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I've been working for a long time to fix a problematic idle in my 1982 k-jet MPG. The IAC and throttle switch are both working well, as is the fuel system, as far as I can tell. I think I have kept vacuum leaks at a minimum.
I believe the problem is electrical, having to do with the ECU which controls the CIS. I know this ECU takes input from the TPS, the A/C, and the ignition coil, as well as a temperature sensor. That's where I think the problem lies. See, the idle is fine before the engine gets hot. Once it's hot, it's as if the ECU tries decides what it's going to do (when I depress the clutch), but in the end it's not opening the valve enough--the car almost stalls, sometimes does (when you've been driving for 30 min or more). If it doesn't stall, the ECU hunts around for a better setting, and sometimes finds it. Note: none of this occurs with the AC on. It's as if the AC signal to the ECU tells it to override whatever is causing the problem.
So I think the problem could be the temp sensor, can someone explain where it is? And where does the wiring go--I'd like to inspect it. Is there a way I can test this temp sensor?
Any other suggestions about what's causing this problem?
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Thanks to all (especially Mario)--I think the problem is finally solved!
I set the baseline idle this afternoon and simultaneously discovered that the accelerator cable was out of adjustment. I did end up raising the baseline idle significantly (it wouldn't even run in baseline mode the way it was set before).
I also replaced all the fuel injector seals. I'd bought some replacements years ago, but never put them in. I checked for leaks while I was in there, and found some. I have a hunch there may still be a vacuum leak somewhere else.
Anyway, I feel like I've got a whole new car! Thanks so much for all your help!
-John
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posted by
someone claiming to be chandrakumar
on
Thu Feb 23 03:48 CST 2006 [ RELATED]
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Very interesting. My wrong theory about what might have been diddled was exactly the opposite, but LUCID had posed the too-lean for correction idea which turned out to be the case as a result of the linkage holding the throttle open as Mario suggested. Good learning example here.
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Thats great. Just give that K-jet some TLC and they run forever. Good luck.
Mario
--
'I've always been crazy, but it's kept me from going insane' Waylon Jennings
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posted by
someone claiming to be 81242DLB21FCA
on
Tue Feb 21 05:07 CST 2006 [ RELATED]
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Sorry I can't give pin numbers but the ecu for the idle control gets the idle speed reading from the low side of the coil, same signal as the fuel pump relay.
Also, if you just disable the idle control system according to base idle adjustment procedure and the problem is no longer present that will help to confirm the source of the problem.
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i'm confused?...
i don't think the k -jetronic has a ecu ?....
CIS system is just mecanical not electronic ...
if it has ecu where is it ?....
sorry for my confusion ..
coper.
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Hello,
This is the confusion:
CIS can mean Continuous Injection System or K-Jet. This by itself does not have an ECU. Now add an Oxygen Sensor (Lamda) and you get an ECU for engine control.
CIS can also mean Constant Idle System which is used on both K-jet and LH. On a K-jet this means that the ECU also controls engine idle speed. This was introduced in 1981 on the MPG models. Please dont ask what MPG means because it could start a whole new thread.
So there you have it, a CIS K-Jet that has a CIS system. They both use a single ECU. By the way the injection system should be called CI (Continuous Injection) and the Constant Idle System Should be called CIS. Hope this clears everything up:).
Mario
--
'I've always been crazy, but it's kept me from going insane' Waylon Jennings
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Thank you very much ...
now... what did you say MPG means? ... (just kidding)
coper.
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Hello,
Having the same car for about 22 years I can give you some info. The temp sensor is located on the block next to the distributor on about the number one cylinder. It has two wires and acts as a variable resistor that changes with engine temperature. When the block is cold on an 82 you will get about 2000 to 10000 ohms. When it is fully warmed up the reading is about 300 or less ohms. The ECU sees these changes and corrects the idle accordingly using the Idle Control Valve. Use any Ohm meter to check the resistance as the sensor warms up. If you want to you can go across pins 9&11 on the Ecu to read the value changes. If the readings are not right check the harness wires to the sensor for problems. If the unit is bad make sure you get the one for an 82 not an 81 (they have different ohm values).
As far as the idle issue have you done the base idle adjustment?. If the base idle is off (low) the CIS will not have the proper control of the idle. This causes some strange idle changes. Find a Bentley,Haynes, or Volvo Green Manual and set it up to spec then see what happens. I assume you have cleaned the IAC also. Let us know how you make out.
Mario
--
'I've always been crazy, but it's kept me from going insane' Waylon Jennings
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Let me add one thing. The best way to check the sensor is to the the connector off the sensor and read the resistance cold. Then put connector back on and let the car fully warm up. Then shut the car down and take the connector off again and read the resistance hot. Compare the actual readings to the values I gave you before and see if they match. Doing this way the ECU is not attached to confuse the readings. I am now going to bed (2am) because at my age it is way past my bed time. Good luck.
Mario
--
'I've always been crazy, but it's kept me from going insane' Waylon Jennings
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Thanks Mario, I just went out and tested the resistance on the sensor with the engine cold. It came in at around 23000 ohms, if I was reading my meter right. Can that be correct? Would that indicate a bad sensor? With the sensor plugged in I started the motor and it idled fine (as it always does when it's cold). Then I tried unplugging the sensor and starting the engine--the idle immediately went to 2500 rpms. So I can conclude that the wiring is at least somewhat in tact, and the sensor is not totally shot. Could it be "fouled" or something? I'll test the resistance tomorrow when the engine is warm.
