Announcement

Collapse
No announcement yet.

'98 Prado, VZJ95R, 3.4L V6 manual, won't rev past 3000 rpm otherwise runs perfect - SOLVED!‏

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • '98 Prado, VZJ95R, 3.4L V6 manual, won't rev past 3000 rpm otherwise runs perfect - SOLVED!‏

    G'day All,

    I don't frequent this forum but thought you guys might appreciate the info.

    I've had a VZJ95R in my workshop which has been causing me absolute frustration.

    Aside from actual testing, etc, I've done internet searches to see if the problems common and if there have been solutions. There are posts from the past from around the world where the fault has been identical though no body has posted a certain solution. In many cases the vehicles have been taken to workshops/dealerships and the faults have not been fixed.
    I'm not saying this is the fix to all 5VZ-FE's that experience this symptom, but in this case it was, its pretty strange and could likely be the cause for the cases that I read about on the net.
    This EFI system is simple and does not incorporate oxygen sensors.

    FAULT:
    The vehicle came in with what felt like a misfire developing at 3,000 rpm and a dead set rev limit at 3,200 rpm while the engine was warm regardless of free revving while stationary or while driving. There was no engine light on.
    While the engine was cold, the engine would rev limit at 4,200 RPM
    In the early stages of testing, using an oscilloscope, I found that the computer was intentionally cutting the fuel injectors to cause the symptom.


    ACTION:
    I started with an ECU scan to confirm there were no fault codes and that the sensor reading that the ECU was getting were all within specification.
    I replaced plugs, leads and coils and then went on to check all the sensor voltages, resistances, waveforms, ECU inputs and outputs. All tested within specification and all waveforms were as specified. All tested at the sensors and at the ECU plug.
    I swapped the AFM, TPS, igniter, CTS with known good units and the fault remained.
    I sent the ECU, immobiliser control unit, key reader, etc away for testing to 2 different companies and no fault was found.
    I swapped the ECU with a known good unit and the fault remained.
    I removed and refit the timing belt to confirm valve timing and also made sure that the keyways were not flogged out.
    I removed the exhaust to confirm there were no blockages suffocating the engines air flow and causing an in accuracy in AFM reading.

    SOLUTION:
    Out of pure frustration the last sensor I swapped with a known good unit was the crank angle sensor and the problem was solved.

    MYSTERY:
    WE had never suspected that the crank angle sensor was the fault for a few reasons:
    The engine was running and perfectly smoothly with no power loss up until 3,200 RPM! When crank angle sensors play up, normally, 99.9999999999999% (it was 100% until this experience) of the time the engine will either not start or it will run and stall when it gets hot.
    We had a good wave form coming from it through the oscilloscope showing 34 oscillations followed by a long reference oscillation.
    The ECU was always displaying the correct engine speed through the scan tool and tacho.
    The ignition timing was always correct which is a setting that the ECU bases off a correlation between the cam angle sensor and crank angle sensor.
    The resistance of the crank angle sensor was to specification.

    THE CONCLUSION:
    Having oscilloscoped the replacement crank angle sensor we were able to see that it had a slightly higher amplitude in the waveform. The EFI system on the 5VZ-FE obviously needs to see an increase in amplitude of the signal along with the crank reference position when accelerating the motor to operate correctly. The lack of signal amplitude is not a fault that is registered by the ECU hence no check engine light.

    ADVICE:
    Although air flow meters are common faults on them and cleaning them often rectifies faults, if any body experiences a rev limit type scenario where the engine otherwise feels great, consider the crank angle sensor. Its not a normal culprit in this situation but obviously is in the 5VZ-FE EFI system due to the reliance of the amplitude side of the signal and not just the reference side of the signal.

    I hope this helps people.

    Cheers,
    Denis.

  • #2
    An excellent write up.
    Thanks for sharing.

    Comment


    • #3
      Yes, thanks for sharing this.
      glen_ep - engineered, 4" lift, 33" 255/85R16, lockers, 4.88 ratios www.pradopoint.com.au/showthread.php?17237 www.youtube.com/user/glenep www.fb.com/groups/ToyotaPrado90

      Comment


      • #4
        My service advisor just received a phone call from a workshop in another State of Australia who had been pulling their hair out and spent days trying to diagnose the same issue. Apparently he came across this thread last night, replaced the crank angle sensor this morning and it fixed the problem. We were so stoked to have the thankful interstate phone call for posting this thread.................... Made my day.

        Comment


        • #5
          Gotta love it when you get those calls or emails. Makes me feel all warm and fuzzy inside lol

          Comment


          • #6
            Good stuff! I have certainly remembered this just incase it ever pops up at work!

            Comment


            • #7
              Fantastic investigative work Denis ! Are you sure the shielding of the faulty sensor was Ok ? Sometimes this can cause issues with amplitude due to noise. Magnetic sensors in particular can be prone to this.
              Baders-1996 Prado 90 Series 3.4L/TRD Supercharger/2.2" Pulley/Xede ECU/Aquamist Water Meth Injection/Pacemaker Extractors/2.5" Custom Exhaust/West Coast Suspensions HD 50mm lift/Detroit Tru Trac rear diff.

