Stalling Mystery

[PrecisionDriven]

Hello Everyone. Can’t tell you all how grateful I am to have a resource to reach out to for help with my van. Haven’t had any luck so far finding a local service center that is willing to work on it. This is my first ever post to any kind of forum so if I am not doing this correctly, or not in the correct place on your site, please let me know.

I have a 1987 automatic with about 270k miles on it. Drove it as my daily driver for the last 7 years but it is now out of service and I have been thus far unsuccessful at resolving the problem. My skill set for carrying out repairs on vehicles is overall good, but my diagnostic skills are limited, which is what brings me here.

The situation began as what I think would be described as a “misfire” by most technicians, but that might not be what is actually occurring. These hesitations when driving were intermittent and the duration was only a split-second. During that split-second, the Check Engine light would come on and off one time in unison with the hesitation, and it felt as if something has suddenly interrupted the fuel or ignition.

Another odd thing that was happening was that, with the transmission in Park, with engine running, and applying enough throttle to hold at about 2,000 RPM, the engine RPM’s started fluctuating up to about 2,200 RPM, then dropped back to 2,000 RPM, then repeated this cycle continually – even though I was not moving the accelerator pedal (I was holding it steady). Similarly, another thing would occur…with the engine at full operating temperature, transmission in Park, and idle engine speed, exactly every 10 seconds the engine RPM would drop down about 200 RPM, stay there for about 1 second, then return to normal idle. This cycle repeated itself constantly.
A diagnostic code indicative of the TPS circuit showed up. I replaced the TPS itself, then cleared the code and it has not returned since then (also, the old TPS had something rattling around inside it so I assume it was indeed needing replacement).
After replacing the TPS, the hesitation issue continued and increased in frequency and intensity until I had to stop driving the vehicle. It then became very stubborn to start (cranked fine but would struggle to start and have a very rough (stumbling) idle at first, which required me to rapidly & partially pump the throttle to keep it from stalling out). If I managed to prevent it from stalling, in a few seconds the rough idle would correct itself and engine operation would seem normal for the moment.

However, before I was comfortable road testing it, I decided to increase the throttle and hold it at 2,000 RPM for a bit and observe the behavior, and about 2 seconds after holding steady at 2,000 RPM, the Check Engine light came on and the engine stalled out, and refused to crank again. I immediately checked for any codes but there were none being reported.

Next, when the engine was cold, I cranked it and let it run at idle RPM to see if it would keep running, but after about 10 minutes, the same stall occurred. Then, I noticed something new happening just after the stall occurs, when the ignition switch is still on but the engine is no longer running due to the stall, the Idle Speed Control VSV was making a loud rapid clicking sound, which I assume was the valve itself opening and closing. VERY strange. I removed this VSV and bench tested it per the instructions in the FSM and it passed all of it’s tests.

Next, I verified power to the spark plugs (by pulling a plug wire, placing a screwdriver up into the boot and holding the screwdriver near the block while bumping the ignition switch to see if electricity arcs between the screwdriver & engine block), and they all seemed okay BUT I decided to replace the spark plug wires anyway (the spark plugs themselves have only about 6,000 miles and were installed 2 years ago). After replacing the spark plug wires, the engine will crank immediately but the idle RPM’s still fluctuate slightly (drops by about 100 RPM, then returns to normal, about every 2 seconds, continually).

I have noticed that after the engine stalls out, the next day it will usually crank immediately on the first try but will not remain running for long before it stalls again, especially if I put the transmission into gear and attempt to drive it even a few feet. It might remain running until I can get it parked better in the garage, if I’m lucky – but then stall out again.

Finally, the last thing I noticed is that now (with engine running) suddenly the AC compressor will not kick on when I turn on the AC switch.

Thus far, using the test procedures described in the FSM (for what that’s worth, and also just a side note, I am using a 1989 FSM, so I hope that’s okay), I have tested and ruled out the following components:
Primary Coil
Secondary Coil
Igniter
Fuel Pump
Idle Speed Control VSV

In addition, the distributor cap interior rotor button contacts were cleaned by scraping off some of that white residue that forms on them, using a dental scaler.
Spark plugs seem to be in good condition.
Spark Plug wires are brand new.

I would very much appreciate any guidance on how to resolve this issue. Thank you so much!

