OBD1 / 1FZ-FE Troubleshooting Help!

[IoN6]

This is going to be loooong, but to put it into some perspective I have been trying to figure this out for close to 2 years now.

I picked up a '93 and it is my first foray into Toyota's. Not knowing what to expect power wise (it had 315's on it when I bought it), I was not too underwhelmed with it. Until I had to get it smog'd and spent a few months doing some maintenance and with each phase noticed it was running better and better. It finally passed and then I just settled in and drove it. Until two summers ago I was driving home from getting a hair cut and went to pull away from a light and it just stumbled, no power at all, but it would idle fine. Then just as randomly as it stumbled, it came back to life and I drove home.

Since that day, I have wanted to drive it off a cliff more than I have loved it.

I limped it along the rest of that summer. Then fall and winter set in and it started running like a champ again. Pretty much forced the issues out of my forethought and continued on with life. Fast forward to spring and summer, and the issue is back. I finally came across a thread on 'mud about non-Toyota Denso fuel pumps actually drawing more amperage than the Toyota labeled ones. I had replaced the fuel pump with a Denso labeled one as part of PM. I ordered up a Toyota one, swapped it and that seemed to have fixed my problem. At least the complete and total loss of power problem.

Fast forward to present day and the issue I have now is that some times it massively down on power. Think e-brake on and trying to pull a trailer down on power. Right on the verge of being a road hazard down on power. I have a TOYOBD1 reader and nothing shows out of the norm (at least to me). And just like the stumbling issue, some times I will hop in it and she'll run like a scalded dog.

I have replaced a lot of parts in this process. Including, but probably not limited to:

• ECU - Mine is an early 93 and had the 89661-60170, swapped it with a 89661-60221
• Injectors - Newer 4-hole 23209-66010 from a 1FZ powered 100/105-series
• EGR Valve and Modulator
• All vacuum hoses
• Plugs
• Plug wires
• Ignition Coil - 19080-66010
• ECT - 89422-35010
• Fuel Pump - 23221-66040
• Fuel Pump Relay - 28380-66010
• EFI Relay - 90987-02004
• Distributor Cap and Rotor
• PCV Valve
• O2 sensors
• Fuel Pressure Regulator
• Fuel filter
• Throttle Position Sensor

I recently deleted the PAIR system and moved the O2 sensors to the manifolds. I also redid one of the harness connectors as it was majorly corroded. The O2 readings from TOYOBD1 appear to be within spec.

When I did the EGR I had the intake completely off, did plug seals and valve cover gasket as well. When I was in there I verified the wiring harness by the EGR pipe by checking continuity from the far end and ECU end of the harness.

I am really, really tired of trying to figure this out and could really use some help.

 

[IoN6]

Will try to add symptoms and things that I have done as I think of them...

When it is "down on power" I have noticed that when I let of the gas it will seem to want to "float" or want to accel a little it seems.

And since I bought it, it had always smelled like it is running rich. Running like a champ or not.

I have also tried disconnecting the VSV's totally from the wiring harness, disconnected the vac line to the FPR and leaving the gas cap cracked.

 

[kurtnkegger]

Have you checked or replace your mass airflow sensor

 

[IoN6]

Have you checked or replace your mass airflow sensor

93/94 has a VAF, I have checked it and it reports voltages within range of what is expected. I do question it though as one of the previous owners opened it and adjusted what I would call the clock spring.

 

[rover67]

does that computer change the ignition timing on the motor? Like does it think something's up an it's pulling tons and tons of timing?

 

[RayRay27]

does that computer change the ignition timing on the motor? Like does it think something's up an it's pulling tons and tons of timing?

On OBD 1's from my recollection and I may be wrong but the OBD 1 doesn't manage timing at all. When you manually set the timing to 3ºBTDC it will run between 3º and like 10º. The only way the timing is managed is by the knock sensors but the ECU doesn't record or maintain that knock information once you turn the truck off. The ECU has to re-learn to retard or advance the timing from the knock sensors. Again I may be way off on this but this is how I understood how it works.

 

[IoN6]

Someone on 'mud said that the timing was all electronically controlled. I can see the timing advance/retard in TOYOBD1, but cannot correlate that to when it is down on power.

Here is a screenshot of the app in 2nd gear not quite WOT.

 

[IoN6]

I have noticed that it knocks pretty bad as the weather warms up. The knock sensors pass the FSM test, but that test is pretty basic. I do have 2 new sensors on my desk that I have been holding off on installing for some unknown reason.

 

[IoN6]

As for the timing, it is set to just over 3*. Think the "width of the marking" of 3*, over.

 

[SteveH]

You're absolutely sure that all the rubber intake hoses from the air cleaner to the throttle body are uncracked and well-sealed?

 

[IoN6]

You're absolutely sure that all the rubber intake hoses from the air cleaner to the throttle body are uncracked and well-sealed?

