PDA

View Full Version : Fast Idle Issue



Warlock28SXT
06-26-2009, 08:45 PM
Yesterday was out boat was running fine. Ran around a bit then stopped @ a local watering hole. No issues to this point. Got back to the boat smelled gas:cuss: found the fuel filter came loose, my fault for not checking everthing after last run. Anyway fied and cleaned up and waited a while to be safe before starting. Now the issue after ideling back down the river I put the boat in neautral and the idle ran up to about 17-1800 RPM????? Shut it down cuz I sure as hell was not going to shift like this. Fired it back up and it was fine. Went back out on the lake and ran it, after slowing down same thing, fast idle. WTF? shut down fired again and fine. If I idle around it's ok but once I run it and slow back down it happens. Any ideas??????? Thanks Jason

MERPerformance
06-26-2009, 08:52 PM
It's efi I take it?

Warlock28SXT
06-26-2009, 08:56 PM
It's efi I take it?

Yes sorry its a 98 502 MPI .030 over(509) MEFI 1.

MERPerformance
06-26-2009, 08:59 PM
Have you checked the idle air control

Warlock28SXT
06-26-2009, 09:03 PM
Have you checked the idle air control

I have not looked at it at all. Looking for a place to start. Thanks merperformance

MERPerformance
06-26-2009, 09:10 PM
Check the counts on the IAC, also what the ECM voltage is internally, you have a scan tool ?

Warlock28SXT
06-26-2009, 09:13 PM
Check the counts on the IAC, also what the ECM voltage is internally, you have a scan tool ?

OK I probably take a look tomorrow. No I do have the MEFI Burn SW though.

MERPerformance
06-26-2009, 09:17 PM
I had a ECM with a high voltage and the engine idle was doing the same as yours, make sure that you do not have an over voltage on the charging system, if so it will change the voltage in the ECM. My ECM had something wrong with it inside and would read a higher voltage than the batt. or charging system was putting out. Check the IAC first before you jump on the ECM, but do check it with a scan and code readings.

Warlock28SXT
06-26-2009, 09:31 PM
I had a ECM with a high voltage and the engine idle was doing the same as yours, make sure that you do not have an over voltage on the charging system, if so it will change the voltage in the ECM. My ECM had something wrong with it inside and would read a higher voltage than the batt. or charging system was putting out. Check the IAC first before you jump on the ECM, but do check it with a scan and code readings.

Will do thanks. I have some files of runs prior to this to compare to. I have my fingers crossed for an IAC problem. I have a manual for values as well.

Warlock28SXT
06-27-2009, 12:29 PM
It appears the IAC is bad. The counts on the IAC were 138 when @ idle. Shut off re start and the counts were at between 8-16. Manual states 0-40 counts (steps) is ok. I checked the plug with a test light, engine running test light grounded and touched all four connections. The light blinks on all four. Connections all clean. When it would idle fast the it was at the same RPM as with the sensor unpluged. Almost forgot the internal voltage of the ECM was 14.4 Vdc. Thanks again merperformance. I'll let you know how it is after the new IAC. Jason

Warlock28SXT
06-29-2009, 05:49 PM
Should have the new IAC by Wed.

Warlock28SXT
07-01-2009, 07:37 PM
Installed the new IAC. Key on for 10 sec key off for ten sec then started the motor. Idels right back @ 17-1800 RPM. What to do what to do.

After it sat for a bit I tried it again. Now it seems to be ok. I have to lake test it to be sure (bummer). I'll let you know what happens.
Jason

Warlock28SXT
07-05-2009, 10:36 AM
Any other ideas? All things pointed at the IAC. Well now there pointing else where. Still does the fast idle after a run. Shut it down refire ok.

Ratickle
07-05-2009, 10:46 AM
Any other ideas? All things pointed at the IAC. Well now there pointing else where. Still does the fast idle after a run. Shut it down refire ok.

Almost all the gearheads are at the race or runs this weekend (where I wish I were:(). You may have to wait till tomorrow eve to get guys back into this one.

Geronimo36
07-05-2009, 11:04 AM
have you checked readings on the TPS??

Warlock28SXT
07-05-2009, 11:06 AM
Almost all the gearheads are at the race or runs this weekend (where I wish I were:(). You may have to wait till tomorrow eve to get guys back into this one.

No worries. Thanks for the heads up though

Warlock28SXT
07-05-2009, 11:09 AM
have you checked readings on the TPS??

I have looked at them. I know the count is zero when @ idle. I don't remember the reading @ WOT. I'll have to look.

