Hello,

I recently purchased a Winnebago Warrior RV Motor home built on the 1992 Toyota Pickup 3VZ-E Chassis. I drove it up 500 miles from where i purchased it and had no issues at cruise speeds. The vehicle is having an occasional problem, when idling at a stop sign or traffic light, the engine will stall, sputter and run roughly, then shut off after loss of power. The check engine light comes on and off during this time as the engine sputters. I ran a diagnostic by shorting the TE1 and E1 terminals, and I am getting 2 trouble codes. Code 12 and Code 14. I would like any and all information regarding what the cause could be and what these 2 codes would have in coincidence to cause this problem.

Thanks,
Toyota Winnebago owner

 

Here's all the diagnosis codes: http://web.archive.org/web/201211190...85diagnosi.pdf While 12 and 14 are both ignition related, don't get too tied up in that just yet. I suspect that as the engine is slowing (and sputtering), that by itself could cause code conditions. I'd start with basic checks; ignition timing, spark plug gap, fuel pressure, ....

 

Thanks for your response. Seeing as this is an intermittent issue, I suspect there is a component or sensor that is malfunctioning some of the time but running well most of the time. I had new spark plugs put in recently so don't think that's the issue. How would I test fuel pressure?

I've read in other posts that code 14 would indicate a problem with the igniter or igniter coil. Based on the intermittency of the problem, is it likely the igniter is going bad but working most of the time but not all the time? Trying to isolate which component could go bad while still working some of the time.

 

Whenever I buy a new vehicle I try to inspect and or replace all tune up items, cap and rotor, plugs, wires, air filter, fuel filter, and vacuum hoses. I do this mainly for my own piece of mind. Another thing that has been known to cause issues is bad grounds. It's always a good idea to clean the battery terminal and all engine and body ground connection points. Good luck

 

Update on this thread. I had a registration problem and needed to create a new account.

I took my RV to the mechanic and he went ahead and diagnosed the rough idle. He checked each wire connection from the distributor and it seemed #6 on the dizzy was not giving spark. He went ahead and ordered a cap and rotor and replaced them. After replacing them he did the same check and #2 on the dizzy was not giving spark. We ended up changing the distributor, ignition control module, and ignition coil. He did the same test again and it seems that #6 and #2 on the distributor are not giving spark, OR giving very inconsistent, weak spark. The other issue is that the timing mark on the crankshaft pulley is dancing around all over the place and not lining up with the timing marks on the engine block. My guess is that this is because 1 or more cylinders are not getting spark from the dizzy causing incomplete combustion.

At this point, my best guess is that this problem is electrical and may involve the connections to the ECU. I went ahead and registered on Toyota's tech info site for 2 days and grabbed myself the ENGINE CONTROL WIRING DIAGRAMS for The 1992 Toyota 4runner and the 1992 toyota truck. Unfortunately, they did not have the diagrams available for the 92 Pickup. I'm hoping the ECU's are similar enough that i can use these diagrams.

On the diagram's PDF, the last page has a section called SERVICE HINTS which has all the standard voltage and resistance ranges for testing different wire combinations with ground wires (E1, E2). There are some parts I don't understand which I was hoping to get an answer for.

VTA-E2 0.1-1.0 VOLTS (IGNITION SW ON AND THROTTLE VALVE OPEN) ?? - What does THROTTLE VALVE OPEN mean and how would I keep it open for the test?
VS-E2 3.7-4.3 volts (IGNITION SW ON AND MEASURING PLATE FULLY CLOSED) ?? - What does MEASURING PLATE FULLY CLOSED mean and how do I keep it closed?

I brought these diagrams to my mechanic and showed him the list of service hints, he told me that testing all these wires would be an all day and very expensive job.

My other concern is regarding the method to test these wires with a multi-meter. I read on another forum post that it can be done by using sewing needles by poking through the shielding to make contact with the wire, then probing the sewing needle.

Any and all feedback is appreciated.

Thanks,
Winnie Owner

 

First, I don't think your issue is electrical. Your symptoms (weak spark only on some plugs, and which plugs change. Dancing timing mark.) point to a bad bearing in the distributor. You have a new distributor (and cap), but I would at least remove the cap and push sideways (in all directions) on the rotor. You should feel only the very slightest movement.

