idle....or lack thereof

[nyernga]

Once upon a time in a galaxy far far away I changed my IAC, in line fuel filter, adjusted the TPS per the service manual and cleaned the TB. Lo and behold the gremlin is still there. Start car and a heavy fuel smell appears, car runs fine but at no specific temp while sitting at a light, the engine begins to "hunt" going from a 500 rpm to 1200 then back to 400 then up to 1200 then if I don't "throttle" the pedal it stalls out. It eventually idles fine again.
No "service engine" light but I did pull 3 codes....a 13 which is an open condition on the O2 sensor. A code 34, MAF sensor, and a code 44 O2 sensor lean (which belies the fuel smell). Since they apparently are intermittent and are simply stored in memory and not triggering the service light I am kind of at a loss on which of the 3 to check. I'll probably just change out the O2 sensor for starters but I am open (unlike my sensor) to any and all ideas.......

Len

 

[Hrtbeat1]

Have you tried resetting the computer to see if the codes come back? From what you say I don't believe they will. I would think it would be one of two things, I've seen both so ... First I would try replacing the coolant temp sensor, its about $6 at Advance Auto. Its hard to see and to get to, below the TB, under the Air duct, at the front edge of the intake manifold. If you have all the Air stuff it's really tough. Should have a three pin connector with one of those latch thingies, IIRC its a 3/4" box or open end wrench (a socket just won't fit.) The CTS is a variable resistor and they have been known to work erroneusly in parts of their operating range, but at the same time work correctly in other parts.

My other thought is the ECM itself. Hopefully its the CTS.

 

[nyernga]

Have you tried resetting the computer to see if the codes come back? From what you say I don't believe they will. I would think it would be one of two things, I've seen both so ... First I would try replacing the coolant temp sensor, its about $6 at Advance Auto. Its hard to see and to get to, below the TB, under the Air duct, at the front edge of the intake manifold. If you have all the Air stuff it's really tough. Should have a three pin connector with one of those latch thingies, IIRC its a 3/4" box or open end wrench (a socket just won't fit.) The CTS is a variable resistor and they have been known to work erroneusly in parts of their operating range, but at the same time work correctly in other parts.

My other thought is the ECM itself. Hopefully its the CTS.

Changed the CTS about 4 months ago. As you can tell I'm psychologically avoiding the ECM as the culprit. :cry I'll clear the codes and see if the come back. If it idled bad ALL the time, it would be easier to figure out but it's got a mind of it's own.

Next stop...............the twilight zone (aka my mechanic)

Thanks hrtbeat,
Len

 

[gmjunkie]

Changed the CTS about 4 months ago. As you can tell I'm psychologically avoiding the ECM as the culprit. :cry I'll clear the codes and see if the come back. If it idled bad ALL the time, it would be easier to figure out but it's got a mind of it's own.

Next stop...............the twilight zone (aka my mechanic)

Thanks hrtbeat,
Len

I had a 91 do this a while back!! I changed the IAC and CTS, Better but no Cigar!! Ck'd all ground's and EGR,EGR and manifold had Crud in it!! nouthen 2 can's of Throd. Body Cleaner would not Fix, Sprayed Let Set,Sprayed Let Set,Sprayed Let Set, about 6-8 times!! Put it together enough to start with out EGR. Now When ya start it it will Take off Like a Runaway Detroit Dsl.!! Start,shut off,start,shut off, 6-8 Times!! That Beech Blew Carbon All over It, My Shop, My Car's, There was not a Vehicle in my shop that did not have Chunk's of Carbon on them!! Took 2 EGR gaskit's,put a little round stainless screen from a water faucet from Hwr.store. Cleaned EGR sandwitched screen between gaskit's inlet side of EGR!! It has not done it anymore!!Belong's to a Customer of mine in Fla. http://www.frontiermotors.biz/services.html A micro piece of carbon can keep EGR open just enough to Screw up Idle and still Not Trip a Light!!( Account's for Gassy Smell too!) Just a thought!! Worked for Me,on a Mountain Not to Far,Far away!! junk!!

 

[tlong]

It's just panting from all the flogging!



You might give David a call at Tom Jumper at 770-351-2633 for his opinion. He would be Yoda in our galaxy.

 

[Moonunit 451]

Have you replaced the MAF burn off relays? There are two, behind the battery. They will not infrequently be the cause of the MAF code and are cheap. Less than $30 for the both of them. I'll try and fid a pic.

Try search for burn off relays or MAF burn off relays. This has been discussed here in the past few mos.
http://www.corvetteactioncenter.com/forums/showthread.php?t=69566&highlight=MAF+burn+relay

 

[nyernga]

Have you replaced the MAF burn off relays?

I replaced both of them some time ago. Probably in the neighborhood of 4 years or so. I may try the EGR cleaning that GM mentions and see if that helps. Then again I may just buy a new one and be done with it.
I'm sure it's something simple since the car runs super otherwise. It ran the hell out of the Tail of the Dragon run 2 weekends ago.
Thanks for the input gentlemen.....

Len

ps: To Tim............I never "flogged" the car......