IAC counts can this be back probed?
Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
IAC counts can this be back probed?
Looked liked I found my ruff idle glitch only to have it return today. I think I may have a IAC or conector promblem. Yesterday I reset the IAC per FSM, idle was perfect. Today started the car and ruff idle returned, stopped the car and did another reset, smooth. Got home stopped engine , restart ruff idle back! Sometime ago I did replace the IAC connector when the tab broke while cleaning the IAC.
Question: can I back probe the connection and read the idle voltage, should be stable at idle at conector and IAC are good? Don't have a scanner as yet to look at the counts! Next purchase on my shopping list.
Thanks
Question: can I back probe the connection and read the idle voltage, should be stable at idle at conector and IAC are good? Don't have a scanner as yet to look at the counts! Next purchase on my shopping list.
Thanks
Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,074
From: Lansing MI
When you say "rough idle" do you mean unsteady ? as in RPMs fluctuating up and down ? or do you mean rough as in misfiring and not smooth ??
The IAC valve wont really cause a rough idle where it seems like the engine is not running smoothly or misfiring in an unstable or erratic fashion, but an EGR valve sticking partially open sure will ...
The IAC valve wont really cause a rough idle where it seems like the engine is not running smoothly or misfiring in an unstable or erratic fashion, but an EGR valve sticking partially open sure will ...
Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
The idle I refer to is more like a miss very interment . Only happens in drive and once the motor is hot much less in frequency. The EGR was replaced in Jan prior to a smog check! Car passed with flying colors. Took the car out today and at any given time it will feel like a light shake or a stumble only at idle in gear.
Would a scan show anything. Been thinking of buying a cable to use with my laptop.
Driving me nuts.
I've replaced entire fuel system from fuel pump to Bosch III, vented distributor cap and rotor. Plugs, wires, ICM and coil and every sensor I can think of
Thanks for your help,I'll double check the EGR.
Would a scan show anything. Been thinking of buying a cable to use with my laptop.
Driving me nuts.
I've replaced entire fuel system from fuel pump to Bosch III, vented distributor cap and rotor. Plugs, wires, ICM and coil and every sensor I can think of
Thanks for your help,I'll double check the EGR.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
What year is the car? I looked at your profile but I'm not adept at spotting the differences from year to year.
The IAC is a motor, so there is no way to tell by measuring where it is set to. You really need a scanner or software to tell you what the IAC counts are.
The IAC is a motor, so there is no way to tell by measuring where it is set to. You really need a scanner or software to tell you what the IAC counts are.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Did you take the IAC housing off and clean all the passages in the TB? Did you reassemble with new gaskets or did you reuse them?
Put it on your BBS (Beg, Borrow, Steal) list. Lets try borrowing one from Autozone. "Buy" it at full price and if you return within 60 days, full refund. See if you can beg one off someone near your area with one. If you were near me, I have an Auto X-ray, Snap On Brick and testing a datamaster.
Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
What year is the car? I looked at your profile but I'm not adept at spotting the differences from year to year.
The IAC is a motor, so there is no way to tell by measuring where it is set to. You really need a scanner or software to tell you what the IAC counts are.
The IAC is a motor, so there is no way to tell by measuring where it is set to. You really need a scanner or software to tell you what the IAC counts are.
Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
That is your first problem. FSM will ASSUME (and we all know what that means) that everything else is perfect but the idle. I use IAC counts from a scanner so I can see if the tach is correct (often not) and if I cannot get it past 0 no matter how far I close the butterflies, I go looking for air leaks. Also timing has to be spot on.
Did you take the IAC housing off and clean all the passages in the TB? Did you reassemble with new gaskets or did you reuse them?
Put it on your BBS (Beg, Borrow, Steal) list. Lets try borrowing one from Autozone. "Buy" it at full price and if you return within 60 days, full refund. See if you can beg one off someone near your area with one. If you were near me, I have an Auto X-ray, Snap On Brick and testing a datamaster.
Did you take the IAC housing off and clean all the passages in the TB? Did you reassemble with new gaskets or did you reuse them?
Put it on your BBS (Beg, Borrow, Steal) list. Lets try borrowing one from Autozone. "Buy" it at full price and if you return within 60 days, full refund. See if you can beg one off someone near your area with one. If you were near me, I have an Auto X-ray, Snap On Brick and testing a datamaster.
Have not found a scanner at any local AZ, Kragen or NAPA, just readers for codes. I use the paper clip to read codes, no codes.
It's a 93 LT1, bone stock.
Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
I let the car sit overnight here's what I found.
Turn key on twice let fuel pump run.
At start slight backfire, intake I believe.
Second start idle smooth.
Watched temp at 104-105 engine started to miss.
Miss there all the way to 196 degrees.
Seems like miss starts as engine goes from Open to Closed Loop! Just based on temp at 104 degrees.
Question: could the miss be from the Bosch o2 sensors that I installed last fall, less than 2,000 miles ago. Read all kinds of good and bad results with the Bosch O2's.
Thanks
Turn key on twice let fuel pump run.
At start slight backfire, intake I believe.
Second start idle smooth.
Watched temp at 104-105 engine started to miss.
Miss there all the way to 196 degrees.
Seems like miss starts as engine goes from Open to Closed Loop! Just based on temp at 104 degrees.
Question: could the miss be from the Bosch o2 sensors that I installed last fall, less than 2,000 miles ago. Read all kinds of good and bad results with the Bosch O2's.
Thanks
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Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
Thanks for your insight on this.
Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
There's that word I was hoping I wouldn't see, however you did say distributor and not the dreaded opti! Maybe there's still hope, car only has 68K on the original. 
I ordered a scanner cable today, should be here before the weekend. I'm not afraid of the opti install, did the water pump and cap and rotor last spring. Hardest part is choosing a replacement.
Thanks
I ordered a scanner cable today, should be here before the weekend. I'm not afraid of the opti install, did the water pump and cap and rotor last spring. Hardest part is choosing a replacement.Thanks
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
There's that word I was hoping I wouldn't see, however you did say distributor and not the dreaded opti! Maybe there's still hope, car only has 68K on the original. I ordered a scanner cable today, should be here before the weekend. I'm not afraid of the opti install, did the water pump and cap and rotor last spring. Hardest part is choosing a replacement.
Thanks
I ordered a scanner cable today, should be here before the weekend. I'm not afraid of the opti install, did the water pump and cap and rotor last spring. Hardest part is choosing a replacement.Thanks
Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
Very true on the mileage gauge. I really think I have read more opti going bad stories with cars having low mileage compared to cars used all the time with higher mileage.
Thread Starter
Racer
Joined: Sep 2011
Posts: 462
Likes: 30
From: Riverside California
Any advise on how to verify the distributor is on its way out? Should I have a shop run a scope or? The idle issue seems to be getting more pronounced each time I start it? No codes as yet!
Recent ICM, coil, plugs, wires installed, fuel system checks out good.
Any advise would be appreciated.
Recent ICM, coil, plugs, wires installed, fuel system checks out good.
Any advise would be appreciated.