              Comment


              • #8
                G'day All,

                We were pleased to receive another thankful phone call from a workshop in NSW today. 3 years after the original post!! They've had a Prado that has had this issue for approximately 12 months. Done all the testing, replacing sensors and parts to no avail. Decided to do a 30 min internet search and found this thread, replaced the crank angle sensor and the problem was fixed.

                I'm certain now its not just a one off problem and must be affecting many 5VZ-FE's.

                Comment


                • #9
                  Originally posted by Jose Street Auto Centre View Post
                  G'day All,

                  We were pleased to receive another thankful phone call from a workshop in NSW today. 3 years after the original post!! They've had a Prado that has had this issue for approximately 12 months. Done all the testing, replacing sensors and parts to no avail. Decided to do a 30 min internet search and found this thread, replaced the crank angle sensor and the problem was fixed.

                  I'm certain now its not just a one off problem and must be affecting many 5VZ-FE's.
                  Having worked on many of these motors, it's not a fault I've ever come across. Given all the symptoms listed, I'd never think to check the CAS. I mean let's face it... bad CAS nearly always equates to no start! Or no hot starts at least.

                  I'll certainly be keeping this in mind should I ever see this problem arise. Thank you.

                  Comment


                  • #10
                    reminds me of working on the delco 808 in Vn/Vp commodores some of them were like that. No fault codes just run shit wont rev change the cas its all good again.
                    I got myself some Big Horn Maxxis and was telling my landrover lover mate he said what size did you get I told him 265/75/16 he said I didn't know they came that small.

                    Comment


                    • #11
                      G'day All. In April I received an email from another happy camper who this post helped out.

                      Thanks to those that have contacted me. It's great to see the post is working. I just wanted to ask that if this post does help you, please add to this thread so everyone can see how big an issue it is.

                      "Subject: 98 Prado - Crank Angle Sensor (Post in PradoPoint)

                      Comments: I just wanted to thank you for your post in PradoPoint.. I experienced this exact problem just the other day with my Prado (220,000 kms) . After Toyota was too busy I went to my local mechanic who confirmed the diagnosis ( I printed out your post) and he was able to solve this unusual problem for $350 in a few hours. So once again, thank you so much."

                      Comment


                      • #12
                        same here with my prado!!! Thanks

                        Comment


                        • #13
                          Good Day, I have a Prado with a 1KD diesel engine, and have this issue too where is is not revving more than 3200rpm on no load and no more than 3600 on load. Have replaced fuel filters, SCVs, MAF, MAP, no codes are coming up and it is driving me crazy. While searching the internet for the umpteenth time, I came across your post and was wondering if this issue can be applicable to common rail diesel engine too prior continuing replacing more sensors as the issue seems an electronic one rather than mechanical.

                          Comment


                          • #14
                            Have you done all the sensor tests in the 1KD manual, page 327 of RM806E? Perhaps boost pressure next?

                            Comment


                            • #15
                              [QUOTE=Jose Street Auto Centre;n22853]

                              G'day All,

                              I don't frequent this forum but thought you guys might appreciate the info.

                              I've had a VZJ95R in my workshop which has been causing me absolute frustration.

                              '98 Prado, VZJ95R, 3.4L V6 manual, won't rev past 3000 rpm otherwise runs perfect - SOLVED!‏
                              11-06-2014, 02:06 PM


                              Many thanks to this Pradopoint forum and many many thanks to Jose Street Auto Centre and Denis's post of 11-06-2014.

                              It's been more than ten months of frustrating dead ends in trying to find a reason and a solution to the misfiring and power failing at around 3000 to 3200 rpm of the otherwise healthy motor in my '97 3.4L Prado.
                              My savvy regular workshop mechanic mate spent a lot of time on it, at the same time we'd been ringing around and talking to Prado mates and industry contacts as well as lurking in online forums without finding any solution to our problem.

                              By this time the Prado was off the road with the misfiring now occurring at 2000 rpm.
                              Then out of the blue, mechanic mate sends me a "Read this 2014 post!!!" text and a link to a Pradopoint post with a highly probable solution.

                              He finds a salvaged 2nd hand crank angle sensor in a box of bits on a parts shelf, we get the vehicle into the workshop to swap the sensor, and fifteen minutes later the motor is revving to 2,3 and 5000 rpm with ease and is running as sweet as.

                              Thanks again to the Jose Street Auto Centre and Denis for the well set out and informative post.

                              Regards from 2022,
                              TJ.
                              Terentius
                              Lurker
                              Last edited by Terentius; 14-05-2022, 07:10 PM.

                              Comment

                              canli bahis siteleri bahis siteleri ecebet.net
                              mencisport.com
                              antalya escort
                              tsyd.org deneme bonusu veren siteler
                              deneme bonusu veren siteler
                              gaziantep escort
                              gaziantep escort
                              asyabahis maltcasino olabahis olabahis
                              erotik film izle Rus escort gaziantep rus escort
                              atasehir escort tuzla escort
                              sikis sex hatti
                              en iyi casino siteleri
                              deneme bonusu veren siteler
                              casibom
                              deneme bonusu veren siteler
                              deneme bonusu veren siteler
                              betticket istanbulbahis
                              Working...
                              X