can a bad circuit open relay cause a 3.0 momentary miss
09-05-2012, 09:24 PM
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can a bad circuit open relay cause a 3.0 momentary miss
Still trying to find my 3.0 momentary miss at any speed. So can the circuit open relay cause the momentary miss. Tryed moving the front harness no big jump in ohms. I'll try anything to fix it.
09-06-2012, 05:37 AM
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The Circuit Opening Relay powers the fuel pump. Considering all the physical damping in the fuel system (including the Fuel Pressure Damper itself), I would really doubt that even a momentary stop of pumping would cause something someone would describe as a "miss." It would either cut out for a few seconds (minimum), or not at all.
In my limited experience, a "miss" is more likely a spark plug not firing than a fuel issue, but just about anything is possible.
In my limited experience, a "miss" is more likely a spark plug not firing than a fuel issue, but just about anything is possible.
09-06-2012, 08:25 AM
#3
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3.0 momentary miss
I'm wondering if the engine miss you speak of happens at any speed? You didn't say if auto or man trans. Mine is a 5spd. When my miss happens in low range it nearly throws me out of the seat almost as if the engine attempted to run backwards. When it happens at highway speeds, it feels like a gun recoil.
It's a very fast event, and Toyota cannot( or choses not to for profit gain) identify a code related to the event description. It started shortly after the factory head gasket job at 103,000 miles. The one thing they did say is that I had a plenum gasket lead, and later an oil leak from the rear main seal which I'd asked them to replace during clutch service at about 150,000 miles.
I know I neglected to change the timing belt for 135,000 miles, but the engine began to cut back on power and run rough after the engine hit 1,500 rpm the second time after I start it and take off. It has been a random event as sometimes I start off and the engine has all the power and smoothness it should have.
I lived with these problems until I developed a water pump leak at 326,000 miles, and the truck is now disassembled for water and oil pump, timing belt and pulleys, adjust valves, and replace valve cover, plenum and intake gaskets.
After visiting several forums, I have decided that it's best to replace the knock sensor and the knock sensor wire because the sensor sits under the intake, and the wire is notorious for being faulty and breaking from all the heat.
I'm hoping that after doing all these things, the engine will seal and regain it's power and mileage.
Although I'm not a mechanic, I purchased the factory manuals with the truck, and because of shoddy service, I eventually stopped allowing Toyota service people to fix the truck. I figure I can do as well if, when I pay someone to do it for me, they fix this and breakd that.
I am finding lots of help in these forums. thank you guys for posting what you know.
It's a very fast event, and Toyota cannot( or choses not to for profit gain) identify a code related to the event description. It started shortly after the factory head gasket job at 103,000 miles. The one thing they did say is that I had a plenum gasket lead, and later an oil leak from the rear main seal which I'd asked them to replace during clutch service at about 150,000 miles.
I know I neglected to change the timing belt for 135,000 miles, but the engine began to cut back on power and run rough after the engine hit 1,500 rpm the second time after I start it and take off. It has been a random event as sometimes I start off and the engine has all the power and smoothness it should have.
I lived with these problems until I developed a water pump leak at 326,000 miles, and the truck is now disassembled for water and oil pump, timing belt and pulleys, adjust valves, and replace valve cover, plenum and intake gaskets.
After visiting several forums, I have decided that it's best to replace the knock sensor and the knock sensor wire because the sensor sits under the intake, and the wire is notorious for being faulty and breaking from all the heat.
I'm hoping that after doing all these things, the engine will seal and regain it's power and mileage.
Although I'm not a mechanic, I purchased the factory manuals with the truck, and because of shoddy service, I eventually stopped allowing Toyota service people to fix the truck. I figure I can do as well if, when I pay someone to do it for me, they fix this and breakd that.
I am finding lots of help in these forums. thank you guys for posting what you know.
09-06-2012, 10:18 AM
#4
The symptoms you are both describing are consistent with code 11: Momentary interruption in ECU power supply. And/or code 42: Vehicle Speed Sensor / SPD signal is not input to the ECM for at least 8 seconds during high load driving with engine speed between 2,750 rpm and 4,000 rpm.
Though it can happen without throwing any codes. It will usually throw a code 11 if the ECU is the early type. But code 42 appears to be hit or miss regardless of the ECU design. Needless to say, you should be checking for codes.
