2004 Johnson 90hp rough idle

I have a idle problem with a 2004 Johnson 90hp outboard model J90PLSR. WOT is good, but at cold starts and after warm-up it fires on the first try, but it idles so rough it normally dies in the first few seconds or dies when I try to put it in gear. This can happen two or three times before it finally will keep running long enough to get it in gear and throttle up. If I start it in neutral with a little throttle it cranks good and fast idles fine. I can then let it run for about 10 sec and then throttle back to neutral and it will not die, but still seems to idle rough. The only time it starts good is after I have been running at full throttle for several minutes shut it off for just a minute, than crank it back up. Six months after purchase had it back to the dealer for this problem and he replaced the fuel pump saying it would not hold pressure, but the start problem did not change and I never took it back. I always install new plugs each year, but that is about it. It seems to be too rich at start-up. It does have the quick-start feature, but not sure if it is working right. Even on a cold morning at 45 degs F it only fast idles for a couple of seconds. Any ideas?

Re: 2004 Johnson 90hp rough idle

I have a 2001 Johnson 90HP. Not sure if they are the same kinda motor, but have been experiencing problems very similar to this. Almost exactly what you described.

Re: 2004 Johnson 90hp rough idle

Thanks, its nice to know I'm not the only one with this problem. I am going to check the warmup temperature switch to make sure that's not the problem. I feel like either the quickstart is not working (advance the timing) or something with the fuel delivery system is preventing the quickstart to fuction properly. I'll let you know.

Re: 2004 Johnson 90hp rough idle

Thought I would give everyone an update. Last week I preformed the test for the Quick-Start feature prescribed in the manual. At warm startup the QS works correctly by advancing the timing for about 5 sec. But with the warmup temp. switch disconnected (i.e. cold start), the QS still only advances the timing for 5 sec. With the temp. switch (I checked the switch, its ok) disconnected, the QS should advance the timing until the switch is reconnected, which would tell the power pack the engine is warm. I went fishing Sat. and the engine acted the same way. I will have the boat at the dealer later this year and I will talk to him then to try to find out the problem with the QS/power pack.

Re: 2004 Johnson 90hp rough idle

I have also experienced the similiar problems with this motor. Whenever the engine sits for a long time or I try to start cold it take alot of cranks to get it started. It also emits alot of smoke initially once started so it seems like it is getting too much oil or gas but figure thats becuase I have to choke it so much to get it started. It finally starts after several cranks and throughout that day after shut off it starts just fine when warm. I have not experienced the idle problem you describe just the rough starting (cold). I took it in to a repair center to have it looked at and they said everything checked out but I was still having problems after bringing in so they were not able to fix the problem. I may need to take it in to another dealer for a second opinion. I only have 20 to 30 hrs on it since I purchased it and has never worked right since I bought it. My warranty is now ran out of course and don't know exactly what I can do with this. I fear that the starter will eventually wear out on me if I continuously have to crank it over several times before it starts. Hopefully someone can shed some light on this as it is very frustrating and embarrassing having to sit at the lauch to constantly crank it over to get it started. Please help if you have any tips or solutions to this problem. thanks in advance

Re: 2004 Johnson 90hp rough idle

As for a quick fix on the starting, if you will put the engine in neutral and give it just a little throttle (1000rpm), it will help the cold startup alot. Once started let it run until the blue smoke is gone, you should then be able to idle it back and it should idle normally. Be careful using the choke. I found out that I was over choking the motor thinking that was the problem. If you do take it to a dealer be sure to ask him about the Quick Start feature.

As I mentioned earlier the QS is not operating per manual on my motor. This could also cause the blue smoke at startup, (my does the same thing). I have not had my boat to the dealer yet, (still waiting on a repair kit for the boat) but I will have him to run a check on the QS and the power pack while there. Hopefully this wil be in the next few weeks. I will post the results as soon as I have them. Let me know if this does not help. Thanks for your reply.