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Hello,
Your reading is high, but the fact the car races when the sensor is off means the sensor and wiring seam to be OK. You might want to check the resistance value again and make sure its not 2500 for ohms your reading, which would be about right for about 70F. Go ahead and check the warm value, but since you car goes to idle it is most likely working properly.
I think you will have to set the base idle to spec to eliminate that as an issue. Then work on from there. Let us know how you make out.
Mario
--
'I've always been crazy, but it's kept me from going insane' Waylon Jennings
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Mario, how do you set the base idle? I thought that this model didn't have an idle adjustment screw. Am I wrong, or are you talking about something else? I'd don't have one of the manuals that covers this engine.
I'll check the warm resistance this afternoon and post again.
Thanks for all your continued help.
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posted by
someone claiming to be 81242DLB21FCA
on
Mon Feb 20 09:21 CST 2006 [ RELATED]
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The base idle is set with throttle stop screw, not an idle mixture screw. It is done with the CI valve disabled. The procedure should be in any manual.
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I'll look into that base idle adjustment.
Meanwhile, I got the reading on the temp sensor. About 2500 ohms cold and 250ish ohms hot, at the sensor. Looks like it's working fine.
Then I accessed the ECU in the kickpanel, hoping to get the exact same resistances there across two of the pins. I remember you saying pins 9 and 11. I tried these on the plug and found no reading (not a circuit). Pins 9 and 11 ON THE ECU had a resistance of about 540, I think, BUT THAT WAS WITH BOTH PLUGS UNPLUGGED (so it wasn't coming from the sensor). I couldn't find the resistance from the sensor anywhere--what gives?
P.S. thanks for confirming that I had my ackronyms right--that's always a challenge:)
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Hello,
According to the Volvo book the sensor goes across pins 9&11. They should a red and blue wire. If the motor is going from high to low idle during warmup, the sensor is doing it's job to the ECU. Check you E-mail I sent you some info on the base idle.
Mario
--
'I've always been crazy, but it's kept me from going insane' Waylon Jennings
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Thanks Mario. I got your email. Which Haynes manual is it? It looks very informative--is there more info in there about the CIS ECU and pins 9 and 11. I'd still like to know how to get the temp sensor resistance there. I just can't get over the fact that my idle problem is entirely temperature related; it gradually gets worse as the engine gets hotter.
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"I just can't get over the fact that my idle problem is entirely temperature related; it gradually gets worse as the engine gets hotter."
The Lambda ECU also changes from a cold default (fixed-rich) mixture to (varying-leaner) O2 sensor-controlled mixture as the "engine gets hotter". Maybe it's rich enough when cold to mask the effect of vacuum leaks, such as injectors seals, etc.
You might try running it "open loop", with the O2 sensor unplugged, just to see if the ECU's default (steady, mid-range) mixture control has any effect.
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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Bruce, I tried your suggestion--unplugging the O2 sensor. It made the engine idle a bit high when cool, but once warm everything was operating just as before.
Does that rule out a mixture problem?
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Does that rule out a mixture problem?
Not entirely, IMO. But I wanted to suggest another possibility, based on there being so few reported problems with the CIS ECU and system in general (maybe one here in the past couple of years).
Reviewing this long thread, I'd suggest:
1) getting a temp sensor reading from ECU pins 9 and 11 to rule that out
2) cleaning the IAC valve (search or see 700/900 FAQ for methods) or swapping in another one
3) clean throttle body
4) set the base idle speed (ask for procedure in a new post, or get the Bentley 240 manual)
P.S. It may not be relevant, but unplugging the O2 sensor should not have raised the "cool" idle speed any, at least not in the first few minutes. Because the ECU doesn't look at the O2 signal until engine temp gets up to 65°. Before that, the O2 sensor is ignored (same as if unplugged).
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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Hello,
It is the Haynes manual for the Volvo 240 1976-1993 and yes it has alot of detail on all aspects of the car. There is also the Bentley manual for the 240 which is considered the maintenance bible by many. If you do any work you should have one or both.
As far as the temperature increase bringing on the idle problems, that is logical if the base idle is not set. The CIS makes small corrections at idle when the car is warm. If the base idle is to low at normal temperature, the car will stumble at acceleration since the CIS can not bring the idle up to spec. When you switch on the a/c the ECU brings the idle up approx 100+ RPM's, which puts into the spec range. When the a/c is off the idle drops. If your a/c works like mine even when the compressor is not cycling but the a/c switch is on, the RPM's go up slightly and go up even more when the compressor kicks in. You could still have other problems, but set the idle up first and see what happens.
Mario
--
'I've always been crazy, but it's kept me from going insane' Waylon Jennings
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posted by
someone claiming to be chandrakumar
on
Tue Feb 21 06:43 CST 2006 [ RELATED]
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Two things could put k-jet CIS out of range of the idle valve correction when motor warm, rich mix or insuff. base idle air. Clues might be in past attempts to diddle mixture or test lambda.
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