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This problem has driven me nuts (and broke) for months. My 1992 745 stalls or runs rough at idle. Runs fine at speeds over 750 rpm. Gets good mileage and has lots of pep. The car uses the Rex/Regina engine management system. Had a new head gasket installed last Sept. Ran fine. Went through a deep puddle in October. Engine stalled out, restarted and dried out, then stalled and went dead four days later. Mechanics get it going but the idle has been rough and stalling problem resurfaces intermittently. No error codes, ever.
I have replaced:
Catalytic converter, Fuel pump; fuel pressure regulator; engine temperature sensor; oxygen sensor; fuel filter.
We have checked fuel rail pressure OK. Disconnected the cold start valve and re-flashed the computer module. Fuel injectors cleaned. Throttle body and switch assembly cleaned. Auxiliary ground run from battery negative to all ground points on chassis, firewall, intake manifold etc.
Idle air motor swapped for a known to be good.
Vacuum lines checked.
After replacing the O2 sensor the car ran fine for a month. Then started stalling again. The stalling seems to start after the engine has been running about 15 minutes. We replaced the new o2 censor with another one, but that did not correct the problem. We swapped fuel computer modules which didn't help either.
State emissions report came back showing the car was running rich.
I am not running rich. I am going broke trying to solve the problem.
What did we miss?
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posted by
someone claiming to be mknabyixyce
on
Mon Jul 19 02:54 CST 2010 [ RELATED]
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posted by
someone claiming to be arthur240
on
Mon Jul 19 03:26 CST 2010 [ RELATED]
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i am looking forward to your message but couldn't find it when I linked.
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It's either nonsense, or as I am coming to believe, a most dangerous virus. Don;'t go to any link.
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posted by
someone claiming to be fixit2002
on
Thu Jul 15 01:51 CST 2010 [ RELATED]
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Check the air filter box to be sure the temp sensor is not stuck and pulling heated air all the time. Remove and clean ALL the grounds on both inner front fenders.
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Oh yes, did I neglect to mention that we also installed a new high voltage spark module and new wiring and a new distributor cap. But that suggestion is a good one. I will clean the high voltage unit forthwith. Thanks
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Thanks to everyone who responded to this post about Rex/Regina problems. After replacing everything electronic and in the fuel system, slowly and painfully over a year and a half, the last repair did the trick. Replaced the radio interference relay, which was screwing up the fuel injectors, and cleaned EVERY connection point. That and a set of new spark plugs restored reliability and performance. Starts at zero degrees every time and uses less gas. That relay was tested and swapped out early in the game, but didn't fix the problem. Go figure. Now I am good for another 200,000 miles or so. As Sherlock Holmes stated famously, when you have eliminated every possibility, the remaining alternative must be be the solution.
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Here's something that won't cost anything to try....
Take the coil/power stage unit apart and clean the internal connections (two or three of them as I recall) and clean all mating surfaces INCLUDING the chassis mount surfaces. This is a known issue with Rex-Regina cars.
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This post has been marked as an answer to the original question.
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"Take the coil/power stage unit apart and clean the internal connections (two or three of them as I recall) and clean all mating surfaces INCLUDING the chassis mount surfaces. This is a known issue with Rex-Regina cars."
Hi Chris,
Your tip to clean the coil terminals is a good one for any no-start, but I don't think you can really call it a Rex "issue". I've had coil connections stop a 240 (Bosch) car too.
And the chassis mounting & grounding made no difference at all when I tested that theory on my 940. It would start and run even with the Coil/Amplifier unit completely removed from its mounting and isolated from any ground, as long as the black ground wire on the fuel rail was connected.
See THIS POST to Chris Herbst for test details.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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Bruce,
I guess I called it a "Rex issue" because I think a lot of people don't consider that they can take the things apart and clean them. You're right though, the Bosch coils aren't at all immune to bad connections or internal faults. Believe me, I'm not one that needs to be convinced that it's OK to own a Rex-Regina car. I'm on my second one, a 92 745. We drove our 90 744 for 16 years - replaced the crank sensor one time and cleaned the coil once. That was it for ignition issues. On the fuel side of the house I think I replaced the RSR and FPR once each (certainly not Regina-only issues). I replaced the fuel pump once at ~150,000. Original O2 sensor still read good after 175,000+ miles. Personally I like not having to fear a failed mass air meter ($250 + ??), or maintaining two fuel pumps.
Interesting research on the coil grounding issues. Thanks for that. When I cleaned mine I cleaned everything included the chassis mount and all I knew is that it worked OK afterward. So not knowing what really fixed it, I've suggested cleaning the mount to people since then. Supported by your experiment, I think it's not a bad idea to clean the chassis mount just to provide some grounding redundancy in case the wire fails.
Take care...
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All good suggestions. The high voltage module is new, as is all the wiring, including that long lead to the bottom of the distributor. I will check and clean all connections again. I changed the air filter (dirty) and replaced a vacuum line that was cracked. I also shut off the hot air intake that enters the air filter basket. Couldn't tell if it opens and closes properly. It seems to be running better - idling more smoothly and not knocking and stumbling on acceleration. Then again, I have been there before also. Thanks to everyone for the suggestions. As Sherlock Holmes believed, eliminate every possibility until only one is left. That will be the solution, no matter how unlikely it may seem.
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