To answer your questions. VTA is the signal from the Throttle position sensor (TPS). The Throttle valve is opened with the gas pedal; put your foot someplace else. VS is the signal from the Volume Air Flow meter (VAF). It's held closed with a spring, and is pulled open by air flow with the engine running. So measure with the engine off (to be complete, you can remove one of the big pipes to the VAF and put your finger on the vane. Make sure it closes all the way.)

Measuring voltages at the ECU is difficult for a bunch of reasons. (Not much room, hard to get a good connection to each wire, ...) I'd start with measuring the resistance right at the sensor. Here's the TPS http://web.archive.org/web/201108151...93throttle.pdf and here's the VAF http://web.archive.org/web/201003261...92volumeai.pdf The advantage of measuring voltages at the ECU is that it is an end-to-end test (you don't have to worry that the wire from the sensor to the ECU is causing an issue.) But I prefer to start with the easy stuff.

Like checking the distributor bearing.

 

Hi Scope,

Thanks for your reply, I really appreciate it.

What doesn't add up is that the distributor is new and I've had the problem with both the old and new distributor. I'm lead to believe the problem is elsewhere as we've changed everything in between the distributor and ECU (ignition control module and ignition coil). I will check for play on the rotor. Maybe the new dizzy could be bad too.

Is there any other component that could cause this? I'm thinking a degraded wire somewhere or contact between the Distributor, ignition control module, and ECU. The wiring harness looks pretty old. I have changed the ignition control module with an OEM one from Ebay, as well as a brand new one from the mechanic's part dealer. So that's 3 modules so far, all with the same symptoms.

I will take a look at measuring those resistances.

Thanks again.

 

Did you replace the plug wires? That won't cause code 12 or the dancing timing mark (well, I guess it could cause that if #1 has a bad wire), but it could easily cause weak spark on some, but not all, cylinders. Plus, they aren't too expensive, and are easy to replace.

 

I haven't bothered with the wires as they look new, and we are testing the spark coming directly from the distributor ports, so wires are ruled out as a problem. The test is done by unplugging the wire from the distributor and holding it close to the port to "hear" the spark coming out.

 

another guess is that the distributor placement is wrong in relation to the crankshaft. The mechanic puts it back in by marking the rotor position of the old one and copying that on the new distributor. I’m wondering if turning the crank shaft to TDC, then lining up the dizzy rotor to cylinder 1 and marks according to the FSM. I believe there’s a notch on the distributor that has to line up when it goes in.

 

 

Well, that's a totally bush way to check for spark. But it doesn't matter; where do you think the spark "goes" once it come out of the port? If it can't get down the wire (and through the plug), you're not going to get any spark at the port. Use the inductive pickup on your timing light on each plug wire. If the light flashes, you've got spark. If no flash, the plug isn't firing. (Do check plug gap; if it's way too big you also won't get spark.)

If the distributor was "stabbed" off one tooth, timing would be off by about 28°. So you'd have a tough time getting it to run at all. But being off a tooth would not cause a dancing timing mark.

But a positive check of timing is worth doing. Your harmonic balancer has an annular rubber ring separating the part on the crankshaft from the part with the pulley sheaves (and timing mark). If that ring wears out (26 years is about right), the outer part can shift and your timing will be WAY off what the marks say. Just get a chopstick or plastic straw in #1, and rock the crank to see if the piston is at the top. Is your timing mark at TDC?

 

Spoke to my mechanic. He took the ECU out and took it apart. Looking at the board he noticed one of the capacitors was melted off onto the circuit board and said this is the problem. Pictured attached:

I also noticed when shorting the E1 and TE1 terminals the check engine light does not flash repeatedly like it’s supposed to. I have tried wiggling it with different sized paper clips and it doesn’t help.

a new computer cost $450 from flagship one. I have searched throughout the internet and could not find a cheaper one.

https://www.fs1inc.com/89661-35760-1...plug-play.html

 

That capacitor has clearly puked its guts. But capacitors don't cost much, and you can probably still read the value. Repairing circuit boards takes a little bit of talent, but not $450 worth. What have you got to lose?

(Check the other capacitors while you're at it. If any of them even look "bulged," consider replacing them at the same time.)