ToyotaViejo

In the process of troubleshooting a few problems tied to idle, fuel economy and mixture, I happened to test the pigtail off the distributor today and have some questions about the result.

My measurements are all "hot" as confirmed with a laser thermometer.

G1-G(-) should be 160Ω-235Ω, and mine comes back at 495Ω FAIL
G2-G(-) should be 160Ω-235Ω, and mine comes back at 493Ω FAIL
NE-G(-) should be 190Ω-290Ω, and mine comes back at 241Ω PASS

I have not measured the air gap in the signal generator under the distributor cap. It's not adjustable (to my knowledge) on the 3vze; nor is it replaceable (again, to my knowledge). Since the leads test bad, why bother with the rest?

I replaced/calibrated my TPS, and put in a new Denso o2 sensor to get my idle and exhaust smell back under control. The truck runs and drives GREAT until about 2600rpm in the higher gears under heavy load. At that point, there is no difference between half throttle and WOT.

Fuel pressure is good, AFM is good, compression is good, cap, rotor, plugs and wires are a week old (properly gapped and installed), coil tests good, igniter tests good.

After the O2 and TPS change, the exhaust smells like nothing at all.

In fact, the truck runs perfectly except for lousy fuel economy and a dead spot in the throttle range above 2600rpm. Flooring it in 4th gear on level ground at 2300rpms does really nothing at all. It does accelerate, but not in the, "my foot is through the floor pan" way. I've driven an identical truck and, while still a dog, was much better mannered.

Vacuum lines should all be good. I've sprayed enough propane under the hood that I'm lucky to even be here posting this. Intake hoses have been replaced.

I have every tool under the sun except a timing gun. It walked away years ago, and this is the first adjustable timing vehicle I've owned since it got loaned out and never returned.

Certainly, without knowing what the timing actually looks like, I can't tell you if it's 10 ahead or 10 behind. I can tell you that it sounds pretty OK.

To the point- The distributor tests bad. It's not mechanically bad (slop, noise, etc), but it is electronically bad. This means that the ECU is probably not getting a proper cam reading (via the G1/G2 signal) from the signal generator.

Is there anything else that can be causing the problem? The distributor is a $300 part for a decent reman, so I'm cautious in throwing the part in if something else is causing the high resistance. It is an aftermarket distributor (factory style plug, but wrong colored wires and no Nippon Denso markings and a sticker from a local shop). Probably a Napa part if I had to guess. I have no idea how old it is.

Also, can a bad signal generator cause poor fuel economy and the power dead spot? It does feel like it could be an advance problem. Jumping T1-E1 DOES NOT change idle speed.

By poor fuel economy, I mean about 12mpg on a 3vze with 40,000 rebuilt miles, emissions with flying colors, 5-speed, 31x10.50 BFG AT tires on a 4.56:1 final drive running Maxlife 10w40. To boot, I drive this thing like an old man. I shift up at 2200-2400rpm and cruise at 1500-1700rpm. I'm not expecting miracles, but 16-17 should be attainable in-town with this thing.

If the distributor bad test is not erroneous or caused by something else, I'll change it out as defective even if it doesn't fix the power/economy problem. After all, one less bad part. But maybe this is My Problem™?

What do you all think?

proeliumfessus

no change when jumpering te1 and e1, I have the same problem

jbtvt

I have no firsthand knowledge of this, but hadn't heard of any resistance checks on the dist, so flipped through Haynes. According to them, the resistance checks only measure the signal generator, so replacing the SG, in theory, should solve the problem of those readings, if not performance. If air gap is out of spec, the whole dist allegedly needs replacing. Check Ebay before spending $300 either way.

ToyotaViejo

Yes, you're right. The resistance checks on the distributor test the static function of the signal generator.

How critical the signal generator is to the overall efficient operation of the engine is unknown to me; but with it being out of spec by a bit more than 100%, it's bad either way.

I cannot find a signal generator for the distributor as a service part. The dealership says to replace the distributor, as does the FSM and the chain parts stores.

Any ideas of who might make one?

I'd be more inclined to get a junkyard part, but with my luck, I'd get one that tests fine electronically and is dead mechanically.

ToyotaViejo

I'm kinda dumb. Really dumb, probably, but at least kinda dumb.