[PNW vanwagon]

i'm no expert. sounds like it could be a combo problem with two or more things not aligning. but i did just see a fix-it post on the toyota van faceboook page that had many of the same problems as your van. he had very clogged fuel injectors - here's a photo he posted:

9133

[PrecisionDriven]

I didn't know there was Toyota Van Facebook page but I will certainly check that out. Thank you for the tip on the fuel injectors. I will add that to my list of things to check. I am not currently on Facebook but can join if needed. Is it possible to view the article you are referring to with a direct link or do I have to be signed in as a Facebook member?

[PNW vanwagon]

you'd need to make an account to view. it's spread out over several posts - so you'd need to hunt them down. he started with trying to diagnose idle / stalling problem like yours. his latest post he had pulled his injectors and dropped his fuel tank and was trying to clean his entire fuel system out from rust. fcebook group is called: 80s Toyota Van 2wd 4wd group

and another good group called: 1984-89 toyota van group

[PrecisionDriven]

Excellent. Thanks again. I have requested to join each of those groups. I do still look forward to additional replies to my thread on this site, as the technical help here seems strongest.

[JPERL]

Excellent. Thanks again. I have requested to join each of those groups. I do still look forward to additional replies to my thread on this site, as the technical help here seems strongest.

It is likely your EFI circuit opening relay. I had this on my 86 Van and it eluded me for months until it got bad enough to replicate. Sorry to say it looks like you fired what we call in diagnosis the parts cannon at your van.

part number
85910-30050

[PrecisionDriven]

The only parts replaced thus far are the spark plug wires. The other components I simply tested. Thank you for the suggestion. Can you tell me where this relay is located and if it can be tested?

[PrecisionDriven]

Oh yes, I also replaced the TPS but it was definitely broken.

[bikeregg]

You just need to go through the engine checking likely suspects.

- check/replace all the vacuum lines
- check the air intake manifold for leaks
- compression check
- I believe the valves are shim adjusted. Very long lasting, at 270k it might be time for a valve job and shim adjustment.

Also, at 270k, it might be time to overhaul the engine.

[PrecisionDriven]

The FSM troubleshooting flow chart did mention checking for vacuum leaks around the air intake manifold, etc. BUT didn't explain how to go about it. Are they just referring to visually checking the air intake hose for cracks, etc.? If so, I did that but it seems to be in good shape.

[PrecisionDriven]

JPERL, did your van have the same symptoms as mine?

[bikeregg]

The FSM troubleshooting flow chart did mention checking for vacuum leaks around the air intake manifold, etc. BUT didn't explain how to go about it. Are they just referring to visually checking the air intake hose for cracks, etc.? If so, I did that but it seems to be in good shape.

There's a few ways to go about it. Visually inspect the vacuum lines. Feel around and pull a bit. If they feel hard, crackly or are loose around the fittings, might be a good idea to replace.

Smoke test. Pull a vacuum line, plug the fitting so it doesn't leak. Light a cigar, puff a bit and blow the smoke into the vacuum line (engine running). If you see smoke coming out anywhere, there is your leak.

With the engine running, spray a bit of WD40 around the intake manifold, vacuum lines and air intake piping. If the engine changes RPMs when you spray around a particular area, you have found where to look.

[JPERL]

Exactly the same. You can't check the relay directly but waht you can do is the next time it dies short or jumper the fuel pump check connector with the ignition on and the engine off. When you short the connector you will hear an audible click coming from the dash when this is shorted as it operates the fuel pump. If you hear no click and no fuel pump, suspect the relay. The other test you can do is leave the fuel pump check connector shorted and then drive.

If it does not stall with this connector shorted then that means the relay is ok and the next thing to check is the AFM because the AFM has a fuel pump switch that completes the circuit when it meters the air and their are resistance checks you can do with the AFM

[Burntboot]

PD - Out of curiosity, have you checked for stored codes?
Thats usually the first order of business when trying to diagnose anything.

[timsrv]

I also believe you may be dealing with more than 1 issue, but one of them sounds like a "Fuel Cut RPM" system issue. It's not talked about much in the manual, but mentioned briefly on FI-74 (87 service manual). It's an emission feature that turns off the injectors while decelerating. It's controlled by the ECU (Electronic Control Unit) based on the info it's getting from the TPS (Throttle Position Sensor). If you're TPS has a specific type of failure it can cause the RPM stall/hesitation issue you describe. When you find out why it won't start, try disconnecting the TPS to see if the other issue goes away. If you can make that problem come and go by disconnecting/reconnecting the TPS, then it's a bad TPS. If disconnecting the TPS does not affect it, then it's either a short in the harness (between wires IDL & E1 somewhere between the TPS and the ECU) or it's a bad ECU.

