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IAT heat soak


kevindawes

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As some of you know if been been having trouble getting my ms install to work well. So far it's fine for about an hour and then starts losing power and becomes undrivable.

Reading around the forums it seems that my problem maybe heat soak effecting the inlet air temp sensor, it seems to tally up with the problems others have had although I don't have a particularly bad hot start problem.

I was wondering if I reloctaed the sensor from just after my air box to my snorkel I could alleviate the problem completely, or at least rule it out and narrow down my quest.

Pro's cons?

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A lot of people run around with their IAT outside of the engine bay - I'd say it's worth a shot as changing its position has got to cost next to nothing and I try to follow the policy of trying the least expensive options first!

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You should be able to rule it out by running with the laptop connected and looking at the air temp values via the MS software - if when you get running issues the air temp is reading as much over ambient there's your issue..

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Thanks to all your your comments.

Nige, in a post I made a few days ago (ego) I uploaded a log of when it was playing up.

Of course it could be my fuel pump or fuel regulator, both were fine before the conversion, and this only happens when the engine is hot.

What I did notice the other day was that while on the motorway the afr needle was way to the right all the time and then it started to progressively lose power. In traffic it barely ran. I turned it off opened the bonnet for a minute and reloaded the tune and it ran a lot better but not perfectly.

I'm running with the lambda authority to zero so it's not that effecting the afr.

My exhaust is new with no leaks so the lambda reading should be reliable now.

What should my air density correction be set to, air temp or coolant temp?

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Kevin

With the system from me and the ECU loaded with my MSQs your engine SHOULD RUN FINE.....

The minute you start changing ecu settings we are all going to be lost, so - RELOASD MY MSQ and

then go for a drive, as soon as the issues start THEN start recording, so we all know we are looking at the log with an issue.

You've rulled out the ECU with my test spare, so its NOT the ECU and its NOT the settings, its something else,

so leave the ECU / ASettings ? MSQ as my MSQ and then we know that is as it should be.

Just becuase it was fine before MSing it means not a whole lot, much was disconnected / reconnected,

some things die in this process, cars that were "Fine last night" can refuse to run the nexct day (been there got the T :D)

To find this you need to be very systematic and go through a process, as its stumping many here inc me, so it has to be slowly

slowly ctahy monkey one step at a time#

Go for a drive, and as SOON as it starts to seriously play up THEN Datalog it !!

Nige

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Nige, to be fair I've done that twice but I will do again as you suggest.

The basic tune ran my injectors at 80% after a few miles. It was suggested that I reduce the lambda authority to zero and that left me a vehicle that runs, albeit not perfectly but its where I am now.

I did have a blown exhaust but I've just had it completely refabricated so this will eliminate this as a problem.

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From memory it was 5%, it was whatever Nige had set it to , I only changed it to zero when it was overdriving the injectors.

Tuning, I was the first time but after that I reloaded the base map and then didn't have the laptop connected and it still played up.

As it is now, for the first hour or short trips it runs great, good power and easily spins the wheels pulling out junctions and in the wet in a straight line. On the motorway it'll pull well for a good while and then gradually lose power until it misfires when you ask for some acceleration, a bit like a coil failing (I've already tried spare ones). It gets really bad once you pull off the motorway and back into normal traffic, eventually you have to stop of a minute and let it cool/reset and then it'll start ok and then run well enough to get you home.

On Saturday I'll spend some time getting some data logs created.

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I would also look at what else is getting used & warm just in case....

Is there a possibility that the fuel pump could be dropping pressure and therefore less fuel being injected per cylinder as you get warm / time ticks up on the journey?

When moving from motorway to side roads you will be calling off more fuel when you accelerate through the revs....

If you let it cool / reset, how long before it re-occurs on the same journey or have you never done this?

Just a thought...

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The fuel pump could be a culprit. It's only a few years old but the tank is old so it may have picked up something.

I haven't had a chance to try as you've mentioned, but stop and restart normally gets it back running again.

I'll order a new one so that can be crossed off the list.

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  • 3 months later...

While your fuel pump may only be a few years old, how old is your fuel filter? I have not yet fitted my megasquirt system to my Rangie but I do have the wideband sensor installed. I noted that my afr's were fluctuating wildly after start up and then going full lean, then all over the shop again at random intervals. Tried lots of different things including new injectors to no avail.

So I said to myself, back to basics boy! Changed the fuel filter (and the air filter) and what do you know? Nice steady AFR's and better driving too.

Might not be the case with yours but it's cheap and easy to do.

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  • 2 weeks later...

Mine turned out to be two faulty fuel pumps. Need to carry one as a spare as I'm really paranoid about them now.

Truck is running well but I'm still tuning so hopefully get it running even sweeter, especially up the rev range.

My only prob now is the timing, when I set the trigger wheel to the marks on the block it wouldn't line up. Eventually found tdc using a scredriver resting on the top of piston #1. The marks on the block were well out but the trigger wheel lined up and the engine fired. I don't think I'm too far away but have no-way I know to calibrate the timinmg to megatune. It isn't pinking nor does it feel overly retarded. I'd like to get it spot on but I don't know how.

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Mine turned out to be two faulty fuel pumps. Need to carry one as a spare as I'm really paranoid about them now.

Truck is running well but I'm still tuning so hopefully get it running even sweeter, especially up the rev range.

My only prob now is the timing, when I set the trigger wheel to the marks on the block it wouldn't line up. Eventually found tdc using a scredriver resting on the top of piston #1. The marks on the block were well out but the trigger wheel lined up and the engine fired. I don't think I'm too far away but have no-way I know to calibrate the timinmg to megatune. It isn't pinking nor does it feel overly retarded. I'd like to get it spot on but I don't know how.

Had this issue with timing on my 4.0 as they have no trimming marks, best way is to find tdc make a mark on your crank pulley, then measure the circumference of the crank pulley divide that by 360 then times it by 10 this will then give you the distance to mark from tdc to make another mark that is 10deg btdc, then use your timing light to adjust the trim in ms

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Thanks Rangie, when I have the radiator off next I'll make some marks and double check my vr sensor. Must admit I'm not too clued up on this and the trim feature but I guess the only way is to have another read up and then have a go.

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