First of all, SES light does come like it should for a second when engine is started

I am totally new to TBI. I've had a TPI swapped car for years now but just picked up an old high mile 1992 5.7 pickup truck. Starts/runs/drives fine but fuel economy is really bad and exhaust smells very rich. No SES light

So I decided to swap the old o2 sensor with one of the new 4-wire NTK (NGK) universal units I've been holding onto for years. I installed it with the 1 signal lead, leaving the heater and signal ground out and figured since I still had no SES light that it was wired correctly

but that didn't help the rich exhaust and I wanted a quick sloppy test so I disconnected the o2 and was surprised to STILL see no SES light. Is this normal for these systems? I dont currently have a code reader but I do have an old AKMCABLE set up for TPI

Sorry it's a long post. Any ideas?

 

If I recall, in order for the O2 to set, it has to dwell around .450V for a period of time after the engine enters closed loop operation. When the O2 is disconnected, the O2 voltage stays at .450V. There are values in the calibration that define an O2 window. If the O2 fails to exit this window and cross-count, itll set a code 13 after a period of time.

 

Also, how rich is it? Like Bob's smoke spewing pickup kind of rich, or just smells a little gassy? If its way rich, the computer may not be able to compensate for it. The allowed fueling corrections are limited to around +/- 15%. Does the engine get up to the proper operating temp and all?

It might not be a bad idea to make an ALDL cable for it and scan the computer. The TBIs only need a simple cable. Radioshack has the stuff needed for it.

 

i done 150 miles without 02 sensor and ses light didn't show up

 

It smells gassy. That doesn't bother me so much but it is always gassy, even after running for a long time. It doesn't seem to get to operating temp easily. Might not at all. I suppose it's not going in to closed loop. How does one make an ALDL cable for TBI?

If the computer were not able to compensate by +/-15% corrections, wouldn't that set a code?

 

Yeah, if it stays like that for a long enough time I think. If it doesnt at least get to 180 deg F, then that could be the problem right there. Maybe somebody pulled the stat or something. These run really rich when its cold.

Search for JoBy on the forums here. He has a link to WinALDL in his sig.

 

i have no idea which computer my truck even has. I looked on Joby's site and the application doesn't seem to be listed.

 

The datastreams for the early TBI ECMs are pretty standard, so the 160 baud cable he shows as well as winALDL will work. There where some minor differences between the cars and trucks, such as the IAT, but you should still be able to datalog ok. Set the ALDL for the 7747. Thats the most likely computer in the truck.

 

I have the nice molded AKMCABLE for my TPI car but I vaguely remember something about a 10k ohm resistor. Will that work with my computer or am I going to have to mod it? I tried asking Andy but he never got back to me.

 

I dont remember for sure, but I think it may work so long as its a serial cable based on the two transister design. The TBI computer doesnt need requests like the later TPI ECMs and TBI PCMs to transmit. Those have UARTs and everything and need to have the correct tables and diagnostic modes requested to link up.

The earlier ECMs just constantly transmit data, scanner or no scanner, so its strictly a one-way connection. Ive used the two transister TPI cable without issue.

Edit: The AKM cable looks complicated, so maybe it wont be compatible with winALDL. I dont think there will be any harm in trying it. The recommended cable is basically a cheap transister, some resistors, and a serial connector for the laptop. Probably much easier to make rather then digging into the AKM cable.