alfisti

Hi folks. I posted this on another forum, but it seems like different people here, and maybe some different opinions can shed some light on this.


Overall problem - car failed NJ inspection with sky-high HC.

Idle:
HC: 2597 (220 to pass)
CO%: .11 (1.20 to pass)
CO2%: 6.9
02%: 10.7

High idle:
HC: 1987 (220 to pass)
CO%: .59 (1.20 to pass)
CO2%: 8.1
02%: 9.0

Car also is idling roughly, occasional backfire at low RPM. It would also stumble at low RPM while driving, so I tend to drive it only above 3,000 RPM.

The car is an '87 Carrera 3.2, all stock (aftermarket cat, though). 245k miles on it. Previous owner advised engine was rebuilt at 140k miles.

Since I've owned it (1.5 years):
- valves adjusted at 226k miles, and at 240k miles
- New cap and rotor 230k miles
- New plugs 230k miles
- New O2 sensor 230k miles
- New alternator at around 238k miles

I brought the car in to my mechanic, who looked it over, and found some additional vacuum leaks (this was last week). I also found a "cold" cylinder while warming up, and replaced the fuel injector (#6, I think - closest cylinder to rear of car, on drivers side bank - while standing in front of the rear of the car, nearest on the left). It actually runs better at low RPM now.

I got an AFR meter (Innovate LM-1) and unplugged the O2 sensor (which mounts just before the aftermarket cat), plugged in the LM-01 sensor instead... and observed 1.10-1.15 when warming up, and after warming up, jumps to about 4.00-4.10. That's very, very lean... I tried to turn the idle mixture adjustment clockwise, and found it wouldn't turn any more. Just to test my own sanity, I turned it counter-clockwise, to try to lean it out and see what shows on the meter. The numbers didn't change at all...

My mechanic is confident there are no more vacuum leaks. He ran out of time in working on the car (I came in last minute, and he had other customers cars committed to work on). If there are no more vacuum leaks, what could be causing it to run so lean? And why won't the adjustment screw have any effect?

Thanks
-Glenn

theiceman

what were your number for your last inspection ? when did the rough idling and backfire start ?

The backfiring and popping certainly indicates you are not getting a complete burn.

unfortunately I am not as familiar with the 3.2 but im surprised the Pelican boys could not help you

alfisti

the numbers above are from the last inspection - last week.

The rough idling/stumbling has been there since I've owned the car.

Thanks

theiceman

no the last one BEFORE that
.. I am curious as to what it looked like when running well..

alfisti

Sorry - I don't have that. Only got the car a year and a half ago. In NJ, the inspection isn't needed until 2 years after the last one, and when I got the car, it had been inspected 6 months prior.

Thanks
-Glenn

alfisti

Just to clarify, it's the Lambda reading that hits 4.0 on the meter. Is that even possible? I must be using the meter wrong.

theiceman

hmm thats too bad .. so i am assuming you dont need to pass smog inspection at point of sale, which means it had this problem before you even got the car.
I was hoping things were fine while you had it and something broke.

alfisti

No - didn't need to deal with smog until now. It runs like a freight train from 3000 RPM+, it's only at idle and very low RPM that there seem to be problems.

Is it possible, previous owner/mechanic turned the mixture screw all the way, to compensate for a vacuum leak they never found? Would that explain the numbers above, and the behavior I'm seeing?

Thanks
-Glenn

Steve Weiner-Rennsport Systems

Check the idle switch on the throttle body as well as the electrical grounds on the left intake manifold.

Vane

Years ago my '85 3.2 had strange mixture problems and it was cylinder #3, the left front cylinder looking from rear, intake manifold gasket that leaked.
This leaned the mixture in cyl. #3 and as the temperature sensor is in that cylinder, it richened the mixture.

I would carefully re-check the vacuum leaks.