auburnhunter

I recently bought a 1989 Toyota 4x4 pickup with a 3.0 V6. It is a 5-speed, has 225K miles on it. The engine was replaced at 80K because someone ran it out of oil.
I picked it up as a project because I wanted a second vehicle to leave at home. I am in the Army and am about to be stationed in Korea.
The guy I bought it from said it had an exhaust leak and felt like this was robbing it of power. When I drove it home it was hard to start and I had to really wind it up in order to make it to the next gear. If I didn't the engine would stall and drag it down. I didn't hear what I percieved as an exhaust leak. I basically ran like crap all the way home.
The next day I started with a tune up. I replaced the plugs (they looked really good), distributor cap, and rotor. No luck. I drained the fuel tank, replaced the filter, and jumped the fuel pump test on the diagnostics block. It was good but still no luck. I removed the intake plenum and cleaned it and the throttle body and the cold start valve and still no luck. I replaced the cracked air intake hose and some vacuum lines and cleaned the air filter but still no luck. The engine is still difficult to start but once started it idles pretty good. When I get in to back it down the driveway, the instant I release the clutch in put a load on the engine it tries to die and I have to pat the gas to coax it back to life.
I used my service manual and tested the VAF on the airbox and the OHMs are within tolerance and when I move the vane I can hear the fuel pump turn on. However if I jump the fuel pump at the diagnostic block it is much easier to start but still will not drive.
I am thinking the fuel pressure regulator or the EGR valve but the manual does not give a good method to test these (it is a Chilton). The EGR modulator is broken but I don't think this would cause this and I will buy one later. Perhaps the catylitic converter? I don't wan't to but another one so I thought I might just cut it off and clamp on a sleeve. I checked the TPS sensor and I think its bad but I have gotten conflicting test methods from my manual v/s other sources. The test for throttle closed is bad but throttle open is good so the engine should run under a load right? What about the charcoal cannister?
I can fix most anything but I'm used to working on tractors, lawnmowers, and pre-1980 ford trucks and the like. Fuel injection, ECU's, and MAF sensors and things like that confuse me. Any help would be greatly appreciatted.

auburnhunter

Well I started it this morning and it actually ran well enough to drive it around the block. It initially was difficult to start so I jumped the fuel pump so that it wold remain on and it fired right up. I was sitting there letting it warm up and I noticed that the TPS sensor was still unplugged from where I was testing it last night! I thought what the heck and drove it like that. I still spitted and sputtered trying to accelerate, but it ran. Then I hooked it back up and drove it. It ran exactly the same. I unhooked the fuel pump jumper and it ran exactly the same. After I got back I removed the EGR valve for inspection. It was not blocked at all. it was quite clean actually, just the normal carbon residue. I tested it and it was good.

After my initial post I retested the VAF meter and reaffirmed that it was within specs for OHMs. Now I'm thinking TPS sensor. Input please.

P.S. I was reading about EGR removal before I inspected it and was considering removal. What I was wondering is, if someone has a completely clogged EGR valve, wouldn't putting on a block off kit accomplish nothing? Its already blocked off.

Master_Yota

does it misfire really bad? check compression. you might be looking at a rebuild.

Windsor

It could be the fuel pump going out, since you had to fiddle with it just to get it started.

Another possibility is that the catalytic converter is plugged.

auburnhunter

I haven't put a pressure gauge on the fuel system but its definitely pumping. The first time tightened down the fuel filter it wasn't enough and sprayed everywhere. Thats why I was leaning toward the fuel pressure regulator.

I removed the throttle body and bench tested the TPS sensor. Turns out it was good. Somehow it had just slipped out of adjustement and had not continuity when the throttle was closed.

I also found that the wires to the O2 sensor were all burnt completely in half except for the shielded one. I rewired it and that turned off the CEL. I thought that was funny b/c I didn't unhook the battery and usually you have to to reset the codes. Before I was getting two codes. I don't recall the #'s but they were pointing to the TPS and VAF.

Also I tested the pickup coil with my ohm meter and it was good. The coil itself was 10 OHMs higher than what the book said was withn specs. Havn't got to the plug wires yet or a compression test. I'll do that next weekend.

