1997 200 EFI Idling issue

[BullCroaker]

Hello all. I’ve read through a lot of threads and don’t see any that match the issues im experiencing exactly. This what I have: 1997 Mercury 200 EFI. Currently the issue is that it won’t idle. It will idle if the port side temperature sensor(the one with three wires) is disconnected and it appears to go into the 10% richer mode. When the sensor is plugged in it tries to run and loses power and dies. Here are things that have been checked/replaced:Computer sent to Tony Brucatto and checked out ok.TPS operating normally an set per spec .026VDCFuel pump is operating normally 36-38 psiInjectors cleaned and leak tested by Injector ManVerified that all connections are good (grounds etc..)It ran fine for about 40 hrs after servicing the injectors and then it started having issues.Thanks!

[BullCroaker]

Forgot to mention that I'm running premium grade fuel from an auxiliary tank to eliminate bad fuel as a culprit.

[hsbob]

there may be a idle control box next to the oil injection box area. it reduces idle on some 90's motors.

[BullCroaker]

There is an idle stabilizer, but it is inactive when the motor is in neutral according the repair manual(see below text) It advances the timing 3 degrees when shifted into gear.

When outboard is idling IN NEUTRAL, shift switch circuit is in the OPEN position and system is INACTIVE.

Has anyone had an idle stabilizer cause similar issues?

[Dave Strong]

97 should not have a shift switch, idle stabilizer advances timing when idle drops below 550rpm. Should start with a complete link and sync, do you have the correct tps tool? Is your manual a Merc manual?

Dave

[TEXAS20225]

x2 Dave i just sold a rebuilt motor to a guy what called his self a mechanic he called me after a week and said something is wrong with it (i started it on a stand for him so he could see it was a killer little 175 it ran perfect) i got to his place( he would not let me install it although i dont charge to install i make it mandatory for just cases like this one) it was on a barge which is why he did not want to bring to my shop and in the water he started it and was smokin like it was on fire i dropped a ddt on it and saw TPI was at 4.00 i said what could have caused that ????? after looking at it for a few minutes i asked you adjust the linkage he said yeah it was idling too fast what he did was move throttle arm via stop screw out of the right link and sync zone where was totally screwed up i reset it and said see here between the pump and plenum that screw there is idle adjustment dont mess with these screws at all , i ran fine he was embarrassed all to pieces but you know i got a screw driver im a mechanic LOL Bull Croaker ( i caught a lot of them )i would throw away all the box's including auto oiler and be happy set timing at 23 degrees and mix your oil lose all yer troubles

[TEXAS20225]

PS the last motor i just assembled ran like crap for two days till i figured the plenum air temp sensor was bad changed it now it runs great

[rock]

PS the last motor i just assembled ran like crap for two days till i figured the plenum air temp sensor was bad changed it now it runs great

I just had the same situation. I think it is the first time I have had one fail.

Rock

[Dave Strong]

x2 Dave i just sold a rebuilt motor to a guy what called his self a mechanic he called me after a week and said something is wrong with it (i started it on a stand for him so he could see it was a killer little 175 it ran perfect) i got to his place( he would not let me install it although i dont charge to install i make it mandatory for just cases like this one) it was on a barge which is why he did not want to bring to my shop and in the water he started it and was smokin like it was on fire i dropped a ddt on it and saw TPI was at 4.00 i said what could have caused that ????? after looking at it for a few minutes i asked you adjust the linkage he said yeah it was idling too fast what he did was move throttle arm via stop screw out of the right link and sync zone where was totally screwed up i reset it and said see here between the pump and plenum that screw there is idle adjustment dont mess with these screws at all , i ran fine he was embarrassed all to pieces but you know i got a screw driver im a mechanic LOL Bull Croaker ( i caught a lot of them )i would throw away all the box's including auto oiler and be happy set timing at 23 degrees and mix your oil lose all yer troubles

When I finish setting up a motor liquid neoprene and a paint pen on all the linkage screws. If it comes back running poor and the screws have been moved your paying for a link and sync again.

Dave

[BullCroaker]

Thanks for all the responses. I wasn't getting any notifications indicating that I had any replies. I do have the correct TPS cable and it is set at the specified .26V. I have the PDF service manual it looks like an official Merc publication. I did follow the section which outlined setting the linkage at idle. Would this cause the issue with the tem sensor causing the motor to not run and when disconnected run in the rich mode?

[TEXAS20225]

you mean the little round puck on the port head ?? with three wires its actually a air temp sensor with them unplugged it will run awful it will load up and run really rich the solid tan wire is a temp sensor for the dash mounted heat gauge,the starboard head puck is a hot horn it has tan blue strip on it

[rock]

So the way it sounds you have a serious lean condition. You disco the temp sensor and it runs so you are fixing the lean condition. Have you checked the air temp sensor in the injection manifold? Top starboard side with 2 brown wires. My guess is iffn it tells the puter it's hot when it's not you will have a lean condition which you are correcting by discoing the temp sensor.

Rock

[Dave Strong]

If you want to check the temp sensors, this is how to do it.


Dave

[BullCroaker]

Rock, You are right, it's definitely a lean condition. I have tested the temp sensor on the intake manifold and it functions properly. Maybe it's one of the boxes Texas says to remove? This is my first EFI motor so I'm learning as I go. How important are the detonator and timing boxes? What is the upside/downside of removing them?

[TEXAS20225]

well let me put it to you this way i rebuild 25/30 motors a year fro a lot of people i leave them all off including auto oiler i never get callbacks on any thing