Hiya folks. I know this is my third thread, but I've done a bunch of work and cleanup and I have just about exhausted all my options - I have exhausted the things I thought most likely.

CPS Replaced w/new from IPD
RSR Replaced w/good used
RSR Wiring pigtail replaced w/good used
Bypassed RSR with a wire splice

Ignition power stage (ignition amplifier) replaced w/good used
Ignition power stage thermal conductive paste cleaned and replaced


Cleaned all fuse contacts and fuses themselves
Cleaned injector grounds and engine head ground strap connections
Cleaned body grounds behing both headlights
Cleaned coil contacts (primary side)

Backprobed CPS and saw a clean, consistent frequency change with engine speed at the most problematic engine speeds.

Disconnected AMM, car stalls when throttle opened
Disconnected TPS (error code 1-3-3 thrown)
Disconnected knock sensor (Error code 3-1-2)
Held my hand on the Fuel Pump Relay (resoldered years ago) while problems were happening - felt no clicking during the episodes.
(I have a spare fuel pump relay I will resolder and substitute tomorrow)


All of these have had no impact on the problem.
This all started the night I replaced the actual heater core, but the car had driven perfectly with the dash torn apart for over a week. I can't believe this is random coincidence.

I'll describe it again from the beginning.

Car starts and idles fine, no hiccups, slightly long cranks, but not excessive to me. Car accelerates with full power - it almost never cuts out if accelerating w/throttle ~>1/3 open.
Driving along at a steady speed, the engine will suddenly lose rpms, the tach and vacuum gauges drop, the gas pedal becomes nonresponsive, and then the car goes back to running normally after a few seconds. This is more common with city speeds (25-40), and is worst between 1500 and 1800rpm. These episodes last at most 5 seconds.

At other times, while cruising at highway speeds, there will be one or many sudden power-losses like the spark is shut off momentarily. These episodes happen either one at a time or several in a row, sometimes pulsing as though someone were flipping a switch on and off. At its worst, I'm trying to cruise along at about 1800rpm. I'm not sure why, but that's where it gets really bad/likely to happen.

I normally can't get more than a block from my house without at least one of these stumbles/stalls happening.


I pulled on all the wiring bundles under the hood and the ones I've moved under the dash (at idle) and nothing has happened.
I also checked for vacuum leaks with starting fluid and couldn't find any.



I'm at my wits' end. I've done everything I can think of and then some. There's an indie volvo guy near here, but he's a little crotchety and doesn't have formal training - but he does seem to know his volvos very well.

Please, someone, make a suggestion. Maybe the fuse or relay panel has a wire coming loose because of how it's been sitting? I moved it around and couldn't create a problem.

FIXED IT! :D

Details here.
https://www.brickboard.com/RWD/index.htm?id=1602774&show_all=1

I just put up a new thread to help finish off this problem at https://www.brickboard.com/RWD/index.htm?id=1595635&nr_no=1

Hopefully, with an answer to that, I'll be able to find what's actually wrong.

Greetings folks. Tonight, I got home from work and set up an in-line spark tester and backprobed an LED into the #1 injector.

The following video is the symptoms I've been having (That's Infected Mushroom playing in the background):
https://www.facebook.com/photo.php?v=10202955534083691&l=1462551880625921802

And this is what I found with my test setup. The video doesn't show it that well because of the camera's refresh rate, buuut what I saw was the green light turning off every time the engine bogged/cut out/whatever.
https://www.facebook.com/photo.php?v=10202955534083691&l=1462551880625921802


So, the EZK appears to be fine. The ECU though... I dunno. Maybe. It does this with the RSR bypassed, so I doubt it's related, unless I somehow damaged the wiring to it.

>It does this with the RSR bypassed, so I doubt it's related, unless I somehow damaged the wiring to it.

To rule out the problem being interrupted power to the RSR you could rig a small test light run to the cabin that gets its power from the 12v feed to the RSR. If the flickers at all you have something new to chase.

On an 88 745 turbo I once found a connector in the engine compartment up stream from the RSR that was breaking down and failed to supply 12v to the RSR. It was located under the cross brace near the master cylinder.

Randy

I knew that second LED would come in handy ;)
I'll check it out.

