2000 5.7EFI Rough Throttle Up

[Reveler's Revenge]

UPDATE:

Over the past several days I have replaced the distributor cap, rotor arm, and plug wires. They were all originals dating back to 2000. The cap actually had the engine paint line on it! I also double checked the firing order to be sure that I didn't goof that up.

The symptoms have changed slightly. The engine will not start unless throttle is wide open. Then it runs very rough until warming slightly and will stall if I drop the throttle back to idle immediately. After less than thirty seconds I can take it back to idle on the throttle without a stall.. Plenty of white smoke during the warm up time and it decreases to almost none once the engine has warmed to approximately 100 degrees. The engine runs at normal operating temperature (170-175...not a degree higher). Once warmed up it is still running rough but but can take a quick throttle up and back to idle without stalling (gunning it). The vibration from the engine seems its worst at 1900rpm. Above that it smooths out significantly but still a bit rough.

I'm open to suggestions but may have reached the limit of my abilities on this problem.

 

[Reveler's Revenge]

Someone local suggested that it could be a timing issue. I'm having a mechanic look into it now. :smt089
I'll be sure to let you guys know what I find...gotta get my girl runnin in time for Memorial Day weekend!!!

 

[JimT]

The IAC has been mentioned several times. The problem now described sounds like a bad IAC. Its a 15 minute job. Swap the one from the engine that runs well. I the IACs go out on both engines in the past two weeks. One failure had symptoms very similar to what you are describing.

 

[kkalsch]

I would check my serial number and if I had the engine that was effected with that service bulletin (No. 2000-14) I would change the sensor under the cap before I did anything else ......

 

[Reveler's Revenge]

I would check my serial number and if I had the engine that was effected with that service bulletin (No. 2000-14) I would change the sensor under the cap before I did anything else ......

Checked it...I'm OL6xxxxx so this doesn't apply. Thanks for the heads up.

 

[Reveler's Revenge]

The IAC has been mentioned several times. The problem now described sounds like a bad IAC. Its a 15 minute job. Swap the one from the engine that runs well. I the IACs go out on both engines in the past two weeks. One failure had symptoms very similar to what you are describing.

Swapped the IAC's and same symptoms. I also screwed up and removed the throttle position senser and started the engine. Now my ECM is running the idle at the default of 1400rpm. Just removed the negative battery terminals hoping to reset the ECM and get this puppy idling right at the least.

 

[Reveler's Revenge]

I have done the following for troubleshooting:

1. Replace distributor cap and rotor button
2. Replace plug wire set
3. Replace fuel water seperator
4. Swapped IAC from STB to Port engine to check - no change
5. Replaced spark plugs with AC-Delco MR43LTS as suggested by my mechanic yesterday.
6. Screwed up by removing the TP (throttle positioning sensor) and starting the engine which set an error code in the ECM - now idling at 1400 (default setting for troubleshooting) - I've just removed the negative terminals on both starting batts to hopefully reset the ECM's...I've done this before in a truck when installing a performance air filter - it worked there so hopefully it will here as well.
7. Sweated out at least 3 cases of beer in the engine room

After replacing the plugs yesterday I noticed that the smoke coming from the exhaust was distincly darker than with the previous NGK plugs. The outboard plugs (cylinders 1,3,5, and 7) were fouled. Looked as if the engine was running really rich. The inboard plugs (2,4,6, and 8) looked cleaner. Hopefully this is not a sign that I have water intrusion and they are getting "steam cleaned".

I'll update this thread later today with the results of the attempted ECM reset. Thanks to you ALL for the great ideas on troubleshooting this issue!

 

[Reveler's Revenge]

Well...after disonnecting all batteries and opening the shore power breaker I let the boat sit for 30 minutes. Then I reconnected all batteries and closed the shore power breaker (was dying without A/C!). I turned the ignition on without starting the engine and let it sit for approximately 9 minutes. I then started the engine. Still idling at 1400rpm and smoking pretty steadily. Black smoke now (same as before I did the reset and seems to be getting worse each time I test something). I am going to try to get the idle back to the correct speed by removing the TP and having someone position the throttle for me so I can ensure that the sensor is seated properly but I have a feeling this is not going to be very helpful. I guess I will be waiting for my mechanic to return on Tuesday...

 

[Reveler's Revenge]

Is it safe to swap the ECM from srbd to port? The mechanic told me he was not able to connect to the port ECM using his diagnostic tool. With the multiple issues I am seeing an a noticeable corrosion issue near the ECM locaton I'm becoming suspicious it may bee bad. Any feedback???

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[Reveler's Revenge]

UPDATE: my mechanic told me to use AC Delco plugs instead of the NGK's that I had put in. I swapped them out, replaced a bad throttle control sensor and took her away from the dock for the first time in 6 months last night!! :smt038

I still noticed some smoke from the exhaust but couldn't check it after dark last night while my wife and I were out. Besides, we were having WAY too much fun to work on her! The port actually turns at a higher RPM than the STBD now. Guess what I'm doing next...:grin:

Thanks for all the help with in this thread guys. I learned a TON from you all and best of all I'm casting off again!