As I’ve said before, own 240’s long enough and you will eventually see one of every problem.

Two winters ago, during a witch’s tit cold snap, my ’93 wagon was a very hard start a couple of times. No check engine light, no codes, so I verified the Engine Coolant Temperature Sensor (ECT) which showed good. The weather warmed and the car started and ran normally, again. I convinced myself the hard start was a fluke and I knew from experience that I would waste a lot of time trying to find a problem without a symptom glaring at me.

A year later, the problem showed up again during an extremely cold period, but this time it lingered. As before, a couple of times the 240 had to be cranked a long time before it caught fire, but this time it settled into a rough idle with a Check Engine light.

Since the car ran well enough, albeit with an irregular idle, I put off getting involved with the repair until the weather warmed. I thought I had wrestled this pig to the ground whenever I pulled the codes – 121 and 232. It had to be the Air Mass Meter (AMM), or so I thought. A known-good AMM proved my thinking in error.

By the way the engine was Idling, I figured it had a vacuum leak. I checked every vacuum line, port and fitting – nada. I then sprayed around the intake with some carb cleaner with no result – more on that later.

So, I began the systematic Engine Management dance. Once all the checks outlined in the Bentley did not reveal ANY queefed out components, I started to go esoteric.

I tried a good Idle Air Control Valve (IAC). I tried a new ECT, grounded but not screwed into the head (replacing an ECT is something I’ve learned to avoid if at all possible). The idle seemed to change when I pulled on the wiring to the ECT so I thought that perhaps the ECT wiring had a fault. I broke out the ECT conductors from the mass connectors for the Engine Control Unit (ECU) and the Idle Control Unit (ICU) and went overland with external conductors to the ECT. No change.

Getting desperate about this time, I tried another Ignition Amplifier, installed new plugs, checked the ignition wires at night, installed rebuilt injectors, installed a new Crank Position Sensor (CPS), tried another Fuel Pressure Regulator (FPR), rung out every conductor in the engine compartment, cleaned every connection and even checked the motor mounts with the engine pulled up by an engine support bar just to make sure. No change.

Being the car was bought used and, now, getting REALLY desperate, I thought perhaps a worn timing belt had jumped time, even though I had to ignore the fact that the car started easily once the weather warmed. The timing belt was OK.

I had arrived at the point of despair where I began to think that I might NEVER find the problem. Although I had checked already, I kept thinking the ratty idle seemed like a vacuum leak. So, I got a fresh can of carb cleaner this time connected to two feet of capillary tubing and, waiting for the wind to die down (during the first go round it had been rather windy), I sprayed thoroughly around each intake manifold flange. Praise the Lord! When I hit the underside of the No. 1 flange, the idle took off.

When I finally got down to the intake gasket, I had to wonder how the car ever ran at all. The gasket hole for the No.1 cylinder was so egg-shaped, it made for a direct shunt to atmosphere. I guess adaptive engine management can work miracles.

In the end, I am kicking myself for not being more careful checking for a vacuum leak, but also I have a renewed respect for instinct. It wasn’t all a waste of time because I was forced to generally freshen up the engine and do some of the nasty tasks (the ECT and the CPS) which will need done eventually anyway.

Rich (near Pittsburgh)

Very nicely written, Rich! It deserves a picture. I wonder if this old one I've been posting for 14 years now lives up to your excellent powers of description... What do you think? Was yours this bad? Or worse?


--
Art Benstein near Baltimore

This girl said she recognized me from the vegetarian club, but I'd never met herbivore.

Only half as bad, Art. The No.1 hole looked much the same, but the others were all right.

It dawned on me (once everything was bolted up, of course) that the cause of this failure was likely the inability of the gasket to accommodate the expansion/contraction cycling of the head/manifold. I think an improvement would be to provide an expansion "joint" in the gasket between the flange holes.

The next time I do one, I will either slice the intake manifold gasket into 4 separate 2-hole flange gaskets, or else cut a slot most of the way through the webs of the gasket between each cylinder, much like what a concrete guy would call a "control joint".

If I wasn't so involved in celebrating wrestling this thing to the ground, I would pull the manifold and install a modified gasket right now . . . nah!

Rich (near Pittsburgh)

PS - I only changed out the CPS because I read a write up you did about a wintertime no-start where you mentioned reading 180 Ω at the CPS. I was reading 205 Ω on the one in the car but the 3 others I had to check all read the same as yours. As I said, I was getting desperate so I ignored what I had heard in a classroom decades ago - "If a circuit ends up within 30% of design, it's precision."

That is an interesting idea, separating the gaskets. No reason I can think of not to. In fact, the Volvo was the first motor I'd seen where the exhaust gaskets were done like that, and speaking of differential expansion...

On the CPS resistance... I find it somewhat amusing to hear stuff like "mine measures 195.4 ohms" based on the number of significant digits reported on modern DMMs. Really the resistance readings are provided only to help someone assure themselves the unit is not open-circuited or shorted. And on acceptable examples the resistance can vary quite a bit with temperature. It is just a long piece of hair-thin wire wound on a bobbin with a magnet in it. It doesn't "wear out" such that a resistance reading would detect, but practically the connections fail inside the encapsulated sensor, so the resistance could rise considerably if it includes a bit of that green copper oxide in the circuit path. But we have to think in orders of magnitude, not tens of ohms. 30% achieved at coil wind time might be a bit sloppy, but over the temperature range they encounter, very real.

The death of the intake manifold gasket in my case was more than just the heat cycling. It was also the years of exposure to gasoline, oil, and other blowby products. It crumbled easily.

More rant on this: We hear so often the advice to spritz around it to find the vacuum leak -- listening for the change in idle. Yet we are talking about cars with computer controlled idle speed. A leak would have to be as bad as yours was, forced out of correction range, to be found this way. Makes a smoke machine seem very useful.
--
Art Benstein near Baltimore

Over the hill: I don't know how I got over the hill without getting to the top.

"Makes a smoke machine seem very useful."

As correct as you are, Art, I wish you hadn't mentioned a smoker - one more thing to find a place for on top of the parts and the dedicated tooling!

Rich (near Pittsburgh)

Man, what a nice write up!

For you to be able to type and keep your thoughts together. Wow!
Yes it is amazing, considering the hair you must be missing and having bruised fingers from rooting about the car.

The things you checked through wins my admiration for tenacity, all the while ignoring your instincts.

Thanks for sharing!
Heck, it makes want to go pull the intake manifolds on all my cars as a routine maintenance practice.
I have only done one and it was on the oldest of my four cars.

Phil

Hi Rich,

Thank you.

How many miles on your 1993 Volvo 240?

What make gasket did you use?

I started to go esoteric.

Coooool.

Thank you.

Duffed.

The '93 has 173kMi. on it.

I have to assume the intake manifold gasket was from the factory. I bought the car used, but apparently well mantained.

Rich (near Pittsburgh)