5.0 Rough On Start Up

[Gaz]

Have put injector cleaner through it, can rule out pump, injectors and regulator though as a few times it has started on gas, in cold start mode (temp must have been ok to start on gas but low enough for open loop) and it had the same symptoms on gas

Have not been able to detect any air leaks yet.

[ebzery]

ok from what i can tell my harmonic balancer has spun .
which has a timing sensor connected to it.
maybe a common problem on the fords v8s au

[Gaz]

It is a common problem I believe, but not the source of mine unfortunately.

Have been trying to get a video of it in the morning, but unfortunately the sound is a little quiet in the video I took so will try get another one tomorrow.

[Cúl-Báire]

Still no luck with this myself.

I've disconnected the IAT - Same Problem.
I've diconneted the ECT - Same problem, but thermos come on aswell.
I've cleanned the MAF.
I've cleaned the throttle body.
I've checked for airleaks on the intake side, and come up with nothing.
I've checked vacuum hoses and come up with nothing.
PCV seems to be working.
Installed Walbro 255lph pump.
Installed new fuel filter.
And once warmed up for a minute or two, the thing drives perfectly; you wouldn't know of any issues.

This one has me stumped!!!...

[Gaz]

Got a video this morning, it's a little hard to hear due to the outside noise, but if you turn it up you can hear the engine stuttering and the tacho not moving for a few seconds before it takes off and the revs then rise.

This was in 1st gear, no clutching. Try to accelerate twice, at 5 and 14 seconds.

Is that similar to yours?

http://www.youtube.com/watch?v=bZd1dulaxvI

[Cúl-Báire]

Yeah mine does the same if I try to take off without letting it warm up, the idle has a real "chuga'chuga'chugga'" to it almost as if it's got a lumpy cam.

It doesn't bother me too much letting it warm up, but it does get annoying at times.

[auIILTD]

Originally Posted by Cúl-Báire

Still no luck with this myself.

I've disconnected the IAT - Same Problem.
I've diconneted the ECT - Same problem, but thermos come on aswell.
I've cleanned the MAF.
I've cleaned the throttle body.
I've checked for airleaks on the intake side, and come up with nothing.
I've checked vacuum hoses and come up with nothing.
PCV seems to be working.
Installed Walbro 255lph pump.
Installed new fuel filter.
And once warmed up for a minute or two, the thing drives perfectly; you wouldn't know of any issues.

This one has me stumped!!!...

Guys, disconnecting the IAT is not going to isolate the IAT from providing incorrect readings. Below is a post I made from doing some tests on what the ECU sees when the IAT is open circuit. This was from a thread called "CAI IAT - How important is it".

Originally Posted by auIILTD

OK, no need for silly freezer bag tests. I have just gone and performed a test by logging the results of ACT (Air Charge Temp) with the IAT unplugged. Interesting result.

Upon startup, the ACT was equal to ECT (Engine Coolant Temp). I thought that this was interesting, but after about 30 seconds, the ACT went to a static 80 degF. IAT circuit was open circuit. You could speculate that if the IAT circuit was short circuit (ie both wires melted to extractors), the ACT would be static at a maximum value. I was not going to short the wires together for the sake of this test.

So with ACT static at 80 degF, what is this going to impact? Going through my tune I have identified some of the following functions that use ACT.

WOT Advance vs ACT - at 80 degF, no advance is pulled at WOT (on my tune - which that part should be stock), but as intake air temp goes over 100degF, timing is pulled at WOT in varying amounts (dependant on Tune). Probably not a critical factor, but timing is pulled at higher temperatures to protect the engine.

Fuel Base OL - your ACT is factor in determining your target AFR in Open Loop mode (along with ECT).

This is just a couple of functions that rely on the ACT. There quite a few others as well to do with cold startup functions. The real impact I believe is that if your IAT circuit is short circuited indicating a really high ACT, you could expect that large amounts of timing will be pulled from your tune when it doesn't need to be.

So in summary yes, the IAT is important. Not critical, but as pointed out originally, important to ensure that your tune is running at an optimum.

Cheers
Stu

My guess would be unplugging the ECT sensor would yeild similar results in the eyes of the ECU.

Hope that helps guys.

[Cúl-Báire]

Originally Posted by auIILTD

Guys, disconnecting the IAT is not going to isolate the IAT from providing incorrect readings. Below is a post I made from doing some tests on what the ECU sees when the IAT is open circuit. This was from a thread called "CAI IAT - How important is it".



My guess would be unplugging the ECT sensor would yeild similar results in the eyes of the ECU.

Hope that helps guys.

Stu, 5.0 would data logging pottentially pick up the error, or would the faulty ECT throw up an error code at all?

[auIILTD]

Originally Posted by Cúl-Báire

Stu, 5.0 would data logging pottentially pick up the error, or would the faulty ECT throw up an error code at all?

Hi Aaron.

