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 Post subject: Diagnosis help
PostPosted: Tue Jul 07, 2015 9:29 pm 
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Location: calgary AB
I recently bought dales old 1990 740 turbo and there's just a few small things I'm having problems diagnosing.
Firstly on cold start up I get surge to almost stalling or stalling. Does it a few times then chills out. I've changed the iac. Checked tps. Cleaned throttle body. And checked all vacumn lines for leaks still unsure.

I also have a I guess you would say stumble (feels like no power for an instant) under hi load or prolonged boost. Very obviously felt in 5th foot to the floor.

When I bought the car the main pump was buzzing and I thought that maybe it wasn't getting correct fuel pressure and that's why I was getting this power cut. So I changed the in tank assuming that was the issue. But pump still buzzes and I still have the stumble. Also changed fpr to no avail.
Any suggestions where to go next would be great

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 Post subject: Re: Diagnosis help
PostPosted: Wed Jul 08, 2015 6:01 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 8:40 pm
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Location: Calgary, Ab
I wish I knew LH2.4 better so I could help you. Did you check the coolant temp sensor? Is there a base idle speed / igniton timing check? Maybe the fuel injectors aren't spraying perfectly and it has trouble adjusting to it when cold.

I'm sure you can download the greenbooks from somewhere, and they'd give you some more diagnosis procedures.


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 Post subject: Re: Diagnosis help
PostPosted: Wed Jul 08, 2015 7:59 am 
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Coolant temp sensor will be the next thing to check. My friend has 6 because he thought they were all bad. Turned out to be a bad ground the whole time.
I've also thrown some marvel mystery oil in the tank to clean the injectors a bit.

I've gone through my Haynes. It says base idle should be 750rpm. The car like to idle around 600rpm most of the time. Bust sometimes is spot on at 750 sometimes higher. Depends how it feels that day haha

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 Post subject: Re: Diagnosis help
PostPosted: Wed Jul 08, 2015 8:48 am 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Jun 14, 2006 4:19 pm
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Location: Lethbridge, AB
Were you the guy asking on the FB group? If so, I'll repeat myself - coolant temp sensor. Not fun to change, but I had a high idle/surging idle issue that I thought may be the IAC or the CTS and it was the CTS. The CTS is used by both the fuel and spark computers. There is no idle set on LH 2.4. My idle (on my old tach) is 900 RPM and while it drifts around a bit, it's pretty constant.

Check the function of your cold start injector and take your injectors in for servicing or service them yourself (youtube). Does the stall only happen when cold? If so, it could be related to the cold start injector. The high speed boost issue could be as easy as a vac leak. I had one (caused by an unnecessary vac port on the intake manifold (engine side of the TB) becoming uncapped while racing) and the car would backfire - buck and feel like it was lean at WOT. Fixed it with duct tape at the track and all symptoms went away...fixed it later with Greg's help and a plug. So it doesn't take much of a bleed to confuse the wastegate signal.

Just a few thoughts.
Craig

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 Post subject: Re: Diagnosis help
PostPosted: Wed Jul 08, 2015 12:41 pm 
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Yeah I'm the guy one Facebook hahaha. That's why the cts will be the next check.
And yes the stall only happens on warm up. It has stalled on me once while driving. It was first gear high revs. Then when I put the clutch in dash lights came on and engine was struggling really hard as in sitting at about 100-200rpm and bouncing up and down then it just died. That's why I thought iac but no dice.

I'm gonna buy some vac line and just start replacing everything. From what I've read it could be a tiny crack or hole that only opens up when there's boost running through the system.
Really appreciating the input

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 Post subject: Re: Diagnosis help
PostPosted: Wed Jul 08, 2015 2:48 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Joined: Wed Dec 21, 2005 7:14 pm
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Location: Missing my garage in Sunnyside
The base idle should be 650 as stated. That is with the idle valve closed or by passed. Cold stall could be a base idle too low and the valve can't open enough to maintain 750. Base idle is adjusted via the throttle plate. Then you also need to check tps adjustment.
Doesn't explain full load miss so could be two issues or a non-idle vale issue creating both problems.
Are you getting any fault codes?