I got a light and shot my timing with the jumper in and the jumper out. With the gun set to "10," the timing marks all line up on TDC. Pulling the jumper, while not particularly audible in the engine) does move the advance up a bit. I set the gun to "8," and all the hashes move to TDC.

The right way of doing this would be to put a tach on the DIAG box under the hood, because hearing a 50rpm change on this engine is like listening for a lizard to fart as a 747 takes off behind him.

Once I knew what to listen for, yeah, I can kinda hear it.

Also, it's important to note that the vehicle should be all-the-way warmed up. Jumpered in and at operating temperature, mine idles at a perfect 850.

So for this fuel economy/performance thing, it basically has to be the distributor/Hall sensor not working, right?

There's no way the timing belt could be a tooth off and run this relatively well, correct?

Between a slightly wandering timing mark and the high resistance in the Hall sensor/signal generator, I really, really, really hope this fixes the problem.

Tommy the Cat

I'm very interested in your outcome. Please keep us posted.

ToyotaViejo

Here's where I'm at sop far:

The dealership wants $700 for a new distributor AND it's not here in town; worst of all I can't return a special order.

I say worst of all because I have ordered 4 remanufactured distributors from two different vendors and every one of them has tested as poorly as the one now in my truck.

A dealership service tech confirmed that I am testing them properly (not that I didn't think I was, but since so many were failing...).

So I went to a Toyota-only junkyard and the guy let me test every one they had (I stopped counting after 10), and while some were better than others, they were all well out of spec.

I've ordered a new part from O'Reilly Parts (Rockport, Rockmount, Rock-something) for basically the same price as an A1 Cardone reman.

Never heard of the brand before, but if it tests within spec, I'll take it.

ToyotaViejo

Done and done.

While there are still a few bugs to stomp (and new ones will crop up, I'm sure), the power and, seemingly, the fuel economy problem(s) are resolved.

Just to be thorough for this wrap-up, I started noticing terrible fuel economy even for 3vze standards of 12-14mpg in town, and very slightly better on the freeway.

Also, the exhaust smelled rich, the idle was way high even after the computer controlled kick-down when it warmed up.

Worst of all, between 2k and 3k rpms, power was dramatically reduced.

There was not Just One Problem™.

The TPS tested out-of-spec and was replaced and adjusted with the throttle body off the truck. Slight improvement in general acceleration and idle.

The Bosch o2 sensor tested nearly out of spec, and was replaced with a Denso. No power or idle change, but the exhaust smelled less rich.

VAFM sensor was cracked open and the spring was tensioned two clicks in the lean direction (clockwise). Exhaust smells fine once the truck reaches operating temperature. No changes otherwise.

Air tube from silencer to throttle body had a small crack under the throttle body clamp. Replaced the hose. No change. I don't think the crack was far enough down to allow unmetered air through it.

PO had installed a K&N filter that was repeatedly over-oiled (to each his own, but I HATE K&N filters) and gummed up the VAFM. The filter, while oiled, had apparently never been cleaned either. I hit the VAFM with carb cleaner and replaced the filter with a disposable Wix (I LOVE Wix; even better than OEM in my mind) filter.

Pulling the spark plugs showed that #4 was cross-threaded (hands down the easiest to get out of that engine, and they screwed it up), and only in about halfway. Crush gasket was uncrushed. Thread cleaner and a new plug and no helicoil was needed. Next time, it will be. Other than that, plugs looked normal, and very worn. Replaced with NGK OEM-style plugs and idle/fuel economy improved slightly.

Wires were in excellent condition and were left alone.

Cap and rotor were probably halfway baked, but were replaced. Slight improvement in throttle response.

I pulled the codes, and a "12" came up indicating a possible lack of RPM information within two seconds of key on. I cleared the code and it never came back. Even after an intentional stall.

The Hall effect sensor/signal generator in the distributor tested bad. I went through so many reman and junkyard (well over 14) distributors that all tested bad, that I began to think I was testing them wrong. Nope.

A $600 OEM distributor, while definitely the best option, was not financially possible for me right now, and no one had one in stock in town to be tested anyway.

O'Reilly Parts (formerly Checker/Shuck's/Kragen) ordered four A1 Cardone remans for me, and most tested worse than the Napa one presently in the truck. I've had good luck with A1 Cardone in other applications, but the Toyota tolerances are pretty bloody tight. There's a reason that a new Denso costs almost $700 after tax.

