HELP...Idle issues

[MT86K5]

I've been having some issues when my TBI 350 is warmed up and I have to sit at a red light or stop for a while in gear. It idles fine in park and neutral but when its in gear and I'm stopped the idle drops down real low (no tach so not sure on RPM's) and acts like its going to die.

Things I've checked so far:
Tested engine coolant temp sensor (ECT) Looks good
Tested throttle position sensor (TPS) Looks good
Cleaned idle air control (IAC) Pretty dirty but cleaned up good and lubed, seems to work fine.
Inspected O2 sensor, it looked normal
Found a possible Vac leak on front of TBI so I repaired it but still no change.
Changed fuel filter.
New plugs wires and distributor.
I also recently cleaned and installed new gaskets on TBI, it made it run a lot better but still no fix.

Another thing that may or may not be related is when its in OD cruising around town, if I give it some gas it seems to chug or kind of shake the vehicle.

Could it be low fuel pressure? EGR? Torque converter? I'm almost at a lost, hoping someone else has had similar issues. I did find a lot of other forums on google where people had the same issue but unfortunately most didn't follow through and post what the fix was.

 

[Burbdood 74]

I'm looking forward to seeing where this goes because that is exactly what I've been battling with my Sub. I wish I had the fix for ya, but it looks as if we'll both learn on this one.

 

[MT86K5]

I did read somewhere that you can unplug the 4 wire connector on your tranny, next to the shifter linkage and if it fixes the problem, you probably have a bad torque converter. I guess its supposed to keep it from locking up but I'm going to get a 2nd opinion on that before I do it.

 

[Burbdood 74]

Well unfortunately the previous owner swapped out the 700R4 in favor of a th350 so that may not help me but I'd give it a shot if I were you.

 

[496truck]

Do a google search on the procedure of how to set base idle on the TBI. Start with that, see if it helps.

 

[diesel4me]

Could be a vacuum leak,or a EGR valve not closing completely...sometimes when the intake gasket are going ,which I hear is common on later GM engines,that can cause poor idle or stalling too...
OOPS..just re-read your post,you already did the intake gaskets...guess that cant be it?...it could be fuel pressure maybe,did you clean the throttle body butterfly and the housing good already??...crud build up there can cause idle issues,as can a ripped snorkel hose going to the air filter...

 

[blazerz]

my egr valve wasn't closing or sealing all the way and it gave me an idle issue a while back......i replaced it with a gm replacement one.....the after market ones looked kinda cheap to me......

 

[MT86K5]

Yea, I'm going to look at the EGR next.

496, I've thought about that. I have the page bookmarked from 3rd gen. The funny thing is it idles normal in park or neutral though and I also noticed last night the cover is still on the TBI over the adjustment screw so I would think it should still be set correct. I won't rule it out though.

Another thing is when the engine is still cold it will idle fine when I come to a stop, it is just after everything gets brought up to temp that it wants to die.

 

[Burbdood 74]

Well I've found my problem. I just got done changing the ICM under the distributor cap, (what a PITA), and all of my problems are gone! I mean absolutely gone. I have a nice steady idle and great power. Throttle response is great and it's not surging anymore.

All of the pain of lying over the engine is worth it and since it's just a few dollars, I'm going to buy a spare one in case my problems come back.

 

[MT86K5]

Well I've found my problem. I just got done changing the ICM under the distributor cap, (what a PITA), and all of my problems are gone! I mean absolutely gone. I have a nice steady idle and great power. Throttle response is great and it's not surging anymore.

All of the pain of lying over the engine is worth it and since it's just a few dollars, I'm going to buy a spare one in case my problems come back.

Excellent! I'll have to look into that. You must be ecstatic.

I just got done spending all day working on mine. I finally got my fuel pressure gauge hooked up, it idles at 11 psi. I also put the cfm spacer on and you can really tell a difference with the throttle response. My first drive it ran great, lots of power and throttle response. After it was warm, I tested my issue I've been having so I stop and leave it in Drive and it seemed better than before. When I get home, I pull in the drive way and test it again then the idle goes to ****.

I'm thinking the computer is relearning everything since I had the battery disconnected. I'm leaving town tomorrow so I'll update when I get back.

So is 11 psi a little low?

 

[Burbdood 74]

IIRC, TBI fuel pressure is in the 11-13psi range so it sounds like your'e doing ok there.

And BTW, I did a happy dance in my carport I was so happy. I'm going to give it a few days to see if it's actually better or I'm just hoping it's better, but I think it's good to go.