starts fine cold - goes pig rich when warm?

[Tim_C.]

I just got my '86 ESiR started with the fairly new engine.

It starts in cold weather just fine. As soon as it warms up, the idle goes way down to where it barely runs and chugs terribly. At the same time, black smoke is puffing in sync with the chugs from the tailpipe. Chug/black chug/black and so on. Obviously the ECU is telling the injectors to open up more than normal. I can rev it up and it is still smooth as silk, but it won't idle when warm.

I haven't had a chance to address it yet. I figure maybe the coolant temp sensor?

I haven't done the TPS/ISC reset on it yet either. It has a 3 wire O2 sensor on it. The only mods are a stainless header (Chad's equal length one), and a TEP T3/T4 turbo. No secondary air box of course. It does have internal mods, but it purrs like a kitten when cold, so I don't see them as a factor for this problem. It still has AC, cruise, everything else.

Any suggestions on where to start are welcome.

[Ryan_V]

I suspect that ECU coolant temp sensor as well.

[Komeuppance]

Ohm out the CTS, or place a 300ohm resistor in its place. It should be 270ohms at 176F.

 

You will definitely need to do a TPS/ISC reset if it's not been done.

 

-Robert

[Indiana]

There is a voltage reading the ECU tries to move the idle motor to. Setting the ISC for a pre87 is completely different from the 87-89 cars. The ECU looks to set that idle motor position and the result is the rpms you are supposed to be at idle that you set before with that unplugged, just about the same way the later system uses. ECU isn't to find an rpm the rpm is the result of changing the sensor value and you have to set the hard parts first. This is why different MAF and turbos with different cfms, different cams and valve can't always be made to work. No PCV valve letting air into the intake for example. The motor does use that to add with the air/fuel so if its not there or the throttle plate is completely closed its all just a big mess and a CTS isn't doing anything to that.

 

These 86 pages are crude but I think you can read them.

 

http://photos-f.ak.fbcdn.net/hphotos-ak-snc1/hs031.snc3/11847_1055408563635_1778479606_110586_3926034_n.jpg

 

http://photos-h.ak.fbcdn.net/hphotos-ak-snc1/hs031.snc3/11847_1055408403631_1778479606_110585_7275600_n.jpg

 

http://photos-d.ak.fbcdn.net/hphotos-ak-snc1/hs031.snc3/11847_1055411563710_1778479606_110603_5431352_n.jpg

Edited November 2, 2009 by Indiana

[Tim_C.]

Thanks everyone. I'll also double check to make sure I didn't leave something unhooked.

[Tim_C.]

It seems I run for 'moron of the year' award at least twice a year.

I asked my friend at the alternator shop if he wired in my O2 sensor. We were eating lunch at Mcd's of all places. The view there is very good in the play area during lunch time! Anyway, he says, no, didn't you wire it in? I was like, "I don't remember, maybe I did"! LoL! Got back to the shop and checked it, since my car has been parked there for the last 8 months or so. Well, the O2 pigtail on the brand new 3 wire O2 didn't have any wires hooked up, but the wires were tucked in the lines along the firewall, so I didn't notice they weren't hooked up. I thought he did it, he thought I did it!

 

It seems to be running fine now. Plan to get the registration tomorrow and start driving it a little. After I give everything the once over of course. I figure if I missed that, what else did I miss! I guess I was so preoccupied on checking for coolant leaks and headgasket issues that I didn't look for much else.

[Tim_C.]

Well, I ran it some more today and it went back to doing the same thing. I'll get more time to work on it soon. I'll start with the CTS and reset the idle and TPS.

[mikec]

What are the letter-number codes on the injectors? It's possible you have an incorrect injector leading to a mega-rich idle. A bad CTS though will also make the ECU think "engine is stone cold" which makes the ECU run the engine over-rich simulating a carb "choke" function. That shouldn't cause massive chugging or smoke at idle though; normally a car with a crappy CTS idles decently but stumbles (bucks) violently when boost pressure builds up.

 

I'd also look for a leaking fuel pressure regulator - just remove the small "L" shaped vac hose coming from the bottom of it. Any gas in that hose or dripping from the regulator means the regulator is garbage.

 

mike c.

[Tim_C.]

Thank you Mike!

Yeah, the injectors are pretty much brand new '86 injectors I bought from Shelby. They looked pristine from the outside too.

I will continue to dig for clues. I think I have a spare CTS. Maybe even a spare MAF if it is the same as '84? I have a few 4-pin MAFs from '83 - '85. I have interchanged those on the non-IC cars, but not on an '86 IC.

There may be more loose or bad wiring. I seem to get about 20 minutes to look at here and there. I hope to look hard this weekend and see what I come up with. I should have most of the day to check it out.

[Tim_C.]

Well, I figured out what it was. The boost sensor solenoid switch was bad. I knew something was odd looking about it, but I didn't know the '86 set-up very well, so I didn't notice that the port on the solenoid that goes to the pressure sensor was broke off and epoxied shut! The one that sticks out to the side of the solenoid. There are 3 ports. 1. The white port which is feed from the intake manifold port above the row of three on the '86. 2. the blue port that goes over to feed the vacuum on the passenger fender. 3. The yellow port that sticks out side on the same end as the blue port and goes to the pressure sensor. That one was broke off. I replaced the solenoid with one from an '83 which looks the same and is marked the same. That was why I was having a hard time figuring out where to put the vac lines there because I had more lines than places to put them. I didn't look close enough to see it was broke off.

Anyway, now it stays idling fine, and runs like a raped ape! I can't believe how strong and smooth this baby is! TEP must set those T3/T4 turbos up for 18 PSI or so when they ship them. It boosts like made to 14 and then the fuel cut hits. I was in 4th and gave it a little gas to where it just barely boosted, and looked down to see I was doing 90MPH! Chad's header really helps that turbo spool quick too, with mega top end. The Aussie roller cam comes on quick and is smooth as silk the whole way. The RPM range is certainly lower on this one compared to my 7500 RPM engine, but it all comes in quick enough to be plenty strong down low, and it is very fun to drive.

I need to bring the boost down so it doesn't hit the fuel cut, and do some more tuning and buttoning up of some things yet. I hope to start driving it more soon, but we just got hit with snow and it looks like winter is setting in.