What causes/fixes it is pretty well covered in this thread.
In short...
It would have to be caused by one(or more) of the issues, or components malfunctioning, listed below.
http://www.motor.com/article.asp?article_ID=271
Though it can happen without throwing any codes. It will usually throw a code 11 if the ECU is the early type. But code 42 appears to be hit or miss regardless of the ECU design. Needless to say, you should be checking for codes.
What causes/fixes it is pretty well covered in this thread.
In short...
It would have to be caused by one(or more) of the issues, or components malfunctioning, listed below.
- Faulty wiring and/or ground connections
- Ignition Switch
- EFI Main Relay
- Vehicle Speed Sensor
- ECU
Dan moves forward with his Toyota service series by looking at two signal glitches that can lead unsuspecting techs into a diagnostic black hole.
In this fourth installment of our Toyota service series, we'll discuss two goofy sensor signals that cause fits for vehicles as well as the technicians testing them. An intermittent vehicle speed sensor (VSS) failure, which usually occurs on late '80s and early '90s Toyota trucks, opens this month's agenda.
The bad VSS signal can cause some very random symptoms during acceleration and/or steady cruise conditions, including intermittent loss or lack of power, bucking or lugging and hesitation or stalling. If the vehicle has cruise control, the driver may also notice that it intermittently disengages for no obvious reason.
With this particular VSS failure, the symptoms don't appear until the vehicle has been driven for some time at operating temperature, so don't expect anything to go wrong when the vehicle is cold. And although these problems occur most often on trucks, they also can occur on any Toyota with a cable-driven speedometer and a reed-switch type VSS.
What's more, don't count on seeing trouble codes, let alone the correct VSS code with these problems. Experience has taught us two things: First, the VSS signal may not fail long enough to set a code; second, the troublemaker reed-switch type VSS we're discussing, which is built into the speedometer head, is called VSS No. 1. (You have to buy the entire speedo head in order to replace VSS No. 1.) VSS No. 2 is in the transmission. When the PCM recognizes a serious discrepancy between VSS Nos. 1 and 2 in this situation, it usually flags No. 2, sending a luckless technician off in the wrong diagnostic direction!
Monitoring VSS No. 1's signal with a digital scope during an extended road test is the best way to verify a failing sensor. Forewarned is forearmed: The shop manual states that if you turn the speedometer cable by hand, VSS No. 1 should switch on and off four times within one revolution of the speedo cable. The troublemaker VSS always passes this test.
As we mentioned, the symptoms listed earlier are associated with a reed-switch type sensor, the popular Toyota VSS of this era. Typically, the PCM feeds a battery-voltage reference signal into this sensor. Every time the reed switch contacts close, the sensor pulls reference voltage toward ground. So it should produce a clean, consistent square wave (Fig. 1 without the noise) that switches back and forth between battery voltage and ground.
Fig. 1 shows a good Toyota VSS signal onto which we sketched the typical electrical noise you'll see if this sensor acts up. Here, the vehicle was idling in gear with its wheels turning on dynamometer rollers. Of course, the faster the drive wheels spin, the more often the VSS switches reference voltage back and forth to ground.
Basically, the noise on the signal makes the PCM think the vehicle is going much, much faster than it really is. This can trick the computer into fuel cut (shutting off the injectors) intended to prevent the vehicle from being driven at unsafe speeds. When this unintended fuel cut occurs, the driver may report that his vehicle began losing power and speed-possibly stalling out for a moment-before mysteriously recovering.
Likewise, the false road speed signal raises havoc with the cruise control and the electronically shifted trans. For example, the trans computer thinks the vehicle is going fast enough to justify high gear or Overdrive. So it prematurely upshifts the trans, lugging the engine down for several seconds and possibly making the vehicle buck. Then the trans goes back to the correct gear range for the driving conditions and the whole episode is over so quickly that the driver has difficulty describing it to you!
In this fourth installment of our Toyota service series, we'll discuss two goofy sensor signals that cause fits for vehicles as well as the technicians testing them. An intermittent vehicle speed sensor (VSS) failure, which usually occurs on late '80s and early '90s Toyota trucks, opens this month's agenda.
