5.0 Rough On Start Up

[Cúl-Báire]

Hey All,

After a little bit of help chasing down a "problem" my car has on cold starts. In the morning, or any time of the day when cold starting the engine idles really rough, bucks and shudders for about 2 minutes, if you try to drive off it coughts and splutters. After a brief warm up, its fine!

Now my wideband is telling me the engine is basicly starving for fuel, during this period of rough running the AFR's lean right out until after its left for sit for a minute. After it's "warmed up" it runs fine, AFR's are good, and there is no sign of a miss or anything.

Now I am stumped, as I recently changed the fuel pump for a Walbro 255lph unit, and changed the fuel filter over the weekend also.

Any ideas as to what could be causing this issue?

[BHDOGS]

oxygen sensor

[Gaz]

When you find out tell me - I've got the same friggin issue. I've done plugs, leads, coils and cam synchro.

Kinda embarrassing bunnyhopping from a stand still like you can't drive.

Is yours ok-ish out of gear (it's rough but idles) and as soon as you slip the clutch it dies?

[auIILTD]

Aaron, I am sure I we had this conversation, but I understand that you have confirmed the heater is working on your wideband?

Another thought, are your using your wideband to signal back to the ECU? Did you use analogue 1 output, and if so, have you checked the programming of analogue 1 with the LM Programmer application? Probably does't explain why it comes good, but thought I woud throw it out there? If you need, I can probably get you a screen shot of the output I have programmed?

Stu

[Cúl-Báire]

Hi Stu,

I don’t recall theconversation however my heater is working on my wideband, as I burnt the hellout of my hand when installing it not realising I’d had it plugged in for a few minutes before installing and it had warmed up... I always let the fuelpump prime, and the controller fire up before starting – maybe I am not letting the sensor heat up enough?



The analogue output is running back to the ECU via the factory loom. It’s wired from wideband UEGO sensor, to controller then back to the factory o2 sensor plug. I am using an AEM unit so I’m not sure the LM program will help me.

I will try let the sensor warm up for a few minutes before starting this afternoon, and see what happens – I will also check out the wiring and make sure nothing is astray.



Failing that, I will give the old sensor a shot and see what happens.

AH

[auIILTD]

Sorry, that conversation must have been with someone else - sorry.

I don't think the wideband is causing your problem - or your narrowband for that matter. The car is designed to run on startup without feedback from the 02 sensors. On startup, the car will go open loop for a period as determined by your tune. I just checked my tune (still stock in that area) and the car will stay open loop for 45 seconds from startup.

I suggest timing more accurately how long the problem exists for. If it is 45 seconds, that could narrow the problem down to open loop mode? Just a thought?

Stu

[Cúl-Báire]

Originally Posted by auIILTD

Gaz, there is HEGO fuse in the fuse panel in the engine bay (under the panel behind the battery). HEGOs have a heater circuit in them that is supplied by that fuse. If they are not heating, you will have issues - obviously they warm up eventually with exhaust temps, hence only being a problem when cold.

Stu

Found it in Gaz's thread, I remember reading some where it a day or so ago so I knew what you were talking about, the conversation just wasn't with me.

I will put a timer on it tonight and see how we come up.

AH

[portokatsiki]

Fellas I had a similar issue on cold start ups the car would idle rough stall a couple of times unless I held the revs also it was running very rich ended up being the coolant temp sensor might be worth a`try

[cedric]

mine does it too, always has, thought it was normal!!!!!!

[Cúl-Báire]

Originally Posted by auIILTD

Sorry, that conversation must have been with someone else - sorry.

I don't think the wideband is causing your problem - or your narrowband for that matter. The car is designed to run on startup without feedback from the 02 sensors. On startup, the car will go open loop for a period as determined by your tune. I just checked my tune (still stock in that area) and the car will stay open loop for 45 seconds from startup.