Finally, O'Reilly ordered me a new Richporter distributor that tested good (and was surprisingly well-made) and I tossed it in the truck on Thursday. It was, quite possibly, the easiest-to-change distributor I've ever seen. Took about 10 minutes start-to-finish; and I did it with the engine at operating temperature.

It came with a lifetime warranty, and is easy enough to change that even if it craps out every year for the rest of the truck's days, I don't mind throwing in a new one as long as I'm not paying for the part.

While I was under the hood, I re-shot the timing as close to 12BTDC as I could (my light is not great), and the tick marks line up perfectly with no fluttering or jumping around. Before the new distributor, the tick marks moved around; DIAG jumpered or not.

Been driving it two days now. Throttle response is remarkably better and my fuel gauge is not moving in time with the accelerator pedal. I never expected to get Prius economy out of this thing but 15-17 in town and 20-22 on the highway should not be a problem for practically anything smaller than a big V8 with a good tune and parts in working order. I know it was originally rated at 14/18, but keep in mind that older engines are less resistive and lower compression than newer engines; and hence turn with less resistance.

It would appear that I'm getting 16/17 in town now (A/C off). I haven't run out the tank yet, nor have I done any amount of highway driving. There is some power in the 2k-3k rpm range that makes it acceptable to drive. I mean, it's a 3vze dog, but even a dog shouldn't have mange. I had a 4-popper Jeep prior to this; so I knew what an underpowered truck feels like; and was not expecting 1UZ-FE performance out of it.

I still want to change the fuel filter and the fuel pump, but that will have to wait for another day and some money. Filter's in good shape externally, so it hasn't been on there real long. The pump is 21 years old and has 240,613 miles on it; some in the desert. A new Denso is ~$200 from sparkplugs.com and I'll replace it before it leaves me stranded somewhere.

I also fixed a broken terminal in the light over the tailgate so the bulb works again. That made a massive power and fuel economy improvement simply by adding photon power to the rear end of the thrust capacitor and opening a channeled envelope in the time-space continuum allowing me to travel in an eddy-free fiber. Kidding. But having a working light back there is kinda awesome.

After a very long post, the moral of the story is: If you have crappy power and lousy economy and you've checked the usual suspects in terms of sensors and air leaks, pay attention to your distributor. Mine was mechanically fine. Very small amounts of play, but well within what "felt" right. It was electrically dead, and since the Hall effect sensor is the ECU's only clue about where the cams are, probably dumped all kinds of extra fuel in to accommodate an inability to measure and advance spark.

FWIW, my 48-hour experience with the Richporter part is positive.

Now to go fix the leaking oil pan, valve covers, rear main, input shaft seal and (possibly) the tailshaft seal. The tailgate lock cylinder will roll the window up, but not down. Gotta get on that too.

Thank you all for your help. You guys have been THREE KINDS of awesome.

jbtvt

Nice update, thanks.

Tommy the Cat

Thank you for taking the time to chronicle your experience. Any updates on fuel economy or general function? How about a part number? My distributor tests just outside of spec and I'm thinking it may be at fault as well. I have a problem getting past 4500 RPM and a lack of power from 3500 up. The VAFM checks good, newer O2 sensor, no codes, fresh tune-up, brand new engine. I have disconnected the exhaust at the cat to no avail, and this is really the only part that tests out of spec by any appreciable margin. The TPS is slightly out at closed throttle at 835 ohms (spec of 300-800) but checks good at all other points and is a fairly new Denso unit. The VAFM test good. New engine has 1,000 miles and no more power than the 200,000 mile engine it replaced despite cleaning massive deposits out of the intake. My mileage has declined from around 20 MPG when I first got the truck in 2007 to around 15 today. There doesn't seem to be a difference whether the throttle is half way down or all the way to the floor, it accelerates the same either way and damn slow at that.

FWIW my truck is a 1990 4wd, 5 speed.

ToyotaViejo

Hey Tommy,

I've been out of town a bit recently, and haven't burned off that whole tank yet. I can say that the gauge is on a half tank and I have about 130 miles on it so far. That is a wicked-good improvement over where I was. 25 percent or so.