Regarding the no start issue, try searching the forum as most of the possible causes have been discussed here previously in great detail. Here's a couple to get you started. Good luck and please update with your findings. Tim

https://www.toyotavantech.com/forum/showthread.php?631-dead-van&highlight=coil+circuit+opening+relay

https://www.toyotavantech.com/forum/showthread.php?983-new-van-owner-needs-help&highlight=coil+circuit+opening+relay

[PrecisionDriven]

timsrv, Thank you so much. So grateful to everyone for the help. The TPS is brand new but I will perform the tests you advised and report back.

[trestlehed]

While checking your fuel injectors, also check the fuel injector connectors.
I was having intermittent hesitation, then only running on 3 cylinders. Turns out my injector connectors
were all heat baked and crumbly after 30 years of baking in the engine bay.

Another odd problem I had a few years ago: I hit one of the rain ruts a little too fast at an intersection
and my engine died instantly. Turned out to be a broken plastic clip where the wiring harness connects
to the back of the air box. Toyota wanted almost $900 for a new wiring harness. I convinced the old Japanese mechanic
to just zippy-tie it back in place. I watched him use 4 zippy-ties. In that moment I went from a possible $900 repair
to just paying the service inspection fee. :thmbup:

[PrecisionDriven]

Hello again, TIMSRV. Reporting back on the results. Disconnecting the TPS did not change the symptoms. Before I proceed with the next step of checking the wiring between the TPS and the ECU, I would need to clarify that my intended method is how I should go about it. But before I get to that part, I came up with an idea that I think will prove very helpful in this matter. Instead of continuing to describe the problem in written words, which are subject to being misunderstood, I thought that a video of the problem(s), as they are occurring, would be the next best thing to actually being here. So I made one. Please watch it and let me know if you still think I should pursue the wiring check. Please watch all of the video, as there are significant things that happen at various places throughout (it’s only about 5 minutes long). If this video changes your mind about what the problem is, please provide me with revised guidance on the next steps.
https://www.youtube.com/watch?v=Hq8BK8bqGrw&feature=youtu.be

If you still think I should check the wiring, I am assuming that you mean I should check for continuity between the IDL1 and E1 terminals of the TPS connector and at the ECU harness.
Thank you so much and I look forward to your reply.

[timsrv]

I think it's a bad ECU (Electronic Control Unit). Get the number off your old one and use it in an eBay search. Hopefully you'll find one for cheap and that will solve your problem. If nothing else it's good to have a spare around and/or to use as a troubleshooting tool.

[PrecisionDriven]

Thank you TIMSRV for your response. Two questions:
1. Do you think it's worth it to perform the voltage and resistance tests of the ECU wiring connector as described on page FI-77 of the 1989 FSM and/or the Fuel Cut RPM test, or should I just skip straight to obtaining a replacement ECU?
2. When replacing the ECU, is it just a matter of connecting the new one, or are there other steps involved that I need to know?

[timsrv]

It's always a good idea to perform tests and follow the manual. I think it's an ECU because it's flashing code while running, but no code is recorded. Also that VSV is controlled by the ECU and it's freaking out. The ECU also controls the Fuel Cut RPM feature and based on a previous post you made I thought that was also acting up. Faulty input to the ECU can cause it do do strange things, but unless it's a power input, it would store code and retain it. Since it's not retaining trouble code(s) I'm fairly confident the issue is inside the ECU. Nothing special about replacing the ECU, just unplug the old and plug the "new" one in. Tim

[PrecisionDriven]

Okay, so I attempted to locate an article on accessing the ECU on TVT but couldn't find one so I just dove in and removed the interior trim piece just to the left and behind the driver seat, only to find what appears to be body metal. Doesn't seem to be any kind of access panel to where the ECU should be mounted. My best guess is that I would need to remove the seat belt retractor and then reach up into the bodywork and pull the ECU out through the seat belt retractor hole. Am I on the right track here or barking up the wrong tree?

[PrecisionDriven]

I was right. I got the ECU out. Took photos of the process for the purpose of posting a How-To article (https://www.toyotavantech.com/forum/content.php?257-How-to-replace-your-ECU) if there isn't one on the TVT yet. Replacement part has been ordered from RockAuto. Spending less is always nice but when it comes to electrical/electronic parts, I feel much more confident in a remanufactured part with a warranty versus the risk of a functionally unverifiable pull-a-part. Anyway, should receive the part and know the outcome before the end of this week, and will follow up with results.

