Severe bucking problem 15 MPH

Hi,

Do me a favor. Here is a link that explains how to retrieve codes on this vehicle. If there are no codes, the light should just stay on, not flash. Take a look through this and let me know if this is what you did.

https://www.2carpros.com/articles/toyota-trouble-code-definitions-and-code-gathering-method-1990-1995

Next, the bucking can be several things. A plugged catalytic converter, fuel pressure issues, major vacuum leaks, and so on. Are there any odd sounds or odors when this happens? Any smoke from the exhaust?

Let me know what code you got for the transmission and if the above procedure produces any engine codes.

Take care,

Joe

Thanks Joe. I did add the jumper (and got an over-drive code). What I did not do was turn of ignition, wait three minutes, and try again, to maybe stop the check engine light from flashing. By the way, most of the time it will run perfectly fine for a couple of miles, then it goes bad. So, we might call that an intermittent issue since it does run well for a short time. When it does start to malfunction, the exhaust smells really rich even at idle. The transmission code was for #1 shifting solenoid (as far as I remember). But, it does shift properly while it runs well. I don’t know if it would shift when it starts bucking as I can get going fast enough for it to shift into second gear.

Hi,

If possible, let me know what the code was you found.

The idea that it smells rich indicates we should check fuel pressure. It could be loading up with fuel due to high pressure resulting from a faulty regulator. I do have another question. Does the check engine light flash when this happens?

Here is a link that shows how in general fuel pressure is tested. Take a look through it and let me know if you feel comfortable performing it.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Also, this could be related to a plugged catalytic converter. It can cause an odd smell and a loss of power. Take a look through this link:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

Do me a favor. After this happens and before you turn the engine off, inspect the catalytic converter (see pic 1 for location). If it is plugged and raw fuel is getting into it, there is a chance it will be red hot. So, check to see if that is the case.

Let me know.

Joe

See pic below.

Joe,

Sorry it’s taken me so long to respond. I blew a brake line, and it was a nightmare to repair. Here are the answers to your questions in no particular order, and a couple of oddities I’ve noticed since driving after the brakes were fixed.

The catalytic converter never got over 700°. It does not rattle when shaken or struck very hard.

The check engine light came on for 30 seconds, then shut off.

I jumped the T1 and TE1 terminals and got no codes at all. The check engine light came on with no flashing at all. I tried 3 different jumpers to ensure I was making type connections properly. There were no transmission codes. I fear the first time I jumped the OBD1 terminals, I did it improperly.

When the engine is malfunctioning the exhaust definitely smells very rich, but no smoke necessarily.

While I am comfortable checking fuel line pressure and regulator, I haven’t the tool, and can’t afford to buy one. Neither can I afford a mechanic with the tool, at $85 per hour. I just can’t do it.

Here’s food for thought: When I first test drive it, it performs well enough, for that mile or two. During this period, the speedometer doesn’t work. As soon as the engine starts bucking, it works again, even though I can’t manage more than 15 MPH.

What are your thoughts now?

Ken H.

Hi,

The idea that the speed sensor starts working is odd. I would have thought the opposite would have happened. Have you checked the vehicle speed sensor (VSS)? The vehicle speed sensor is used to monitor actual vehicle speed. Vehicle speed information is used by the ECU for fuel injection, cruise control, and electronic control of the automatic transmission. We may have a lead.

IF you haven't already, we need to check the VSS. I attached the directions below. Let me know if you are comfortable performing them.

Next, there is a brown wire with a red tracer that runs from the VSS (part of the trans control module) to the ECU and then changes to green with a blue tracer to the instrument cluster. We need to check those connections. Make sure they are tight, clean, not damaged, have no corrosion in the connectors, and none of the pins are pushed damaged. The ECU is located behind the right kick panel (where a passenger would rest his right foot). You know where the instrument panel is located (LOL).

Since the speedo is activating when it happens, I think it's either causing the transmission to shift into the wrong gear. For example, driving a manual in 5th gear at 10 mph. That would cause a bucking.

Pay attention when it happens if the engine RPMs are extremely low.

Let me know what you find.

Joe

See pics below Note: Pics 2 and 3 are from one page. I had to cut them in half to make them readable. I overlapped them so you can follow from one to the next.

Joe,

I was wondering if that speedometer activity might be a clue. I am comfortable doing those tests, but may not get to it until Thursday. I will absolutely write back with the result. And, by the way: your description of trying to drive in fifth gear sounds really close to what I am observing, only I’ve only seen that on a standard transmission. Indeed, the tests you suggested will be my next move. Thanks. “Talk” to you soon.
Ken H.

You are very welcome, Ken. Hopefully, it will be something simple to repair.

