sort of stumble at idle

[Toms007]

Since returning from CruiseFest I have had a little issue with a little stumble at idle, sometimes when it stumbles it shakes the whole car, sometimes it just slightly noticeable. Only when in gear and only at idle. If I rev up just past idle 800-900 RPM stumble goes away. (makes me think IAC, but why only under load?)

Here's what I have done/checked:

#1 no SES light and have checked, No codes set either in History or Current.

#2 I have changed Fuel Filter, opti, plugs, wires, WP, Injectors all within the last 6k miles

#3 Cleaned TB and MAF within the last 8K.

Things I haven't done that might be problem solvers. Remove and clean IAC and/or EGR.

Other thing, this morning after I put my AutoXray 6000 on to check for codes and scanned the computer for what it was doing...the stumble went away. What's up with that? Not to say it won't return but I was shocked that it went away like that.

Any suggestions/comments/help? I am thinking that I should go ahead and remove the IAC and the EGR and clean them, can't hurt either way.

 

[JimBobC4]

edited post. I just reread and saw the opti was new.

 

[gmjunkie]

Since returning from CruiseFest I have had a little issue with a little stumble at idle, sometimes when it stumbles it shakes the whole car, sometimes it just slightly noticeable......... I am thinking that I should go ahead and remove the IAC and the EGR and clean them, can't hurt either way.

I'd definitely be checking the EGR,Tom!!Sometimes after a Long Warm Up,Like a Long Cruse to Ohio and back!! A chunk of Carbon can break loose from seaming No where and be bouncing around in the EGR and is too Large to get through the pintail!!Sometimes they can hold them close to wide Open and they won't idle at all,or sometimes just a small piece gets between the pintail and seat,holding it open a Milli Fraction!! And will cause your Exact problem!! Basically acts like a small vacuum leak (Because,Thats what it is,Only Internal and Not External!!) and will cause your Exact problem!! Some auto parts stores sell a special gasket for the EGR that will eliminate this problem for around $12-$14,but I usually make my own for about $6-$7!! Consists of 2 EGR gaskets with a Stainless screen sandwiched between them on the Exhaust Port of the EGR!!

 

[Toms007]

Junk, what is required to clean the EGR out?manually digging cr@p out or is there some kind of spray cleaner?

BTW, Thanks.

OK, I did a search and found out that you recommend a carb or throttle body cleaner. How about the stainless screen, where do you get that?

 

[gmjunkie]

Junk, what is required to clean the EGR out?manually digging cr@p out or is there some kind of spray cleaner?

BTW, Thanks.

OK, I did a search and found out that you recommend a carb or throttle body cleaner. How about the stainless screen, where do you get that?

I get the screen at my local True Value hardware store!!On 4.3's and some V8's I can use a stainless faucet screen!! Others like yours,I believe it will need to be a little larger and more rectangular,if they don't have any Bulk Stainless screen,(They usually do!!) I'll buy a Cheap Stainless Food strainer and cut it up!! I've even been known to Steal one from the Wife!! Depending on the size,I can usually get enough screen out of one to make 6-7 of them!!This is a purdy common problem on vehicles that set around allot or has higher miles!! You can put a New EGR on them,but they'll just do it again if a screen is not place!!

PS Screen must be Stainless!! Aluminum or Reg Steel will burn out very Quickly!!

 

[LT4man]

Tom, I only run "Top Tier" gasoline.

Running a container of Techron every couple tankfuls certainly will help.

Just a couple of ideas for you down the line.

SAVE THE

 

[Toms007]

I try to only run Shell, Mobil, P66, BP in mine. I also run a bottle of Techron through mine about every fourth tank or so.

Junk, I'll pick up some stainless screen next time I'm in the "big city".

 

[Toms007]

Ended up going to the big city today and picked up a food strainer (nobody had stainless screen stock). I have the gaskets coming in the morning, so I'll try to get this accomplished tomorrow....notice I said try. I'm going to remove the IAC and clean that out as well.

We had wind damage to the roof back in May, insurance tells us that we need a new roof, the roofers were supposed to start August 11, they show up today and say we got moved up and they are starting tomorrow morning! So I have to get the pickup and car out of the garage before they get here, so they have access to the driveway for their truck to dump the tear off shingles into. I won't be able to use the driveway at all tomorrow, so I need to get the wifes' car out, so I can let the vette down. There are some drawbacks to having the vette on a lift and the other two vehicles in there with it, sometimes it's just not very handy to have to move things around.

 

[gmjunkie]

Ended up going to the big city today and picked up a food strainer (nobody had stainless screen stock). I have the gaskets coming in the morning, so I'll try to get this accomplished tomorrow....notice I said try. I'm going to remove the IAC and clean that out as well.

