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SmokinVette.com Forums : Corvette Forums : C4 Corvette Forums : C4 Tech & Performance : 86 TPI Idles Rough, Surges, and Stalls?
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Old 05-09-2011, 08:22 PM   #1
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Default 86 TPI Idles Rough, Surges, and Stalls?

Hi, Im new to the Forum, this is my second post

I recently bought an 86E TPI and its got an interesting set of issues, especially with idle. Id like some opinions and input to start planning a repair route please. Its got a freshly rebuilt motor and trans, AIR pump delete, EGR is connected directly to the plenum(that right?), some hoses are plugged with blots and screws(dislike), its less than perfect I want to fix and restore it, versus watch it rot away.

On start up, the idle drops to 400/500RPM then goes up to 1200RPM, then the idle lowers to and alternates between 600 and 900 RPM. It never stays constant. Its stalling under a minute after start up, and it will stall once the idle drops if I rev it while its in P. Also stalls sometimes when shifting into gear(from R to D). I tried changing out the fuel pump with a new one, but then it would not start. I changed the plugs and wires but to no avail. Any help would be appreciated! This car has potential and Im more a body man than I mechanic, but I love wrenching and getting dirty so Im not afraid to get into it! Want this C4 to actually look and run smoothly like I believe a Vette should
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Old 05-10-2011, 04:14 AM   #2
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Check your MAF sensor.
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Old 05-10-2011, 06:15 AM   #3
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Quote:
Originally Posted by Seabee 86 View Post
Check your MAF sensor.
That was my first thought.
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Old 05-10-2011, 06:20 AM   #4
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My first thought is not your MAF sensor. Rather than going out and spending even more money on something that may or may not work. Your time would better be spent cleaning up your vac lines.
I'm willing to bet that is where your problem lies.
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Old 05-10-2011, 10:07 AM   #5
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Idel Air Control Vavle (IACV).

Also Chech the Pink Wire next to the Fire wall next to the distributor you have look stright down between the firewall and the motor to see it, This wire for the spark Advance or anti knock box on the passside by the Heater fan.

I broke mine during the motor swap the pink wire I also had a IACV go bad on me all these cause the problems you are having after you check for vacume leaks.
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Last edited by Marv02; 05-10-2011 at 10:12 AM.
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Old 05-10-2011, 04:53 PM   #6
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I agree with Marv02, an Idle Air Control valve is a possibility.

I would agree with Slvrvette only if the OP's condition got progressively worse. If it just one day started running like garbage, that sounds more like a faulty component, unless of course a vac line got disconnected.

Either way all are good suggestions; be sure to give your car a thorough diagnosis and as was stated by others, don't just throw your money away at what you think is wrong.
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Old 05-10-2011, 05:54 PM   #7
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Quote:
Originally Posted by Seabee 86 View Post
Check your MAF sensor.
Quote:
Originally Posted by Hotrod View Post
That was my first thought.
I has a brand new MAF sensor. Ill try cleaning it with MAF Cleaner...

Quote:
Originally Posted by slrvette View Post
My first thought is not your MAF sensor. Rather than going out and spending even more money on something that may or may not work. Your time would better be spent cleaning up your vac lines.
I'm willing to bet that is where your problem lies.
I will replace them and get back to you on that

Quote:
Originally Posted by Marv02 View Post
Idel Air Control Vavle (IACV).

Also Chech the Pink Wire next to the Fire wall next to the distributor you have look stright down between the firewall and the motor to see it, This wire for the spark Advance or anti knock box on the passside by the Heater fan.

I broke mine during the motor swap the pink wire I also had a IACV go bad on me all these cause the problems you are having after you check for vacume leaks.
I try to look for this pink wire after work... Oh, this Corvette has no heater or A/C unit and lines. Have an 85 parts car I will be taking the parts from to install it onto my 86. I will order a new IAC soon. Maybe an EGR valve at the same time?

Quote:
Originally Posted by Seabee 86 View Post
I agree with Marv02, an Idle Air Control valve is a possibility.

I would agree with Slvrvette only if the OP's condition got progressively worse. If it just one day started running like garbage, that sounds more like a faulty component, unless of course a vac line got disconnected.

Either way all are good suggestions; be sure to give your car a thorough diagnosis and as was stated by others, don't just throw your money away at what you think is wrong.
Corvette had this problem when I purchased it 2 months ago. BUT, it has gotten worse with the addition of stalling after revving, stalling after starting, and stalling twice while I was at stop lights in the city...

Last edited by C4TPI; 05-10-2011 at 05:58 PM.
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Old 05-10-2011, 06:19 PM   #8
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Stalling a lot? Hows your fuel pressure?
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Old 05-10-2011, 07:21 PM   #9
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Quote:
Originally Posted by Seabee 86 View Post
Stalling a lot? Hows your fuel pressure?
I'll check it with a fuel pressure gauge and report back. It stalled on me twice while I was driving in the city one day shortly after I bought it. Also stalled twice when I shifted from R to D in a parking lot. I inspected my fuel pump and saw debris in the strainer so I tried changing out the fuel pump, but that only led to a no start situation. I had fuel at the injectors, but no fire. Put the old pump back in and it started up with some effort... I was listening to the idle today(it wasn't stalling under a minute after start up anymore), I noticed that when the idle drops, so does the tone of the fuel pump noise. Wrong pump maybe? The plastic connector tip on the wiring harness matched up though...

Edit: Fuel pressure is at 39/40PSI

Last edited by C4TPI; 05-10-2011 at 11:45 PM.
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Old 05-11-2011, 04:14 PM   #10
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This car has an EGR Valve but no EGR Solenoid... Read on Ecklers a faulty/broken EGR solenoid causes rough idle and stalling... Should I look into this is well? I have an EGR sol. from an 85 Corvette if that would work?
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