Hello Will,

In the video looks like the green light cut out momentarily when you partly release the throttle (during the sound of engine goes down a bit). Or was it the throttle was steadily maintained but the engine cut out nevertheless?

There is fuel cut-out during throttle release (part release or full release) to reduce emissions. Fuel pulses depends on feedback from the CPS but totally controlled by the ECU (as in case of throttle release). On Bosch LH system all fuel injectors are fired simultaneously (common mode injection) only the sparks are timed to specific cylinder.

Does your engine uses distributor sensor for spark? Usually for 1990 model and above it doesn't (the CPS is used instead). But just in case it does, check its electrical connections (for that sudden loss of spark you've mentioned).


Distributor with hall sensor for spark.

Regards,
Amarin.

The engine lost rpm as a result of losing injector pulses while I held the throttle steady. It's got a crank position sensor, which is brand new.

I think I should chase the wiring harnesses around and check the connections, then see if I'm losing a signal somewhere from the EZK to the ECU (I probably moved the wiring doing the heater core!) and then go from there.

Hello,

I guess no one mentioned about spark plugs and its wires (plus wire to coil too). Internal wiring (within the plug's porcelain casing) might break if exposed to high heat like in turbo engines. Ignition wire usually lasts up to 3 years or less if exposed to turbo heat. Check or replace these.

You did mentioned like the spark was turned off momentarily..

Hope these helps.
Amarin.

Hmmm. The wires are custom from Kingsborne and new within the last 6 months.

The plugs, however... HMMmmmmmmMMmmm

No sure what turbo you have but consider waste gate issues?
--
Post Back. That's whats makes this forum work.

Do you think that would cause the cut-outs?

If it opens it dumps the boost. If it stays open, no boost at all. Do have a blow off valve? Also above the drivers foot is the overboost protection.
--
Post Back. That's whats makes this forum work.

I checked the wastegate actuator today and found.....

The metal link-pin between the actuator arm and the lever arm that moves the wastegate was disconnected! I reconnected it and installed a 1/16" cotter-pin.

It remains to be seen if that was the problem the whole time.

good deal. I know without it, no boost. It's possible that the intermittent could also be the culprit.
--
Post Back. That's whats makes this forum work.

Aaaaand that wasn't the problem. I do have boost back again (yay). I think the jerking from the cutouts made the lever arm detach, but I'm still having them happen.

I bought an LED to backprobe into an injector and an inline spark tester to check to see if I'm losing spark, injector pulses, both, or neither.

If I understand correctly, the LH system (ECU) has to get a signal from the Motronic system (ICU) for the injectors to be pulsed - in other words, if I lose spark, I'm going to lose injector pulses.... right?

"...if I lose spark, I'm going to lose injector pulses.... right?" YES

"the LH system (ECU) has to get a signal from the Motronic system (ICU) for the injectors to be pulsed" NO, because you don't have the Bosch Motronic (about which I know zip). Your have the Bosch EZK-116 Ignition Control Unit. The Motronic CU is a combined FI and Ignition CU used on other cars.

Search lucid start run sequence for more detail.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Ohhhh, right. Derp. Thank you!

No blow-off valve. I'm still thinking it's an intake leak or collapsing hose or something.
I will check to see if the wastegate is sticking though.

Update:

Now I'm getting no turbo boost - as in I never get actual positive manifold pressure.

I bought an inline spark checker and an LED to rig up a (backprobed) noid light. I'll see if I can figure out what the heck is happening, since it will now do the blips in park.

I'm feeling like this might be a bad turbo inlet hose or a cracked intercooler. The mixture definitely feels wrong. I'm going to make a pressure adapter tomorrow so I can pressurize the whole system.
Turbo spins freely, and I've now tried 3AMMs + my original. One of them made it die at any throttle, but the others all ran pretty much identically to my original.

When I started getting no boost, my first thought was a plugged cat. I pulled the pre-cat bung nut last night, and other than the exhaust note, nothing changed. I am not getting any kind of backfire from the exhaust, just getting blips of silence.

This is literally the most infuriating issue I've ever had. ... Well, maybe the PS pump bracket was worse. Only the tail-light short I had for years was more annoying.

Didn't you find an extraneous wire under the dash when you replaced the heater core ? If you have removed it, have you tried putting it back ?

Greg

Yes, I did, and somewhat to my dismay, reinstalling it did not help.

