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240 Rough start LH2.4

D.E

tvåförti
Joined
Sep 15, 2010
Location
Mora, Sweden
Hello!

My LH2.4 equipped 245 is having a bit of an issue. This has been going on for a year or so and has not been getting worse.

When cold starting, summer or winter, it wants to stall right away. If I counteract with the gas pedal it?s fine. If I let it stall it?ll usually crank right over and idle on the second attempt.

When hot starting it can sometimes take quite a few cranks to get it to fire and if I let the key go too soon it?ll stall and flood and be really hard to get going.

The idle seems pretty rough but I don?t think I?ve ever had a redblock idle smoothly.

I have no fault codes.

So far I?ve replaced:
O2 sensor
Spark plugs
Intake gasket
IAC valve
General tuneup

So what do you think it might be? Intank pump? Leaky injectors? Any suggestions are appreciated.

Thanks.
 
When engine is cold, remove spark plugs, then turn ignition-key to on position....fuel pumps should run for several seconds (do you hear them?).

Then do a smell test on each cylinder, with your nose
 
When engine is cold, remove spark plugs, then turn ignition-key to on position....fuel pumps should run for several seconds (do you hear them?).

Then do a smell test on each cylinder, with your nose

Good tip, will definitely try that. Thanks. :)
 
If the above doesn't work, consider replacing ECT sensor which was my source when I had similar issues. With the last 240 rolling off the line 27 years ago it's not unreasonable for our sensors to be aging out.
 
How does your EFI fuse look?

Ours looked great from the outside, but caused issues similar to yours. When I tried pulling the fuse, it was all melted inside the holder. Pulling it out and reconnecting a few times was a good temporary fix, but nothing beats cutting that sucker off and replacing it with a weather tight holder. The car starts and runs so much better after dealing with that crap for about a year. lol
 
This car has been used very little the last few years but it has now become the daily driver again. First day driving it to work and it refused to start in the afternoon. Turned out the EFI fuse holder had melted as volvowagoon suggested. :-P

The cutting out, hard starts and no starts are now completely gone but it still has a rough idle. I know Redblocks always idle a bit tractor-like but this one is particularly lumpy. It keeps steady revs but feels like one cylinder misses every few seconds, unevenly and not in a rhythmic fashion.

I did a tuneup and it now has new wires, rotor, cap and air filter but that didn’t make a difference. Previously replaced the plugs, intake gasket and IAC valve. Not sure where to go from here. Throttle body gasket? Intake hose? Any other suggestions?

It has an A-cam and the valves are shimmed to spec.
 
TPS working properly? Take out fuel rail put all injectors in plastic soda containers and then do that LH 2.4 test where it will fire the injectors and you can watch them spray or not spray or watch them leak down.

How does it idle when you unplug the AMM?
 
Things to check for smooth idle goodness:
1. Injectors are clean and flowing properly.
2. No air leaks between the MAF and the cylinder head: injector o-rings, gaskets, vacuum hoses, etc.
3. Coolant temp sensor not in correct range: I've had 2 new temp sensors that didn't have the correct resistance when below ~65?F and the car would idle like it had a really big cam in it, but would run fine once the coolant got warm. This was fixed with a VDO sensor that had the correct range.
 
Things to check for smooth idle goodness:
1. Injectors are clean and flowing properly.
2. No air leaks between the MAF and the cylinder head: injector o-rings, gaskets, vacuum hoses, etc.
3. Coolant temp sensor not in correct range: I've had 2 new temp sensors that didn't have the correct resistance when below ~65?F and the car would idle like it had a really big cam in it, but would run fine once the coolant got warm. This was fixed with a VDO sensor that had the correct range.

Had the same issue with my car. Turns out the intake hose between the MAF and throttle body had several small holes worn on the bottom. Only saw them when I lit a flashlight inside.
 
Lol ‘rough running’ FI redblock? What are you doing wrong or neglected pos 500 dolla holla cars are you buying much like my various field rat money pits that take a lifetime/life-sentence to properly fix up/sort out where every repair turns into a mini-restoration? :rofl:? :roll:

Is the compression, valve lash (& leakage?), vac leaks & sensors all working? :lol:

I mean, I get it…the front mount distributor cap that can trap moisture & cause it to miss when Parked over damp/snowy ground vs. the B18/B20 dist in a nice oily cloud by the crankcase vent middle of the engine w/plastic crankcase vent box/no more thru-flow crankcase venting for emissions sux, but uh…if the belly pan is sealing tight & radiator is blocked off for winter, & it’s boockheated w/working airbox pre-heat it should achieve good longevity & Economy?