The bad VSS signal can cause some very random symptoms during acceleration and/or steady cruise conditions, including intermittent loss or lack of power, bucking or lugging and hesitation or stalling. If the vehicle has cruise control, the driver may also notice that it intermittently disengages for no obvious reason.
With this particular VSS failure, the symptoms don't appear until the vehicle has been driven for some time at operating temperature, so don't expect anything to go wrong when the vehicle is cold. And although these problems occur most often on trucks, they also can occur on any Toyota with a cable-driven speedometer and a reed-switch type VSS.
What's more, don't count on seeing trouble codes, let alone the correct VSS code with these problems. Experience has taught us two things: First, the VSS signal may not fail long enough to set a code; second, the troublemaker reed-switch type VSS we're discussing, which is built into the speedometer head, is called VSS No. 1. (You have to buy the entire speedo head in order to replace VSS No. 1.) VSS No. 2 is in the transmission. When the PCM recognizes a serious discrepancy between VSS Nos. 1 and 2 in this situation, it usually flags No. 2, sending a luckless technician off in the wrong diagnostic direction!
Monitoring VSS No. 1's signal with a digital scope during an extended road test is the best way to verify a failing sensor. Forewarned is forearmed: The shop manual states that if you turn the speedometer cable by hand, VSS No. 1 should switch on and off four times within one revolution of the speedo cable. The troublemaker VSS always passes this test.
As we mentioned, the symptoms listed earlier are associated with a reed-switch type sensor, the popular Toyota VSS of this era. Typically, the PCM feeds a battery-voltage reference signal into this sensor. Every time the reed switch contacts close, the sensor pulls reference voltage toward ground. So it should produce a clean, consistent square wave (Fig. 1 without the noise) that switches back and forth between battery voltage and ground.
Fig. 1 shows a good Toyota VSS signal onto which we sketched the typical electrical noise you'll see if this sensor acts up. Here, the vehicle was idling in gear with its wheels turning on dynamometer rollers. Of course, the faster the drive wheels spin, the more often the VSS switches reference voltage back and forth to ground.
Basically, the noise on the signal makes the PCM think the vehicle is going much, much faster than it really is. This can trick the computer into fuel cut (shutting off the injectors) intended to prevent the vehicle from being driven at unsafe speeds. When this unintended fuel cut occurs, the driver may report that his vehicle began losing power and speed-possibly stalling out for a moment-before mysteriously recovering.
Likewise, the false road speed signal raises havoc with the cruise control and the electronically shifted trans. For example, the trans computer thinks the vehicle is going fast enough to justify high gear or Overdrive. So it prematurely upshifts the trans, lugging the engine down for several seconds and possibly making the vehicle buck. Then the trans goes back to the correct gear range for the driving conditions and the whole episode is over so quickly that the driver has difficulty describing it to you!
09-06-2012, 08:30 PM
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Its a 91 4runner 3.0 5spd 4x4, 31" tires. The buck, intermittent loss of power for a second, momentary hard miss, jerk, does it at any speed now slow, steady cruising, accelerating and decelerating. Its getting alot harder to make it jump out of gear. Also NO CODES. I first changed all of the ignition parts then distributor,coil, ECU, 3 different year speedo's, Efi relay. Started checking the wiring and connectors with ohms meter. Complete top end and belts. I will change out the speedo cable.
09-07-2012, 07:51 AM
#6
I doubt changing the speedo cable is going to make any difference. Unless it broke.
The only component it looks like you haven't already changed that might be causing it is the ignition switch(or was that included in "all of the ignition parts"?). Unless there's still some wiring that needs checked/repaired/replaced.
The only component it looks like you haven't already changed that might be causing it is the ignition switch(or was that included in "all of the ignition parts"?). Unless there's still some wiring that needs checked/repaired/replaced.
Last edited by MudHippy; 09-07-2012 at 07:53 AM.
11-05-2012, 12:37 PM
#7
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Greetings guys, I'm finally back with some results. My major "tuneup" did much for my truck, but the code 52 remains unchanged. I have increased power after checking the engine timing and it runs smoother with less hesitation while accelerating. I unplugged, treated and replugged every connector I could access between the shock sensor and the ECU, including those on the ECU itself.
