When I first start my car, a 1992 240, it runs well. However, if I turn it off and leave it for about 5 minutes or so, start it, and try to drive it, it runs horrendously. Eventually it decides to get with it and run normal, but I'm getting tired of going 40 mph in a 60. Ha. Anyway, things I've done to it include:
- Cleaning the throttle body. (It was nasty. It helped a little, but didn't solve it.)
- Cleaned Air Mass Meter. (No change to the situation.)
- Injector cleaner. (Seemed to help a little.)
- Last year the in-tank pump was replaced, so it wouldn't be that.
Perhaps the flame trap should be cleaned or replaced? Also, through research, I learned that perhaps I should check my O2 Sensor.
What else would you guys recommend?
Another tid-bit of information is, that it doesn't do this in winter. Only summer.
Thanks!
Evan Piveral

 

is it throwing any ODB error codes? even if the check engine light isn't on, read and clear the diagnostics on both pin 2 and 6, see http://www.volvoclub.org.uk/faq/Engi...iagnosticCodes

 

Nope, no codes. I've even let the car die on its own to if it'd give me a code, and it didn't.

 

when the engine is hot and you're going to park it for awhile, remove the right passenger footwell right side kick panel, the one right up against the inside of the fender, and behind that is your ECU. car switched completely off. unplug the ECU and use a ohm meter to read the resistance between pin 13 (the engine temp sensor) and pin 17 or 5 (ground) on the harness plug (if you use a small bright flashlight, you should see numbers in there), and with the engine fairly hot, it should be around 300 ohms. come back in a couple hours when the engine has cooled down to ambient temperature and measure it again, it should be something over 2000 ohms depending on the exact temp, or as high as 6000 ohms if its freezing (32F/0C)...

• 32F (0C)-- about 6000 ohms within a range of +/- 10%
• 68F(20C) -- about 2300 ohms
• 104F(40C) -- about 1300 ohms
• 140F(60C) -- about 600 ohms
• 176F(80C) -- about 300 ohms
• 212F -- about 190 ohms

if this reading is way out of whack, then its possible your wiring harness has issues or the engine coolant temp sensor is bad (connection problems are more common than actual sensor failures).

see Engine Sensors for more on this.


does your engine have a cold start injector? this is a 5th fuel injector stuck into the middle of the manifold, but I think by 92 they were mostly history. they are only used on cold starts (newer ECUs double-shot the main injectors to do the same thing).

 

Never mind. The car finally gave me a useful code, and it confirms something I suspected. So, I left it off for like 10 minutes to change to go to work, came out, started it, and it gave me a check engine light. I was somewhat giddy at this. Checked the code, which was 2-1-2. Missing o2 sensor signal. However, my car actually idled well all day today. Even after start and stops. Although, it was a cooler day today.
Edit: Which sensor do I need? And or how can I tell? (two wire vs. three) and where abouts are these located?

 

the O2 sensor connectors are right near the windshield wiper motor on the firewall. there's 2 connectors, a single pin connector with the signal, and a 2 pin connector with the power to the O2 sensor heater.

 

Ah... So a three wire should do.

 

This was suggested to me. Perhaps my catalytic is bad. However when I feel the exhaust it seems to be pushing it pretty well. I don't quite think that it would cause the high idle, but low would be understandable. I still bet its the o2 sensor. But I figured I'd ask.
Thanks!

 

Took my car to a mechanic. My car runs a little better when the AMM is disconnected. So, I'll probably replace that in the near future. Also, I'd like to remove the Idle Control Valve and clean it. Perhaps it's what's throwing the AMM off. I looked up the symptoms of bad idle control valves, and one is bad idling. Do you think I should clean the valve, replace it, or replace it and the AMM?
Thanks.

 

clean the idle control valve. also the throttle body, as they can get gummed up

there's a test mode on the LH2.4 cars (1989+) which pulses the IAC, so if you plug it in, and hook a clean hose up to one end, and blow gently into it, and run that test mode, you should feel your airflow getting chop-chop-choped as it clicks on/off/on/off during the test mode. this is "DTM 3" on the ECU side (pin 6) of the OBD-1 diagnostic block under the hood, see Engine and OBD Diagnostic Codes

 

Iv'e done the throttle body not too long ago. I'll check it again though since it has to be removed to get at the IAC. Anyhow, is it possible that the AMM is trying to compensate for the IAC? Because it did run better when it was unplugged.

