Engine has rough idle and missing on acceleration
10-12-2012, 07:36 PM
#11
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No soot.
Cylinder compression is 158-162. Can't check fuel pressure, because I don't have the equipment, so I will have to try and barrow or have someone check it.
The IAC ohmed at 10.0 (normal per merc is 10.1) ECT sensor is difficult to get to to ohm it.
I'm think maybe the ECT is bad and just didn't display a fault code, but I want to check some other things before I start "guessing" even though I can pick-up an IAC from NAPA and a ECT locally for about $90.00 total.....
Cylinder compression is 158-162. Can't check fuel pressure, because I don't have the equipment, so I will have to try and barrow or have someone check it.
The IAC ohmed at 10.0 (normal per merc is 10.1) ECT sensor is difficult to get to to ohm it.
I'm think maybe the ECT is bad and just didn't display a fault code, but I want to check some other things before I start "guessing" even though I can pick-up an IAC from NAPA and a ECT locally for about $90.00 total.....
10-14-2012, 12:30 PM
#12
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UPDATE:
I practically ohmed every possible part and sensor I could get to and they all were within the Merc manuals limits.
Plugs, wires, injectors, ECT (which is a pain to get to) IAC, MAP.
Also, I pressure tested the cylinders all were fine (158-162) fuel press was fine.
So I took after all the testing with and without a scanner, I took a shot-in-the-dark and did:
- Put some Mercury Quick clean in the tank with 10gal; pulled the cool fuel filter assembly out and poured 1/2oz in the reserviour.
- Replaced the plugs with AC 41-983.
- Replaced the IAC with one from NAPA.
Total cost = $125.00
Ran it cold yesterday and did not duplicate the problems I was having...
It idled smoothly, accelerated without any missing or lack of power. Once I got to operating temps, there was no changes, ran great.
So, I don't know what made the difference, Fuel/injector cleaner? new plugs? new IAC? or maybe a combination of all three? Who knows.
I am just like the majority of the DIY people that don't "throw" money at parts and HOPE it solves the problem, but after so many dead ends I guess I got lucky.
I will run it again Monday cold and see what happens. This is what was so frustrating, the that I had to wait for the engine to be in a start-from-cold state.
IMO: I think it was a bad IAC even though it ohmed 10.0 (manual calls for 10.1)
I practically ohmed every possible part and sensor I could get to and they all were within the Merc manuals limits.
Plugs, wires, injectors, ECT (which is a pain to get to) IAC, MAP.
Also, I pressure tested the cylinders all were fine (158-162) fuel press was fine.
So I took after all the testing with and without a scanner, I took a shot-in-the-dark and did:
- Put some Mercury Quick clean in the tank with 10gal; pulled the cool fuel filter assembly out and poured 1/2oz in the reserviour.
- Replaced the plugs with AC 41-983.
- Replaced the IAC with one from NAPA.
Total cost = $125.00
Ran it cold yesterday and did not duplicate the problems I was having...
It idled smoothly, accelerated without any missing or lack of power. Once I got to operating temps, there was no changes, ran great.
So, I don't know what made the difference, Fuel/injector cleaner? new plugs? new IAC? or maybe a combination of all three? Who knows.
I am just like the majority of the DIY people that don't "throw" money at parts and HOPE it solves the problem, but after so many dead ends I guess I got lucky.
I will run it again Monday cold and see what happens. This is what was so frustrating, the that I had to wait for the engine to be in a start-from-cold state.
IMO: I think it was a bad IAC even though it ohmed 10.0 (manual calls for 10.1)
