Hi-

Currently my stock 1986 Trans AM 305 TPI has been running rich at idle. At idle in closed loop the BLMs go right to 108. The integrator usually sits around 100-105. Exhaust smells rich but no black smoke. Idle is smooth, runs and drives down the well otherwise, but with an occasional stall at a gentle tap of the throttle, such as when moving up the line at a drive through takeout window. Per the advise of another third gen member I replaced the single wire O2 sensor with the 3 wire AC Delco but my BLM at Idle still goes to 108. The previous owner states they replaced the fuel injectors with new AC Delco. They do not recall which model number was installed. I ran an ohm test on each injector and got a reading of about 19 ohms on each when hot.. 19 seems high as I was under the impression stock injectors should read 15.5 -16.5 ohms. Before I replace these injectors I would like to know other members thoughts on what else could be causing my low BLM at idle. Does a 19 ohm reading raise any flags? Maybe the previous owner installed 22lb injectors accidently?

TPS: .54 volts
Vacuum at idle: 21
MAF reading at idle: 9
Fuel pressure at idle: 38 PSI ( with regulator vacuum connected)
Fuel pressure at idle : 47 PS! ( without regulator vacuum connected)
BLM at idle closed loop: 108
Injector Ohms: 19
Computer controlled timing at idle: degrees 14

 

I was just going through something very similar to what you have going on with the rich condition, high MAF reading, and 108 BLMs (my INT number was 80). My car also had a twitchy idle after revving sometimes. I switched out my almost new Delphi MAF with my factory Bosch on a hunch and everything went back to normal on my scanner and no more weird idle so far. A member mentioned it could be O2 sensor, leaky injectors, faulty FPR diaphragm or an ignition part could be going bad as well, likely on the driver side seeing as how O2 is there.

Take a photo or two of your injectors and post it, a lot of guys on here can tell what they are with just a photo. I think you have the right idea about the injectors being done, did you check them hot, cold or both? Does your fuel pressure drop fast after shut down?

 

@Reddragon88gta Thanks for your reply. I took a look at my MAF and ironically it appears the previous owner had installed a new Delphi unit rather then a Bosch!

Should have mentioned that after about 45 minutes the fuel pressure slowly drops to about 25 and holds and I tested the fuel injector ohm readings while hot.

I will upload some pictures of my injectors in the morning.

 

19 ohms seems pretty high when hot. If they are the stock multec injectors they're pretty prone to coil failure....especially when hot

 

Attached are pictures of the injectors I have, Can anyone identify the make/model of them?

 

Not multecs, any part number on the upper plastic? Would be on the side flat pad probably.

 

Thanks for tuning in @Tuned Performance . I looked over the injectors from every possible viewing angle (while installed ) and I do not see a part number marked.

 

Without any identification number or markings hard to tell what you have.
if you would send out for flow testing would be more than remanufactured injectors.
i was under the assumption coils impedance is lower when they degrade.

 

I understand the general consensus agrees that 19 ohms when hot is high. I believe I will try swapping in a Bosch MAF first since I have one handy and if the BLM don't change I will buy the reman injectors recommended from @southbay08 .

 

the resistance is indicative of coil failure on the lower end however if the resistance on some injectors is supposed to be in the 16 range...19 seems high
what were they cold???

 

The cold resistance is 18 ohms across all the injectors. @southbay08

 

Mine LOOK original.......the car has low mileage but I know the p/O did some tinkering......those look identical to the injectors I have...no identification on them whatsoever..........of course lol

I can't figure out if they are stock though, but physically those look exactly like mine. .

 

The PO of my car claims they are new AC Delco units that her sourced off eBay.

 

@Reddragon88gta What is the correct mass airflow reading supposed to be at idle ? Is 9 high?

 

6-10 gps is a normal range at idle

 

MAF readings are grams per second. At idle, the reading should be near the displacement of the engine. So 5.0 liter engine will usually consume 4.8-5.2 g/s. It can and will fluctuate but it should roughly be around that. I little high and a little low is normal. 9 on a 5.0 is not unless someone has information that I'm not aware of.

 

I am currently running an after market Delphi and another commenter mentioned that they had a similar issue I am having with high BLMs at idle. I am going to take their advice and swap out the Delphi for a good working OEM Bosch unit and see if my numbers change.

 

This is a nice reference for reading data scans, it’s from my 88’ service manual:

 

Geez quite a range for blm and low iac counts

 

Looks like my MAF reading at closed of 9 is out of the acceptable range (4-7). I appreciate the fact sheet. Super helpful.

 

Swapped out the Delphi for an OEM Bosch MAF and my BLM issue is fixed!! No more 108 BLM at idle in closed loop. Now it is a healthy 127-128! Thank you so much. @Reddragon88gta

 

Glad you got it resolved. For future reference, the photo you posted appears to show original Bosch injectors.



My '86 TA has the same injectors. They've been removed and cleaned once, so I have a pretty good record of what they are.

 

Thanks for this posting. I have the same issues with my 350 camaro. And after following the discusion here, i'm wondering why my readings for airflow at 1000 rpm shows 2800 grams/sec.?