Here's something else though. After I did this it started right up so I decided to check the timing. It is reading way to the left of the 10 BTDC that the book calls for. Like way off the scale to the left! It sounded like it was idleing a little high so I moved it to 10 BTDC. It idled way low and backfired when I gave it gas. I set it back where it was and parked it for next weekend. Could my timing belt have slipped or the distrubutor have worn out?

No it doesn't backfire when I drive. In fact tonight if it was on flat ground it accelerated smoothly through first and second gear. As soon as I have to stop and go up hill its starts to drag down and just crawls up the hill barely running. Thanks for the input so far. Kepp 'em coming guys.

limon32

I'd replace that EGR modulator ASAP. Mine was bad (had a hole in it actually) and the truck wouldn't idle well at all and had really bad low end torque.

thook

Your truck doesn't have a MAF system, so don't worry about that. But, EFI's are basically a relaying of battery current from any given electronic sensor/device under specific circumstances giving specific voltage amounts to the ECU. In other words, with a coolant sensor, when the coolant is cold, resistance (read in ohms) is high and therefore voltage is high. The ECU reads that to mean a cold engine and keeps the timing kicked up and the fuel pulse higher until the coolant gets warm. Then, resistance is low and voltage is low. Then, the ECU reads that as a warm engine a adjusts the timing and fuel pulse to normal operating conditions..........like 850 rpm at idle. It's more than that, but that's to give you an idea.

With the FPR, you can use a guage, but generally if they're bad it's because of the diaphragm in there. So, if you pull the vacuum line from it and find fuel, then it's bad.

As for the TPS, the manual only covers testing at open and closed positions, but nothing for the inbetween positions. In other words, a bad spot along the track (interpreted by the ECU to mean the throttle is moving) could cause a jump or drop out in signal to the ECU and make it accelerate poorly.

It's possible your mechanical timing could be off. I think I'd go ahead and check that. At top dead center on the compression stroke (crank at 0* and cam marks lined up........so you'll need to pull the timing cover back a bit to see) your rotor should be between 11 and 12 o'clock. If it's not there, it's out of timing.

auburnhunter

I know there isn't a MAF on it, but its grandaddy, the VAF meter sits right there on the airbox. That thing can cause a lot of problems. I tested it per the manual, but I'm still not 100% that its ....well.. 100%.

When I checked the TPS, I checked the full open and full closed per the manual, but I also checked it through its full range of motion. I did not get any spikes or dead spots so I am still confident that the TPS is good.

I got a compression testor and will start on it again tommorrow. Also I'm going to unhook the battery to reset the CEL and see if it makes a difference since I never did it when I fixed the burned O2 sensor wires. Next I'll check the resistance on the plug wires and I think I'm going to go ahead and gut that catalytic converter.

When I checked the coil, the primary circuit tested 10ohms over spec (I get test leads that vary that much sometimes so I'm not too worried), but the secondary circiut I couldn't get to test at all. I got infinite resistance. If there was that much, how is it even throwing a spark? Did I miss something and test it wrong or could this be the culprit? Perhaps this is why I'm getting a strange reading when I checked the timing?

limon32

When I put my new O2 sensor in, the CEL cleared without me reseting it.

abecedarian

before you gut the converter, do a test run with it disconnected (yes, open pipe) and see if it runs better and if it does then maybe gut the converter, but if it don't you know the converter isn't the problem.

As for the coil, they're not expensive so buy a new one and try it. if it gets better, all the better, if not, you have a good spare for when things go bad a few hundred, thousand miles from now.

auburnhunter

I fixed the modulator. The bottom vacuum nipple was broken off so I sanded it flush with a dremel and attached an adaptor I had laying around with epoxy. No leaks, cleaned the filter, tested good, $25 saved.

auburnhunter

Well I finally got around to running a compression check today. The results were good:

#2 166 #1 170
#4 162 #3 179
#6 165 #5 175

I had to have a long talk with the #5 cylinder. That thing was a biatch to do. The #'s are within specs except there is more that 14psi difference b/w #4 and #3. Its so close though that I'm not worried about it. This made me confidant enough to put a little money into it so I changed the oil!

