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1989 740GL non-turbo, auto trans, 110k total miles
A few weeks ago I transported the car to our AZ condo. It was running like a Swiss watch, but started to get hard to start when hot, now requiring half throttle to start it after being driven. Cold start is still instantaneous.
Then it started stumbling when put into, or taken out of gear. At that point, once it regained its idle speed, it idled smoothly.
Now the idle speed varies even in neutral, or in drive while stopped. It still runs fine on the highway, but my wife (who is AZ using the car) is freaking about having it strand her. Unfortunately, I am in TX 1000mi away, and because of surgery can't get out there to look at it.
I've done a LOT of reading (FAQs, Forum posts), and am guessing it's probably the Idle Air Control valve (idle stabilization circuit), or remotely, a bad engine temp sensor (under #3 intake runner), but can't be sure, of course. Another possibility is the TPS, throttle position sensor not switching to idle mode.
We see that it is SUPPOSED to have a start injector, but can't find any installed. Anyone know for sure if there IS one on the LH2.4?
The engine doesn't act like it's an ignition or injector problem, as it never has a "hard" miss even under load.
Our son is there and is willing to do some troubleshooting if I can get him data.
From what I understand from extensive reading (and see), the car has the Bosch LH 2.4 Jetronic system, with a TWO terminal IAC. I read the resistance of the IAC motor should be 14-18ohms. Not sure if applying 12v to the terminals momentarily to check operation is permissible. Son already flushed the IAC w/ brake cleaner, but read that it could take several flushes w/ carb cleaner, though he says he can reach in and the vane appears free. Because of age, we're reluctant to pinch off the IAC hose tightly as a diagnostic procedure, but maybe we could plug the ends or something.
The car has a "Check Engine" light installed, but while it has occasionally started coming on during start (it didn't use to), it always extinguishes quickly in a second or so and doesn't leave a trace.
Any personal experiences with such symptoms, or suggestions would be most helpful.
Thanks,
Bob
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Have you checked tested or thought of the Ignition Module - Bosch 0227100124, mounted on the left (driver's) side fender wall. This is often overlooked, the hot vs cold conditions lead me to believe this is your problem.
Good luck
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Hey BobbyC,
hmm, I've had similar problems on my '89 740-
did you check the OBD? check the readings, and it will tell you which component is not functioning correctly.
If the oxygen sensor is not working correctly, (with the very hot air in AZ. it may affect the sensor) and that could affect the IAC and the AMM.
If the IAC has been cleaned and replaced and the oxygen sensor has no readings, it could be an air leak. Take a look at the FAQS on ways to check for air leaks.
That''s about all I can suggest- good luck and let us know how the issue was resolved.
Volvosenior.
--
89-740 GLE;91-940 Sedan ;98-V90 Wagon ___ all running well
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O2 Sensor fairly new, though that doesn't mean it can't have gone bad. I haven't yet checked it, of course.
OBD is early on the list, and will have son who lives near where the car now "living" (1000mi from home) check OBD, clean IAC again and power it w/ OBD function check utility program, clean the throttle body, check for a bad (leaking) fuel pressure diaphragm, check the ECT sensor, and test the TPS setting at idle.
Some have suggested that Radio Suppression and FP Relays can act funky when hot as well.
Hopefully, one of those will be the culpret, and I'll post when it (and I) are happy again.
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Hi late to this thread, had a friend with a 700 turbo some years ago who battled a problem like this for a few months, he sold the car and then found out the problem was the connector for the coil. One can use a small flat blade screwdriver to pry the female connectors in a bit for better bite on the male plugs.
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I have had a similar problem with my 89 740 non-turbo. Check the Air Mass Meter. Install a known good one and drive for a while. Barring that, remove the connection to the AMM, start the car, then see how it idles when hot. I'll bet the problem is with the AMM.
el Raidman
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Thanks-
Before I left AZ, I did that (when it had the hard hot start, and stumble when put into/out of gear problem, but the idle was still steady), and as I remember, it was AWFUL w/ the AAM unplugged, but smoothed right up when plugged back in.
I'll have our son do it, though.
The AAM was replaced w/ a new OEM unit about 20k miles ago, and before transporting the car, I sprayed the hot wires with CRC Air Mass Sensor Cleaner (though at the time the car was running/starting perfectly).
Since being in AZ (about a month and maybe 300mi of driving), the problem has progressed from only hot-start problem to other symptoms slowly.
Bob
How SHOULD the car run w/ the AAM disconnected?
