The ole 86 is still not running right. Still boggs off idle when cold. Seems to take forever (10-15 mins) to come to operating temps (200-220). Fans kicks on at 220'ish. Once at temp the idle surges from 600 to 1000 rpm. It never seems to run "smooth". IT does have good power when I "get on it". Pops out of exhaust after revving or decelerating (still open headers). Idle surge is reduced but it seems to run like crap if I run it in Field service mode (A&B grounded). Removed spark plugs to do a compression test - Odd Cylinders look real good - Even Cylinders were sooty like running rich.

Compression test results:
1&2 - 170
3&4 - 165
5&6 - 160
7&8 - 150 &155

Vacuum at idle - 16 & steady

Stuff done since delivery on the flatbed and not even turning over:
Bought FSM
Disabled/bypassed VATS completely - got it running
Replaced MAF and both relays (getting codes)
Replaced ecm temp sensor (front of intake) (getting code)
Replaced Fuel pump, fuel filter and fuel injectors (FIC)
Removed and blocked off cold start injector
Replaced intake gaskets
Readjusted valve lash
No play in the dizzy (even though that sounds fun)
Visual inspection of valves, springs, and pushrods
Checked several times for vacuum leaks (only vacuum connected currently are the PCV, brake booster, and fuel pressure reg - all else capped off)
New cap and rotor (purchased plugs and wires today)
Set minimum idle as per Tech Tips
Changed oil and filter twice
Replaced coolant lost during intake removal (looked fine)
Checked timing (cant find the tan/black wire to unplug but it was at 20 deg BTDC at idle. unplugged ESC and it was at 6 BTDC)
Installed long tube headers
3 wire o2 sensor in collector (have verified closed loop operation)
Removed AIR system and blocked off the EGR (wasnt hooked up when purchased)
Knock sensor wire connector missing (need to replace)

Another strange observation - There is no EGR and the knock sensor is not connected YET - I have never gotten a code for either one.
Idle does temporarily (5 mins or so) smooth out if, while at temp, I shut down, disconnect battery (like clearing codes) and then restart.

Currently I am not getting any codes under normal operation. I get codes if for example, I remove the MAF or TPS plug while running.

And if you haven't seen my other posts, it is an 86 with an OEM roller cam motor (not sure what year), one 128 head and one 113 head. This has been a crazy, mostly fun, and quite frustrating journey so far.
At least I haven't broken any bolts off or stripped any nuts in the last two or three days.

Sorry for the long post, but I am long winded and I'm trying to cover all the bases.
Thanks for any suggestions and help that you all can provide.

 

128 and a 113 head? were these heads milled to the same height? if they weren't couldn't that mess up the push rod length? I have to think that chambers in the heads match cc wise? maybe it is just me but i couldn't see myself mixing and matching something so important. if that is working for you then fine. but as you described the different sides are burning differently. i would tend to think the issue is in the different heads.

 

They are not on there on purpose. I just discovered "the difference" this past weekend. I don't know if there is any major differences in the heads. I have zero history on this project.
I even stripped the valve covers this weekend (they were painted black) and they appear to be made of different materials. One appeared to be more porous - if that makes any sense.

 

Well I can bet the reason why Odd (driver's) cylinders look good, is that the single O2 sensor is in the driver's side exhaust...
So your odd cylinders are having the AFR adjusted by the O2 sensor and it isn't translating to the other side because it is a different head.

I would guess that the 113 is on the driver's side and the 128 is on the pass.

 

You must be psychic - yes the 113 is on the drivers side. Not sure that I follow why that would not "translate" to the even (128) side. ECM should adjust the whole system, shouldn't it? Going to change the plugs tomorrow (depending on the rain) and the wires. Then I will definitely be able to see how the cylinders are acting.

How about the compression test? I did it once when I first got the vette (3 months ago) and the readings were the same this weekend. Are they OK?

I'm really starting to wonder if it is not an ECM problem with the "no codes" for EGR or knock sensor (damn computers are going to be the end of us yet). AND - I'm not really comfortable with the different head thing. They should be close enough - but I always was taught that engines don't work on "close enough".

I would really like to know who owned/worked on this car and kick them in the teeth.

 

You're right. There could be multiple issues at work here, but the reason why I knew was that the 113 was on the driver's side is that it is a much better head than the 128. It will flow more air. To balance that extra air flow (detected by the O2 sensor in thee driver's side exhaust stream) the computer adds more fuel, now you have the 14:1 AFR in the 113/driver's side bank the computer is shooting for.

