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240 '84 244 DL: Cruising hesitation, great idle, desperate situation.

jsw8671

New member
Joined
Jul 14, 2016
Location
Central Ohio
Howdy! I was wondering if I could get some help with my '84 244. It has recently developed a surging (stalling, lack of power) problem when driving. It idles great, and runs/accelerates fine when driving at low speeds, but when cruising on the freeway, after a while it starts surging and progressively gets worse to the point of having to pull over. It will idle fine without being restarted though, and still accelerates fine at lower speeds.

Extra details: LH Jetronic 2.0. I previously had to jump the fuel pump relay (terminals 30 to 87) with a switch due to it not activating on its own (points to a problem with the ignition switch or junction box I believe). The system relay (right next to fuel pump relay which connects to the MAF, Lambda tester, and control unit) was having intermittent trouble and would have to be occasionally disconnected (then re-connected) to get the car to start. This relay (system relay) was rapidly switching on and off while the car was 'stalling' and in order to get home I jumped terminals 30, 86 and 87. This reduced the problem, but after several miles of driving I still ended up with random/intermittent loss of power, though with less consistency and shorter duration.

I noticed that there is a function within the control module that shuts off fuel during engine braking (via greenbook). Perhaps whatever is responsible for this information is faulty? I have no idea what that would be though.

Plugs, wires, cap, rotor, and air filter are all about a month (or two) old. Thermostat in the air-filter box is removed (extra intake hose added). All vacuum hoses are intact, and I thus far have not managed to track down a vacuum leak via hose inspection or propane application.

Where should I be looking? I have a few hundred miles of driving ahead of me over the next couple days, and I'm not at all confident that she'll make it at this point...
 
2.0 isn't my forte, but you mention surging as well as lack of power and hesitation? Is that correct...?
 
2.0 isn't my forte, but you mention surging as well as lack of power and hesitation? Is that correct...?

Kind of...I guess less 'surging' and more 'stalling'; it loses power and the throttle becomes unresponsive, then jerks back to life. This will sustain for a couple of seconds in spaced out intervals initially, then it becomes progressively worse until it's powerless for probably up to ten seconds at a time with some 'stuttering' (quick on/off) thrown in for good measure. It will not show any symptoms sitting in the driveway while idling or revving. It very occasionally will drop power, then surge while coming to a stop as well (then idle fine, and accelerate fine until it's been driven for a couple minutes).

It revs up and down constantly with the MAF unplugged (idles fine with it plugged in, but the resistance readings were slightly high). The coil resistance readings are on par. Fuses have been cleaned and replaced. TPS clicks at the beginning of throttle movement as it should. Both fuel pumps run without excessive noise.
 
Does 2.0 use an ECT (coolant temp sensor, but for the ECU... not the gauge)?

Are you manual?

When my ECT failed on my 2.2 manual car it would seem to jerk itself around while cruising because it was stalling and the load would shift from the engine driving the trans to the trans driving the engine and would just fire back to life. I had a handful of times where it just wouldn't restart, and ultimately I'd pull over and within ten seconds of calling it a sh*tbag it would fire back up. It seriously just made me question whether or not I was in a horror movie for a while, but then I cracked out the multi-meter and was like oh... it's not a horror movie, but this 25 year old GD sensor failed in the middle of winter.

6 in one hand if you ask me though lol.
 
My first step with mysterious electrical problems is to wiggle the harness a little near all the major connectors while the engine is running; if the issue is caused by a poor contact, this usually disturbs them enough to make it show itself.

I would check the ignition harness as well, although I'm not sure a problem there lines up with your symptoms.
 
Does 2.0 use an ECT (coolant temp sensor, but for the ECU... not the gauge)?

Are you manual?

Nope, this one is an automatic, but it does indeed have a temperature sensor for the ECU. I was thinking along those lines, but failed to find any serious description of symptoms of that sensor failing until now. I will start the unpleasant process of trying to figure out how to get my hands down in there to unplug it and test it. Does anyone have a link to the resistance vs. temperature chart I read about somewhere? Also: I assume the sensor is screwed into the water jacket and I can expect a coolant shower should I have to remove it?

And: I have done much wiggling of wire harnesses and haven't yet managed to cause symptoms, but, I haven't ventured down under the intake manifold yet...
 
LH 2.0 green book:

Link to volvowiringdiagrams

Page 6. Demonstrated values:
-10 C: ~10k ohms
20 C: ~2.5k ohms
80 C: ~0.3k (300) ohms.

Looks like there's a diagnostic section in there as well which may be helpful to you. Page 11.

Yes, the coolant temp sensor is in the water jacket.


Edit: Book says it's grounded via the intake manifold.
 
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Ok, so via the Greenbook testing procedures it looks like the temp sensor and TPS are good. The MAF gave me a reading of zero resistance though (spec is 3.7, and I tested it stupidly earlier). I happened to have a spare MAF...also no resistance (between terminals '6' and '7' on the ECU connector). Could the MAF give me these symptoms and be so sporadic and only after 'heating up' and driving for a while? Sounds not quite right to me...
 
FWIW the temp sensor is NBD. I've always been able to remove my idle air hose/valve (though I just did it last week without touching it) and have enough access. Get the right combo of extensions and it's cake. I'd probably prefer to test it off the car, but the month prior I tested it in situ by getting alligator clamps on the 2 pins while off the car and then like a GD surgeon put it back on without dropping the clamps. This seemed pointless after I did it though, but I was chasing a lead so....
 
Well the AMM does use a heated wire... maybe it's hotness is slow?

I'll be honest though it sounds like you've got some rogue electrical gremlins you'll need to trace to TRULY get to the bottom of this no?
 
My first step with mysterious electrical problems is to wiggle the harness a little near all the major connectors while the engine is running; if the issue is caused by a poor contact, this usually disturbs them enough to make it show itself.

I would check the ignition harness as well, although I'm not sure a problem there lines up with your symptoms.


I had similar issues recently and wiggling all the connections with the engine running, found the problem to be at two of the four fuel injector cable connectors on cylinder 3 & 4.

Disconnect each fuel injector connector and inspect the two pins inside. My problem was caused from one of the two pins not being secured in each connector, resulting in fuel delivery issues. Pull back the connector boot, reset the locking tab on the pin, reinstall the connector. This resolved my issue and was a simple 10 minute fix in all.
 
I had the same symptoms and replaced the O2 sensor with the correct 3 wire config and my hesitations went away...
 
I had similar issues recently and wiggling all the connections with the engine running, found the problem to be at two of the four fuel injector cable connectors on cylinder 3 & 4.

Disconnect each fuel injector connector and inspect the two pins inside. My problem was caused from one of the two pins not being secured in each connector, resulting in fuel delivery issues. Pull back the connector boot, reset the locking tab on the pin, reinstall the connector. This resolved my issue and was a simple 10 minute fix in all.

That's the issue I was having (pins creeping out of position) but on the distributor Hall sensor instead. Suspect his issue was different though.
 
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