We had wind damage to the roof back in May, insurance tells us that we need a new roof, the roofers were supposed to start August 11, they show up today and say we got moved up and they are starting tomorrow morning! So I have to get the pickup and car out of the garage before they get here, so they have access to the driveway for their truck to dump the tear off shingles into. I won't be able to use the driveway at all tomorrow, so I need to get the wifes' car out, so I can let the vette down. There are some drawbacks to having the vette on a lift and the other two vehicles in there with it, sometimes it's just not very handy to have to move things around.

Tom when you get the EGR off, Try this before you start cleaning and messing with the pintail!! It will give you a Idea if it's leaking before you start!! (Bottom part of the post!!)

http://www.corvetteactioncenter.com/forums/showpost.php?p=897740&postcount=15

 

[Toms007]

Tom when you get the EGR off, Try this before you start cleaning and messing with the pintail!! It will give you a Idea if it's leaking before you start!! (Bottom part of the post!!)

http://www.corvetteactioncenter.com/forums/showpost.php?p=897740&postcount=15

Thanks Junk, I will do that first. Hey when I stopped in at the parts place today they were asking me if was planning to break the studs off when I removed the EGR valve....I think they were just pulling my leg, but should I soak those nuts down overnight before trying to take these off, or am I not going to have problems?

 

[Toms007]

Pulled the EGR off and it was cruddy but when I sprayed the cleaner in it didn't leak or seep around the pintle. I went ahead and clean it up pretty good. I stopped up to the parts store to get my gaskets and they ordered the wrong ones...Oh well I wasn't going anywhere in the Vette today any how.

I also took the time to remove the IAC and clean it up as well, it wasn't too bad either, but I gave it a good cleaning too. I think I'll pull the intake air tube and clean the TB while I am at it.

 

[Toms007]

Well, it appears that my problem is gone. I got the TB cleaned yesterday and everything re-assembled today and fired it up and no stumble. I'll let you guys know if anything changes.

 

[JimBobC4]

Pulled the EGR off and it was cruddy but when I sprayed the cleaner in it didn't leak or seep around the pintle. I went ahead and clean it up pretty good. I stopped up to the parts store to get my gaskets and they ordered the wrong ones...Oh well I wasn't going anywhere in the Vette today any how.

I also took the time to remove the IAC and clean it up as well, it wasn't too bad either, but I gave it a good cleaning too. I think I'll pull the intake air tube and clean the TB while I am at it.

How do you clean out the IAC ? is it safe to just squirt some carb cleaner in it ?

 

[LT4man]

Tom, that's pretty cool. Looks like you got to the root of your problem.

As a maintenance idea, depending on the miles you put on in a year, what you did should probably be done about every 15-20k.

As a side note, I NEVER clean the EGR valve on my LT4.

Can the class tell me why?

SAVE THE

 

[LT4man]

How do you clean out the IAC ? is it safe to just aquirt some carb cleaner in it ?

I would suggest removing the Idle Air Control motor. Made sure it faces down (electrical connector facing up) and spray either carb cleaner or throttle body cleaner onto it. Use a soft bristle toothbrush or a rag to wipe the carbon off the pintle. Spray a little into the TB. Reinstall the unit and you should be good to go!

SAVE THE

 

[Toms007]

That's pretty much the routine I used to clean the IAC. I used CRC Throttle body cleaner and sprayed it onto the pintle/spring and gently (with an old tootbrush) brushed that area. Then I sprayed some into the IAC opening in the trottle body.

I can only guess that the LT4 doesn't utilize an EGR valve.

 

[gmjunkie]

Can the class tell me why?

SAVE THE

Is this a Multiple Choice Test??
1.You always use Name Brand Quality Fuel.(Moble/Exxon,Chevron/Texeco,Shell,exc.)
2.You never store your car unless it has a full tank.
3.You drive your car Daily,if weather permits.
4.Your car is always properly warmed up.
5.Your car is always properly tuned.
6.Your car is always properly serviced.
7.You'd Never let a MoonShine toting HillBilly drive it.
8.Your car is always locked in the garage with the keys and fob in it and it don't go anywhere!!!
Damn Gregory,Sorry I just couldn't resist that!!

 

[gmjunkie]

I can only guess that the LT4 doesn't utilize an EGR valve.

That would be my guess too!! Every one I've had just had a plate on the back of the intake!!

 

[JimBobC4]

That would be my guess too!! Every one I've had just had a plate on the back of the intake!!

LT4's are just too darn cool for an EGR valve. They are so clean and efficient they don't need one.

 

[Toms007]

Is this a Multiple Choice Test??
1.You always use Name Brand Quality Fuel.(Moble/Exxon,Chevron/Texeco,Shell,exc.)
2.You never store your car unless it has a full tank.
3.You drive your car Daily,if weather permits.
4.Your car is always properly warmed up.
5.Your car is always properly tuned.
6.Your car is always properly serviced.
7.You'd Never let a MoonShine toting HillBilly drive it.
8.Your car is always locked in the garage with the keys and fob in it and it don't go anywhere!!!
Damn Gregory,Sorry I just couldn't resist that!!

I saw that one coming!