car running super rich
Registered User
Joined: Nov 2002
Posts: 4,784
From: Jacksonville
Re: car running super rich
I don't post here very often but I'm almost ready to give up on this car. Okay the car is a 97 formula and it's running extremely rich. Engine is fully forged 355 with low compression, I think about 9:1. Cylinder heads are LT1 casting ported/polished, Procharger D1SC pulleyed for 15 lbs boost (3.4 inch). MSD opti and ignition box. Running 42 lb injectors and a tune from Mark Romans. Car dynoed 2 years ago 480 hp with a 3.7 pulley which was about 12 lbs boost. Had the car emissions tested and hydrocarbons were off the scale, like between 500-1000. now questions...
1. A buddy of mine who is an old carb guy says my injectors are way too big and therefore the reason it's running so rich. Are they too big?
2. This is probably the major contributor but maybe not the whole issue but the coolant sensor that is in the drivers side cylinder head is not connected. Another buddy thinks (he looked at the electrical schematic) this is just to report the temp for the dash guage. Is this sensor the one that turns on the o2 sensors and closed loop? Also I can't find a loose wire so how do I find it?
Either way I don't think the car is going to closed loop. Any help greatly appreciated.
Dave
1. A buddy of mine who is an old carb guy says my injectors are way too big and therefore the reason it's running so rich. Are they too big?
2. This is probably the major contributor but maybe not the whole issue but the coolant sensor that is in the drivers side cylinder head is not connected. Another buddy thinks (he looked at the electrical schematic) this is just to report the temp for the dash guage. Is this sensor the one that turns on the o2 sensors and closed loop? Also I can't find a loose wire so how do I find it?
Either way I don't think the car is going to closed loop. Any help greatly appreciated.
Dave
Between the cam and tune you're not likely to pass emissions with that setup.
Thread Starter
Registered User
Joined: Sep 2001
Posts: 29
From: Suisun City, California
Re: car running super rich
just a quick thought, i had a problem with my car feeling sluggish the more i drove it. After a PCM reset it would be great, then would slowly get rich/slow again. Turns out my LT/1.6 rockers were a little too noisy for the knock module, switched over to the lt4 module and haven't had a problem since. If you pull the PCM fuse for 60 seconds, and the car runs much better it might be worth looking into.
Also, a simple Freescan or Datamaster log will tell you if the car is going into closed loop or not. Along with codes. Also, that IAT sensor is important and if its not working correctly it could be causing an issue. Also, fouling plugs can cause poor performance as well, so check and replace.
Also, a simple Freescan or Datamaster log will tell you if the car is going into closed loop or not. Along with codes. Also, that IAT sensor is important and if its not working correctly it could be causing an issue. Also, fouling plugs can cause poor performance as well, so check and replace.
Thread Starter
Registered User
Joined: Sep 2001
Posts: 29
From: Suisun City, California
Re: car running super rich
Your injectors are likely bordering on being too small for your app. Fuel injection doesn't work like a carburetor. As long as the drivers can control the injectors and the constant is set in the computer it will meter out the correct amount of fuel (assuming the tune is accurate and the injectors/fuel system are capable of keeping up).
Between the cam and tune you're not likely to pass emissions with that setup.
Between the cam and tune you're not likely to pass emissions with that setup.
Registered User
Joined: Jul 2004
Posts: 1,174
From: MI
Re: car running super rich
Hello. My app is similar. 97ss 383 with D1 and 7.6 to 3.4 pulley drive. The D1 has a 4.44:1 step-up ratio. Also I have a MM6 trans with a 3.73:1 Moser rear. 72#/hr seimens injectors with an acceleronics driver. About 14 to 15 psi @ the manifold.
My app also started very rich. I leaned out the open loop afr cals. That really helpp with short term afr starting.
I have done alot of adjustment to the flash program in closed loop mode. I still run a 1 bar MAP. The temp sensor is very important for directing the PCM.
I have also done the following to help low speed cruz afr driving it to 14,7.
Modified MAF cal downn 2%, and modified the BLM matrix boundries. This really helped vehicle drivability for me.
Zeroed PE vs temp. I only use PE vs rpm. I used a dyno-jet wide band to tune WOT fueling mode, mostly on road tests. I found that PE vs temp fueled excessive in WOT mode.
Lowered the temp value so the PCM moves to closed loop mode faster (in the fuel map editor tab).
My app had a problem with the temp sensor due to my use of Evans NPG coolant (also no T_stat), and it runs very cold < 160*. So I had a problem of not moving to closed loop control.
Hope this helps since our apps are similar. Use LT1_edit version 2.2 to flash my OB2 PCM.
B.
My app also started very rich. I leaned out the open loop afr cals. That really helpp with short term afr starting.
I have done alot of adjustment to the flash program in closed loop mode. I still run a 1 bar MAP. The temp sensor is very important for directing the PCM.
I have also done the following to help low speed cruz afr driving it to 14,7.
Modified MAF cal downn 2%, and modified the BLM matrix boundries. This really helped vehicle drivability for me.
Zeroed PE vs temp. I only use PE vs rpm. I used a dyno-jet wide band to tune WOT fueling mode, mostly on road tests. I found that PE vs temp fueled excessive in WOT mode.
Lowered the temp value so the PCM moves to closed loop mode faster (in the fuel map editor tab).
My app had a problem with the temp sensor due to my use of Evans NPG coolant (also no T_stat), and it runs very cold < 160*. So I had a problem of not moving to closed loop control.
Hope this helps since our apps are similar. Use LT1_edit version 2.2 to flash my OB2 PCM.
B.
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