car idles very rough

[turbotbirdguy1979]

my 99 sho has been having problems after you drive it for a while,when you shut it off,it starts and dies and after it fires up it idles very rough until you give it a quick rev,but now it sometimes wont start at all you have to crank it for a while.Ive cleaned the IAC motor didnt help at all.check engine light is not on and the car is mostly stock except for KN panel filter and exaust.the cams were welded at 50000 And also it seems that after it gets hot it loses its power.secondaries are opening fine.Coil pack?I would think If it was one of em it would be running crappy all the time.I thought that maybe some oil came off my KN and got on my mass air sensor but I took that off and cleaned sill no help.Maybe CPS?I am lost.I just hope its not the muffler bearing... any help would be great!Thanks

 

[MichaelH]

Show me the Codes

Well, I have two Gen II's, not a III, but I would think the usual suspects would be involved. First, take it to Autozone and get the codes read. I understand they'll do it for free.

That should tell you a lot. Then, of course, you should know if it's one of the sensors. If the car doesn't throw any codes, then you would probably want to look at the plugs, plug wires, plug wells for oil/water, and vacuum leak test.
Also, fuel pressure (dying fuel pump?) and fuel filter.

Also, did you recently unhook the battery for any length of time? You would need to run the idle reset procedure (at least you do on Gen II's). You would also run the idle reset procedure after cleaning the IAC.

I'm sure someone else will chime in with more things to check.

 

[99V8SHO]

The only thing involved with resetting the idle is disconnecting the battery for abou 15 minutes then reconnecting and starting the engine up and letting it idle for about 5 minutes.
Sounds like a problem with fuel delivery to me.

 

[MilTownSHO]

The only thing involved with resetting the idle is disconnecting the battery for abou 15 minutes then reconnecting and starting the engine up and letting it idle for about 5 minutes.
Sounds like a problem with fuel delivery to me.

Actually there is an idle reset procedure to go through to teach the car how to operate while under a full load. You'll have to search to find it

 

[MichaelH]

Idle Reset Procedures

Yes. There are procedures for Gen I and II. I thought from the reply by 98V8SHO that you don't need to do them for the Gen III. I have my Gen II book at home (and I'm not there to look it up), but it's something like this after the battery has been disconnected for some time.

"Start the car and let it warm up to operating temperature - at least 5 minutes. Then put a full load on the engine by turning on the A/C to MAX, the headlights on bright, and radio. Then I think you step on the brakes, put it in gear with the brakes on for a short time and turn the steering wheel, kind of like the KOER tests, and let it run under full load for about 15 minutes."

 

[SHOZ123]

The Gen 3s will learn idle on their own in about a minute. But the actual procedure is....

Idle in park till it settles, idle in drive till it settles, turn on A/C in drive and idle till it settles, shift to park and with the A/C still on idle till it settles.

 

[Ian Macoomb]

I'm betting on the coils (as I always do). Did you have the plugs changed recently? It seems to be a common problem after the coils have been removed for something like a cam weld or plug change.

I've had all of those symptoms before. But the stalling when coming to a stop thing only happened to me a few times. Ditto for the stalling and not wanting to start for a couple of minutes.

I've also noticed that above 3400 rpm it's not noticeable. Seems to be most noticeable at idle.

Try starting off in 2nd and floor it from a start. Bogging the car like that seems to set a pending code showing the offending cylinder.

 

[99V8SHO]

Actually there is an idle reset procedure to go through to teach the car how to operate while under a full load. You'll have to search to find it

Sorry that I was not clear the first time, lol. I was talking strictly gen3s. Sorry for the confoozion.

 

[turbotbirdguy1979]

I did a scan on it and there are no codes not even in memeory.Checked fuel pressure though 28 to 30 psi at idle.I dont know if that is normal im guessing not.Does anyone know what it is supposed to be?thanks

 

[Tim Rice]

DPFE maybe??

I'll check my shop key 5 info here at the shop but 30psi f/p at idle sounds good, you may want to check Delta pressure feedback EGR, (controls EGR flow) its both vacuum and electronic if I'm not mistaken (lots of Furd experience but new to the Yamaha thing) the port at the surge tank may be carboned up if the EGR has been flowing when it wasnt supposed to, what does the Threottle body look like?

Timmayh

 

[Tim Rice]

fuel pressure spec

Operating pressure for your fuel pump should be 30-40 psi (310-415kpa)

Timmayh

 

[turbotbirdguy1979]

I think that sensor was replaced a while ago,but that doesent mean it cant go out again huh?Wouldnt that put up a code though?

 

[SHOwallen]

My 99 has a similar problem. It idles really rough when your in park. It never kills and always starts fine. I'm not getting any codes and I had my fuel pressure checked and that was fine. I'm wondering if I need a new coil pack or plugs. The plugs were changed at 60k and it now has 97k. Or do I just need to reset my idle with the procedure talked about above. Also if I were to change the plugs would I need to lower the engine to get at the back plugs?
thanks

 

[turbotbirdguy1979]

I would imagine if one of the coil packs was going out it would set a code?

 

[Ian Macoomb]

I would imagine if one of the coil packs was going out it would set a code?

Eventually it will set a code. But, it has to get pretty bad to do so though. I've had limited sucess by bogging the motor when it's acting up. From a stop throw it in 2nd and floor it. Then check for pending codes.

 

[turbotbirdguy1979]

I dont have a manual second Ive got a 99,this is kinda off the subject but do these things have a trunk light?Kinda stupid question but I dont see one any where.I still have my window sticker and this thing was 30,147 :ruhroh: new.no hood light or trunk light or glove box light?WTF!my wifes saturn at least has a glove box light.