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Discussion Starter · #1 ·
I had hijacked and posted a few times in another thread but figured I should be polite and start my own. My '91 4x4 p/u, 22RE, started running crappy. Acted like a fuel line prob - like it wasn't getting gas (stalling, etc.). Changed the fuel filter (what fun) and you can hear the fuel pump running when the ignition is turned to "on" so I'm fairly sure it's not that (especially since I could smell a lot of gas). After changing the fuel filter, it will run (barely) but seems to be running vey rich (black exhaust smoke) and is missing. I finally figured I'd check the codes even though the CEL wasn't on - it did give me a code - 13 which indicates the distributor. (Since resetting the codes and running for a short time it has not given any code at all). Plugs look bad like it's been misfiring. Distributor seems ok - gap is ok, cap has no cracks, rotor looks fine, resistance on wires is ok, etc. Resistance on coil is ok but I get nothing on the ignition control module, which is why I am now suspecting it is the problem, but I'm not sure. Anyone know how to test it? Autozone says they can't test this particular one, all the other part stores say they don't test them. New ones run $250-$300 and I'd kind of like to know that the module is the problem before spending that $ on an electrical part that can't be returned. I've been through the Pick-A-Parts to find one just to throw on the truck to test but haven't been able to find one. Regular junkyards still want $100 & up (for a 20 year old part that might burn out tomorrow? no thanks). Any advice would be appreciated!
 

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Discussion Starter · #2 ·
Spent some more useless time at more Pick-A-Parts. This igniter just isn't out there. Checked for spark and instead of being blue-white it seems a bit yellow. Going with the cheaper things first, I'm going to change the coil tomorrow.
 

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Discussion Starter · #3 ·
More and more confused...

Truck still not running well. :( Been a while since I've posted but here is an update of what I've done since:

new coil - spark better, still running rich/ratty/missing

checked compression, which was still ok but lower than I wanted - thinking valve job will be coming but not causing this issue

since originally I got a code 13 (which hasn't repeated) I swapped in a new distributor/rotor/cap - no good

I started suspecting fuel line probs again. By the way, spark plugs were ALL black, and they only had maybe 10,000 miles on them at the most. Checked fuel pressure, which is fine, although the fuel pump & fuel pressure regulator run with the key on, engine off EVEN without the terminals at the check connector shorted out - not sure if this could have anything to do with it?

Checked the O2 sensors (2 of them since I'm in CA) - the resistance on both were a little high (7.9 ohms or so - if they were the problem shouldn't the resistance be low?) and they appeared very black, also pulled the catalytic converter, which I think is ok - it's dark but you can see light through the middle of it, but it did feel very heavy. Not much debris came out of it. Started the engine without the O2 sensors or converter and it the engine still vibrated a bunch and it acted like it was still missing.

At a loss, wondering if I'm into a timing chain problem. Please, any ideas or suggestions are appreciated.
766FDFEF-AE60-89FA-F6EB-0340AB6FB3FD
1.03.01
 

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Sounds like you are troubleshooting OK just haven't hit the right combo yet. The problem is running way rich, correct (therefore the miss due to plug fouling)? You have spark so I think that is not the problem. There is too much fuel----how about the fuel pressure regulator? Search for threads on here, there are a few with that problem. Also try cold start valve leaking/not shutting off (some threads on here too). Just for info, how many miles on engine and has the timing chain been replaced? It could have jumped a tooth or two but I don't think that would cause the excess fuel problem. Keep us updated.
 

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Discussion Starter · #5 ·
Thanks for the reply! Actually right before I saw you replied I bit another bullet and ordered a fuel pressure regulator online (for a 19 year old truck parts sure aren't cheap). After some more research I decided that the regulator/fuel pump should not be running non-stop with the engine off / key on unless the check connector is shorted out at +B and Fp terminals. I think it should run for a few seconds until it builds up pressure and then shut off, correct? I didn't notice this until I started having probs so maybe the regulator isn't controlling the pressure correctly. I did a fuel pressure check yesterday and it came out ok, but I read another story of someone with very similar problems and it turned out to be the regulator even though their pressure was within specs also. The only difference in their story was that pressure dropped immediately after shutting off the engine. My pressure dropped slowly to about 15-18 psi after about 2 mins, but it may have been leaking a little at the banjo bolt fitting at the cold start injector where the tester gets hooked in - couldn't get a perfect seal (book says it should stay above 21 psi for at least 5 minutes after engine cutoff). So I will try replacing the regulator, pray that's it and update this thread when I do. Probably won't have the part in hand until next week.