Knew I forgot to list some stuff I had done. Intake hose was replaced too. I am reasonably sure there are no leaks, but I will need to verify. IIRC I did a vacuum test and it was within range, but I can do that again at the same time.

 

[SteveH]

Another 'stupid suggestion' - my brother had a bunch of odd OBD-1-non-traceable issues in his '93 after an engine swap, and later found all the spark plugs were quite loose. He installed/tightened them, but either forgot to recheck them or the crush washers did some more crushing when he wasn't looking. Worth a check and quick to do.

 

[IoN6]

Another 'stupid suggestion' - my brother had a bunch of odd OBD-1-non-traceable issues in his '93 after an engine swap, and later found all the spark plugs were quite loose. He installed/tightened them, but either forgot to recheck them or the crush washers did some more crushing when he wasn't looking. Worth a check and quick to do.

No such thing as a stupid suggestion, especially at this point!

You know, I have noticed that the plugs seems excessively loose when I have changed them every time. I have meant to re-torque them, but never did. Will try to get out today and do that.

 

[ccslider]

In that picture is that showing its retarding the timing -17 deg?

Look at the ignition system, coil and inside the distributor.

If you try to brake torque it does it stumble like it has a weak spark and is being blown out?

 

[IoN6]

In that picture is that showing its retarding the timing -17 deg?

Look at the ignition system, coil and inside the distributor.

If you try to brake torque it does it stumble like it has a weak spark and is being blown out?

Correct. That was near WOT in 2nd gear, so accelerating "hard". The timing advance/retard appears to be correct, no? Accelerating would advance the timing, or X number of degrees before TDC in an attempt to accelerate.

No?

For the brake-torque I assume you mean stand on the brakes and gas at the same time? It tries to pull, not stall.

 

[rover67]

It’d be a positive number. X number of degrees before TDC. That picture makes it look like it’s running 17 degrees retarded from the static timing set point of 3 degrees BTDC That is unless I’m thinking of it wrong or it’s reported backwards or something. I might expect 17 degrees of total timing advance under those conditions but not 17 degrees retarded.

how does the reported timing change when it is running well? What timing does it report at idle? Does that correlate with measured timing using a timing light? If you rev it in neutral with the timing light on it can you see the timing advance?

if it is in fact retarding the timing that much that might be your issue. The. It’d be a matter of figuring out why.... maybe a knock sensor is telling the computer is seeing tons of knock?

 

[IoN6]

It’d be a positive number. X number of degrees before TDC. That picture makes it look like it’s running 17 degrees retarded from the static timing set point of 3 degrees BTDC That is unless I’m thinking of it wrong or it’s reported backwards or something. I might expect 17 degrees of total timing advance under those conditions but not 17 degrees retarded.

how does the reported timing change when it is running well? What timing does it report at idle? Does that correlate with measured timing using a timing light? If you rev it in neutral with the timing light on it can you see the timing advance?

if it is in fact retarding the timing that much that might be your issue. The. It’d be a matter of figuring out why.... maybe a knock sensor is telling the computer is seeing tons of knock?

I think that may be a UI issue with the app. It always shows the number as a negative, to me anyway since it is before TDC it makes sense to see a negative number. But I can see the other way too.

For example, if I do not select this box it thinks the AC is on when it isn't...

 

[IoN6]

Another 'stupid suggestion' - my brother had a bunch of odd OBD-1-non-traceable issues in his '93 after an engine swap, and later found all the spark plugs were quite loose. He installed/tightened them, but either forgot to recheck them or the crush washers did some more crushing when he wasn't looking. Worth a check and quick to do.

Just spot-checked holes 1 and 2. Both were 14ftlbs, don't have the time to do all 6 before my next call...

 

[rover67]

I'd stick a timing light on it (when it shows the symptoms) and see what the timing is doing as you rev it up a bit. Just to know for sure. Then you could see if the app is saying what you think it is also. Timing changing can make motors feel like they are hanging also. IAC can be doing weird stuff too. anyhow with a simple rev you should be able to watch the timing take off towards advanced.

But thinking basics, it's gotta have fuel air and spark (and compression) to run and make power. My bet is compression is fine just given the fact it runs ok some of the time. I am guessing it can get what fuel it needs given the work you've done to the fuel related components. My guess is it can get all the air it wants being a cable throttle body and probably has a decent filter on it and such. SO it kinda leaves ignition and mixture as commanded by the ECU. My guess is mixture is decent???

For it to be that down on power i bet the mixture would have to be mega whacked. BUT timing could explain it..... No misfires/random rough running so i don't suspect plugs/wires/cap/rotor really? at least that's my thinking?

maybe the distributor has something loose in it like a pickup or something?

 

[IoN6]

With the ECU not in diagnostic mode I can confirm that the timing changes with engine revs.

I thought it might be a faulty distributor but someone on 'mud said that the timing adjustment is all controlled by the ECU, so no moving parts in the dizzy itself. The only pass/fail is if clearances are not within spec.