Magic Medicine
07-06-2009, 09:41 AM
sorry to hear your still having issues Jason

Warlock28SXT
07-06-2009, 10:45 AM
sorry to hear your still having issues Jason

Thanks Andy. I'll get it. I'm off this week so I can look into it further:biggrinjester:

Warlock28SXT
07-09-2009, 05:20 PM
have you checked readings on the TPS??

Do you or anyone know, is the step count for the TPS 0-100? @ WOT // TPS voltage 4.43 volts, TPS % 99.89. TPS step 64????

Geronimo36
07-09-2009, 09:34 PM
I'm not sure, I don't have the diagnostic manual to see exactly. Maybe someone else knows?

Also it might be good to check the seat of the IAC cavity for carbon build-up. Also, maybe your new IAC is messed up as well?

Someone had a simalar problem on here once before and they replaced the TPS, still the same problem. Then swapped IAC's from one engine to the other and it turned out the new IAC was bad...

Warlock28SXT
07-10-2009, 09:40 AM
I'm not sure, I don't have the diagnostic manual to see exactly. Maybe someone else knows?

Also it might be good to check the seat of the IAC cavity for carbon build-up. Also, maybe your new IAC is messed up as well?

Someone had a simalar problem on here once before and they replaced the TPS, still the same problem. Then swapped IAC's from one engine to the other and it turned out the new IAC was bad...

I cleaned the seat & cavity. I never thought it could be a failed new one, but I agree, I'll look into it. Thanks for your input.

Ratickle
07-10-2009, 02:38 PM
ANy new updates? I'm feelin your pain and am ready to start PM'ing people.....

Warlock28SXT
07-10-2009, 02:41 PM
ANy new updates? I'm feelin your pain and am ready to start PM'ing people.....

Nothing other than Geronimo36's wich I have looked at. He did bring up a good point about another bad IAC. We shall see. Thanks
p.s. No need to PM anyone on my account. It is what it is.
Thanks to MERPerformance and Geronimo 36 for the help/guidance

Geronimo36
07-10-2009, 02:54 PM
Warlock, I called my buddy who was my boss/mentor when I worked at the marina... He had a good suggestion... When it's idling high, check the timing because the TPS controls the timing curve. That's somehting I had not thought of. He's also going to look up the TPS output readings for us.

Another suggestion, check the throttle plates shaft/bushings for wear. That's a GM TBI system from the 80's and they were known for wearing out the bushings and causing an air leak.. It might not be the problem but it's just a suggestion...

Have you also checked the Map sensor readings? If you have an air leak it will show up.

Warlock28SXT
07-10-2009, 03:02 PM
Warlock, I called my buddy who was my boss/mentor when I worked at the marina... He had a good suggestion... When it's idling high, check the timing because the TPS controls the timing curve. That's somehting I had not thought of. He's also going to look up the TPS output readings for us.

Another suggestion, check the throttle plates shaft/bushings for wear. That's a GM TBI system from the 80's and they were known for wearing out the bushings and causing an air leak.. It might not be the problem but it's just a suggestion...

Have you also checked the Map sensor readings? If you have an air leak it will show up.

Thanks Geronimo36, I will look into these things as well. THis is exactly the kind of info I am looking for, what all ties in/plays a part. I will have the boat out tomorrow and I take a look. Thanks again.Jason

MERPerformance
07-10-2009, 09:49 PM
Sorry still not fixed yet, been working 14 hr days. The ecm has a set idle rpm, could it be shorting out or getting a voltage reading that changes the IAC? I'am out of ideas to help, Maybe you can call Mark @ Precision Marine.I would check for air leaks first. Any chance the intake is leaking at the port gasket

Warlock28SXT
07-11-2009, 10:56 AM
Sorry still not fixed yet, been working 14 hr days. The ecm has a set idle rpm, could it be shorting out or getting a voltage reading that changes the IAC? I'am out of ideas to help, Maybe you can call Mark @ Precision Marine.I would check for air leaks first. Any chance the intake is leaking at the port gasket

Thanks, I totally understand. I will be checking more out today on the lake. I have yet to monitor the engine while this is happening. I will let you guys know what I see later tonight. I am going to bring the old IAC with and maybe swap it out as well. Thanks again. Jason

Ratickle
07-12-2009, 09:59 AM
Thanks, I totally understand. I will be checking more out today on the lake. I have yet to monitor the engine while this is happening. I will let you guys know what I see later tonight. I am going to bring the old IAC with and maybe swap it out as well. Thanks again. Jason

Any updates?????

Warlock28SXT
07-13-2009, 10:25 AM
Any updates?????

