Good evening

I have a few questions (and a story)

I am a a reformed car neglector and a novice at repairs but I am a quick learner and I am humble enough to know when I do not have enough "expertise" to repair components myself, however, after getting fed up with shoddy high cost low quality repairs (I once brought my beauty to Volvo service after I could not engage 2nd gear- I was told I needed a new tranny to a tune of SEVERAL thousands of dollars- brought it another shop and it turns out my U-joints were completely worn- my tran was fine-) and I could go on and on, So, I taught myself some stuff and with the helpful forums and repair manuals I have made some beginner repairs (water pump, exhaust, IAC) but have found i really enjoy working on it- although i would prefer it not break down.

I have a 92 240 wagon 5speed M47 trans, 3.1 LH engine, non turbo no egr, and about 250,000 miles (odometer broke a long time ago) but I keep a "loose" record of miles

Recently the idle has become very erratic and "loops". It would began to shake and shudder and then began stalling at most stops- eventually it began shutting off while driving anytime I depressed the clutch to brake or slow down, "feathering" the accelerator at stops could prevent the stalling and car will immediately restart each time after stalling without issue

I replaced the Air Idle Control Valve after testing it with a multi-meter and getting a reading of 4ohms (instead of 8ohms recommended by Bentley manual)- I do feel like the RPMS are a little high (no tachometer- I have ordered one to test with) however the RPMS could be completely normal and I may have just gotten used to low RPMS

While the idle is still erratic it is not as dramatic as before and is no longer stalling at stops

However there is new and more pressing issue- now randomly the car intermittently does not respond to acceleration (either by depressing the accelerator or by manipulating the throttle pulley directly (I cannot see any issues with the throttle pulley and cable as it pulls and snaps back freely and all moving parts move freely as well). The car starts up fine and runs well while cold- there does not seem to be any warning this is about to happen and it is very recent (this past week), but while driving along the car will began to slow down and even while depressing the accelerator all the way there is no response- there is SOMETIMES a delayed half response. It is only when I depress the accelerator that there is no response and the engine boggs and dies. There is some engine knocking if I depress the accelerator while the clutch is depressed (trying to rev the engine for a response). but that is it- I shut the car off and wait a minute to restart it and drive maybe a block's length before it does not respond again. There is some "slight" surging while driving but it is not often and not very dramatic. lights on dashboard all light up when I start the car and go out as soon as I start to drive but it has always done that. The only warning lights I get are "Brake Failure" and I have no issue with my brakes so I am not 100% reliant on dash lights

I removed the Air Filter to check for blockage and tested the Air mass Flow sensor (MAF), (reading 110 ohms vs Bentley's 108), replaced the air boot from the MAF to the throttle body, and cleaned the throttle body (no blockage but definitely "gunky") . This made no improvement in drivability. I did notice wet black oily substance inside the boot and in the opening of the intake manifold looks more like "spray" than leakage

I was able to limp home for a few blocks and then she drove the rest of the way without this issue. I tested the Throttle Position Sensor (TPS) and got a reading at closed throttle of 1500 ohms (1200 at closed throttle was Bentley recommendation) and ordered a new one.

I did an OBD and got fault codes of lean/rich mixture at idle and at cruise. Fault at O2 sensor (ordered a new one) and fault at fuel injectors (ordered). I have also ordered a PCV with flame trap and hoses set and a new vacuum check valve and boots, and a new Throttle Position Sensor. I have not yet been able to do an OBD of the ECU since I need a partner to depress the accelerator but will this week.

I have not had any engine overheating readings as the temp gauge stays in the middle after warming up (it has overheated in the past when i had a leaking water pump which I replaced last summer and had no issues since- so I believe the temp readings are accurate). I have had 3 fuel pumps replaced in 12 yrs and in 2016 the fuel pump relay was replaced-however i am still having issue with the fuse #6 (fuel pump fuse) which has never resolved even after replacing the pumps


My questions:
Other than the parts that have been ordered what issues should I be looking for to solve the drivability issue and intermittent no response?

Is an "over-reading" of ohms an indicator of an issue just as an under-reading is? (i.e. real life reading of MAF at 110ohms vs Bentley's recommended 108 ohms)

How reliable are ohms readings and what is considered "drastically different" in regard to mutli-meter readings vs Bentley repair manual suggestions?

I am also having an issue with the fuse box as i am burning -not blowing Fuse 6 (main fuel pump) which is supposed to be a 16amp fuse- the car will not turn over with a 16 amp fuse i have replaced it with an 8 amp fuse which I do not fully install (it is kitty cornered in the terminal) -what would cause this? How would I fix/diagnose this)

Another question is (and remember I am new to this stuff) can I test the fuse box terminals? and if so what kind of reading should I get? or will it each terminal reading be different based on the accessories managed by respective terminals? AND how do I test for a short-like where do I even start?

I truly appreciate your time and response

S

 

I'd say you have a bad MAFS based on similar symptoms I had on my 1993 240. Those readings didn't work in my case either and the OBD2 is far from reliable.

 

Yeah - OBD is not intended to diagnose engine problems. It is mainly intended to let you know when there are problems with the emissions systems. Usually the lean/rich adjustment code is an indicator of a faulty MAF or leaks in between the MAF and the intake. I see you replaced the accordion hose that runs between the two so that should eliminate that as a source of leaks. Also check vacuum hoses as they can let in unmetered air. Your MAF you ordered should eliminate that as a culprit as well - unless you ordered a non-Bosch replacement as those have proven unreliable from what I have read on the forum here as well as on brickboard. Really, though, that may be your only choice as I don't see much offered for replacement on the LH3.1 system.

As for the IAC and the TPS, I haven't really seen a lot of failures there although the IAC can get sticky and needs a good cleaning. Checking Ohms on it really isn't much of a test. I'm not really all that familiar with LH3.1 but if the IAC is the same then the test I ran was to apply 12v across the two terminals and it should switch on. The ECU would pulse between on/off to regulate air flow. Same for the TPS. On the LH2.4, the TPS is just an on/off switch that tells the ECU to start running the IAC vs. throttle body to regulate the air flow to the engine. LH3.1 may be different - you'll have to sort that out. I have never seen a failure (I have had 3 volvo 240s each with over 200k miles) of a TPS. They do need to be properly adjusted though. Bently should tell you how to do it.

I would be concerned about your fuel pump fuse. If it is blowing the normal fuse then and heating up the 8 amp fuse then there is a problem. Remember, the fuse is there to protect the wiring of the car so if it is blowing then there is something drawing too much current on that circuit. Replacing it with an 8 amp fuse is masking the problem and removing the safety margin in the wiring. The fact that you have replaced the fuel pump three times indicates some other problem. Keep in mind, there are TWO fuel pumps in your car - a pre-pump in the tank and the main fuel pump under the back seat on the right side of the car. If it was the main pump that was replaced three times then it would be best to check the pre-pump in the tank. The main pumps on these cars last forever as long as the in-tank pump is kept operating properly. Usually the in-tank pump fails causing the main pump to work harder and fail prematurely. This can all be diagnosed by following the instructions on this page: In the Tank - 240 Volvo Tank Pump and Sender

 

Ok- good stuff...I agree that the wiring issue is the bigger issue as who knows what that is causing. I have made an appt to get it checked as I do not have the expertise or where-with-all to diagnose that.

Thanks again

 

Thank you- I am goon hafta see- I did disconnect the MAF and the engine immediately died....But I do not know if that even proves or disproves anything yet...