Data logging would definately tell you if you ACT or ECTs are not reading within the expected range. My guess is that a faulty sensor will provide an erraneous value or results similar to what I found above.

As for error codes, I or Matt (5.0 ED) have not been able to read error codes. From what I understand, to read error codes, you need the bastardised OBD2 version reader used by AUs

Stu

[Cam]

I know Gaz said he'd replaced his.. But have you replaced your cam synch? I had 3 workshops spend in total 20+ hours trying to diagnose a rough idle issue on startup and an intermittent "miss" I had on the road / dyno. I changed my cam synch after it became noisy and my issues suddenly disappeared..

Just a thought..

[Gaz]

Originally Posted by Cúl-Báire

Yeah mine does the same if I try to take off without letting it warm up, the idle has a real "chuga'chuga'chugga'" to it almost as if it's got a lumpy cam.

It doesn't bother me too much letting it warm up, but it does get annoying at times.

Yeh, it sounds good.. until you try to take off!

I don't mind the wait, unless I'm in a rush, which is most days for me


My IAT tested ok when I tested it. Checking the voltage and resistance of it when cold returned numbers consistant with the ambient temperature.

Removing it from the car resistance values changed moving it from shade to sun and even blowing over it gently changed the resistance values and the numbers returned were consistant with air temps on the day.


You say on startup with the IAT unplugged the ACt followed the ECT until 30 or so seconds, could have it been 45 seconds and the switch to a static 80degF be standard in closed loop as opposed to matching the ECT is open loop?

If the IAT was plugged in during warmup (open loop) would the figures still match ECT figures for the same period of time?

Guess I should double check the results at the ECU plug to rule out a damaged wire.. seems unlikely several of us would all have damaged IAT wires though!

[auIILTD]

Originally Posted by Gaz

My IAT tested ok when I tested it. Checking the voltage and resistance of it when cold returned numbers consistant with the ambient temperature.

Removing it from the car resistance values changed moving it from shade to sun and even blowing over it gently changed the resistance values and the numbers returned were consistant with air temps on the day.


You say on startup with the IAT unplugged the ACt followed the ECT until 30 or so seconds, could have it been 45 seconds and the switch to a static 80degF be standard in closed loop as opposed to matching the ECT is open loop?

If the IAT was plugged in during warmup (open loop) would the figures still match ECT figures for the same period of time?

Guess I should double check the results at the ECU plug to rule out a damaged wire.. seems unlikely several of us would all have damaged IAT wires though!

Hi Gaz.

I certainly do not have the magic answer, I just thought that I would point out that one factor, the IAT is not as simply tested as simply making it open circuit as my test mentioned indicates. My test indicates that the ECU will insert values regardless of the IAT. I am certainly not saying it is the IAT, just throwing my experience out there.

With the IAT in open circuit, it could well have been 45 seconds (not 30) that the ACT followed the ECT. Until the ECU went closed loop. With the IAT plugged in and functional, the IAT reads actual independant values (as you would expect).

I am also not convinced that your test of voltages that show 'consistant' are in actual fact accurate, but it is a fair test that tells us that the IAT is responding to temp changes.

It probably is not your IAT or even your ECT sensor, but we do know that these are factors in your startup conditions. At least on person has advised that they have fixed this very problem by change of ECT sensor. How expensive can an ECT sensor be? Depending how much problem bothers you, will of course dictate the amount you spend.

I will try and get some voltages for you at startup in cold condition with corresponding actual values. This may better isolate the sensors without spending some $$$$.

Hang in there guys.

Stu

P.S. I will also add that my car when started without any throttle can sometimes chug chug and then sometimes stall. A stab of the throttle to give it a rev has always corrected the problem.

[Cúl-Báire]

Originally Posted by auIILTD

How expensive can an ECT sensor be? Depending how much problem bothers you, will of course dictate the amount you spend.

I have been quoted $98, $108 and $110 for an ECT Sensor (all today) - I might have one tomorrow if I can be bothered driving 30 minutes to the ford dealer.

Edit: Actually my father inlaw has an AUIII XR8 might hit him up to come round and try his sensor first

[auIILTD]

Originally Posted by Cúl-Báire

I have been quoted $98, $108 and $110 for an ECT Sensor (all today) - I might have one tomorrow if I can be bothered driving 30 minutes to the ford dealer.

Dearer than I would have thought. Let me get some voltages and corresponding temps to help you identify good or bad.

Stu

[Gaz]

Appreciate Your help and advice Stu, your knowledge is valuable.

From my research, ect and iat sensors have the same calibration in regards to their resistance and voltage returns at the same temps. Both my sensors are certainly returning similar results at ambient, and the cluster diagnostics shows the temperatures id expect.

On this front I'm starting an auto sparky pre apprenticeship in a week (yes I'm leaving that pretty late in life and motivation for me to spend as little $ as possible) so I'll figure this out if it kills me!

