Ran my first data log yesterday and spent half the night researching what everything means.

As far as I can tell, all sensors are reading as they should, but my BLMs and INTs are extremely low.

From what I've learned, if the INT drops below 128, the BLM is supposed to lower to help bring that number back up, but the ECM is reaching its limits at 108, and the INT is not budging from below 90.

The car smells like raw fuel while running, and after a few minutes the idle hunts very badly and the car will eventually stall.

Am I correct on how the ECM is supposed to work? If so what could be causing the BLM and INT to be so low?

 

Oh and also, the car has had coil, cap and rotor, ignition module, injectors, coolant temp sensor, and spark plugs all replaced in the last year.

 

Looks like you're $8D with that 1990 IROC. What did you log with, Tunerpro? If so, go ahead and shoot me your datalog and I'll take a look at it.


ultm8z@yahoo.com

 

I data logged with TTS data master, but unfortunately I was unable to save it. If I do anther tomorrow and figure out how to save it. would I be able to send it to you? Thanks!

 

Unfortunately I don't have the TTS system. Only Tunerpro.

Unless you can export a .csv file or something? I can pull it into Excel and take a look.

 

You have a choice that the O2 sensor is silicone poisoned, or there is a mechanical issue that is causing excessive fuel to enter the engine. Take a look at a few spark plugs, see if they are black (too much fuel), or bone white (lean).

If bone white I would suspect the O2 sensor.

If black, the first two Items I'd look at is the FPR and the injectors. Pull the vacuum line off the FPR and smell it/look at it for signs of fuel. If so the diaphragm is bad.

If the injectors are still the OEM Multecs, replace them. Otherwise send them out for a cleaning. Dirty injectors spray more then they are supposed too.

RBob.

 

Thank you for the advice RBob, I will pull some plugs tonight and see what they look like.

ULTM8Z: I actually do have tuner pro downloaded as well, just found data master simpler to figure out my first time. I will see if I can get a log with tuner pro when I am home today.

 

Tried to get tunerpro to connect but for some reason cannot get it to recognize my car, so i did another log with datamaster and paid closer attention this time.

With key on and engine off:
MAP kpa reads 101.9
BLM and INT sit at 128
TPS volts 0.59 and % follows throttle position.
Idle Rpm reads 3188?
IAC position reads 12
IAC min reads 46
Air-fuel ration reads 6553.60?
02 volts reads 451

After cold start Open loop:
MAP kpa reads around 35
BLM 118
INT sits at 128
TPS volts 0.57
Idle Rpm reads 1000-1100
IAC position reads 111 to start, slowly drops to 65
IAC min reads 46
Air-fuel ration reads 10.9 slowly climbs to 14.7
02 volts reads 400-moves slowly up to about 950

Car enters closed loop, begins to run rough:
MAP kpa reads around 40
BLM 108
INT 80-90
TPS volts 0.57
Idle Rpm reads 700-800
IAC position reads 65
IAC min reads 46
Air-fuel ration reads 14.7
02 volts reads 200-950

throughout the whole log, spark advance stay between 15-25, and at WOT the BLM and INT read perfect at 128, and MAPkpu reads 100ish. I also recorded two knock counts, where spark retarted to about 3.

Is there anything here that jumps out as obviously wrong? Should the MAP sensorread higher? Im going to check FPR and spark plugs right now..

 

The vacuum line off of the FPR has a strong odour of gas, but looks dry. Would it smell if the diaphragm was still good?

 

Intuitively you'd think you shouldn't be able to smell fuel out of the regulator. Do you get an increase in pressure when you plug the vacuum line back in?

What is your fuel pressure anyway? Adjustable regulator?

Are you running factory injectors?

Is there any kind of noticeable misfire?

Your datalog seems reasonable... though obviously the 108 BLM is noteworthy...

 

I'd say it is bad. The reason it is dry is that engine vacuum quickly evaporates the fuel in the line.

Engine vacuum also pulls in a lot of fuel from even a pin-hole in the diaphragm.

RBob.

 

Keep the vacuum line off of the FPR (plenum side) and do a key on w/engine off, if you see fuel come out of that vacuum line during the fuel pump prime then the diaphragm is bad. If there is no leak, then hook a fuel pressure gauge to the schrader valve during key on as well, and watch to see how fast the accumulated fuel pressure drops after you key off. If it drops fast, then your injectors are leaking and the O2 correction can't keep up with the increased and excessive fueling...

 

Pulled the vacuum line off of the FPR and ran the car today, and although the car seemed to run better, no gas came out of the line. This has me second guessing the bad FPR.

I'm going to get my hands on a fuel pressure gauge sometime this week, but I might pull the FPR apart before that and check to see if there is any visible damage on the diaphragm. Thanks again for all the help and suggestions.

 

If it runs good until it goes closed loop that would support the bad O2 sensor.
If you had a leaking injector or FPR you would probably be blowing black smoke at idle.

 

Sorry for the lack of progress updates, I started a new job last week and have been very busy and haven't had as much time to look at the car or update this thread. I checked the FPR. And everything seems fine there. I was also thinking that an O2 sensor may be my problem, so I disconnected it, and ran the car at idle for about 10 mins, car runs a lot better and BLMs and INTs stay at 128. I will be replacing the O2 sensor in the next couple days and hopefully this solves my problem for good. Thank you everyone for the suggestions and advice. I will update when this is solved.

 

The reason it went to 128 is because you forced open loop. That 128 is not indicative of how the engine is actually running. But if it runs better in open loop, it could be the O2 semsor.