On start up the engine was surging to a very high idle, 1800+ RPM. Holds that idle for 3 - 4 seconds, then returns to normal
If the ECM is put into Diag Mode, Key On Engine off, disconnect IAC.
Key off, Reconnect IAC, remove Diag jumper, The engine starts like you would expect it to. ( this is a very repeatable process )

right after i bought the car ( 3-4 months ago) I replaced:
plugs
cables
rotor
cap ( but not the coil)
replaced all flexable vacuum lines
did the T.B. bypass
TB dis-assemble and clean
New IAC
New MAF and Burn off relays

This weekend i have :
disconnected the cold start circuit
the only thing i have done new to the car is repair my interior light circuit ( bad door switch) and re-install the fuse.

Engine now starts with an initial idle now of 1500 - 1600 rpm,
returns to normal with in 1 second, then immediatly starts to stumble( also did this before i disconnected the CS circuit), Exhaust smell ( and smoke) indicates the engine is running very rich, and now the dash is acting odd. RPM indicates 4500 - redline at an idle, Oil pressure indicates 45 - 58 psi and a red light ( but also jumps all over), Speed indicator appears to read correctly, and voltage reads 12.2 ( measured 13.0vdc at the battery termnals with engine at idle).

now it did this the other day on my way into work, and when i went out at the end of the day, Dash worked properly, and did not appear to be running rich, voltage indicated at 13.0 . start up was as noted above.

 

When you replaced the IAC did you clean the bore under the TB and assure there was no debris in it? Have you cleaned the TB bore and throttle plates?

A scan tool would tell you what coolant temp the the ECM is seeing and what voltage it is seeing also.

You might want to check battery terminals and look for a loose ground.

BTW, when my MAF died the engine would surge and die, nothing as mild as you describe, and no codes.

 

yep, pulled the TB out, cleaned it inside and out, paying particular attention to the IAC bore.

 

I sort of have the exact oposite....My car cranks, cranks, then cranks, then sputters a little then it goes from low RPM to higher *normal* but it dont wanna go lol...
C4Dreams

 

in chasing possible ground issues being the fault, i found i am missing the ground strap ( braid) from G-104 - G-101, have replaced that,
Now where exactly is G-201, per helms it is behind dash left side near column, have look every where ( well obviously not everywhere) and am unable to locate it... any one? exact location of G-201

 

Yea, that sucks; it's one of the few parts not shown in a wire routing diagram.

I've not had my left hush pannel off yet; hope someone here has been into that area.

 

a picture, Best guess, even strong suggestions?

 

well drive in this AM went smooth, still starts with a high idle ( 1800 rom), dash currently working as expected ( still has digit elements missing in center section), Heat of the day will tell ( i hope) as thats when it seems more apt to start messing up.

 

I tuned ported my 84 two years ago and sent my engine harness out for modifications. The car didn't run when I got it back. I got credited for $1300 from my Credit card. I learned a few tricks in trouble shooting it myself in my quest to make it run. I found many problems by lowering the computer and using a digital voltage meter to test all wires for specific voltages indicated in the shop manual. Ground wires can be check for continuity to the metal frame. These are the wires that plut into the computer. You can use the computer voltage chart in a shop manual to check all voltages to the computer. My 89 shop manual indicates grounds wires to check for CONTINUITY TO GROUND" are:
B3, D1, D3, D10, (A11,MAF SENSOR GROUND), A12,
I used to do this as a last resort but now check it now before anything. I have been able to find any engine electric problems by testing all wires for voltage specified in the manual. Check under driveablity and emissions for the PORT FUEL INJECTION ECM CONNECTOR IDENTIFICATION CHART
If your stuck for good you may want to try this.... good luck!!!