The problem is, this computer assumes the motor is the same on both banks and does not monitor AFR on the passenger side. Thus when it richens things up to its set AFR, the side with 128s don't have as much air making their effective AFR much more rich.

Now as for the other issues, it depends on what you want to do with the motor. But I would probably start by trying to get a square setup on there with matching heads. It could be your bad idle is caused by the surge occurring by dumping too much fuel into the passenger bank OR it could be a vacuum leak OR other things, but it is hard to know with this odd setup on the motor. That would be where I would start but maybe others know more...

Also, I feel your pain...

 

Now I follow you - makes sense. I feel that there is a complete tear down in the near future. If I'm gonna pull heads then I might as well check rings and bearings and the list goes on. My budget is limited - so I will have to be careful of the "while I'm in there" syndrome.

 

The open headers could be causing your idle problems. The O2 sensor is ussually mounted in the collector and the short collector could be allowing air back into the system making the O2 sensor readings incorrect. Add at least 20" of pipe onto each header (or the Y-pipe) and see if your idle problems go away. I do not believe the 128 Vs. 113 head is a big problem. The heads flow similar amounts of air but the exhaust port on the 113 head is better and that head will make a little more power. The power difference will be the greatest at WOT high rpm. At idle there should be little difference between the two heads.

The poping in the exhaust after you rev the engine is the result of the open headers. the mixture burns slowly when cylinder pressure is low and lean. When you let off on the gas with open headers the mixture is still burning (because it is lean and at low pressure) when it leaves the cylinder and enters the exhaust pipe (that is the pop you hear).

I cannot answer why you haven't seen a code for the EGR or knock sensor yet. Maybe you haven't driven the car long enough for the EGR code to appear. The knock sensor code will not be set until you go to WOT after the engine reaches 195 degrees. Have you ever floored the car after it reached 195 degrees or more?

 

I don't have tags/insurance on car yet so no I haven't driven it for any extended time and I have not done WOT yet. I have gotten into it but not WOT. I thought open headers may cause problems - need to get to shop to put the duals on ASAP. It's also upsetting the neighbors and limits me to daylight running only. Still going to try to get a 113 head to match.

 

5150? The previous owner?

 

With open collectors, reversion will bring fresh air into the collectors and will give a false reading. On my bracket car, there is a huge difference when I monitor aft with open headers vs a y-pipe.

 

I would check and see if there is a knock sensor code. you are supposed to have a systems check with the computer just after starting it up, and no knock sensor could be pulling back the timing.

 

The 1986 car does not check the knock sensor circuit until the car is at WOT after the first time it gets above 195 degrees. It will advance the timing a drastic amount and listen for knock if no knock is detected it will assume the knock circuit has failed and set an SES light. If you never go WOT after 195 degrees or never let the engine heat up to above 195 degrees the knock circuit check will not happen. (It is a strange way to check for proper knock sensor operation)

 

I read that in the FSM that WOT after 195 but it also said that it runs the test once per start up. That had me confused but I think bjankuski, that is correct. It is a crazy way to test for knock though.
If I can't find that bypass wire connector to set base timing, what are my options? I disconnected the ESC and it showed 6 deg BTDC. Reconnected it and it went to 20 deg BTDC. Is this accurate? It does advance with throttle, also.
IIRC that time it showed a code. Hard to remember - there have been so many codes. It was a happy day when I was able to drive the neighborhood and not have the SES light come on.
Haven't gotten to change the plugs and wires yet - end of the school year and every evening has been band concerts, awards ceremonies, presentations, etc...

 

Update:
Had 2.5 all stainless dual exhaust put on yesterday with x-pipe and Magnaflow Turbo Mufflers and LT1 style tips. Cost was a little more than I budgeted but it was well worth it. The idle is SMOOTH now and the hesitation is very slight when it is cold. Changed the plugs and put new Accel custom length wires (what a PITA).

Thanks everybody for the input I guess that exhaust makes a lot of difference.

New problem. Get a code 33. I wont say it is intermittent but it sort of is. It does not happen every time but most times during my cruises through the neighborhood today and on my way from the muffler shop. Driving along just fine and then all of a sudden, loss of power, SES light, rough idle (not surging). Reset codes and then it is fine for a little while. Really, I can stop the engine, reset ECM, start back up and drive and not get the SES light.

Time to break out the FSM and volt meter. Guess my wire chasing is not over yet. Going to change out the MAF (still under warranty).

Also, drove quite a bit and still no SES for the EGR.