Hi all, I have two conditions I am troubleshooting on my 85 240.

since mid June, there's been about 5 or so incidents where the car died and would not start for a period of 5-10min, only to start back up and operate normally after that time elapsed.

The first time happened about 3hrs into a 12hr trip; I had to stop on the highway due to a traffic accident, and after idling in D for 5min, the car died. I tried to fetter out the problem, but after 10min, the car started and subsequently completed the remaining 9hrs without issue. I was able to maintain speed on hills, stopped for gas and turned off/turned on the car with no issue, etc.

The worst and most recent time this condition happened was about a month ago. I had driven about an hour away for work, and on the return trip, the car died just short of completing the trip home. It started back up, only to die again after a few minutes. This cycle of dying/no start repeated several times as I limped home. The car sat for a few hours, and since I've had no issues with dying/no start.

I have not gone on any long trips (1hr+ one way) since this last trip that resulted in the dying/no start condition.

In addition to this intermittent condition, the car has developed an intermittent high idle in P. This started only in the last couple weeks and seems to only happen intermittently. Occasionally, it will, after driving and putting it into P, idle high and then almost 'die' - the idle will drop precipitously, only to rev back up high after a second. I have no made any adjustments or alterations to the TPS or throttle body in months. Related to this, despite replacing my IAC with a known working one in the last month, my idle bypass screw does NOT alter the idle speed at all. Grounding the ECU and turning the screw does nothing. Additionally, the idle speed DECREASES when switching on the AC.

Here are the diagnostics I have since August:
- battery - 12.9V
- battery @ idle, unloaded: 14.09V; loaded: 13.9V
- most ECU inputs at harness are in spec - did NOT do the oxygen sensor test of separating connector and grounding green wire; but there's no continuity at harness with sensor connected. my MAF heated wire reads 2.9ohms resistance, but my meter's limit of accuracy is such that this reading could be in the 3.5-4ohm spec listed in my manual. the other specs at the MAF are good. AC micro-switch operates as it should - hence my concern that the idle does not INCREASE when AC switched on.
- fuel pump relay pins out in spec
- ignition system in spec (did not backprobe the ICU; coil secondary resistance (terminal 1 to center) was a little high, but in spec with meter's limit of accuracy)
- in-tank pump operating and drawing 3A power

open questions:
- ICU? did not backprobe. I've read others having intermittent ICU faults that result in dying/no start.
- O2 sensor. I've only confirmed the wiring from it is good.
- IAC sticking open? I haven't pulled it to check it since I just replaced it a month ago, but that could be causing the high idle in P..
- intermittent fuel pump failure? both pumps operated during the ECU harness test and car has driven normally 90% of the time, so not suspecting this.
- i hardwired my tail lights in May; could there be some interaction a wiring fault back there and the instruments on the fuses for the tail lights? (mainly fuse 13 since that block shares the turn signals and fuel injection system)

any thoughts or tips in solving these two problems - the dying/no start and the high idle - are much appreciated.

 

Lets work on the engine stops running -

What is the date on the fuel system relay? Cracked solder joints are common, and cause failures when hot (after being driven a while) Visual inspection with a magnifying glass on the relay circuit board might reveal cracked solder joints commonly where the wires powering the electro magnets in the relay are soldered on.

What does the fusebox look like - any corrosion on the tips of the fuses? Are the fuel and feeder pump fuses held in tightly?

The 25 amp fuse under the hood (if you have one) connected with a red wire to the battery that powers the fuel injection system - those are notorious for having a bad connection. They are exposed to the elements, I know bad design.

Have you looked in the distributor cap?

The ignition control units get cracked solder joints at the electrical connector - take the ICU apart, circuit board out and look for cracked joints on the back side - the board is covered in silicone rubber so it might be hard to see through. Volvo made little sleeves to go on the pins in the connector - #1324909 to help create a better connection, make sure there is one on every pin that's used.

 

thanks for the reply. I should have included that I replaced the main ECU wiring harness with a D Barton one and replaced the fuel relay with a new unit in April of this year. The distributor cap and rotor were replaced in Oct 19, hall effect sender replaced April of this year.

I was under the impression the ICU couldn't be removed without damaging the harness connector? Bentley suggest this but could be wrong.

will be back wth more once I poke around. thanks again.

 

the volvo change order for those pin sleeves only added them to the low signal inputs, like from the hall sensor.

to remove the connector from the Chrysler ICU, you have to pull it straight off, NOT rock it and yes, tis likely very stuck on there. when you plug it back in, use quite a bit of dielectric grease

re that fuel injection fuse near the battery, the stock white plastic fuse holder turned to junk with age.... I replaced them on my 240 with waterproof marine holders and again, used quite a bit of dielectric grease on the fuse contacts and on the weather cover.

 

The 25A blade fuse by the strut tower appears fine, being a new holder and fuse with the wiring harness I put in. I also seemingly didn't have any issues with intermittent dying/no start from the previous 35yr old fuse holder/wiring harness covered in electrical tape. so i don't suspect that's the issue.

my 240 is currently my only car so I am nervous to pull the ICU harness connector and ICU box - until I get my 940 online in the coming weeks. I will say the ICU connector at the ICU box looked gunky so I sprayed electrical cleaner on it. so that remains a real possibility for the dying/no start condition.

however, regarding the idle - and possibly the dying/no start, too - my suspicion is some fault in the ECU still, particularly given the correlating idle problem. the car typically idles normally in P at first start-up for the day, then will idle noticeably higher in P through the rest of the day. the car also will drop below the idle RPM in D after letting up the accelerator, then 'air up' and rev up back to the idle speed. combined with the IAC grounding terminal and idle bypass screw doing nothing, plus the AC micro-switch input being correct but not resulting in a higher idle... i mean, doesn't that pretty much point to an ECU failure??? what am i getting wrong?

my IAC resistances check out and the valve will operate normally; i replaced my ignition coil with one where the resistances are in spec; there's no air leak or hose failure that I can find; and the wiggle test of connections doesn't reveal any obvious faults either. so what gives?? is there a need to pull the throttle body and inspect the idle screw/idle screw passage? I set the TPS back in June and the screws are still tight on it, so it hasn't moved... I haven't tested it, but since the car runs/drives normally, i assume it's not a TPS issue.

i really think there's something wrong in the ECU management of the idle components. any thoughts??