 

With the AMM unplugged, the ECU goes into "limp mode" or "open loop mode" meaning it uses a pre-determined air/fuel mixture based on engine speed rather than using feedback from engine sensors (AMM, temp, o2). Since it runs better in this mode, I suspect that you have some problem with one or more of your sensors. Since you are throwing a code for the O2 sensor, start there and make sure it is functioning properly. From there, move onto the others (AMM, coolant temp, etc).

 

How should I go about making sure the O2 Sensor works properly? Also, where is the coolant temp sensor located?

 

the O2 sensor should only have very minimal influence on drivability, its used to fine tune the mixture to maintain the right lean burn such that the catalytic converter performs optimally. If this is an LH2.4 car, the ECU itself will report if the O2 sensor is out-of-range (high or low) via the onboard diagnostic box.

the O2 sensor connectors are on the firewall near the exhaust header, there's a rectangular 2-pin connector for the heater, and a single pin round connector for the actual sensor. disconnect that 1 pin connector, slip in a short thin piece of wire (like one strand from a piece of lamp cord or something), and reconnect the connector. hook up a digital voltmeter to that wire and ground (can't use an old analog meter, this requires a high impedance meter, which digital meters qualify as), on a DC volts scale. start the car, after it warms up and goes into lambda correction, you should see a signal that wanders between something like 0.1 or 0.2V and 0.8 or 1.0V, back and forth fairly rhythmically. if you gently rev the engine up a bit higher, it should swing about once a second, at idle its once every few seconds. if you see that, and the time high is about equal to the time low, then your lambda (o2 sensor) is working.

[this is the test procedure I used on a 1991 mercedes 300E KE-Jetronics car.... its a very similar O2 sensor, so I expect a Volvo is the same, but I've never had to do this on a Volvo].

 

oh. the engine coolant temp sensor is one of 3 sensors under the intake manifold. the other two are 1) the temp sensor for the gauge on the dashboard, and 2) the anti-knock sensor. the dashboard sensor only has 1 wire, the knock sensor is flat with the wires off to the side, while the ECT has 2 wires, and is /probably/ the rearmost of these sensors, but I've seen suggestions that they move around somewhat randomly.

 

I'll trouble shoot the o2 sensor when I can. I checked the IAC today, and it was fine. I used some lengths of wire and the battery. Opened and closed like it should. I bid on an AMM on ebay. Even if it doesn't fix it, it's good to have a spare. One thing that concerned me was, when the mechanic I took it to to troubleshoot it, was, he was unplugging and plugging the AMM while the car was running. I've read elsewhere that this can ruin them. Anywho, next thing I'll get is an o2 sensor. I've seen that you can inspect o2 sensors by their looks. I may visually inspect it as well.

 

only time I've had to replace O2 sensors is when the car was having trouble passing smog. actually, I think its a good idea to replace them every 100-150k miles as they start to get tired and slow about then.

never had one cause any sort of running problem. you should be able to unplug it and run just fine (but not pass smog). LH2.4 will throw a check engine light and code, of course.

 

Yep. Car runs nicely when it's unplugged. Albeit, it is a little rich. I'll just replace all the sensors. It's not gonna hurt, and should probably be done. I must also do new spark plugs. I haven't done them in the year I've had it, and I'm sure it should be done.

 

if/when you get spark plug wires, be sure to get the Bougicords cord set (ipd and fcp sell them). rotor and cap should be Bosch. plugs can be bosch or the ngk equivalent, I've had good luck with both.

 

Indeed. I was looking at them on FCPEuro. I just went out and tinkered with it a little more. I've noted that, when the o2 sensor is unplugged, idle steadies out to 1000 RPMs. When I drive it w/o the o2 sensor, it's a big doggy, but better than when it's having a bad spell of running. I believe the next time it's running horrendously, I'll unplug the o2 sensor and see if it improves. So, I shall buy an o2 sensor, and keep the AMM as a spare. Even though mine is probably good, I already bid on it. Ha. The only thing that confuses me is, buying an o2 sensor. It looks like you can get just the sensor, and you solder it to the old wiring harness, or there are extremely expensive ones with the harnesses. Which should I get? It's so odd.