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Old 07-15-2021, 02:36 PM   #1
midnight_man
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Default B234F volvo 740 help with mixture

Hellou guys,

I found that amazing site...about volvos.

I have Volvo 740i here in our garage (workshop) which has problems with starting, mixture and so on... This old car is not very popular here so...not any knoweledge here.

ECU is old..does not have diagnostic output....

What I found is..that car is lean..on idle almost stalling...in full load is refusing to run..
We bought new pressure regulator cause old was DEAD....

I suspect MAF is cheating ...cause when I push little air into MAF, mixture will go better...

There is no chance to buy new MAF on this car....we have 2 spare ones which both doing same thing.

I am able to change maps in ecu....or I can change MAF voltage curve to fit "broken" MAF?

But..as first I want to try repair that car....

Can you advice me little? Are those MAF all bad? What else can do this? Is there anything more to check? Thanks!
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Old 07-16-2021, 02:12 PM   #2
dl242gt
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This is a 16v engine? I thought all the factory 16v engines ran LH2.4 injection so if that is what is in your car. The diagnostic box should work on it. The symptoms you describe could very well be the maf sensor. Have you tried disconnecting the sensor and seeing if it starts and runs?
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Old 07-16-2021, 03:53 PM   #3
midnight_man
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Hi,,thanks for response..yes it is 16V...what is diagnostic box? It has just some pins to blink led codes :(


I suspect MAF ...yes... but how to check?
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Old 07-19-2021, 09:45 PM   #4
dl242gt
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Yes, the led codes is what I meant. Check what codes may be set. See if it runs a little better with the maf disconnected. Disconnect the maf and start the car and see if it idles better.
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Old 07-29-2021, 07:52 AM   #5
FreeEMSFred
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FWIW mine runs solid once warm, but has always been very hesitant if you lean on it when cold. Never bothered to do anything about it as once warm, it'll do skids all day. That and the stubborn shift to 2nd for the old auto are the only two major driving weaknesses of the car. Sounds like this is a different issue though as mine runs great once warm.
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Old 07-29-2021, 12:03 PM   #6
Mr. V
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OP:

You might want to bookmark this site as it will prove quite helpful with 740 repair issues.

http://www.swedishbricks.net/700900FAQ/FAQSummary1.html
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