To MAF or not to MAF, that is my ?, 90 240 DL

cgreygoose · Post by **cgreygoose** » 03 Apr 2011, 11:05

From my previous posts, I think I've checked , adjusted and/or replaced most items that would help me get the best out of my 240, in terms of acceleration at all speeds,ie. new plugs, wires, cap & rotor, airfilter, TPS, fuel pressure reg., speed sensor, cleaned (twice) all hoses, throttle & body, removed new gasket, etc, flame shield, PCV, all vacuum lines, new ECU, did the Seafoam per directions on this forum, changed all fluids, new tires,

My question(s) is this, why does my Volvo drive & accelerate better when my MAF is unplugged? I've replaced MAF, no difference, put my old one back on, no difference, left it unplugged and it drives like I think it is meant to. Why does it run better? What should I do? Will it cause damage?

It appears that my

cgreygoose · Post by **cgreygoose** » 08 Apr 2011, 08:34

I really need some help on figuring out why my Volvo runs & drives better while the MAF is disconnected. I bought a new MAF no change. Question, when I put my meter on the old one to check resistance I get 2.8, the Haynes manual says it should be between 3.0-4.5. When I checked the new MAF, I got the very same resistance of 2.8. That leads me to believe that the MAF is NOT the problem. Could the air control valve or oxygen sensor be part of the problem??? I'm just guessing right now and I dont' have the funds to keep buying parts in hopes of fixing this problem.

The codes I get are still the same 4.1.1- LH 3.1 Throttle sensor signal missing or faulty. & 1.2.1.- Fault in signal for air mass meter. both the TPS & MAF are new. I even had the Volvo shop adjust the TPS as well as throttle linkeage etc. I'm now checking for any vacuum leaks but I'm stumped. Has anyone experienced this problem? I get really really bad acceleration under load. It's as if it's getting unmetered air, which results in not getting enough fuel to the system. I'm tempted to drive it in the "limp home" mode and forget the MAF.

any idea's ???????

thanks,

aaron

Post by **billofdurham** » 08 Apr 2011, 12:11

Sorry for the delay in replying but I have been on foreign soil for a few days.

You have checked the resistance of both MAFs and come out with the same figures. Have you checked the voltage? The attached shows how to do it and also how to check the IAC.

240 LH3.1 MAF and IAC tests.pdf: (544.59 KiB) Downloaded 1302 times

Leaving the MAF unplugged won't do your fuel figures much good.

Bill.

cgreygoose · Post by **cgreygoose** » 11 Apr 2011, 12:01

that's ok. I thought that perhaps I violated a forum rule by my new post. anyhoo, we did do a voltage check which turned out good. dad continuity from ECu to MAS, good. rechecked TPS, oxygen sensor all good. still have same problem. found a couple of small leaks but fixed them to no avail. it's gotta be something so remote or right in front of our eyes, just missing it.

cgreygoose · Post by **cgreygoose** » 12 Apr 2011, 08:08

You sent me a pdf download last time with the directions to check for voltage & resistance. We used it and came up with numbers not exactly but within limits i guess. Question though, when reading the haynes manual we confused between the LH 2.4 & LH 3.1 directions for checking the MAF & Tps. we deduced that the LH 2.4 matches best. we looked at both schematics and my MAf has 6 prongs & has the 5 terminal plugs with the 6th one on the multiplug empty. Whereas the schematic for the LH 3.1 is showing only 4 terminals. Make sense?

Still can't figure this out. I have a buyer for this volvo but without the acceleration issue fixed the deal is dead.

Post by **JDS60R** » 12 Apr 2011, 08:32

If the car runs better off the MAF then you have an Air/fuel issue.
You mentioned that you checked you Oxygen sensor. If you are talking about a resistance check on the heater circuit and then a performance check on the signal genrating between .1 and .9 volts then you have not checked it performance. You can only check its performance with a second good known sensor or a gas analyzer . Let me ask a few qualifying questions to help.

How old is your Oxygen sensor?
How many miles on it?
What brand is your oxygen sensor?

Post by **JDS60R** » 12 Apr 2011, 08:38

On a 1990-1993 240 check the Vin to determine LH 2.4 or 3.1

Check fifth and sixth characters
88 =LH2.4
82= LH 3.1

cgreygoose · Post by **cgreygoose** » 12 Apr 2011, 10:05

thanks for jumping in here to help. thanks for the Vin help, mine is YV1AA884 and so on... confirms it being LH 2.4.

The oxygen sensor has not been checked other than unplugging it to see if the car drove worse, which it didn't. I[m very close to the point that buying parts in hope that it works is too costly. I realize that I've got unmetered air and it's causing me to not get the fuel necessary. how does the oxygen sensor play a role in this problem? I will see how much a new sensor will be and try to install it later today and will post back.

cgreygoose · Post by **cgreygoose** » 12 Apr 2011, 15:11

FINALLY WE ARE DONE. IT TOOK THE 3RD BOSCH MASS AIR SENSOR FOR THE PROBLEM TO BE FIXED. WE ARE DONE!!! THANK YOU TO ALL.

cgreygoose · Post by **cgreygoose** » 12 Apr 2011, 17:07

well, it's never quite over till the fat lady sings. after putting it back together again, I got the 1-1-1. code and my check engine light went off. I drove it around and it seems to be fine, got back in and started it up and the check engine light comes on again. the code is for the MAS again. 4-1-1. What to do now? it drives nice but the light troubles me, especially after shelling out for another new Mass sensor. I tried resetting the OBD but it wouldn't let me.