B234F volvo 740 help with mixture

midnight_man · 07-15-2021, 02:36 PM

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!

dl242gt · 07-16-2021, 02:12 PM

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?

midnight_man · 07-16-2021, 03:53 PM

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?

dl242gt · 07-19-2021, 09:45 PM

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.

FreeEMSFred · 07-29-2021, 07:52 AM

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.

Mr. V · 07-29-2021, 12:03 PM

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

07-15-2021, 02:36 PM	#1
midnight_man Newbie Join Date: Jul 2021	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!

07-16-2021, 02:12 PM	#2
dl242gt Old and boxy but good. Join Date: Jun 2002 Location: S NJ, a suburb of Phila.	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? __________________ Dave, 1982 242 turbo. 338k miles. MVP coilovers and 3" exhaust. Flowed 405 with a V15. Cossie turbine housing with upgraded compressor housing. 90+, IPD remote oil filter. Some other goodness, too. Been lots of fun over 25 years. Restored in 2k. Now ready for a 2nd restoration. 1993 245 Classic, 435k miles, enem V15. IPD bars and chassis braces. Simons sport exhaust from Scandix. sbabbs ezk chip. Been a good road warrior. Genuine Volvo rebuilt leaky M47.

07-29-2021, 07:52 AM	#5
FreeEMSFred Board Member Join Date: Nov 2009 Location: Kiwiland	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. __________________ FreeEMS.org - the open source engine management system My Volvo Adventure (No 56k). My non-Volvo turbo truck. My gold 1991 240 wagon! My blue 1990 740 16v sedan!

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07-16-2021, 03:53 PM	#3
midnight_man Newbie Join Date: Jul 2021	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?

07-19-2021, 09:45 PM	#4
dl242gt Old and boxy but good. Join Date: Jun 2002 Location: S NJ, a suburb of Phila.	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.

07-29-2021, 12:03 PM	#6
Mr. V Board Member Join Date: Jul 2004 Location: Portland, Oregon metro	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