Kind of..... I ran the boat laptop hooked up slowed to idle took it out of gear and it stayed @ idle. Huh? Ran it a couple more times and it stay @ idle. So I was now a bit confused. I had the boat docked (we were @ a party on the lake) I had to move the boat for some people. Got it fired up moved it gave it a little gas backing up back to idle out of gear and then it did it(fast idle again) you know I did not have the laptop hooked up just to move the boat.:(
Took it out again seeing as it now happend and agian when I was monitoring it would not do it. Packed away the laptop and went to take the boat out. All was still working normal. When I drove it on the trailer and came back to idle and out of gear it did not just fast idle it was "hunting" RPM's 700-1200 up and down up and down. Did not get it out Yesterday. Jason

Geronimo36
07-13-2009, 10:51 AM
How much vacuum is the engine pulling at idle? Could also be a vacuum leak and when the engine is cold vs. hot it causes it to leak, eg intake gasket.

Personally I'd try and get a new IAC that you could put in and verify the new IAC you bought is/was bad but I guess that's hard not having parts available for testing... I hate changing out parts but sometimes when it's an intermittent problem it's good to start fresh again.

It could also be a voltage problem with the ECM. May also check all grounds to the ECM.

I hope this isn't too much info but I'd probably start from scratch and just take a systematic approach. It seems like it's going to take some time to diagnose since it's intermittent and kinda makes it harder that you have a single engine.

I just had a weird intermittent problem last week with my buddy's boat. We put a new 357 Magnum in it and above 4k rpms it would intermittently pop out the carb... Since the engine was brand new and sat for years I thought maybe something was stuck in the carb... Sometimes it would happen and other times it wouldn't.. On a huntch I decided to recommend replacing the ignition coil and now the boat runs perfectly... He also picked up 10 mph with the new engine over the old!!! :)

Geronimo36
07-14-2009, 10:24 AM
Warlock, I got the TPS info for you.

The system is a 5/5 system meaning it uses 5 volts input for reference to run the system. So from the ECM you should see 5 volts on the input wire. From there you read voltage on the output wire (3 wire system, input, output, ground). The TPS voltage reading at idle should be .5 volts, WOT should be "near" 4.5 volts. There are no steps in-between and you should see a smooth voltage transition as you open the throttle from idle to WOT.

Hope this helps!

rvw
07-16-2009, 01:55 PM
In addition to the voltage requirements for TPS as previously mentioned make sure the percent of TP is 0% when the throttle is closed. If the % of TP is above a certain value the ECU will think it is of idle and the idle control program will not be running.

One more thing you can look at with MEFI is the the Desired IAC position along with the Actual IAC position. Same is true for the Desired Idle RPM and Actual RPM. If the Desired is close to the Actual it is not your IAC.

Rick

Warlock28SXT
07-21-2009, 10:22 AM
Sorry guys it been a while. I've been trying to put some cash in my pocket. The boat is hooked up to the truck and I'm heading to the lake shortly.

Warlock28SXT
07-21-2009, 10:24 AM
Warlock, I got the TPS info for you.

The system is a 5/5 system meaning it uses 5 volts input for reference to run the system. So from the ECM you should see 5 volts on the input wire. From there you read voltage on the output wire (3 wire system, input, output, ground). The TPS voltage reading at idle should be .5 volts, WOT should be "near" 4.5 volts. There are no steps in-between and you should see a smooth voltage transition as you open the throttle from idle to WOT.

Hope this helps!

Geronimo Thanks. I was looking for the step count. Is it 0-100? I appreciate the help. Thanks again Jason

Warlock28SXT
07-21-2009, 10:25 AM
In addition to the voltage requirements for TPS as previously mentioned make sure the percent of TP is 0% when the throttle is closed. If the % of TP is above a certain value the ECU will think it is of idle and the idle control program will not be running.

One more thing you can look at with MEFI is the the Desired IAC position along with the Actual IAC position. Same is true for the Desired Idle RPM and Actual RPM. If the Desired is close to the Actual it is not your IAC.

Rick

Rick If the desired vs act are close then what? How close is close? Thanks Jason

Geronimo36
07-21-2009, 10:59 AM
Geronimo Thanks. I was looking for the step count. Is it 0-100? I appreciate the help. Thanks again Jason

Maybe I misunderstood your question, I'd have to look again.

Diagnostic manual didn't talk about step-count from what I read, only voltage reading from idle to WOT. The TPS voltage reading at idle should be 0.5 volts, WOT should be "near" 4.5 volts. Should see a steady increase in voltage from idle to WOT.

Warlock28SXT
07-21-2009, 11:10 AM
Maybe I misunderstood your question, I'd have to look again.

Diagnostic manual didn't talk about step-count from what I read, only voltage reading from idle to WOT. The TPS voltage reading at idle should be 0.5 volts, WOT should be "near" 4.5 volts. Should see a steady increase in voltage from idle to WOT.