I put some gas treatment in it today, but I'll have to wait for the stores to reopen to get actual water remover (methanol I think).

Any 90+% drugstore alcohol will work. Isopropol is the best. It mixes well with water and gas and stays in solution.

Greg

Do you have a problem in the ignition switch? Momentary loss of KPII due to switch wear? Can you rig up a voltage tester to test this when operating?

Interesting idea, but the gauges keep on working while it happens. I've got a voltmeter on the dash, but I don't know if that is what you mean. You mean running a VM to the ignition switch? I've tried playing with the key (wiggling and jiggling it) and it hasn't made anything happen.

Then that is likely not the problem.

These issues will keep you awake at night. At least you know other brick owners have had similar experiences.
Before you tear anything else out and replace it, check the exhaust - are there any leaks anywhere? have the gaskets been replaced recently? Also the Electronic temp sensor may not receiving the correct readings from the coolant. take it out and check the surface. Could be pitted. and the connections also.
Take the crank sensor off and clean it well. sometime it gets oil on the face and this interferes with the computer receiving the proper impulse.
Of course I have had idling issues with my '89 740, and had to completely go through all sensors, connections and etc. Seems like it's always something....
--
89-740 GLE;91-940 Sedan ;98-V90 Wagon ___ all running well

As far as I know, there aren't leaks - I was thinking maybe it's a plugged/rusted out catalytic converter?
I replaced the crank sensor (and tried cleaning the old one before doing that)

The exhaust gaskets are about 4 years and 15,000 miles old. I am missing a spacer for one of the manifold nuts, and it keeps backing out. I don't want to overtorque it, so I'll pick one up from the JY next trip. The manifold seems tight though.

I'll pull the ECT and check it. Maybe I can de-scale it. I used to have a spare, but who knows where it wound up.

Cheers

Some exhaust systems have a removable bung in front of the cat for testing purposes. If you have one, remove and drive and see if the issue comes back. The bung usually has one spot weld so it doesn't unscrew driving down the road(ask me how I know it can happen)
What about some locktight on that nut?
--
Post Back. That's whats makes this forum work.

Hmmm. I don't recall seeing one. What's it look like? Not the CO plug...

Loctite would work, but I'd like to replace the spacer. It's there for a reason.

I don't think the exhaust is the issue. After all you've done, I'd take a look at the ECU and EZK ground points for corrosion. I'd also buy a used ECU and try that. It appears as though something electrical is malfunctioning in either the FI or ignition system, probably the latter. Coil might also be suspect.

I thought about the coil. Its resistance wasn't out of spec, but that doesn't mean much.
I don't think its the coil because it happens more at low rpm and all but disappears at >1/2 throttle. In fact, the faster the engine is running, the better it runs. This is why I feel like it's a good bet that the AMM is to blame - the AMM is most accurate at low and medium airflows, but when it's flowing fast, the AMM is less accurate. I would expect a bad coil to get worse with heat (it does) and worse with higher rpm (it doesn't - it gets better).

Or more like the ECU depends more on the AMM input at higher rpm, so the problem disappearing at higher rpm (it's pretty much nonexistand above 3300rpm) makes me think the AMM is flakey.

Look for a used AMM and give it a try.

Go back to initial diagnosing rather than throw parts at it.

You said the tach drops,
if it winds down with engine rpm its fuel related,
if it drops dead to zero then its ignition.

I would run a timing light into the car so you can watch the spark when it stumbles. If it stumbles due to fuel starvation the spark will not be affected.

Have you ruled out a fuel issue? Is tank full when these symptoms occur? Can you hear the in-tank working?

There's no way this is water in the fuel .... right?

2 people have said that filling up their cars with fuel from my work has given them water in their gas. I'm not sure how they knew, but maybe I'll dump a bottle or three of rubbing alcohol in my tank tomorrow and see if it helps.

Opinions?

Back east there are bottles of stay-dri or some such name sold to combine with moisture in the fuel system. It was actually possible for fuel systems to freeze, as the seasons change.
It's not common out here at all, but if you can find some I recommend it.

Yes, go to your local parts store and ask for dry gas. It will take care of moisture in your fuel system. Another option is Marvel Mystery oil. That can be added to either your gas tank or directly to your engine oil.

my 92 240 will operate on ethanol, but is not happy about it, at all.
Any way you got really old, or ethanol tainted fuel?