 

Probably not - those were very reliable -

 

then what explains the idle being wonky? Why would the car idle high in P/N and not increase the idle for the AC and not respond to the idle bypass screw/grounding of the IAC test terminal? Those all are governed by the ECU, right?

the past few days the car has been cranking much longer than normal before start so I now have that issue compiled in all of this...

I am getting more concerned that the car is going down and may be beyond my current skills. but i'll dig into more and come back if I can find anything helpful.

 

The culprit in your wonky idle might be -

The idle motor, or idle air valve, or IAC, or whatever you want to call it - - If you take it apart (which you can't w/out destroying it) - has an wound armature, a couple of magnets, 3 brushes touching the commutator and a valve that lets in more or less air to control the idle speed. The armature moves slightly one way or the other to let in more on less air. Hence the 3 brushes, to be able to make it spin in both directions, but it only spins a few degrees in each direction. If you listen with a stethoscope to yours you should hear a buzz, that's the armature wiggling back and forth very slightly as the control unit reverses the polarity - wiggles more one way to let in more air - you get the picture. What happens after x years is the brushes dig slots/divots/holes in the commutator (since the motor does not spin, it just wiggles back and forth) and the brushes get stuck in the groove, or fail to make good contact after the brush rubs completely through the commutator - How do I know - after replacing one years ago I took the old one apart, then used it to explain to customers why their idle would get wonky and why this expensive part would fix their idle.

 

I replaced the original IAC with one from a 87 car just recently and the idle was fine for at least a few weeks after that. when my original IAC no longer worked, the idle was lower than spec, not higher. though I suppose, given how the valve works, it's equally likely that it would fail in a closed or open position resulting in a lower/higher idle depending.

thanks for the continued info and help.

 

was the old IAC you replaced all gummed up? thats the most common failure mode

 

Many times I have unplugged the IAC/idle motor with the engine running (making sure it was adjusted to stay running) - then plug in a new or different IAC to the wiring harness - I could then observe the valve opening and closing trying to control the idle speed - say unplug an injector and watch the valve open, open the throttle and see what happens, turn the ac on - might be a good way to test your ecu.

 

the old IAC failed because, as hoonk said, I broke it taking it apart.... live and learn.

I'll try that diagnostic with the IAC. the other test I figured would work is to cover up the intake manifold hole from the IAC = should idle lower.

 

when you replaced the IAC, did you also replace the hose bits that connect it? they frequently crack or otherwise fail upon removal/reinstalling, and any air leaks here will mess with your idle by letting in unmetered air.

 

i didn't replace either hose. neither appear cracked but I have wondered if un-metered air is getting in through either. I will check. (lots of checking to do this week!)

is there a new part to replace this IAC? or just old stock? FCP seems to carry an IAC that looks like the proper one but there's no way I'd pay the price for it: https://www.fcpeuro.com/products/vol...70-850-9454745

 

thats the IAC for an 850 & newer which is a rather radically different car and engine. and a genuine Volvo part.

 

ah, okay. i knew it didn't come up a fitting a 240, but i wondered. in any case, that means the only IACs for LH2.2 available are from parts guys and old stock? I think the replacement one I am running now cost me like $20 from the guy I buy from. not bad.

 

the ECU is communicating to IAC. grounding test terminal does switch the IAC. this confirms the IAC is working and the ECU is not mis-managing it?

grounding the test plug, I backed the idle bypass screw all the way out then back in and the idle did change a little. but then on next start, it was high again.

I have not adjusted the TPS since I last adjusted it when I did the idle time and ignition timing. and it hasn't changed position anyway.

the car was acting like it was going to die driving home - dying then surging out of the hole. but it didn't actually die. i had drive about 30minutes to a job and then 45minutes home stuck in pretty bad traffic, sitting in D a good bit. the idle started the dip while sitting and then, out of the whole, the car was bucking.

i wiggled tested the fuel pump wiring at the main fuel pump, the wiring in the engine bay to ECU and ICU and can't seem to pinpoint a fault or create the dying condition. i also checked the spark by jumping hall sensor b to c and the spark was strong.

i am now thinking more ICU fault.

 

And this is the car you have not disconnected the ignition control unit to inspect the connection and look for cracked solder joints on the back of the circuit board - usually at the 10-12 pin connector?

 

right, i'll probably do that within the next week or so. wrapping up getting my 940 online before I risk damaging/being unable to reconnect the ICU.

 

i don't know how helpful this observation is. but following this flowchart (https://www.volvo-forums.com/index.p...e=post&id=5403), my ignition timing advances with the RPM increase even when the vacuum hose is disconnected from the ICU. I am not sure what my idle rpm is, but it is higher than 750rpm. the ignition timing was around 17-19* BTDC; increasing the rpms yielded a 25-30* BTDC ignition timing.

of course, since I am idling pretty high for whatever reason, this may be a useless observation.

as one other thought. i have not properly set the CO in the lh2.2 AMM. however, given the cars generally reliable operation, I doubt this is significant.