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1998 Evinrude 70HP 4 stroke poss IAC valve failure

C

chris_holt

Contributing Member
"This engine is low hrs and in

"This engine is low hrs and in meticulous mechanical condition. Suddenly it began having cold start issues. Turn the key and it fires instantly and runs 10 sec. then quits. Runs 10 sec. then quits. etc. If I play with cold start lever, I can make it run at 2000rpm and it will stay running with the check engine light and buzzer on. It will run like this for 30-45 sec., then light and buzzer goes off and engine runs perfectly all day. Next morning, same thing. The ECU is storing no codes, and all sensors have been tested and are within specs. ie:cam sensor, crank sensor, MAP sensor, IAC, closed throttle switch. The only sensors I can not find test procedures for are the intake air temp, and cylinder temp. Is there a possibility that the IAC is in spec, but not functioning properly,or what else can cause the ECU to prematurely terminate the cold start map."
 
"Just guessing here Chris. Is

"Just guessing here Chris. Is the engine building oil pressure quickly enough? Wondering if it is dropping out on low oil pressure once the startup delay times out. Running the engine faster builds oil pressure before it times out. Again, I have no experience with this engine so I'm just guessing.... If the alarm is going off, there should be a code stored. Might be the best place to start troubleshooting."
 
"Thanks Dcramer, I will put a

"Thanks Dcramer, I will put a guage on it on Monday and check the pressure on startup. I will post results when I know, that is assuming I can find a test port!"
 
"You will need to hook it up t

"You will need to hook it up to a comp to get the answer.
Oil will set off 'No Oil' warning and not 'check engine'.
My guess is that you have a voltage/ground issue somewhere.
Clean all grounds, even harness/ECM ground. All registered sensor faults (alarm set off) will store codes.
As for the IAC you need the comp to check the cycling."
 
"I did not bother with the oil

"I did not bother with the oil press. test today, however I actually removed the IAC and verified it is clean. I also re-installed a fuel pressure tester so I could monitor during running. The boat had been inside all day and nice and warm and when I started it it stayed running and no light or buzzer went off. I am sure now it is temp. related, but not sure how. When it was running for the first 3-4 mins., it also had a couple of misses, or hicups that I believe may have made it stall if the engine had been cold sitting outside. I am trying to make the old Evinrude software on the 3.5 inch floppy work with a newer operating system so I can plug in, but I am looking for old school mechanic solutions in the interim."
 
"Install the floppy on a memor

"Install the floppy on a memory stick, then normally ready to go_On the other hand I've never seen the 4-stroke (Mitsubishi) program on a floppy? You may need an XP operating system to make it work.
Have you tried changing plugs?"
 
"From what I understand Window

"From what I understand WindowsXP or prior is required as it is DOS based software. Time to find an old desktop. I have tried transfering to a cd via and external drive, but it will not read. As for the plugs, I did all the basics first,ie: cylinder inspection with scope, compression 220,200,200,220, new engine oil, new gear oil, new plugs etc. The fuel test showed nice constant 35psi all through the startup and run, even while missing."
 
managed to get software to wor

managed to get software to work on an old desktop (I think) I will plug in today and post results...Thanks
 
"Although resistance tests sho

"Although resistance tests showed IAC valve to be good, and removal and visual inspection looked good, the diagnostics showed 6 IAC failures but no stored codes. I have ordered a new valve and will replace it. Thanks to all for the help!"
 
"I ordered the new software on

"I ordered the new software on cd, and it works with Vista. It is also way easier to use and allows more testing procedures. I hooked it up and managed to get the motor to fail on start-up with the computer on and hooked up...lucky. It immediatly logged cyl. temp sensor failure. Ordered new part, and all is well. Thanks to all for the help...Chris"
 
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