Tuning Help

[86DarganGN]

3 years ago I purchased a 86 GN and just got it out of the garage last week. I bought the car blind. The motor would not idle and ran rough at low RPM. The motor had an extra fuel injector attached to the throttle body and wires and relays that I new was not stock. Extra wires went to the gas tank and under the back seat to the trunk. I removed all the extra hoses and wires but the car still would not idle. I replaced all of the emission control stuff, IAC, TPS, vacuum check values and vacuum hoses, thinking that must be the problem but still no luck.

At that point I figured my problem was internal. I removed the intake; the gaskets did not seem to be sealed very well. I had the heads reworked and the machine shop said I also had several bad value seats and replaced everything. At that point I was only going to R&R the leaking rear main seal when I looked at the main bearings I knew I was in for an engine overhaul instead. I removed the engine and the same machine shop overhauled the engine:

Bored .030
New pistons and rods
Polished the crank
Balanced the assembly
New oil pump
New lifters
New Iskey 208-208 P/N# 1194-CY cam

Bolt on parts
3", aluminum 3 row radiator
3" SS flat flange down pipe Adjustable waste gate
3" SS test pipe
2 ¾” exhaust system
SS cross over pipe W/ new gaskets
New 42.5 lb injectors
Adjustable fuel pressure regulator
E3.42 spark plugs
Hot wire kit
Walboro 304 fuel pump w/ basic install kit
Scanmaster 2.1
93 octane Red Armstrong Chip
TA 49 Turbo
Heated O2 sensor
3 bar map sensor
3” LT1 MAF
MAF Translator
2800 Stall convertor
Knock gauge and sensor
Oil pressure gauge and sensor
Temp gauge and sensor
Boost gauge and sensor

I drove the car about 125 miles. I followed the engine break-in procedures very carefully. I purchased most of the bolt on parts listed above from the late Jay Frick. Jay was semi local and agreed to help tune my care. From what I have read my AF is low, Bl high and Iac is high.
My first tuning data;
02 117-730
AF 04-05 (note the AF started at o6 went to 04. I changed the translator base setting from 3 to 5. The AF went to 07 for a while and worked itself back to 4 after driving.)
L8 29-31
Bat 14.
Int 123-133
Bl 157
Clt 168
Ats127
R 800-925
Tps 42
Iac 48-51 (note the Iac was 36 when the engine was started, after the overhaul. The Iac jumped to 72 during the first 50 miles. When I changed the MAF translator base setting from 3 to 5 , I could adjust the IAC to 48 but no lower. Is 10-25 what the target rate should be?)
Cc 09-245

I drove the car again until the engine was at operating temperature and confirmed my fuel PSI was 43. I removed the negative battery cable and switched the translator back to the basic setting then replaced the negative battery terminal. When the engine was started, the IAC was a 0. I had never seen it below 36 before. I adjusted the throttle plate until the IAC was 17 and the TPS was 38. The engine was still running fine and I thought I had my problem solved! I was excited, all of the numbers looked in line, MAF 6, Int 123, Bl 129, rpm 800-825 and holding steady. I drove the car about 30-35 miles. The IAC crept up to 28 but the car ran well. I stopped to get gas and turned the engine off. Since my TPS was 38, I adjusted it to 42 before re-starting the engine. When I started the engine the engine, the IAC was up to 98 and the TPS was still at 42.

Now I am really confused. Will the IAC change each time the engine is shut down?

I looked for an exhaust leak and did not see or hear anything. If the problem is an exhaust or vacuum leak would the engine run that well only until I shut the engine off?

My current readings are:
02 103-730
AF 06
L8 39
Bat 14.
Int 123-131
Bl 118
Clt 164
Ats105
R 925-975
Tps 42
Iac 74
Cc 15-252

Any suggestions would be greatly appreciated.

 

[lolo86GN]

This website might be helpful to you...... lots of good reading material... http://www.vortexbuicks-etc.com/basics.htm

Look up the section about adjusting the tps and IAC... when you adjust one it can throw the other one off so follow the directions and see what happens. If you had exhaust leaks your BL would be above 128 and not 118 like you stated. anything below 128 means that your ecm is pulling fuel to compensate for a rich condition.

What kind of translator are you using by the way? Is it the regular translator or another model?

 

[86DarganGN]

This website might be helpful to you...... lots of good reading material... http://www.vortexbuicks-etc.com/basics.htm

Look up the section about adjusting the tps and IAC... when you adjust one it can throw the other one off so follow the directions and see what happens. If you had exhaust leaks your BL would be above 128 and not 118 like you stated. anything below 128 means that your ecm is pulling fuel to compensate for a rich condition.