This all said the early LH2.4 ecus, late wiring harness with shady crimps or corroded connectors on the late 1993 cars or more electrically complicated adaptive memory 2.4 cars, old beat cars, bad sensor readings some of the time, worn/uneven compression engines (n/a -‘84 redblocks are pretty tough & hard to kill at least…tho B230s are beam counter garbage :e-shrug:?), vac leaks, dirty injectors etc they’ll run like poop?

I hate the adaptive memory & prefer the LH2.2 & earlier manual window stripper DL cars. Adaptive memory it’s harder to nail down correct specs for all the sensors & relies on its diagnostic loop which mostly sucks on most OBD1 cars (not that I want the ecu to do anything besides make the car/engine go at all/don’t want full integration).
The 81-87 2.5Bar fpr has a lower failure rate & stirs the fuel less / stresses the fuel pump less on the halfass 240 fuel tank revision compared to the 88+ 3-bar setup…

That said, they *finally* galvanized all the body & stiffened up the chassis such that the windshields were less prone to leak with the flexible flier opening crappy 240 chassis & integrated flush rubber gasket & better butyl goop job 1989+…

…they had it right for chassis stiffness, body proportions & maneuverability & extruded super toxic rubber gasket -‘69 on the original 140 design…but then it wouldn’t pass new safety regulations 1970+ & they cheaped out.

Only took Volvo until ~1989 to properly rust proof (hot galvanize the whole car & better get the water to fall thru it drainage wise w/proper primer & paint) & stiffen the cheap flexible flier long ‘safety’ v6 engine compatible McPherson 240 front end up with thicker harder inner metal in key locations up front…only took the stooges/special needs/special olympians @ Volvo 20+ years from 1969 when they had it mostly right (other than the Hot galvanizing, seam sealing & drains/smaller raised separate cowling openings). :roll:

Paging cleanflametrap for his Bosch FI homebrew laboratory factory test bench & picture gallery… :lol:
Accepting donations now for the $250,000 of time/trouble effort it would probably take to acid dip, hot galvanize, & epoxy primer & super toxic electrostatic paint a straight 145 recombining the best parts of all of them ‘68-‘93

It should start smooth if it’s in good repair, tho it won’t fast idle @ a little higher rpm’s that Bosch designed them to to burn leaner appropriate to ambient air temps /not wash the thing down idling or crank a solid few rotations to build oil pressure with 0w-30 quality oil in extreme cold before it fast idles on the EFI Volvos 1970-1995 & the wax pellet for the airbox t-stat doesn’t last very long…
 
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Do you have the values for the ECU temp sensor? After I replaced mine -- I also checked the signal from the head to the ECU to ensure no breaks -- it now fast idles when started in cold(er) weather.

You could check for some vacuum leaks, like throttle body gasket, by spraying carb cleaner while it idles and see if RPM increases. IMHO, if a car has been sitting for, as you mentioned, years I would be concerned with dried/hard hoses and electric connection corrosion.
 
Lol ?rough running? FI redblock? What are you doing wrong or neglected pos 500 dolla holla cars are you buying much like my various field rat money pits that take a lifetime/life-sentence to properly fix up/sort out where every repair turns into a mini-restoration? :rofl:? :roll:

Hey! This is a $600 POS. :cameron:

Do you have the values for the ECU temp sensor? After I replaced mine -- I also checked the signal from the head to the ECU to ensure no breaks -- it now fast idles when started in cold(er) weather.

You could check for some vacuum leaks, like throttle body gasket, by spraying carb cleaner while it idles and see if RPM increases. IMHO, if a car has been sitting for, as you mentioned, years I would be concerned with dried/hard hoses and electric connection corrosion.

How do I measure the sensor? Ohm values hot/cold?
 
It?s not really rough running, just that I think the idle should be more stable.

I?ve noticed that every so often when I go to start it, it?ll fire up on like the first revolution. Could this be a sign of leaky injectors dripping into the cylinder?
 
Usually if injectors are leaking down when turned off it makes it hard to start the car after a shut down like ten minutes later cause it's flooded but usually will then start after sitting a while.

As I posted above, if you can find 4 clear plastic pop bottles you can do that injector test see how they spray, see if they leak down after turning off.

4. Diagnostic Test Mode 3: Injection System Component Activation Test

Turn the ignition ON to KPII and install the cable into socket 2 for fuel-injection-related tests.
Press the button three times for one second each time (waiting between >1 and <3 seconds before pressing again)
The diagnostic unit then sequentially tests the following components: engine coolant fan (if equipped), fuel injectors, idle air control solenoid valve, carbon filter solenoid valve (if equipped), cold start valve, radio suppression relay and fuel pump. No code is produced: you have to listen or feel each in turn to make sure it is operating.
Exit by switching off the ignition.
 
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Do you have the values for the ECU temp sensor?

I do.

rZfBZbR.jpg


Now you do, too.
 
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