Greetings!
My 740 is getting the following error codes from the OBD in socket 2
312
213
113
The current symptoms my car has are
Car stalls sometimes shortly after starting
Fuel consumption is INSANE!!
Rough Idle
The 113 error is what's really peaking my interest.
Here's what the ODB code states according to volvoclub

LH 2.4 Fault Condition
Fuel trim (lambda control) too lean or rich
LH 2.4 Causes of Fault
Mixture incorrect; O2S wiring fault
LH 2.4 Symptoms
High fuel consumption
Motronic 1.8 Fault Condition
Fault in Injector 1,2,4
Motronic 1.8 Causes of Fault
Fuel Injector

Now I'm not sure what LH 2.4 and Motronic 1.8 stand for. This error code does really seem to some up my problem though.
I'm a bit confused as to where the problem lies since it says o2 sensor wiring and faulty fuel injector.
Should I try replacing the o2 sensor or the fuel injector?
Thanks for your time!
P.S. - It may be worth noting that my Cat is currently hollow and I'm completely missing a muffler (Cat was clogged/ I live in the hood so I guess that explains the muffler somehow) I'm curious if this could be messing with the o2 sensor. The problem came about shortly after having to hollow out the cat. I'd like to work around this without having to completely redo my exaust system. I know it has be done eventually but right now I'd like to just improve my fuel / o2 ratio.

 

Check your grounds on the fuel rail. make sure they are tight and good condition.

The o2 sensor might be faulty... might. but check grounds on furl rail first. That is a 3 wire sensor. check to make sure they are plugged in.

The cat has nothing to do with the problem, unless there was contamination to the o2 sensor, or it was broken in the process from the work done.

If grounds fine, then you could probably just put a new o2 sensor in and it would fix it. o2sensor is a major part of the mixture control.

PS. LH2.4 and Motronic are the Engine management system the car could have. you should have LH2.4


Edit: you can check the function of the o2 sensor if you have a volt meter. The sensor toggles between 0-1 volts and there is a range for the idle loop. I just don't remember what the range is. could be from .5-.8 or something like that.

 

to test the Oxy sensor, disconnect the single wire connector, slip in a couple inch long single thin strand of copper wire (like, from splitting some lamp cord), snap it closed again, wrap this thin wire around the red + probe of your volt meter, and put the - probe on a good ground. start the car and wait for it to warm up. put the volt meter on a DC Volts scale, and if it has manual ranging, set it for the single digit volts range (so it reads x.xx volts) with it idling, the voltage should swing from around 0.1-0.3 volts to around 0.6-0.8 volts and back every couple seconds. if you gently rev the motor up, the swinging back and forth should be faster. as long as its swinging back and forth you're in 'lambda control', and the Oxy sensor is functioning. the exact voltage doesn't matter.

 

Thanks for your replies guys! My o2 sensor should be coming in the mail any second. Unfortunately I don't have a multimeter so I was unable to test before I purchased one. The car's well over 100k so I figure it'd be worth doing regardless.
I read another forum where someone was going threw almost the exact problem as me with a 240. It turned out he had a bad FPR that was leaking gas and that in turn caused the o2 sensor to fail. I removed the vacuum hose of my FPR. I definitely smelled gas! When I started my engine and looked for a leak i didn't see one or smell one. I let the car idle for a few minutes, no gas leak yet I did smell gas in the vacuum hose.
Would these lead any of you guys to think my FPR is faulty? I'm 100% certain that the vacuum line smelled like gas.

 

The leak is inside of the FPR, drops of gas are getting through and getting into your intake. I'd replace it ASAP, easy task too, takes like 5 minutes.

 

Thanks for your reply! Do you know where I would find these fuel line grounds? Are they near the FPR or under the car somewhere?

 

Hey guys! So far I've
Replaced O2 Sensor with a new Bosch O2.
Cleaned MAF thoroughly with rubbing alcohol and let it sit all day.
Swapped The FPR with the cleanest one I can find from my local PickNPull.
I'm still running rich! My pockets not so much anymore :/
Does anyone have any other ideas of things I should check?
I'm still getting all the same errors.

 

You can go broke throwing parts at it. Did you test the oxygen sensor before replacing? Do you have a voltmeter?

