short and sweet: rough start and idle

Downtownandy · 09-22-2013, 04:17 PM

Hello all. I've posted before and done some research in other threads and still have not been able to diagnose the problem.

Short and sweet: 85 euro carrera. No o2 sensor, steve wong chip. Everything else stock.

Doesnt want to start and if it does it doesnt want to stay running at idle unless I rev it. Once im out on the road its good until I have to come to a stop sign and idle.

Replaced chts, fuel filter, icv, put a multimeter on the cap and rotor. I have a spark. If I disconnect the chts in the bracket and then try to crank it for like 10 sec, then reconnect it and crank it, it fires right up and stays idling okay for a few min.

Any thoughts please? Need to get this 9 month old issue fixes.

Guardsred911 · 09-22-2013, 06:18 PM

02 sensor relay under the passenger seat? I have an '80 SC, so not sure if it's the same, but I had similar symptoms... it was a $12 fix

steely · 09-22-2013, 08:18 PM

check for vacuum leaks and that the idle (micro) switch is ok too. make sure the new icv is vibrating/buzzing, otherwise the dme isn't giving it 12v or providing or drive signals.
My PO told me I didn't need an O2, but when I hooked it back up, it actually helped.

Downtownandy · 09-23-2013, 03:56 PM

I have checked it for vacuum leaks with some carb cleaner, it did bog down a little at some spots, but its hard to even get it to idle long enough to check it. Doesn't it seem strange that if I unplug the chts and give it a few seconds of turning the key that when I reconnect it (and it smells of unburnt fuel) it fires right up and stays idling fine? I know there is something goin on with the fuel system but I cant nail down what..

steely · 09-23-2013, 06:47 PM

That is odd about what happens with starting just after you re-install the cht, but if you have no O2 sensor and another real problem, I don't know how to figure how it would react by introducing a 3rd problem (chts disconnect).

The bogging you got when you sprayed carb cleaner is odd too, I would have expected it to perk up. My guess (as in guess) is that you might be running rich. Re-adding the chts might lean it back out a bit, but I don't know why it wouldn't start in the first place (before you removed it). Would be interested to know if you always ran w/o the O2 sensor, and if the basic mixture settings were changed.

if the TB idle micro switch isn't working, the DME never gets the idle signal to position the ICV properly. And if the ICV drive transistors die in the ICV (it has happened), the ICV won't position properly. Check the micro, check the center ICV pin for 12v and feel for buzzing.

Hopefully some others can offer some better ideas.

Downtownandy · 09-24-2013, 07:28 PM

I am definitely running rich. Bought the car just over a year ago and the problem started about 6 months ago. Haven't done a valve adjustment since I've owned it, if that makes a difference. I will try to troubleshoot the tb switches.

Downtownandy · 09-24-2013, 07:31 PM

Ive never had an o2 sensor. Theres a homemade test pipe where the cat was, and the PO said he likes it running a little rich and the performance was better w/o the o2 sensor.

steely · 09-25-2013, 04:58 PM

I think the rich part might be a prob, the only thing I can suggest is to get her a bit leaner to see if that is the issue, and then go from there.

Can you check the plugs to see how they are not fouling?
Maybe do a search here for similar conditions / path forward.

Downtownandy · 12-12-2013, 11:21 AM

Well since I havent resolved this through everything I've tried, im going to go pay $95/hr to get it figured out