Throttle response is much better; with only one caveat. It's still an absolute dog in 4th.

I'm working on a theory that will require way heavier math than I'm presently willing to do, but I think 4th gear just stinks.

This transmission (R150) has a "powerful" 5th (overdrive) gear compared to other things I've driven in that it will easily accelerate. 5th was not a pull gear in basically anything else. Ok, my buddy's Carrera 4S pulls hard in every gear.

But 4th seems to have a hard time in my configuration. Like 3 is the tall, in-town gear and 5 is the cruising gear and 4 is a brief means to an end. If I shift into 4 and let the rpms hover at 2750, it has pull. If I have it in 4th at 2000 and put my foot through the floorpan, a whole lot of nothing happens. It does accelerate; but not quickly.

Despite this, the truck will bark the tires in 1, 2 and R with little coaxing.

I'm 4.56 final drive on 31x10.50s, by the way.

Needless to say, I'm perplexed.

I totally 100% believe you when you say you were getting 20 on it "new." I'm not sure how. Maybe your version of in-town is different than mine.

Most of my driving is 30-45mph stop-and-go traffic. Lots of speeding up and slowing down. In fact, I have yet to drive more than 25 or so miles on the highway in any one trip. That will change soon.

That in mind, I know I absolutely babied the truck when I got it. I upshifted at 2200 rpms every time. These days, I find myself upshifting at 2500-2700. Right there, I've lost mileage - and it has nothing to do with the truck. I'm just more comfortable in it knowing exactly what it will do and driving it at that limit.

To wit, my wife drives a 2007 Civic we bought brand new. It presently has 32000 and change on it. I very infrequently drive it; but I did take it on a 1000 mile road trip this spring. I got about 37mpg in it; and it's rated at 32 on the highway.

My wife just got back from a slightly shorter road trip and got about exactly 32 average. I chalk that up to her DRIVING the car, and me taking it easy since I'm not that comfortable in it.

My point in all this is that some 20% of your economy is in your right foot.

Bearing that in mind, on anything this old, there isn't just one problem.

4500rpm is the end of the world for these engines. They make top power at 3800, methinks. But, if you have a bad distributor, that would move forward the end of the world.

That in mind, you say that 835Ω is slightly out of spec at 300Ω-800Ω. My FSM doen't show anywhere close to those values in any test. Mine shows closed to be 470Ω-6100Ω closed on VTA-E2.

Take the time to remove your throttle body (and the TPS therefrom) and soak the heck out of it in carb cleaner. Blow compressed air through every jet in the thing until it's sparking.

You might also check to see if your dashpot is properly adjusted (see FSM). The butterfly in your TB should not actually close all the way - close, but not all the way. If the stop isn't properly adjusted, you're wasting your time on the TPS.

Then, using a DMM, feeler and FSM, reset your TPS before you put the TB back in the truck.

People around here love to tell you to look for vacuum leaks. And that is stellar advice. What we forget is to look for vacuum blockages. The system works both ways...

Does your truck idle down "automatically" after it warms up? If not, you might have a bad temperature sensor that is keeping your ECU from going into closed loop mode.

If your distributor is out of spec, it's out of spec and IS contributing to problems. We all like to think that engineers just do things to make life complicated, but if something is supposed to be within a certain spec, well...

Good engineers "failproof" equipment by making sure that systems work even if components fail. We are a perfect example. Things are broken, but the truck still runs to the point that we can get back and forth; if not economically.

If you have a well rebuilt engine, your power problems are right there. It takes thousands of miles for a gas engine to settle down and break in. Tens of thousands for a diesel.

Check your fuel and spark.

Finally, look at your emissions numbers. I know that people think emissions do nothing but hurt economy (and from a theoretical standpoint, they're largely right), but the vehicles are generally designed to run best with all emissions systems in good working order.

In my case, extremely high CO levels were the tipping point for a bad testing distributor and worn tune up parts to be called bad in my mind.

Now, my idle and loaded HCs are quite a bit high (still passes). That gives me a few areas to explore.

Generally, these things are a pain in the butt to diagnose. So do what your doctor tells you to do, and keep a log of everything. What symptoms you notice, what you were doing, what you changed, etc.