I'm heading out now, when I record the info it gets it all TPS voltage and step count. I was just wondering, the voltage readings are listed in my manual. I hope to find something. Thanks again Jason

Geronimo36
07-21-2009, 11:18 AM
No problem, good luck!!!

Warlock28SXT
07-21-2009, 02:25 PM
No problem, good luck!!!

Well it started idled fast and then ate the raw water pump impeller. I will get one asap and try again. TO BE CONTINUED.....................

Magic Medicine
07-21-2009, 04:05 PM
Well it started idled fast and then ate the raw water pump impeller. I will get one asap and try again. TO BE CONTINUED.....................

dam son you have all the luck

Warlock28SXT
07-21-2009, 05:56 PM
dam son you have all the luck

It's not easy bein me:biggrinjester:

Ratickle
07-21-2009, 06:02 PM
It's not easy bein me:biggrinjester:

You didn't bump up against Gino did you????:ack2:

Warlock28SXT
07-21-2009, 06:33 PM
You didn't bump up against Gino did you????:ack2:

Nope our cats are ok:biggrinjester:

Geronimo36
07-22-2009, 09:03 AM
It's not easy bein me:biggrinjester:

If it makes you feel any better... On Saturday I ran the ocean in 4's and when we came off plane I popped the hatch to make sure everything was ok. When my buddy peered into the engine room he saw the alternator split in half!:ack2:

So I leave the wheel and have a looksee and it split apart so much you could see the windings inside the alternator.:eek: So I say to myself, WTF!:huh:

So we're idling in the inlet, 30-45 minutes from home and still about 45 minutes to where we're going, and I start making phone calls to friends and marina's trying to find an alternator and NO LUCK! When I realized I couldn't find one I get in there and see if I can fix it.

Turns out all 4 bolts that hold the alternator case together seemed to have fallen out.. I find two of them in the bilge and bolt it back togther. the alternator wasn't working properly after that but I didn't let it ruin my day and continued on. We took a bunch of kids for a ride at Shore Dreams then headed back home. On the ride home the ocean settled down, there were still 4's but we had a following sea. Ran all the way home with no issues and even ran the boat on Sunday. New alternator coming this week!:driving:

Warlock28SXT
07-23-2009, 09:45 AM
If it makes you feel any better... On Saturday I ran the ocean in 4's and when we came off plane I popped the hatch to make sure everything was ok. When my buddy peered into the engine room he saw the alternator split in half!:ack2:

So I leave the wheel and have a looksee and it split apart so much you could see the windings inside the alternator.:eek: So I say to myself, WTF!:huh:

So we're idling in the inlet, 30-45 minutes from home and still about 45 minutes to where we're going, and I start making phone calls to friends and marina's trying to find an alternator and NO LUCK! When I realized I couldn't find one I get in there and see if I can fix it.

Turns out all 4 bolts that hold the alternator case together seemed to have fallen out.. I find two of them in the bilge and bolt it back togther. the alternator wasn't working properly after that but I didn't let it ruin my day and continued on. We took a bunch of kids for a ride at Shore Dreams then headed back home. On the ride home the ocean settled down, there were still 4's but we had a following sea. Ran all the way home with no issues and even ran the boat on Sunday. New alternator coming this week!:driving:

Wow that's crazy. Never heard of or seen that before. Glad you got tp keep running and nothing more got damaged.

Geronimo36
07-23-2009, 10:31 AM
I've never seen one split apart like that either but I guess there's a first for everything!

Warlock28SXT
07-28-2009, 12:51 PM
It might not idle correct but it runs great.......just ask the local water patrol:( Anyway I just ran it in the trailer. Here is what I saw. Desired IAC vs act position is the same(step count of 47 a bit high) both @ 141 key on engine off. The TP % is 1.95% and the throttle follower jumps 0-5 (in the step count) TPS voltage is .8 volts steady all with throttle fully closed, vac is 14 in.hg. MAP is 63 kpa. After it ran for a bit the idle started to hunt again, not like before just a couple hundered r's, but never the fast idle ~1800. Hope this info helps. If I missed something let me know. Thanks guys. Jason

Geronimo36
07-28-2009, 05:14 PM
not sure how much of a difference it makes but the info I have shows you should have 0.5 volts at idle and % of TP should be 0%. Not sure if the .8 is out of range but seems a little high according to the info I have.

Warlock28SXT
07-28-2009, 05:43 PM
not sure how much of a difference it makes but the info I have shows you should have 0.5 volts at idle and % of TP should be 0%. Not sure if the .8 is out of range but seems a little high according to the info I have.

Agreed it seems a bit high. This is the first time I saw the TP % and the position(step) be anything other than 0. The voltage has also never been that high @ idle, was @ about .6 volts. Maybe time for a new TPS?