Demon Jinx

Guys I am getting there!!!! Scooby had a severe misfire at 3500rpm. Did everything I can think of finaly I checked Throttle position sensor and got the voltage right. It was 1.1-5.5V got it to 0.9-4.7V. Now it runs alot better BUT it still hesitates a bit at around 4800rpm. Feels like a flatspot. What is the standard for idiling on the boost gauge? Mine sits on -0.8??

Demon Jinx

Any ideas guys??
Please help!

drb5

iTrader: (4)

What all have you done so far to fix it?

musso2010

I assume you have checked the basics, ie-plugs, coils, etc...
What are your mods?

Demon Jinx

Hi Musso I have replaced all the plugs, Checked and changed coil packs adjusted throttle positioning sensor as to the right spec, checked for any air leaks on intake also checked and cleaned fuel strainer in the tank. This car is stock standard no mods. I am wondering if it cant be valve timing because it start the misfire at about 4500rpm.
Any Ideas??????

drb5

iTrader: (4)

Tried changing the coil pack distributer thing on the offisde turret?

Tried MAF either?

Demon Jinx

Havent tried the ignitor though and shouldnt I get a fault code if it is the MAF?? can the MAF be tested??

musso2010

A dying MAF wont bring up a fault code. Usually they only throw a code once theyre totally knackard.

To check the MAF, find the pinout at the ecu (jollygreenmonster.com), shove your test probes into the back of the sensor ground and the MAF sensor signal pins and make sure they're pressing firmly enough against the pin shells to get a good contact. Take someone with you to hold/watch the meter and go for a drive. You (or your passenger) should see the voltage fluctuating between around 1 and 5 volts. The more air being taken in, the higher the voltage.

If you accelerate hard, you should see the meter reading rising steadily and consistently. If at any point you see it dropping significantly out of the trend while you are accelerating (so, for example, you see a progression like 3.20/3.30/3.35/2.00/3.50/3.60), and you know you didn't lift off the throttle, this is a warning sign.

Would also check the igniter, but look at the MAF first.

Demon Jinx

Hey Musso thanks alot I am sure this will help alot will try that tomorrow first thing
Is there any way to test the ignitor?

musso2010

Not that i know of mate only find a working one and fit it... but i dont think an igniter failure is that common really. I had similer problems, and went down the same path you did, and found it was the timing in the end...

Demon Jinx

Timing? Cam timing? I actually have the same feeling!!!!!!!!!!

musso2010

Yeah, the woodruff key on my crank had ripped apart and advanced the timing 2 teeth. Car ran fine, but just felt really slow... almost like a non turbo... Its all good now though!

I shudder at how much i spent on sensors and plugs etc... to eliminate the problem. Checking the timing was the last resort.

Demon Jinx

I get the feeling that my cams on pasenger side might be out and thats where the cam sensor is located!! I will check that also tomorrow!!! I know that the cam belt has been changed and after that car never ran right again thats according to the previous owner.

musso2010

Well that would be something to look into after doing a MAF check. Looks like your on the right path now though mate.

Demon Jinx

Will keep you posted thanks mate!!!! One more thing what symptoms did you have when timing was out?

musso2010

Occasional missfires on boost, a severe lack of torque. The car almost felt like i was towing something. It drove awfull, and lacked power. Ticked over fine, but stalled occasionally for no reason. What symptoms do you have?

Demon Jinx

It runs fine to 3500RPM then its starts to backfire and pop and at about 4800rpm tends to pull a bit better but still pops etc.

musso2010

check the maf first, cause ive seen similer problems being down to a faulty maf.

Demon Jinx

Got timing sorted out and took it for a test drive!!!! It ran so nice 100% for about 10kms then the crap started again. Only difference is I can here the turbo boost as previously I couldnt here it. took covers of again to check maybe it jumped a tooth but nope its still fine. Doesnt make sence it ran fine and now same story!
Any Ideas?

musso2010

Try resetting the ecu.

Demon Jinx

Hey guys left her to cool down and started again ran 100% again! As it got to operating temp same old story started misfiring.... Any ideas? Will reset the ecu now and check if it makes a difference!

musso2010

So basically once the car is hot, it starts to misbehave. Mine was exactly the same. Are you 100% your idlers and tensioners are ok, and that your not skipping teeth? Did you check the MAF?

Demon Jinx

Tensioner and idlers are all ok was your timing out?

musso2010

yeah it was out by 2 teeth, the cam gear behind the crank pulley had slipped cause the woodruff key had bent. did you check your keyway on the crank?

Demon Jinx

Yes I did! So you reckon that my problem is timing? Crap weird though why will it run 100% when cold and start with crap as soon as it heats up!!!!

musso2010

No... if your keyway isnt damaged and then causing the cam gear to slip, and you have timed the belt correctly etc... then i believe you can rule the timing out. I had similer problems to you, and my timing was out.

I think that your problem may now actually be electrical...

Demon Jinx

Ok will check maf and ignitor and take it from there!!!!!

Demon Jinx

Tested MAF, reading is spot on! What i did find is that my ogygen sensor gives a standard reading or 3.0!!!!!!!! Even if the car is switched of?? Just want to check in the morning when its nice and cold what reading it gives me! Can that be my problem??

musso2010

To test -

Connect the positive multimeter probe to the sensor output wire and the negative probe to earth. With the engine running if all is well the voltage shown on the meter should flicker up and down the scale changing at least twice a second between about 0.1 and 0.8 volts -- the average reading should be about 0.4-0.5 volts but it should never be steady at this voltage. Flick the throttle open and the voltage should flicker, rise for a second or so then fall again. This indicates the ECU is receiving input from the sensor and is responding properly.

A steady voltage of between 0.4 and 0.5 V is a sign that the ECU is running in open loop mode . Either the engine is not fully warm or it may indicate a bad connection or a faulty water temperature sensor or an ECU fault. It could also indicate a problem with the sensor heater so check the heater is getting power and is properly earthed.

Demon Jinx

If unplugged I get a resding of 0.3! If plugged in the oxygen sensor gives me a reading of 3.0!!!! And it stays steady! Ok so where do I find the sensor heater? I will check the temreture sensor also and check what reading I get from there.