lathens

Hi guys,

Driving at constant speed, car runs like crap. Seems like it is "loading up". If i push in clutch and rev, it clears up for a few seconds then runs like crap again. When i take off from a stop at WOT, it sputters a little then runs like a bat outta hell until I back off the throttle and slow down to constant speed then it runs like crap again. It's really sucking the fuel too. Any ideas please?

lathens

OK, drove to work today and car used 9.5 gallons of gas in 80 miles. Normally averages 17 mpg. Loading up with fuel really bad. I forgot to mention, this started immediately after I installed a new opti. I have double checked all the electrical connections and vacuum lines and I don't see anything I screwed up. Any ideas please? If I got the vacuum lines on the bottom of the opti reversed, could it cause this?

Injuneer

Have you checked the fuel pressure? Let the pump prime without starting the engine. Note the pressure when the pump shuts off, then watch how fast the pressure drops. This will detect the possibility of leaking fuel injectors or fuel pressure regulator.

Any chance you have an Aeromotive AFPR?

I don't see how crossing the vent and vacuum lines on the Opti could cause the problem. What brand is the Opti?

lathens

Hi Fred,

Have not checked FP. Will do.

Nope, not an Aeromotive AFPR

The opti is the GM with one year warranty from Summit: 1996 PONTIAC FIREBIRD ACDelco Optispark Distributors 19212300

https://www.summitracing.com/parts/a...model/firebird

Ya, I didn't think crossing the opti vacuum lines could be a problem. Pretty sure they are right anyhow.

Thanks,

Loren

lathens

Hi Fred,

Did as you suggested with the FP. FP immediately came to 42 psig. I turned the key off and it stayed at 42 psig for 12 minutes until I had to leave for work. Any other ideas?

Thanks,

Loren

Injuneer

Is it possible you knocked the harness connector off the coolant temp sensor on the water pump housing?

lathens

Hi Fred,

The coolant temp sensor on the front of the WP hasn't been plugged in for years. I am thinking Ed Wright disabled it when I had the car dyno tuned. I have a Meziere pump. Does this make sense?

Thanks,

Loren

lathens

Hi Fred,

Took it to Autozone and had it scanned. Guy said the only fault was a coolant temperature sensor code P0118. I just assumed this is the one that isn't plugged in (the one on the WP). Do I need to change the sensor?

Thanks,

Loren

Injuneer

The PCM needs coolant temperature readings for multiple functions. The obvious one is cold start enrichment. Just like the choke on a carb, when the engine is cold it richens the air fuel mixture significantly, and raises the idle RPM. Coolant temp is also a factor in setting the target A/F ratio in power enrichment (PE) mode = roughly WOT, but not exactly. The PCM turns the fans on and off based on the coolant temp sensor reading. Are your fans running all the time?

Lacking coolant temp sensor input causes the PCM to default to an internal "guess".

I can't conceive of any reason a tuner would disable coolant temp input. Plug it in. Doesn't matter what brand/type the water pump is. P0118 turns on the SES light. Is your SES light even working?

lathens

Ya, SES light is on...has been on for years and car has run great. The coolant temp sensor in the cylinder head is plugged in. The one in the WP isn't. I honestly can't remember why or how long, but it has ran great for years without it? I don't get it. Do you?

Injuneer

The temp sensor in the driver side head is only for the dash gauge, has nothing to do with the PCM.

So in all those years you drove around with the SES light on, and never wondered why, or had the codes read?

And you didn't feel it was important to include any of this info in you original post?

lathens

No, since i've been running without it for years I didn't think there was any reason to mention it. I can't even find the plug anymore. Can you tell me what the wires look like. I will go to a salvage and get a new plug and splice in. I'm sure are right that I need to have it connected...but I think I determined the root cause of the problem. See next post.

lathens

Hi Fred,

While researching my optispark purchase on the internet and by reading reviews on Summitt, I found there were many cases where people have received a bad optispark straight from the factory. I also found a post where someone said it was a good idea to start your car after the opti is installed but before installing everything else to confirm the new opti is functional. So, I did this. MAJOR MISTAKE. What I didn't think through is that the mass airflow was unplugged. So, it has taken the computer three days to relearn and I have multiple fouled plugs! Will be removing headers and doing plugs this weekend Sorry for wasting your time on this one Fred. Guess I should have put this in my first post too.

Loren

Injuneer

Shoebox's harness photo. Double click on the sensor to get an enlarged view of that portion of the harness.

1995 Z28 A4 Engine Harness

Pigtail part #'s, again from Shoebox:

1993-1997 F-Body Part Number Collection

lathens

Thanks Fred...and Shoebox!