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Welp, take a look at (http://www.brickboard.com/FAQ/700-900/HotStartProblemQuickReferenceGuide.htm) as well as the greater (http://www.brickboard.com/FAQ/700-900/).
You can damage the AMM (or MAF) sensor by unplugging/plugging with the engine running. Possibly the fuel control system computer, too.
Air (vacuum) intake leaks?
Faulty engine control systems coolant temp sensor.
Fuel pressure regulator leaking fuel into the air intake port (manifold).
Also, PLEASE (http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm)! Check them codes!!!!!
The 700-900 air box also has a flap valve that controls whether air intake comes in fresh of off the exhaust manifold pre-heater intake as controlled by a sping loaded thermostat. At least disconnect the pre-heater solder accordion hose from that shroud pre-heater plate on the exhaust manifold.
Clogged fuel filter. faulty injector relay, fuses, weak fuel pump(s), leaking injectors ... and on and on. Search the brickboard. Check them OBD codes and report back!!!!
Kitties are SO DAMMM FUZZY!!!!!!
Keep cool!
Cool and Misty Evergreen Tree
--
Cool and misty!
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Welp, take a look at (http://www.brickboard.com/FAQ/700-900/HotStartProblemQuickReferenceGuide.htm) as well as the greater (http://www.brickboard.com/FAQ/700-900/).
XXX Have done that and distilled it into the questions I asked and the areas I am looking at, actually.
You can damage the AMM (or MAF) sensor by unplugging/plugging with the engine running. Possibly the fuel control system computer, too.
XXX Thanks-Beside the previous poster, I have seen that recommendation before.
Air (vacuum) intake leaks?
XXX I already instructed son to check spraying around gaskets and such. If there WERE a leak, I suspect it would create a lean mixture that would cause a "miss" at idle rather than a wandering rpm, but you never know. Also having to crank a hot engine w/ open throttle would appear to suggest too MUCH fuel and not enough air, but again, hard to say.
Faulty engine control systems coolant temp sensor.
XXX ECT was my first thought at hard-tot-starting (too much fuel), but now the problem has progressed quickly to unstable idle, and stumble when changing the idle-load on the engine.
Fuel pressure regulator leaking fuel into the air intake port (manifold).
XXX Never thought of that w/ a bad regulator diagphram. Will check that one for sure!
Also, PLEASE (http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm)! Check them codes!!!!!
No codes shown. I understand codes will only show if the "Check Engine Light" is actually displayed, and they go away when the light goes out (UN-like OBD II systems that retain a code)?? Can you verify that codes ARE retained even if there is NO Check Engine Light illuminated?
XXX BTW, here is the only chart showing codes (copy/paste):
http://screencast.com/t/UWmfWNMXd1
Are there more codes possible than this w/ LH2.4?
The 700-900 air box also has a flap valve that controls whether air intake comes in fresh of off the exhaust manifold pre-heater intake as controlled by a sping loaded thermostat. At least disconnect the pre-heater solder accordion hose from that shroud pre-heater plate on the exhaust manifold.
XXX Easily done.
Clogged fuel filter. faulty injector relay, fuses, weak fuel pump(s), leaking injectors ... and on and on. Search the brickboard. Check them OBD codes and report back!!!!
XXX- Clogged fuel filter: Replaced 300mi ago after tank flushed and new Bosch fuel pump/filter installed. Plus, if it were clogged, I doubt it would run perfectly under load at any driving speed when fuel demand is MUCH higher than at idle?
XXX Injector relay. Again, would it run under load at 60mph if the relay were faulty?
XXX Thanks, Bob
IS there a start injector on the LH2.4 system? I cannot find one. Some diagrams say "yes; others don't say "yes/no."
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How about the radio suppressant relay, which sends current to the injectors. When was the last time you replaced this one? I've had a no-start condition with this relay either burned out itself, or the connections push out of the silicon insulation. good luck,
el raidman
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How about the radio suppressant relay, which sends current to the injectors. When was the last time you replaced this one?
XXX- I have to admit it's probably the original one.
I've had a no-start condition with this relay either burned out itself, or the connections push out of the silicon insulation.
XXX-The car has never NOT started. It's just hot it needs throttle and cranks for 2-3 seconds when hot (and now idles poorly, and surges when shifted into/out-of gear).
Cold, the car never fails to start on the first revolution.
XXX-Does the Radio Suppression Relay cause wandering RPM at idle?
I never quite understood the naming of this relay, anyway!
good luck,
el raidman
XXX- Thanks-Bob
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