4.3 EFI Will Not Idle!!! Not IAC Need Suggestions!

C

chris41483

New Member
Jul 23, 2008
256
Selma, Alabama
Boat Info
2000 Sundancer 270
Engines
twin 4.3 efi, Alpha 1
I have a 4.3L EFI engine that will not idle. Actually, it refuses to run at all below about 1200rpm. Whenever the engine drops below 1200 (approx), there is one long beep (same beep heard upon turning the key on initially), and then the engine dies. Above 1200, I have no issues whatsoever; good smooth power. I replaced the IAC thinking that was of course my problem, but to no avail. Money down the drain...again! I took the flame arrester off and started the boat this afternoon, and watched the injectors behavior. Immediately after the beep (actually during, the beep is long), the injectors stop spraying, and engine dies. replaced fuel filter today, no change. I believe it has to be electrical, but do not have enogh knowledge in this area. I have spent the past few hours searching this site as well as google, and have had no luck. Anybody know if this is more common than I have found? Can a sensor do this? All gauges read normal when this happens.


Any help greatly appreciated!!!!!!:huh:
 
Hi Chris,


Just had a look at the trouble shooting.....24 pages! Could be anything from low fuel pressure to a sensor.
Step 1 is to ...
Was the “On-Board Diagnostic” (OBD)
System Check performed?

I would give your mechanic a call about now unless you can borrow a OBD reader?
You could spend more money trying to fix this yourself than a merc mechanic will cost you for 1/2hr of time to tell you the problem.
Modern engine controls are great....until they stop.
All the best. Mike
 
It sounds like either the speed sensor on the crankshaft or camshaft sensor. Best way to tell it use the OBD tool. As annie said, you could do a lot of parts changing before you find the problem. I don't beleive it's a component issue but a component controller issue: sensors, harness, ECM... ??
Just my opinion.
 
What is the oil pressure? The fuel pump has a low oil pressure cut off. The alarm you hear when starting the motor is low oil pressure, then it clears once enough pressure develops (should clear pretty quickly). There is an oil pressure switch that shuts the fuel pump down when oil pressure is low.
 
Thanks for the input guys!!!!

I live in the middle of nowhere, and the shop I use is very nice, and very cheap, but it takes them forever to get around to these things. I have a 200 mile trip coming up next weekend, and they can't look at it before then. I can use the boat the way it is (annoying, but it will work). That being said, I would like to do as much troubleshooting as I can before the trip, b/c the marina doesn't have time to look at it.

I have 2 engines, so the parts swapping/troubleshooting isn't going to cost me anything but time. Just looking for suggestions on where to start. I will start with the oil pressure switch, I suppose it could be worn, but the engine has plenty of pressure.

It is hard for me to imagine it is anything other than some type of pressure switch. It seems like for the problem to be repetitive in the same manner, it has to be intrinsic of the engine parameters at low speed. ie...a clogged filter would behave the same at any engine speed, and a wiring short behaving this way would be too much of a coincidence.

If you have any more ideas, please let me know, I am no expert, and have been screwed by my own assumptions before!
 
Just to add a little something for your own piece of mind/clarity. You have an oil pressure switch, as mentioned by Good Grief. You also have an oil pressure sender that reports to your gauge. The gauge can read fine, even though the switch is blinky.
 
ok, did some parts swapping; traded the map sensor, iac valve, and oil pressure switch with the starboard engine. both engines unaffected. I have been messing with this thing all day. why can't I ever have an easy problem!!!???
 
Here's some more stuff to check, It's straight from the manual.... Let us know if you have a manual and I'll stop posting.
Sounds like you have had a rough day... Hope you have a better one tomorrow!


Check for proper operation of Ignition Con-trol (IC) circuit and the Knock Sensor (KS) circuit.
Check integrity of the primary and second-ary wiring.
Check condition of IC module, pick-up coil, distributor cap, rotor and spark plug wires.
Check ignition coil for cracks or carbon tracking. Were cracks or carbon tracks found?
Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned elec-trodes or heavy deposits. • Refer to Distributor Ignition System. NOTE: If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
Check the injector connections. Correct as necessary.
Check ECM grounds for being clean, tight
and in their proper locations.
Also check that battery cables and ground
straps are clean and secure.
 
Thanks so much for the suggestions, I really appreciate the help!

I just got it fixed. It was the p/u module in the distributor.

I read for hours in my manual and on the internet, and could not find anything that was exactly like my situation. I then started trying to go backwards. I started researching the syptoms of each individual part going bad. I couldn't find anything outside of the common stuff. I spent a lot of time researching the distributor pickup because I have had problems out of those before, but could not find anyone linking a p/u module to an idle problem. Everything I read was the opposite, there was a revving problem. Anyway, the last part I checked was the problem.

If only we could check the last part FIRST!!!!!!

Thank you everyone for the input. I hope this helps someone down the road, because I was unable to find this peticular problem posted elsewhere.
 
Chris, I just logged on to see how you were doing. That's great that you figured it out. Posting the steps you took along the way is very helpful as I'm sure someone, including myself, may be in a similar situation in the future. How did you go about determining the module was bad?
 
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