder, but I would just test the VAFM first using a multimeter: http://web.archive.org/web/201209071...33volumeai.pdf.

 

I think I had the 24 and 31 codes on mine. I purchased a new VAFM from NAPA. Took care of my problems.

 

If, big if here, you're not getting a CEL currently, AND it's running so well, did you try clearing the currently stored codes out, and THEN seeing if anything pops when you drive it?
Those codes may be still stored from when the PO was working on it.

Simple procedure: Pull the negative battery lead for a minute or so, then put it back on. Any codes reading now? CEL on?
Drive it for a bit. Any CEL? Any codes to be read?

You want to see what it's doing now, not then, if you see what I mean. If the same codes pop out, fine. If not, do ANY codes come out when you read them? If they do, what are the current codes? The same ones, fine, great. Deal with those problems. If they don't, no codes read out, or new codes, deal with THOSE.

I don't mean to say you're wrong or right. Just a possibility of what may have, or may be, going on.

Good fortune, and enjoy your truck. Remember, it's darn near a classic, and they never run 100%. At least not for long. There's always something to fix

Pat☺

 

That will work to reset codes, but it will knock out all your radio pre-sets, etc. If all you want to do is reset codes, pulling the EFI/MFI fuse doesn't mess with the radio/GPS/whatever. You will probably lose learned fuel trim, but that will come back quickly with a little driving.

 

Congratulations on that purchase! Yep, clear the codes and get a fresh diagnostic start. You got in cheap, so you can dump some money into reconditioning and still be ok.

 

Thank you so much for the responses everyone, I tried pulling the EFI fuse, couldn't get it out and didn't want to damage it so I disconnected the negative battery terminal and decided to to clean all the ground connections since so many people say that is so important.

I found out that my grounds/electrical wiring is different than everyone else's which could definitely be part of the problem. I posted pictures and questions on this thread:
https://www.yotatech.com/forums/f116...l#post52447257

So far I've really just driven it a mile or two since clearing the codes, I will do more driving today and check to see which ones came back. I noticed immediately after cleaning some of the grounds that the headlights are pretty much twice as bright. When I did drive it it was running about the same which overall is well, it just idles really rough at 500rpm which causes the whole truck to shake & the doors rattle whenever I'm not moving, then whenever I am driving and I press the clutch in to change gears it drops to 200-300RPM for a second while I'm changing gears or in nuetral, so it's always dropping super low and that's the issue...Once i'm in gear and driving, it runs perfect.

Also I was reading through the receipts from the previous owner, and the Throttle Body & Airflow meter were just checked out like 8-9 months ago and the mechanic said they were both good. If the same codes come back I will definitely pull the air flow meter & throttle body and check them with multimeter.

I'll post back later once I've driven it a bit and rechecked the codes. Thanks again everyone for your responses

 

One thing I noticed: Several of the grounds you showed were ring terminals, bolted to the body. All well and good, but under the terminals is paint. They may be getting some connection from the bolt, but under the terminals should be clean, bright, shiney, bare metal. The terminals themselves, as well, definately showed signs of corrosion. They should be clean and shiney as well.

The battery terminals must be replaced. No question. The ones shown, are very prone to corrosion under the metal bars holding the wires on.
I got some Marine type terminals. Just have a screw post sticking up from the terminal, and use a wing-nut to hold the wires. Then I put heavy, crimped on well, and heat shrunk, ring terminals on the wires going to the battery, either positive or negative. The ring terminals go down onto the screw posts easily. They are quick and easy to remove too, without actually taking the terminal off the battery. Very easy to keep clean, as well. Since I only use the gel-cell type batteries, like Optimas, corrosion isn't really a problem any more.
Since I put them on every battery, if I need to move one of the batteries from one truck to the other, like if I leave the lights on after driving during daylight (ahem!), I just pull the wires off, and swap the battery. Same if I need to pull the negative lead to work on something. Take off the wing-nut holding the wires, and off they come. No way for the leads to touch something they shouldn't accidentally.

Shortly after I bought each truck, I replaced the wires going to the battery. Both positive and negative. Now I have nice heavy wires, 1-0 IIRC going to both negative battery leads. The main ground wires for the whole system. The two grounds are in better shape as well, one to ground on the engine, I think it's #1, and the other to the body. The positive goes straight to the starter, a 2-0 wire, and another, through the fusible link, to the fuse box in the engine compartment. A 10 or 8 Ga wire, connected to the fusible link.