I suggest timing more accurately how long the problem exists for. If it is 45 seconds, that could narrow the problem down to open loop mode? Just a thought?

Stu

The problem lasts for 45 Seconds, then comes good. I reckon both Stu, and Portokatsiki are on to something!

I recall the coolant temp sensor causing similar problems with later Holden 5.0's on startup as well.

[auIILTD]

Originally Posted by Cúl-Báire

The problem lasts for 45 Seconds, then comes good. I reckon both Stu, and Portokatsiki are on to something!

I recall the coolant temp sensor causing similar problems with later Holden 5.0's on startup as well.

I guess that verifies that the problem is only occuring at open loop on startup which pretty well eliminates the o2 sensors as the cause.

So what that means is that whatever is causing the problem is possibly eliminated when the ECU goes closed loop (ecu changes fuelling based on o2 sensor feedback). Given that the ECU tune has not changed, it must be a sensor that is used for open loop fuelling. I will go through my tune tomorrow to sus out what issue could contribute. ECT sensor could be a cheap obvious starting point.

Hopefully someone with more knowledge can jump in here?????

Stu

[wrexed03]

Far out must be that time of year. I have similar issues. Changed ect sensor plugs leads coils and o2sensors and tried another maf. Mine runs really lean and a little rough on idle.
Also running a walbro pump which was installed a couple of months ago.
Will be trying a spare pump i have here on the weekend.

[Gaz]

Now we are getting somewhere.

Let us know what you find stu, thanks for the assistance.

[auIILTD]

Guys, on initial look at my tune for O/L startup I have seen the following factors.

RPM - not a factor in the symptoms as described.

ECT - Engine coolant temp - initially all I can see is this used for determining the delay before going closed loop, your target fuelling at open loop (none of which would make it lean regardless of ect value) and startup fuel lambda subtractor value (makes it richer at startup on a temp/time scale). Summary - yes the ECT could be a factor, but as yet, I have not seen a temp table or function that would make it go lean based on a faulty ECT reading.

ACT - Air Charge Temp - as measured by your IAT. There is a fuel multiplier to make the fuelling leaner at extremely low temps and at extremely high temps. This multiplier on my tune does not have a value greater than 1. It is one in the nomal range and less than one at ACT extremities (makes fuelling richer). ACT is also part of the formula for the function above for O/L startup (temp/time scale).

So I am guessing that either of these sensors could be playing a part, but in both cases a erraneous value would richen the fuel and not necessarily lean it out?

Aaron, when you let your WB warm up prior to starting, what values are you seeing when the problem occurs?

I will keep looking, but I do not really think there is much else that is monitored in O/L mode apart from your MAF. Have you cleaned your MAF? I know gaz said he changed his, but we could be looking a differenent issues. A dirty MAF and an erraneous air flow reading will be compensated for in C/L mode.

Stu

[BHDOGS]

ect sensor might be an issue for a few of the other cars having this issues in the thread as its starting to get colder in the mornings now?

[auIILTD]

Originally Posted by BHDOGS

ect sensor might be an issue for a few of the other cars having this issues in the thread as its starting to get colder in the mornings now?

MMM, so might the IAT? It measures temps too. Only difference being ECT will never read minus temps as frozen water does not flow and most cars you would expect are running anti-freeze. IAT will measure minus temps.

I guess it depends on where you live as to how much the temps are getting colder in the morning

[Gaz]

Is the 45 seconds coded in, or is it based on ECT to determine when to switch to closed loop?

Checked mine this morning and it was closer to 90 seconds before it was good.

[auIILTD]

Originally Posted by Gaz

Is the 45 seconds coded in, or is it based on ECT to determine when to switch to closed loop?

Checked mine this morning and it was closer to 90 seconds before it was good.

Gaz, looking at my tune, there was two delay times set. One was delay for temp#2 and one was for temp. On my tune they where 90 and 45 seconds respectively. I could not find any reference to what temp#2 was.