What kind of translator are you using by the way? Is it the regular translator or another model?

I have a MAF Translator, "Horse Power in a Box". 6.25

 

[lolo86GN]

I asked about the translator since you said you had been adjusting the settings... You stated that you moved the base setting to 5... That setting will give you a lean idle witch is exactly what you have with the 118 BL reading. So that looks OK though i'm no expert.

 

[SS502]

I would upgrade the chip, had a Red Armstrong 93 chip in my car when I first bought car, Not knocking him, just a little old school. I use Eric's @TurboTweak, but I hear Full Throttle Speed is also a good choice. Just my opinion. Again, not knocking Red.

 

[dennisL]

Quite often the IAC does go to a different number each time you start the engine. The reason is the ecm cycles the iac each time the engine is shut off. Then, on the next start it opens it a specific number of steps, as programmed in the chip. During warm-up the IAC count changes (goes down) and while driving, it will go up as you push on the throttle.

You can manually reset the IAC before checking/adjusting it, which ensures the actual IAC position and the ecm's perceived position match. Basically it synchronizes the two. You should manually reset the iac after replacing it.
Manually “reset” the IAC by performing the following:
1) Jumper ALDL connector pins A and B. (top right two pins)
2) Turn the ignition on but do not start the engine. The ECM sets the IAC count to zero. Wait 30 seconds so the IAC has more than enough time to seat the pintle. Leave ignition on.
3) With ignition still on, disconnect the IAC electrical connector. (Be careful, not much room.)
4) Turn the ignition off, remove the ALDL jumper, and reconnect the IAC electrical connector.
This establishes the seated or zero reference point. The next time the engine is started, the IAC will go to a count of 150, then count down (extend) as the engine warms.

I know its a pain in the ... but after making an IAC adjustment, check/adjust the tps to 0.44V, shut the engine off. Wait a minute then restart and check/adjust both again. The iac and tps adjustments interact with each other. The ecm cycles the iac at shut off and startup. Eventually, they settle into the "proper" numbers.

 

[86DarganGN]

I would upgrade the chip, had a Red Armstrong 93 chip in my car when I first bought car, Not knocking him, just a little old school. I use Eric's @TurboTweak, but I hear Full Throttle Speed is also a good choice. Just my opinion. Again, not knocking Red.

I have read the same thing on other posts but I did make some improvements today.
I removed, checked and replaced the IAC. The IAC and the air passages were squeaky clean. I started with the basic throttle plate adjustment at one thread past the housing. When I started the car the IAC reading was around 56. I drove the car until the engine was at 164 degrees and made very small adjustments clock wise to the throttle plate screw. I also adjusted the TPS and turned the engine off after each adjustment. After approximately 6 adjustments I have made a considerable improvement. With the car in park;
My current readings are:
02 103-730
AF 05
L8 32
Bat 14.
Int 123-133
Bl 137
Clt 167
Ats134
RPM 875-900
Tps 42
Iac 11 (was 74)
Cc 00-254

Any suggestions would be greatly appreciated.

 

[86DarganGN]

I asked about the translator since you said you had been adjusting the settings... You stated that you moved the base setting to 5... That setting will give you a lean idle witch is exactly what you have with the 118 BL reading. So that looks OK though i'm no expert.

I have the base setting at 3.

 

[turb0buick57]

If you were semi local to Jay Frick, I would send a pm to stagemonster(jason) on this board. He is from around the monroevile area and works on a lot of Turbo buicks around. Good honest guy to know and a big help if your into these cars.

 

[lolo86GN]

I have read the same thing on other posts but I did make some improvements today.
I removed, checked and replaced the IAC. The IAC and the air passages were squeaky clean. I started with the basic throttle plate adjustment at one thread past the housing. When I started the car the IAC reading was around 56. I drove the car until the engine was at 164 degrees and made very small adjustments clock wise to the throttle plate screw. I also adjusted the TPS and turned the engine off after each adjustment. After approximately 6 adjustments I have made a considerable improvement. With the car in park;
My current readings are:
02 103-730
AF 05
L8 32
Bat 14.
Int 123-133
Bl 137
Clt 167
Ats134
RPM 875-900
Tps 42
Iac 11 (was 74)
Cc 00-254

Any suggestions would be greatly appreciated.

Those look good to me.... Only thing is that your TPS might need to be a little bit higher at idle... most will set it a .42 with key one engine off and after starting the car you should see .44 on the scanmaster... If thats the best you can get it to then i wouldn't worry much about it. Don't forget about WOT voltage either.. Should be set at anything over 4.0.. Besides that your numbers look pretty good... The BL at 137 is ok as anything +/- 10 will do...