All the fuel in CA seems to have ethanol in it (10%), if you believe the signs on the pump that says "oxygenated".

I don't know if the gas is flakey, but I had been buying my gas at a chevron in my town, and I've put 2-3 tanks worth of this stuff from my work in it and been having problems most of that time.

Sounds like the dry-gas is worth a shot. If that turns out to be the solution....

Ethanol will not affect performance other than gas mileage. Try the dry gas but I'll bet the problem is elsewhere.

Tank's full, In tank works. I'm sure it's electrical - either losing spark or injector pulses somewhere. Just not sure why...

Have you tried a known good AMM?
Dan

I have not ... don't have one sitting around, unfortunately. It's an -016. The only one I have sitting around is an ... uh .. I forget the number, maybe -008 from an 84 240, and that one's bad heh.

But that guy near my work probably has one!

I had cutouts similar to what you describe for many months, did all you did and more, and eventually the AMM threw a code. Different AMM cured it.

Car threw a 1-2-1 code tonight - Bad signal from AMM.
Mileage is down to 17mpg for the 2nd tank in a row.
Also, interestingly enough, it will not go into positive manifold pressure now (no boost). Not sure why exactly, maybe too rich as a safety measure.

Also, I remember cleaning the ground for the ECU (passenger footwell) a couple years ago after the engine swap.

I'm going to try to get a used one tomorrow. I'll have to save up, but I may eventually buy a brand spankin new one.

*Before I buy a new one*... Where does the AMM wiring run?

Maybe?

https://www.brickboard.com/FAQ/700-900/EngineTurbo.htm#Lack_of_Turbo_Boost
--
Post Back. That's whats makes this forum work.

Your turbo hose burst!!! Why did this happen? Where did the intercooler crack off? Are you sure the turbo is spinning?

That was my first thought as well, but it started when the 1-2-1 code threw. I checked for vacuum leaks and visually and physically inspected all the hoses airbox to intake, and none of them are ruptured.
I'm sure it's because of the mixture, and also the car pulls loads of vacuum with my foot off the gas, so that makes a massive intake leak less likely.

I would get a couple of used ones no need for new.
Dan

Time to get one, you know you need it anyhow.
Dan

This might very well be a coincidental problem and has nothing to do with the heater core R&R. You know, it is said that car problems generally come in three's...:)

Don't know the coil's resistance, but it is probably worth trying swapping coils. The coil might be fine when cold and not start acting up until it gets somewhat warm. Do you have a known good one? If not, I'm sure a boneyard has them cheap or maybe ask your Volvo guy if you can borrow one.

What about the ECU? Have you tried swapping that too? The randomness of the problem makes it sound like it could be a bad ECU.

I haven't tried swapping the ECU yet, but I wonder if the AMM is to blame - the rpm range where the problems occur is still low enough that the AMM reading matters quite a bit, and that intermittently weirdly high idle could be another symptom.


I'm seeing that the coil's primary side should be about 0.6-1.0 ohms and that the high-tension should be between 6000 and 8500.

Man I feel for you. When my AMM went bad, loss of power, bogging down, backfire. I thought I blew a head gasket between cylinders. Then coasting off the road, reving in neutral was fine. The minute I put a load on it all the symptoms came back. On another side note, when my fuel pump relay went out, the no response everything just starting dying. It didn't act like fuel starvation, just died. Good luck. Hey look at your AMM connector and see if any pins backed out. I'm just grasping since you have covered alot.
--
Post Back. That's whats makes this forum work.

After it was doing it pretty regularly when I drove home last night, I let it cool off a little, went back out and restarted it and managed to get it to act up in my parking lot. So, I backprobed the O2 sensor while holding it at about 2000rpm.

What I saw was this:
O2 sensor sweeps quickly between 0 and .9V (analog meter), and looked like it was doing normal oscillations at first.

Then, when I noticed that the blips would happen, the meter would peg at 0 and then somewhat slowly move back to oscillating. Every time the engine missed, it pegged at 0.


If I remember right, that means that the mixture is extremely rich (maybe no spark?) ... or is it extremely lean?

**Scratch that, it's lean**. Hmmmm.