[auIILTD]

Cool, good luck with the auto sparky stuff. I am sure you will have it sorted yourself in no time!

I am a telecommunications technician myself, so the electrical side of things is all pretty logical for me.

Cheers
Stu

[Evgeni]

I accidently broke a ect sensor a few years ago and went to order another one from Repco. Had a minor coronary when I was told it was $140. Opted to pick one up from the wreckers for $20.

If it helps with your troubleshooting, both IAT and ECT are thermistors, meaning their electrical resistance increases or decreases with temperature.
Typically a transitor on the ECU will send out refernce voltage (5v) on a feed. This is done as battery and alternator output can be variable.

If you back probe at the computer when the engine is cold you are either going to see minimal voltage or 5v on the signal wire and vice versa when the engine is hot. From memory, I think ECT resistance decrease with temp, meaning that voltage increases with temp. IAT's are the other way around.

If you backprobe at the sensor and compare this to the reading you get from the reading at the computer, it will tell you what condition the wiring is in.

[auIILTD]

Thanks Evgeni. That is exactly what I was planning to do to give these guys a reference voltage/resistance across each of the temp sensors. Having tuning software, I am also able to correlate these voltages/resistances directly to a temperature.

I think that there is no real need to probe at the computer to verify wiring. Nothing has changed on the wiring side to my knowledge. Chasing a wiring fault would be absolutely last resort.

Sorry guys ran out of time today to this test.

Stu

[Gaz]

Stu,

These are the figues I've been working off. Let me know if yours are similar when you get a chance to have a look. (apparantly there can be ~10% error in the sensors)

It also says that ECT and IAT sensors have the same resistance and voltage returns at the same temperatues, my tests have confirmed that.

[CODE]Temperature Voltage Resistance
F C Volts K ohms
302 160 0.12 0.54
267 131 0.20 0.80
250 120 0.30 1.18
230 110 0.36 1.55
212 100 0.47 2.07
194 90 0.61 2.80
176 80 0.80 3.84
158 70 1.04 5.37
140 60 1.35 7.60
122 50 1.72 10.97
104 40 2.16 16.15
86 30 2.62 24.27
68 20 3.06 37.30
50 10 3.70 58.75
32 0 3.97 65.85
14 -10 4.42 78.19
-4 -20 4.87 90.54
-22 -30 4.89 102.88
-40 -40 4.91 115.23[/CODE]

[Cúl-Báire]

The plot thickens, I changed the ECT today, same result!

The issues have gotten worse over the cooler months, it used to "chug" on cold start up only, now it's doing it on warm start up as well.



I am thinking of taking it down to chiptorque and have them put it on the dyno to see if they can suss whats wrong with it. Would be perfect timing to do a power run pre topend rebuild.

[Gaz]

Yep, still just dealing with it here too..

I've now got a scan tool which isn't much help, no codes that are obviously pointing to the problem.

[humpmeimfamous]

It's been a few months since the last post? My car is an AU2 LTD, so auto, but still has the rediculous cold start idle, or rather OPEN LOOP idle... has anyone had any success here, other than the ECT sensor..?

[raised by monkeys]

Hi guys, has this problem been resolved? Im also speculating oxygen sensors because its the only thing i havent replaced. Ive replaced most common faulty/short lived parts on my ute known to AU owners inc. the sinister cam sync, and mine still has a little buck on cold start.

[Gaz]

Nope, still dealing with it.

I replaced my 02 sensors, still has the issue.

I've done;
Cam Sync
Coil packs
Leads
Plugs
O2 Sensors
TB clean
ISC clean
maf clean

Checked the codes, it occasionally threw a cam sensor and coil pack fault, but I reset those and they didn't re-appear over a month or so.

[Placey]

Hey guys! Want to re open this thread forom the dead as I want to see if you guys have resovled it.

I have the exact same problem and have done the same things as you guys. .

Any word??

[Gaz]

I've given up and just idle up the street with no throttle for 30 seconds.

[Placey]

I wish to awaken this thread, I have had this problem for a rediculous amount of time, letting car idle to warm up or it will just freak out if I even touch the throttle, very irritating and would love an answer..

has anyone heard anything? Thank you.

[Gaz]

Turns out mine was gas related.

Since the conveter crapped itself i've been running on petrol and have had no issues.

Being a SVI system, running on gas alter's the ford ECM's parameters, so when warmed up it was fine, but starting on petrol when cold it was using the corrected gas parameters obviously throwing the afr's way out.

[Scaffy]

For anyone having this problem, when warm at idle, if you disconnect the isc, does it keep idling? If not, wind the idle screw in a few turns, plug isc back in and restart. Unplug again. When you unplug and it keeps idling, back off the idle screw until it's idling just below normal ~ 650rpm. Turn car off, plug in isc and start again. If it's idling super high after start up, disconnect the battery for a couple of hours, then try again.

If when you unplug the isc the first time it doesn't stall, then this won't be your problem...