Take care and I'll talk with you later in the week.

Joe

Thanks. I’m looking forward for my results.

Ken,

I was thinking about your car problems and wondering if you were able to make any progress.

Joe

Not as yet. I’ve had a couple of issues that have come up that preclude my work on the truck. I have something important to do tomorrow for which I’ve had to spend a lot of time preparing for. Once that is over with, my weather report app says it will be cool, but certainly not so much as to spend some outdoors time poking in and out of any number of electrical connectors.
Thanks for sticking with me. Ken H.

No problem, Ken. I just remembered you said Thursday, so that's why I asked. I don't want to be a pain. LOL

Let me know how things turn out for you.

Joe

You’re not being a pain whatsoever. I consider your thoughts helpful. And yes; today I have upwards of 6 hours for nothing but testing. I’m pretty sure I’ll be writing you again soon. Thanks.
Ken H.

I forgot to mention that it shifted into second gear the other day while the engine was bucking away.

Joe,

So here was my day. First, I went to remove the negative battery cable. The terminal broke straight away. I followed the highlighted wiring diagram. Being mildly dyslexic, I spent an ungodly amount of time looking for blue/green wire. The iPad was charging, so I had to go back to the apartment to recheck. Anyway, by that point I had checked every terminal, and none had corrosion. I scampered under the truck, but there were a number of wired solenoids or sensors. Well, I don’t know the location of the VCC. One website suggested it was on the transfer case. That turned out to be useless anyhow since my dedicated flashlight quit working while looking. That’s when I gave up. I had earlier dismounted the computer so I could see the wiring. So, I grounded the case and reattached the broken battery terminal using a little finesse. I wanted to check if I had everything connected right, so I tried starting the engine. I know I have a dead spot on my starter (to be repaired later) but rapping on it frees it up. After doing that, I went to start it a second time. It cranked over once then quit. I went to make sure the battery terminal had a good connection, which it did. I proceeded to check the battery voltage. Nine volts. My disconnected battery drained while I was working. I threw in the towel. I have the tools put away and the battery on a trickle charger. Man, this is getting old. In addition, I have back problems, and being scrunched under the dash has left my lumbar region aching like heck. That means working on it tomorrow is out. The weekend is going to be a total washout with rain expected nonstop until Monday. I’ve never had this difficult problem on any Toyota truck I’ve ever had, and I’ve had four since my early 20’s; although this is my first V6 automatic. Ergo, you won’t be hearing from me till next week sometime, late. With weather and working elsewhere, I’ll have little time until Thursday and Friday to plug away at it again. I’ll write when I can. Thanks again. Ken H.

Ken,

The battery shouldn't have drained if it was unplugged. Do me a favor. Take it to a parts store and have them load test it before you reinstall it. I think you have a bad battery.

I will watch for your reply next week. Let me know if there is anything I can do to help.

Take care,

Joe

Can’t get to a parts store with no transportation. I’ll have to do a workaround and bring it every night for a trickle charge, and watch carefully what it does.

Sounds like a plan. Let me know what you find or if I can help.

Take care,

Joe

Joe,

I changed out the ignition coil, put in a new battery and changed the spark plugs. This is all after spending all the time trying to trace the computer wiring. Here’s the kicker: when trying to install plugs on the right bank, I found all the intake ductwork was in my way. So, I pulled it all out; simple enough. But what I found was a major break in the tube that was attached to the throttle body intake manifold. It was impossible to see before actually disassembling it. I had to cut away all of the broken and cracked part of the duct, which left it too short. For a temporary fix, I basically glued the tube onto the fuel injection air port. The improvement was astonishing. The only problem I apparently have now is a low idle speed when the engine goes into a closed loop. I’m going to need to change that one tube, but for now my shitty looking repair has done wonders for its performance. So, in the end, the throttle body was sucking the air it needed through the broken tube. So, when the Mass Air Flow Sensor kicked on, it had no air passing through it. This sent a message to the co outer which tried to adjust to the condition. But all it could do was overcompensate by fluctuating on every rotation of the crankshaft, it would add fuel, then shut it off. Hence the bucking situation. I’ve driven around town for a while with no more problems than that of the low idle at temp. What do you think about that? I’m going to start looking for the broken part after this letter.

Ken H.

Here is a picture of the ugly yet temporary fix. Yucky but functional.

Hi,

The fix may not be pretty, but it's functional. The idea that that was broken created a huge vacuum leak so certainly, that was the problem.

If there is a pick-and-pull salvage yard, you should be able to get a replacement for really cheap.

I'm glad you found the problem. Let me know if there is anything I can do to help when you get the replacement. Also, please feel free to come back anytime in the future. You're always welcome here.

Take good care of yourself,

Joe