Your prob could be the same - yours is just happening when temp is below temp#2, and I do not know when that is.

Stu

[5.0 ED]

Stu is spot on about the o2 sensors taking over and pulling the tune back in line.

Basically something isn't correct and then the o2 sensor takes over and pulls it all back to run correctly, so there is a fault with a sensor or something. However it does seem that the o2 sensors are working fine and that is why it comes good.

I'll just put up a list of possible causes i can think of a lot are easy to check etc.
Dirty Maf
Faulty IAT or ECT
Air leak in intake system between maf and TB or even elsewhere.
PCV is it working correctly?, is it still in the intake manifold?.
The breather to the rocker cover is it in good order, is the rocker cover cap sealing?
Fuel pump/Fuel regulator, need to check fuel pressure is up to scratch.
Brake booster is it leaking vacuum?
All vacuum lines need to be checked to make sure they are all sealing?

Any leak, weather it crankcase or vacuum or anything does effect the open loop tune, so all these need to be discounted first. Every bit of air that enters the engine needs to come through the maf sensor first..

[Gaz]

As a quick test I unplugged the IAT and ECT on cold start and the issues were still there.

Is there a default mixture if these sensors aren't detected or do I really need to test them to eliminate them?

[Gaz]

Tested my IAT and ECT with multimeter - they are reading fine so that's another possibility eliminated.

Really just leaves vacuum leaks. Still learning my way around the windsor, but I can't find any obvious leaks.

Any of you blokes had any success?

[Cúl-Báire]

I reset my ECU today, it seems to have helped a little, no obvious leaks anywhere on the intake or vacuum lines.

[Gaz]

I noticed an improvement the first time I reset it, but goes back to normal the next day.

Just had a look at the PCV valve, should they be completely shut at idle? pulled mine out and it was sucking air at idle, strong enough to stick itself to my hand.

Covering it made a *slight* difference, but was a bit hard to test drive it with my hand covering it.

[ebzery]

so im not the only one with this problem thats about the time i first noticed any problem about a month ago.
so i changed oil, plugs, air /oil filter running smoother but my fuel useage is right up!

[cedric]

anyone had any luck with this

[Gaz]

Nope...still annoying me.

So far i have;
Changed plugs
Changed coils
Changed leads
Changed cam synchro
Changed pcv
Tested iat
Tested ect
Tested and cleaned maf
Tightened manifold bolts
Cleaned isc
Cleaned throttle body

Running out of ideas!!

[irdonn]

I've had similar idle issues with mine. It wasn't completely fixed until it was tuned. I know it was the tune that made the difference because I can unplug the QH and it goes back to having a few cold start issues. Expensive fix though, if you're not really interested in going down the tune route.

Ian

[cedric]

mine also pings bad and always has ,would the two be related

[Gaz]

Anyone else had any bouts of wisdom appear?

Looking at a different approach over the weekend I rolled out of the driveway and slipped the clutch without any throttle to get moving. Gettin up to around 10-20k's in first not using any throttle (which it seemed to do okayish, without crapping itself) then *feathering* the throttle you could feel the car slowing and the engine dying. That's from touching the throttle as lightly as I could.

You would think this leads to only a MAF or TPS related issue? That only lasts while the ECU is in open loop...

[auIILTD]

Originally Posted by Gaz

Anyone else had any bouts of wisdom appear?

You would think this leads to only a MAF or TPS related issue? That only lasts while the ECU is in open loop...

Does not have to be MAF or TPS. You are talking open loop. All that means that the ECU is not taking any notice of the AFRs. When in closed loop, the ECU can make adjustments to fuelling based on the feedback from the o2 sensors. That means that it could still be fuel pump, fuel regulator or injectors just as a start.

Have you run a injector cleaner through it? From what I can see, you still have not ruled out a unmetered air leak.

Sorry more questions than answers, but just thought that I would throw it out there.

Stu