Another standard and annoying question: Checked compression? I've seen (and done) plenty of engine rebuilds where the HG just isn't quite right or the valves are out, or the timing is off. Compression will give you a good picture of all those things.

Heck, you can do it on cylinders 1 and 4 (the two easiest to reach) just to get a baseline. If compression on those is lower than about 160, you've got a bad build.

I'm sure now I'm just scaring you. Start with the little things, and even at 15mpg, be thrilled you have something that will get you from A to B reliably, if not economically.

I moved to the 4Runner from a 2005 Wrangler 2.4l that, in 36,000 easy miles, had leaky axle seals, a leaky valve cover, a leaking valve guide in #3, a broken fuel gauge, and death wobble unlike anything I've ever seen on a SFA vehicle. 7 years old, 36000 miles. Original owner. I'd much rather have a 21-year-old wrencher that cost me a couple grand than a brand-new one that cost me $20k.

Drop me a line if you need more help (assuming this little bit of story time was helpful at all), and I'll see what I can do.

Come to think of it, my intake looks like the inside of a BBQ...

Colombo

ToyotaViejo...

Excellent messages... thank you!

I'm having all the same trouble you were having but don't want to lay out a pile of cash for a new dizzy if I don't need one.

Can you give some details (or paste a link) where I can find out how to diagnose mine?

Thanks!

ToyotaViejo

You can download the full factory service manual here. Same thing I used.

http://www.ncttora.com/fsm/index.html

Colombo

Thanks... I actually already have the FSM, I just didn't think it was in there. I looked and found it this morning but didn't get a chance to re-post that info so that you didn't have to go to any trouble. Sorry!
Since I got you though... Is there anything other than the resistance between the terminals that needs to be checked also? I thought I read something about a gap or clearance or something.

Thanks again!

ToyotaViejo

No worries, man.

On the 3VZE, the harmonic pickup in the distributor is neither adjustable nor replaceable as a separate part. It makes no mechanical contact, so it shouldn't wear down. That's not to say it can't corrode. Mine was so rusty that I doubt it worked at all.

You can check for play in the distributor by gently tugging on the rotor shaft as if you were pulling it out of the engine bay. Any more than a tiny bit of play indicates the gear is shot. Similarly, you can twist it clockwise and counterclockwise to test the gear. If there's a significant amount of play, it's shot.

Before you go ripping the thing out, though, unless there's obvious damage or wear, change the cap and rotor. There are like three places in the world that still manufacture caps and rotors, and most of them are kinda junky. Even the ones I get at the dealer are pretty inferior.

For what it's worth, the aftermarket parts store distributor has worked fine for the last several months.

Tkelly5

Hi toyota viejo, thanks for an awesome article. I too would like to test my pigtail resistance on the distributor, can you post a diagram of the pigtail showing the location of the g-g1-g2-ne pins? Or a link/page in the FSM that details it. I tried to look cannot find it..thanks!! TK

Gevo

OK. I'm joingin in on this thread a bit late, but I just had my share of experience with distributor spec so I'm gonna put in my 2 cents. Also, I didn't read most of the thread.

If you are getting spark and your timing on all plugs is within spec, then don't worry about the spec on the distributor pickups. All that does is tell the computer the locations of the cams.. etc... So even if its at 500 ohms and doing it's job, leave it. I don't know squat about proper timing methods otherwise.

Gevo

Follow the colors of the wires. Aftermarket distributor rarely will have the right color wires. You can see the color wire going into which location on the connector.

mxoliver115

Thanks for the post. Well done.I'm having an issue maybe you can help. At temperature it runs good. And while its warming up before the RPMs drop runs OK. But between them when u hit the gas it will almost die before picking up. It doesn't smell rich .
I checked the resistance at the distributor plug and they all ground out. Or max out my ohm meter. Maybe I'm not doing it right but either way I'm going to replace it tonight. All other sensors check out good. I thought it was a temp sensor for a long time. Its got a new cap and rotor and wires compression is between 180- 190. I'm getting about 14 mpg but I think it has lower gears for what ever reason because I'm running 30s ,3200rpm on the freeway at 70. I haven't found another post on here with my symptoms.

mxoliver115

I put an new distributor on yesterday. It helped the majority of my issues but it still has a huge hesitation when cold . any thoughts? Everything that I know how to do checks out.