GRX

I just got her running again (new setup, 87 cam instead of a supercharger cam profile). All is well but the AFRs climb to a steady 16:1. No "check engine" light comes on. Is this normal for '85s? This was happening with my previous setup. Everything is new...injectors, MAF, ECM, O2 sensor. There appear to be NO leaks. Exhaust is TIGHT between cylinder head and O2 sensor. Help!

red L98

im sure its the tune , my brothers car had the same problem but it turned out to be bad wiring harness , we had to rewire the whole car . check the volts on each injectors and the mass air. if everything checks ok then you just need a tune . it could also be fuel filter

Mo_Bandy

GRX,

I agree with Red...

Mine at idle after first starting will go to about 12 as it warms up with the A.I.R. pump running will go to about 15.6 then back to 14.7 ish...

I would adjust up your power enrichment... at cruise with your supercharger you should be around 14.4 "ish"...

I'd check your fuel pressure... what are your injector pulse widths at , at idle... ? you should be around 1.8 ms ~ maybe a little less~

What are your gm/sec on the maf at idle?

If you have a adjustable fuel regulator I'd push your fuel up a touch... What injector size are you running?

Feel free to email or pm me if you want to take this offline...

Mo

STL94LT1

16:1 in open or closed loop? My car reads really lean in open loop, as long as the air pump is running. The air pump will dillute the a/f ratio.

GRX

red98 - Shouldn't be an issue. All is stock compatible. Cam is an '87 roller; heads are AFR180; CR is 9.2:1. The MAF should compensate for the minute extra breathing.

GRX

Mo - I have an adjustable fuel pressure regulator. Adjusted with vacuum off to 48psi. I have yet to hook up a scanner but no codes are thrown.

GRX

STL94LT1 - In open loop it is around 14:1. As soon as it goes closed, it creeps up to 16:1. Took the car for a run around the block and it has alot of power...but I didn't look at the afr meter. Without any further investigation, and for discussions sake, is it POSSIBLE that in 1985 models, at IDLE, GM tuned for economy?????? I mean, at 16:1, man, that is real economical!!! As I said earlier, with my previous setup, this was happening too. (Note: SC not running) Dang, I wish I had had a AFR meter before when all was stock to compare.

STL94LT1

16:1 in closed loop will cause problems, serious problems.

GRX

Anyone know when the air pump cycles? Does it cycle at idle?

Mo_Bandy

Mine, runs for a few minutes at first cold start , it depends on ambient temp. It will as posted above cause your AFR to go to 16's mine is around 15.8 at idle only with the supercharger.... you need tocheck it at cruise, as also posted above 16 cruising around is too lean in my opinion.... I would say it should be at least in the 14's...

Mo

red L98

if i got this right you had a blower cam and the car was tuned for this cam and all you did was take the blower cam out and go back with a stock cam . right??

if thats what you did what was the spec of the old cam and the new cam ?? it could be the LSA diffrence whats making the car run lean

red L98

it can also be a bad wide band 02 sensor , they can go bad if you run race gas or if they have lot of use on them .. trust me i know lol

GRX

I'm using the stock prom. Actually an updated prom I got from GM last year.

tjwong

One question, where do you have your wide band o2 sensor placed? If its just stuck in the tail pipe at the rear of the car you maybe getting dilution. The best place for the sensor is in the exhaust pipe just down stream from the collectors. On most of the cars I have tested in this manner with GM controllers and in closed loop, the PCM or ECM will control to 14.7 plus or minus a tenth or two. The AIR pump usually fires up on cold start ups to get the catalyst going once its in closed loop it shouldn't come on.

GRX

tjwong - WBO2 sensor is about 4 inches downstream of O2 sensor.

tjwong

Does your WBO2 have the ability to perform a free air calibration? If so do that so that the sensor is calibrated correctly to your electronics box.

GRX

Ok, I tightened the oil pan bolts. Then cleaned with acetone the bulhead connector contacts (by the battery), and my AFRs bettered to about 15.4:1 !!!!!!!! Any ideas why? All input appreciated.