If you don't have a voltmeter I suggest that you go pick one up. You can get one fairly cheap - under $30. Read up on diagnosing different engine systems. Take a look at this page:

https://www.brickboard.com/FAQ/700-9...linjection.htm

It has good writeups on the engine fuel injection system. I don't know what "insane" fuel consumption is (10mpg? 15mpg? 20mpg?). If it is around the 10mpg, I would suspect a leaky injector. Higher could mean bad engine coolant sensor or exhaust leaks upstream of O2 sensor. These are areas to check. Check first. Confirm diagnosis. Replace appropriate parts.

 

an automatic 240 should get around 25 mpg average if you're not thrashing it. maybe as high as 27-28 on the highway going a steady 65mph and again, not thrashing.

 

They are in the red circles.

 

the reason there are two different ground spots on the fuel rail is that one is used for the 'power' stuff and the other is used for the 'signal' stuff (sensors, computer). keeping the electrical noise from the power stuff out of the signal stuff makes it all more reliable.

 

Thanks for the link! I'm going to try cleaning and soldering the ground wires. I went ahead and picked up a multimeter, I set it to 200ohm and tested each of the fuel injectors. I got readings of 2.6 - 2.8 on each of them. What could be causing all of these injectors to be so low? Everything I've been reading says it should be above 10. And yes, I'm getting around 10 mpg. IT SUCKS!

 

I noticed that the cable connecting my MAF is missing a set of teeth. Could this be my/a problem. I haven't been to the junkyard to see what other connections are supposed to look like but my gut tells me that this could be an issue. When I disconnect the MAF the car idles much smoother

 

the wiring diagrams show 5 wires connected.

pin 1 - brown - ground
pin 2 - blue-green - to ECU pin 6 (ground)
pin 3 - blue-red - to ECU pin 7 (input to ECU)
pin 4 - blue-white - to ECU pin 8 (output from ECU)
pin 5 - blue-yellow - power from main relay

(ok, those are from my 1992 740 diagram, which is also LH2.4, 1990 is probably same colors).

pin 6 is drawn connected on B200G/B230G, which is a higher performance european version, no idea what it does.

 

oh. if the car idles smoothly with the MAF disconnected, its almost certainly a bad MAF.

 

Good to know! It's a little bit jerky but it does idle much quitier. I've read that if you unplug your MAF while the car is running then your car should die if the MAF is working properly. Mine does not. Does that rule apply to a 1990 Volvo?

 

plugging or unplugging the MAF with the ignition ON could fry it. its not what us computer folks call 'hot pluggable'.

 

It'll kill the MAF sooner than anything, I wouldn't do that on any car.

What you do is unplug the MAF with the ignition OFF, then attempt to start it, if the car starts and idles fine you need a new MAF.

If you car struggles to start then your MAF is good.

I repeat though, plugging\unplugging your MAF\AMM with the engine going will wear your MAF out.

 

SUCCESS!!!!

I pulled a MAF out of a 240, popped that sucka in, now I'm no longer getting that check engine light! The car drives so much better and sure my mpg has improved significantly (I'm no longer watching deplete as I drive around town)
Thank you sooo much for all of your guys input and for helping me fix this problem! You dudes rule!
I have 2 more questions that maybe someone can answer easily.

1. The Maf sensor's plug has a second small connector that has no where to go in my 740. When I grabbed that MAF out of the 240 I saw that the plug I'm referring to goes into a large hose that's connected to air box. I bought that hose with the electrical connection since I know my 740 doesn't have that connection. Does anyone know what that connection does and is it worth swapping that hose in? I didn't want to just do it since I have no clue what that connection does and the previous owner may have bypassed it for a reason. If my description is too hard to understand I'll take a picture tomorrow!
2. How the hell do I take these speakers of my 740. I've managed to blow out all but 1 speaker in my 740 (within the first month of owning it) The speakers look like their held in by 4 bolts that don't appear to have any means of removal (No Phillips head, Torx, just a perfect circle in the middle. I've taken the door panel off but I couldn't figure it out.

 

the speakers are rivetted in. drill them out.

they are a weird non-standard size on 740/940 doors... these adapters fit in their place and let you install standard 5.25" speakers quite neatly.
PVC Speaker Adapters - CNC Machined - In Stock or Custom Made