TPI conversion running real rich
06-11-2003, 09:43 PM
#1
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Car: 91 RS
Engine: Carb 350
Transmission: 700R4
TPI conversion running real rich
so me and some buddies are about done with the swap of a TBI to TPI...so far everythings goin decent...its a pain but nothing crazy...jus very time consuming...anyways...so we fired it up today...its running realllllllllllll rich..i mean jus pumpin out black smoke...i dont think i need an adjustable fuel pressure regulator because everything is from a 91 going into a 91..ecm intake blah blah...so everything should be set right? im purty sure...but the big thing i think we ran into is the oxygen sensor..thats still a sensor set for tbi...so it thinks it needs more gas when its getting a ****load already...so if we upgrade the oxygen sensor that should take care of the problem because then the computer will know what PSI should be going into there and it'll know what actually is right 
? any help is appreciated!
? any help is appreciated! 
06-12-2003, 08:35 AM
#2
I'm not sure there is any difference between a TPI and TBI O2 sensor. They're both single wire sensors that plug into the exhaust manifold.
One thing I would REALLY REALLY suggest doing is getting yourself a good scanner- AutoXray, or an SunPro Actron (like I have). It'll tell you alot about what the computer is seeing and doing.
Here's my suggestion:
If you're running that rich and the computer is unable to correct it any leaner, I'd recheck your O2 sensor wiring. If the computer is seeing no voltage from the O2 sensor, it's going to assume a super-lean condition and just throw a ton of fuel into the mixture. I had this happen to me when I converted to a three-wire heated sensor. There was no trouble code, but it was running slobberingly rich.
Try this- go to the ECM and find the O2 sensor wire (it's purple). Get a digital voltmeter and probe the back of the back of the wire at the ECM connector- that is, put the positive probe on the purple wire and put the negative probe to ground. With the engine running, you should see the voltage bouncing around from about .1V to about .9V. If it is stuck at either extreme (not moving), then there is a problem on the O2 circuit- either the sensor or the wiring.
One thing I would REALLY REALLY suggest doing is getting yourself a good scanner- AutoXray, or an SunPro Actron (like I have). It'll tell you alot about what the computer is seeing and doing.
Here's my suggestion:
If you're running that rich and the computer is unable to correct it any leaner, I'd recheck your O2 sensor wiring. If the computer is seeing no voltage from the O2 sensor, it's going to assume a super-lean condition and just throw a ton of fuel into the mixture. I had this happen to me when I converted to a three-wire heated sensor. There was no trouble code, but it was running slobberingly rich.
Try this- go to the ECM and find the O2 sensor wire (it's purple). Get a digital voltmeter and probe the back of the back of the wire at the ECM connector- that is, put the positive probe on the purple wire and put the negative probe to ground. With the engine running, you should see the voltage bouncing around from about .1V to about .9V. If it is stuck at either extreme (not moving), then there is a problem on the O2 circuit- either the sensor or the wiring.
06-12-2003, 09:25 AM
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Very good post....but don't overlook the simple things.
You have a 305 right? What injectors did you use when you swapped to TPI? If you used 22lb injectors ( 350 TPI )it will be pig rich....even more so if you're running a 305 PROM in the ECM.
Check for nasty exhaust leaks and vacuum leaks. I've seen 'em cause a false lean to the O2 sensor, which in turns makes the ECM think it's running lean, and all of a sudden it's pig rich from the extra gas being sent in....
HTH
You have a 305 right? What injectors did you use when you swapped to TPI? If you used 22lb injectors ( 350 TPI )it will be pig rich....even more so if you're running a 305 PROM in the ECM.
Check for nasty exhaust leaks and vacuum leaks. I've seen 'em cause a false lean to the O2 sensor, which in turns makes the ECM think it's running lean, and all of a sudden it's pig rich from the extra gas being sent in....
HTH
06-12-2003, 02:46 PM
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Car: 91 RS
Engine: Carb 350
Transmission: 700R4
alright so we're back to another problem...no power from the ecm to the diagnostic port..does this mean the ecm is toasted?? hope not...
06-12-2003, 02:57 PM
#5
Check the inline fuse on the ECM battery power circuit- it might be blown. Then check the fuse on the ignition power circuit.
In fact, I'd just go ahead and check every fuse on the vehicle just so you don't go chasing phantom electrical problems.
In fact, I'd just go ahead and check every fuse on the vehicle just so you don't go chasing phantom electrical problems.
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