I installed a new oil pressure sending "switch" from Autozone. They assured me that it was the correct part for my SR5, but of course as soon as I connected it, the receiving unit,s plastic rail inside the unit ripped apart from the high signal. Fortunately, information found within this forum told me that what happened was expected if a switch rather than a variable gauge was installed. The good thing is that I was able to convince Autozone that my problem was the fault of their computer's not being specific to the SR5 pickup and resulted in their selling me the wrong part. I couldn't have done that without the info provided here, then tracking the part numbers through two Autozone suppliers and finding their errors in part number specs. Autozone paid for a new oil pressure receiving unit for my dash. I purchased a new sending unit from Toyota. Anyway, the new oil pump (not from Toyota) has a higher than previous idle pressure, and it doesn't vary much at high RPMs except with a cold engine.
Now, after seeing all that has been done by 54runner54, I see no need to repeat those things. I noticed that while I had the dash cluster out the first time to check my wiring, the speedo unit spilled oil into the cluster. I couldn't determine how since I was aware of the fluid being there and was careful to not tip it to allow spilling. The speedo still works and is accurate according to its correlation to the dash tach. I don't have access to a scope to check the waveform but I can say that I am not having problems with the cruise control---never have.
I didn't mention it, but I also removed my injectors and soacked their bottom ends in seafoam overnight and installed new rubber seals and o-rings. I am wondering if my injectors with 326k on them might be triggering a code 52. That's about the only clue I have that might be related to uneven firing except I cannot be sure about my accuracy in adjusting the valve shims.
If I can replace my injectors, I will redo my valve adjustment. I feel more confident about it now, and I can admit that I probably made some errors if for no other reason than the possibility of having left some trace metal under the shims as I struggled to replace them.
I plan to use this replacement injector:
Remanufactured Multi Port Injector 842-12130 GB Remanufacturing.
I will buy from Rock Autoparts.
GB describe a process where the clean and spec their rebuilds to match oem guidelines, then further match 6 injectors to perform within similar tolerances for smoother performance. Can anyone speak for GB?
I installed a new oil pressure sending "switch" from Autozone. They assured me that it was the correct part for my SR5, but of course as soon as I connected it, the receiving unit,s plastic rail inside the unit ripped apart from the high signal. Fortunately, information found within this forum told me that what happened was expected if a switch rather than a variable gauge was installed. The good thing is that I was able to convince Autozone that my problem was the fault of their computer's not being specific to the SR5 pickup and resulted in their selling me the wrong part. I couldn't have done that without the info provided here, then tracking the part numbers through two Autozone suppliers and finding their errors in part number specs. Autozone paid for a new oil pressure receiving unit for my dash. I purchased a new sending unit from Toyota. Anyway, the new oil pump (not from Toyota) has a higher than previous idle pressure, and it doesn't vary much at high RPMs except with a cold engine.
Now, after seeing all that has been done by 54runner54, I see no need to repeat those things. I noticed that while I had the dash cluster out the first time to check my wiring, the speedo unit spilled oil into the cluster. I couldn't determine how since I was aware of the fluid being there and was careful to not tip it to allow spilling. The speedo still works and is accurate according to its correlation to the dash tach. I don't have access to a scope to check the waveform but I can say that I am not having problems with the cruise control---never have.
I didn't mention it, but I also removed my injectors and soacked their bottom ends in seafoam overnight and installed new rubber seals and o-rings. I am wondering if my injectors with 326k on them might be triggering a code 52. That's about the only clue I have that might be related to uneven firing except I cannot be sure about my accuracy in adjusting the valve shims.
If I can replace my injectors, I will redo my valve adjustment. I feel more confident about it now, and I can admit that I probably made some errors if for no other reason than the possibility of having left some trace metal under the shims as I struggled to replace them.
I plan to use this replacement injector:
Remanufactured Multi Port Injector 842-12130 GB Remanufacturing.
I will buy from Rock Autoparts.
GB describe a process where the clean and spec their rebuilds to match oem guidelines, then further match 6 injectors to perform within similar tolerances for smoother performance. Can anyone speak for GB?
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11-05-2012, 02:20 PM
#9
Registered User
You can rule out, or confirm the COR by connecting the+B and FP terminals in the diagnostic box under the hood. This bypasses the COR, if the symptoms persist it isn't your culprit. If they stop, check VAFM switch adjustment.
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