I also noticed you didn't show a picture of the ground wire going from the head to the body. It's at the rear, driver's side of the head. It's attached to one bolt holding the hook used to lift the engine, with it's other end going to the body behind the valve cover. Is it there? If not, you need to make one, a 10 Ga wire, ring terminals both ends, and attach it. It's an important ground point for the head. It helps keep the differential metal corrosion between the head and block to a minimum.
The ground you showed right above the alternator is OK. As long as it's THERE, whichever one of those two bolts it attaches to isn't all that important. It's the ground for the alternator. Both ends must be clean, however. Corrosion, dirt, oil etc, degrades ground connections very quickly. Very little corrosion can have a very great effect. See your message in the other thread about the headlights

The picture of ground #4 you showedd is in an acceptable location. Mine was attached to the other bolt on the horizontal bar yours is attached to, when I got it.
That is an important ground. It's for the injectors. That's why there are 4 wires in it, one for each injector. Make certain, once again, everything is nice and clean, and that all 4 wires are still tight in the crimp. I haven't had any trouble with them, but I understand that if you move the terminal around too much, the wires can get loose, or get broken strands. Very bad mojo indeed! if you can slide a piece of heatshrink onto it, it will help hold the wires in the crimp, and help to keep them from breaking strands off as it's moved around. Taking the intake apart, etc. As always, the meltwall, or FIT-300 type heatshrink is the best choice. The "glue" on the inside, that flows around everything inside it when you apply heat to shrink it down, helps hold everything nice and tight.

I have to go now, but I hope this helps a little. I'll look at your pictures more later on, to see what else I can see
Pat☺

 

If you do decide to get down to shiny metal on those body-mount grounds, make sure you coat the entire area with some liquid electrical tape to prevent corrosion/rust.

 

Thank you so much Pat, that doesn't help a little, that helps a lot. You just saved me hours of research and headache. I wish I could return the favor but I cannot yet. +10 Karma is all I can give you right now, and my thanks. Alright so I just ordered marine type-terminal and heat-shrink. I've got several other priorities regarding this truck I want to tackle first, but once I've had this truck running well for a while I would like to upgrade the sound system eventually down the road so I'll probably upgrade to some bigger wiring at that point, so thank you for the info in regards to that.

Yes, it is there, I didn't take a picture of because this is the only ground I have that is in the same spot as everyone else's and looks correct lol.

Cool, I've never heard of this product before, found it on amazon for $7 and it's in available in red too so it will match me Purchased. I did sand down the body-mount grounds and I applied dielectric grease to the contacts, but that seems like a good additional measure to take as well, thank you!

 

My pleasure. Glad I could help!
I knew all those schools I got in the Corps, and the 30+ years experience as a radar tech, would come in handy

Another possibility you can use, as long as the area is nice and clean, no dirt or grease, is clear nail polish. Works like a dream. Spread it on any exposed metal, including where the bolt meets the ring terminal, and where the ring terminal meets the bare metal of the body. Then out to where the regular paint is. Seals everything up nicely. Keeps out dirt, oil, gasoline, etc etc. Then, if/when you need to remove the bolt for whatever reason, it just cracks and flakes away, ready for the next time.
Very cheap and readily available, although after a while, my wife made me start buying my own, rather than stealing hers

That "extra ground" you show coming off the negative lead of the battery and going to the body is NOT extra. It's an absolutely essential ground. It grounds the body, and all the things that are tied to it for ground, to the battery. That's one of the heavy wires off the negative lead I put in. I tied it to a bolt going onto bare metal on the body, and yes, I painted it with nail polish
No, I'm not like "that". It's just a handy, cheap sealer, is all. If there's one thing I am, cheap is it!

Remember, as far as heat-shrink goes, the melt-wall, or FIT-300 kind, is what you want for any use on autos. It keeps everything out better than the other, or FIT-200, heat-shrink, which hasn't got the glue inside. Fine for electrical, and electronic, uses in general, but for automotive use, you want the FIT-300. Heatshrink also strengthens where the connector you use, like a ring terminal, Y-terminal, whatever, mates the wire. That's a known weak-point in electrical connections, but heat-shrink makes it much stronger.

Good luck to you!
Pat☺