I rechecked the diagnostics for the check engine light and here is what I came up with: code #'s 21, 24, 31, 41, ans 43. Wow.

21 I took care of and fixed the burned wires on the O2 sensor but I haven't tested it and I might as well put another on. I bet its the original.

24 points to the Intake Air Temperature sensor. Can this be cleaned on the VAF meter? I'm still not sure that thing is good. everything on it checks EXCEPT I cannot get a resistance reading b/w the THA and E3 terminals. Also, when I move the vane the OHMS increase, but not from high to low consistently, they increase but kind of jump around. What exactly does "increase in a wave motion" mean?

31 points to VAF meter again.

41 Is the TPS but I adjusted that and think it is good.

43 Is a starter signal circuit. Not sure what this one means. Could this be why the thing takes sooo long to start?

EGR and Modulator both tested good. After doing all this i started it up, still takes a long time. I drove it around the block and I have to say its much better. Accelerated more smoothly. When I came to a stop it would initially be difficult to get going but once rolling accelerated normal (relative term) but when I stopped the idle seemed to surge. Need the next round of input guys! Keep 'em coming.

I came back to edit this post because before I closed shop for the night I thought I would see if I could set the timing tonight. I tried to set it at 10 BTDC like the manual says but it just will not run at this setting. It backfires through the intake when I give it gas at this setting. To get it to run smooth it sits completely off the scale. I'm guessing somewhere around 30 BTDC! In fact I think if I didn't run out of adjustement on the distributor it would run even better if I advanced it more. I had planned on putting on a new timing belt soon. Has it jumped a cog or something?

thook

Not sure. I can't see it from here. But, did you check the rotor position? That'd tell you.

So many codes. I'd almost think the ECU may be having problems. But, that's a last resort.

I'll have to refresh my memory on the coil specs, so later on that..........unless someone answers first.

As for the AFM, run a search on "AFM testing". There's a thread I'd started a while back and made revisions/updates to over the course of time as I learned and experienced more with the dern thing. Anyway, there's some info in the thread that would answer your questions, I believe.

auburnhunter

I read the thread on VAF meter testing, and after reading the whole thing, I'm still not quite sure if mine is good or bad. So many conflicting veiws. While searching for it I found another thread in the Newb forum were a guy had a problem where the engine stalls until it gets over 3000 rpm and then it feels like it gets a shot of nitrous. This is exactly what mine does. A lot of people chimed in and had the same problem but they never figured it out.

Today I removed the catylitic converter and looked at it. there was nothing there, just a big empty chamber that I could see all the way through. Definitely not restricted! I didn't see where anyone had done anything to it so I was a little confused. While I was working on it I found my exhaust leak on the flange after the crossover. I replaced the gasket and a stud that was missing as well as the gaskets on the converter. I also put on a new O2 sensor and unhooked the battery to reset the computer. When I started it up the ground that comes off the negative terminal and bolts to the body melted and caught on fire! What the h#ll! Other than unhooking the battery and plugging in the O2 sensor I didn't do any electrical work so why would this happen now? The terminals on the cables are the aftermarket clamp on style (which I hate and never use). Could this have happened if my main negative cable was corroded or broken and the small one to the body was my ONLY real ground?

After all this I finally did get it started and it ran like absolute crap. Way worse than before I fixed the exhaust and O2 sensor. I'm at a loss here. I really think the problem lies with the timing/ignition since I can't get that right. Next weekend I'm going to replace the timing belt and after that I think the distributor might be bad.

abecedarian

When checkign / setting the timing, you jumpered the diagnostic connector's T1 & E1 terminals? If you don't, the timing will read off the scale.

auburnhunter

Yes I did, but when I jump them there is no difference in the timing. Its the same with or without the jumper wire.

abecedarian

Okies. That suggest that maybe the throttle position sensor needs adjusted.

clutchsmoke

My bet is the timing belt has skipped a tooth. The ignition timing being off would support this, I would pull the front apart and check it.