[timsrv]

I'm fairly confident it's your ECU, but there's not an easy way to be 100% sure until you swap it. Now that you have hundreds of dollars on the line I certainly hope I made the right call. My apologies for assuming you knew how to access. Here's a couple threads where that is discussed:

https://www.toyotavantech.com/forum/showthread.php?1647-Periodic-flashing-of-check-engine-light-and-brief-stall-while-driving-87-van

https://www.toyotavantech.com/forum/showthread.php?3617-Check-Engine-light-what-check-engine-light&p=41526#post41526

Your PDF is awesome! Thanks for the contribution! Tim

[PrecisionDriven]

TIMSRV,

You sir, R O C K!

Stalling Mystery solved! It was indeed, the ECU. Got my ECU from RockAuto today. It actually arrived with a bent terminal in the 10-pin connector.

But with my magnification lamp and some needle nose pliers, I got that terminal straightened out and the ECU installed. Engine fired up within less than one second on the first try and ran well. Absolutely no visible smoke from the tailpipe. Allowed the engine to idle until full operating temperature, then tried to invoke the problem but could not. Shut the engine off, allowed it to cool for a while, then repeated the test for invoking the problem but could not. Next, I road-tested it with no issues. Shut the engine off and allowed it to cool for a few hours, then road-tested it again to complete two drive cycles, with absolutely no issues. I can’t tell you how happy I am with this outcome. I am indebted to you. I am also very thankful to ‘PNW vanwagon,’ ‘JPERL,’ bikeregg,’ ‘trestlehed,’ and anyone else who responded to my thread. Everyone’s responses have been added to my Knowledge Base for future reference if needed. This was a challenging problem that finally ended in victory. Time for celebration! Thank you all. I just can’t thank you enough. I had big plans for this van cosmetically, car shows, etc. – which I can now pursue thanks to the help from you. I’m no expert on these vans, but I sincerely hope that I can help others in the same manner on this website forum. I have other minor issues, for which I will start a new thread IF needed. But as for the Stalling Mystery……this is my “signing off.”

[timsrv]

I think dancing bananas are appropriate here :yes: :dance2: :dance1::dance1::dance1: :dance2: :thmbup:

[trestlehed]

PrecisionDriven, congrats on your victory!

Also, I didn't know that Rock Auto is a parts source for ECU's.
Good to know!

[PrecisionDriven]

Yes. RockAuto had them under the category of Electrical, AND will accept returns on this item. PartsGeek.com also sold the same exact one BUT accepts no returns on electrical/electronic parts, which I went with RockAuto.

[JPERL]

No ECU's availiable for 1988 and 1989 Model Vans

[SoORYotas]

Well I have been chasing a 'miss' issue for about 2 months on the '87 4x4 5spd 334k miles. At first only at speed, a flicker of the CEL and a momentary hesitation. No codes from the ECU. As I was still setting a baseline for this van I bought two years ago went ahead with plugs, rotor, cap and wires. No change - momentary flicker but no codes. Replaced ignitor - still no change. Drove it around for a days and finally pulled Code 11. Well knowing some about the PO maintenance prior to my purchase I was discounting the AC switch, TPS and Neutral Switch. ECU!! Heck of a jump and the last listed item for Code 11 but what made me try this first is I went nearly a month with the 'Miss' but never recorded a code. EBay Swan Auto had one used ( I don't believe a Cradooone rebuild is the way to go). Received today and put in. Run about 40 milers so far, multiple restarts, freeway and around town. Idle is more consistent on restarts also. Not missing at all. So there may be something to the aging of the ECUs when they do not record an event but you saw the CEL blink.

Just this guy's observation and it may not be correct for you.

SoORYotas

[RayVan]

:bluevan:
I think it's a bad ECU (Electronic Control Unit). Get the number off your old one and use it in an eBay search. Hopefully you'll find one for cheap and that will solve your problem. If nothing else it's good to have a spare around and/or to use as a troubleshooting tool.

[BlackCircle33]

Hey, thats my picture with the clogged injectors! ive since cleaned them and rebuilt them.
Also took my tank to a radiator shop to have it cleaned out, painted and sealed.
She runs like a dream now!