As far as miles, I've got about 210,000 on it and no, the timing chain has never been replaced, so I figure I'm headed down that road and maybe even a valve job soon even if the pressure regulator fixes the problem.
766FDFEF-AE60-89FA-F6EB-0340AB6FB3FD
1.03.01
 

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Wow, 210K on original timing chain (& guides!) is great. Obviously, though, you can easily check for jumped timing chain by just checking the timing while running. You know a lot about mechanics and I'm sure you will get it fixed. There are so many variables that the same problem can have different symptoms. Certain parts can be expensive, no argument there. I'm waiting to see the final diagnosis and repair.
 

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Discussion Starter · #7 ·
Update: still running crappy.

New fuel pressure regulator made no difference - still runs with key on / engine off.

Changed the plugs & wires for the hell of it - no difference.

Pulled the coolant temp sensor & tested resistance in & out of hot water - checks out ok. Also checked resistance on air flow meter - checks out ok.

Pulled the O2 sensors again and tested voltage while hitting them with a propane torch - voltage seemed very irregular so I thought maybe I'd found my prob. Replaced both sensors with new Denso ones. No good - still running crappy. Although now I am getting code 42 - speed sensor. Don't really think that would be the problem though.

My brother in-law knows a dude that is a mechanic for Toyota. I think I'm going to see if he can have a look at it. I'm getting tired of pumping money into this thing without any results. I've put in about $500 over the last couple of weeks and at some point I guess I have to decide whether to keep doing it or retire the vehicle. I suppose it could be the ECM, but those run about $400 and up...
 

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Discussion Starter · #8 ·
Update: Fixed!!! (except for making sure it passes smog)

Had the Toyota wonder dude come over the other night to check it out. It took him about 7 minutes to figure out the problem: air flow meter. Wish I'd had this guy's number a month ago - would've saved me quite a bit of cash. I had already checked the resistance of the afm and it checked out ok, but the problem was that the return spring was broken, keeping the flap wide open, but the electronics of the thing were still working. Just finished installing a new Python afm (rebuilt, Amazon.com $195) and the truck started up fine and sounds very good! Heck, I just about have a new truck with all the damn parts I've been buying. Anyway, hope this info helps out someone with similar difficulties!
 

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YOTA Master
'93 2wd P/U
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I know it is a bit late for the author of this thread but I thought I'd throw this out there for those who follow.

Generally speaking, Ohmmeters are not what you need for accurate diagnosis. I mean they have there place, but too many people put too much emphasis on them.

In order to get to the root of a diagnostic problem your friend is the volt meter. In the factory diagnostic manual you will find pinout voltage readings for the the EFI and ignition system, including the airflow meter.

More often than not you will find good readings with your ohmeter and a voltage test would show the problem. Conversely you can sometimes find bad ohm readings and the part would be OK, this would also show on the volt reading.

It also helps to have a good fundemental understanding of the system you are testing.

Hope this helps.

Victor
 

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Discussion Starter · #10 ·
Good advice. However for the air flow meter the only testing method shown in the factory service manual was to check the resistance and I didn't come across a voltage test procedure anywhere. I have a volt meter and could have used that (in fact I did for the O2 sensors, which tested bad but weren't the problem), but I would have had no idea what the proper voltage should be. Thanks for the input - although late for me . :)
 

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YOTA Master
'93 2wd P/U
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In the factory manual there is a chart in the diagnostic section that gives voltage readings at the different pins on the ECM. I can't remember off the top of my head the specs but it says that voltage between VS and E2 should be X-volts with the measuring plate fully closed, and Y-volts with the measuring plate fully open. I'm thinking if you had done this test, it would have stood out that the measuring plate had no tension on it.
 
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