1991 740 non turbo starts hard, bogs, sputters, front-fires

Post by **billofdurham** » 03 Jul 2010, 12:19

I have known various sensors fail and not set a code. The OBD on the early cars was basic unlike the all singing, all dancing OBD11, which can also miss a fault.

Bill.

dnarby · Post by **dnarby** » 13 Aug 2010, 15:19

Hi Bill, & everyone...

Well, replaced the O2 sensor...

No joy. Same behavior as before.

About ready to part it out of it's misery.

dnarby · Post by **dnarby** » 23 May 2011, 15:59

Looks like the problem was a crankshaft sensor... AND the fuel pump.

Thanks for the help.

Post by **billofdurham** » 24 May 2011, 11:29

Thank you for the update.

Bill.

rickb78 · Post by **rickb78** » 18 Jun 2011, 19:35

The OBD indicates there's a problem with the air temp sensor, 91 740. When I try to remove the sensor, which is a somewhat tight fit for large arm/hand, the plastic case comes off but the wires are still in the sensor mount screwed into the crankcase. How do you get the wires out?

timdk · Post by **timdk** » 25 May 2014, 14:49

resurrecting ancient thread to thank op for excellent description of problem.
I'm dealing with EXACTLY the same problem and I am very glad to see I'm heading in the right direction. Good descriptions make for good reference materials.
I worked my way through this problem every Sunday afternoon for 2 months, came to a similar conclusion. FPR, fuel pump, bad gas...and now I will check crank sensor too.
should have just checked the interweb in the first place, could've saved some weekends.
thanks,
Tim

woc2 · Post by **woc2** » 25 Nov 2014, 13:45

Im having similar problems. Diagnostic box says MAS Meter and O2 senser. Went to junk yard, got an mas meter from a 740 Bosch 016 but when I got home the meters have same part number but they look different inside. Original Volvo ( In my car ) has a what it looks like a saxophone leed inside, and the meter I got from the j/y looks like it has 2 different size fillaments, one big one smaller. I wonder what the difference is.

woc2 · Post by **woc2** » 28 Nov 2014, 07:21

I replaced the breather box, flame trap, cleaned Mas sensor, and changed o2 sensor. Its a different car now. I have noticed increased horse power, and a free breathable engine. Running perfect.

93Regina · Post by **93Regina** » 28 Nov 2014, 20:34

dnarby wrote:25 Jun 2010 - Disconnecting the air temp sensor didn't change anything (but it did register 1-2-2 on the fuel self diagnostic, which is good to know). It also threw 3-1-1 on the fuel diagnostic, but my speedometer is intermittent (I use my GPS for a speedo). Ignition diagnostics threw 1-1-1.

Solution - 23 May 2011 - Looks like the problem was a crankshaft sensor... AND the fuel pump.

Most interesting...fuel pump not up to specs would cause hard starts, etc., but, getting a 3-1-1 code that ends up being a crankshaft sensor issue, is most puzzling.

I've got a recent 3-1-1 code on a 1993-944, but I renewed CPS last year....and vehicle runs fine, including cruise control.

I'll try installing an used Bosch CPS, and see what happens.

1991 740 non turbo starts hard, bogs, sputters, front-fires

Re: 1991 740 non turbo starts hard, bogs, sputters, front-fi