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 Post subject: Re: Diagnosis help
PostPosted: Wed Jul 08, 2015 6:32 pm 
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No fault codes I had some when I bought the car. Cleared them and havnt had any come back. Also today the fuel pump was buzzing harder than ever. And while at idle I was getting some smoking out the tailpipe definitely blue. And I could only see at idle. Not constant just random puffs.

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 Post subject: Re: Diagnosis help
PostPosted: Thu Jul 09, 2015 8:03 am 
Haha, I just built a W24 Octo-Turbo, now what?!

Joined: Wed Dec 21, 2005 8:03 pm
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The random puffs used to happen. No real rhyme or reason to it and it never happened often enough to be concerned. The car never burned oil between changes.

I remember the CTS was a bit of a pain when I put the engine in the car. The engine was set up for LH2.2 and the sensor on the car wiring harness had a different thread. I had to add an insert to match the 2.4 sensor to the thread in the 405 head. That wouldn't preclude it from being an issue...just be aware of that.

Did I give you an external pump as well? Check to make sure the internal pump is working before you change anything else.

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 Post subject: Re: Diagnosis help
PostPosted: Thu Jul 09, 2015 10:16 am 
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Yeah I was just curious if I should be concerned about it. Just seems like a bit of blow by possibly. So should a sensor for lh2.4 fit in?

Yes I have an external pump as well. Thank you for that haha. I tried pulling the fuse for the interal pump while car running no audible change in main pump. I also tried listening for the in tank. I really couldn't tell if it was running. When I changed it I checked all the connection on the unit as well as the wires coming out all seemed good so unsure where to go from here

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 Post subject: Re: Diagnosis help
PostPosted: Thu Jul 09, 2015 5:42 pm 
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Just a small update, when I got gome from work I checked again for the sound of the intank pump running and im sure I could hear it, had a piece of fuel line in my ear the other end in the tank. So im guessing the main pump was just stressed over time.

So now my plan is on pay day of course im going to order plugs, wires, cap, rotor, fuel filter and buy some vac hose, do a full tune up, and replace main pump and cts see if that does the trick

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 Post subject: Re: Diagnosis help
PostPosted: Fri Jul 10, 2015 2:19 pm 
Haha, I just built a W24 Octo-Turbo, now what?!
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Pumps aren't cheap. Change the fuel filter first. Check voltage at the pump.

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 Post subject: Re: Diagnosis help
PostPosted: Fri Jul 10, 2015 4:27 pm 
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I have one already. Dale kindly hooked me up when I bought the car. But I'll make sure it needs to be replaced before I replace it

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 Post subject: Re: Diagnosis help
PostPosted: Sat Jul 11, 2015 8:01 am 
Haha, I just built a W24 Octo-Turbo, now what?!

Joined: Wed Dec 21, 2005 8:03 pm
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The LH2.4 CTS did not fit the spot in the 405 head so I had to add a threaded insert to make it work. It is still the correct CTS for that injection system.

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'67 123GT
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 Post subject: Re: Diagnosis help
PostPosted: Sat Jul 11, 2015 12:14 pm 
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Ok cool so a new one should go in fine? As long as I dont mess it up haha,

Also is it the sensor closest to the firewall kinda behind/beside intake runner 4?

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 Post subject: Re: Diagnosis help
PostPosted: Sat Jul 11, 2015 5:19 pm 
Haha, I just built a W24 Octo-Turbo, now what?!

Joined: Wed Dec 21, 2005 8:03 pm
Posts: 2852
Location: T2C
rick-deckard wrote:
Ok cool so a new one should go in fine? As long as I dont mess it up haha,

Also is it the sensor closest to the firewall kinda behind/beside intake runner 4?


Yup...a new one should go in fine. I believe it is the one closest to the firewall...a real pain to get to without pulling the intake manifold off.

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