Trbomike

I'm at my wits end. This is my brother's car and I hooked him up with a guy to do the 305 TBI to 350 TPI conversion. It's been 9 months and it's still not right. The cruise, speedometer/odometer and horn do not work; The gas gauge when full only goes to 3/4. If the oil pressure gauge is working, it's always in the red and at 3K gets to 15. It overheats and has slight backfires (pops) some times while just cruising. Its a speed density system. I don't know all the details because the guy turned out to be such a liar that I don't what actually was changed and what wasn't. I had another guy try and tune it as well to get the gauges to work. I think the temperature and the voltmeter are probably working, but I just don't think the oil pressure and gas gauge are correct.

I'm going to hook up an oil pressure gauge this weekend to verify oil pressure. if the dash gauge turns out to be correct then that could be adding to the overheating as well as the 105 feels like temps

he moved some of the pins around to try and get the dash to work. He said the speedo worked for a little bit then it went to zero. I think that the engine harness used is from an 89 Firebird but I'm not sure.

I'm in the Houston area, so if there are any experts i could take this to and get the issues resolved, let me know. Thanks!

Trbomike

I replaced the oil pressure sending unit this morning and that cured the low oil pressure.

Pocket

iTrader: (24)

Speedo will not work directly with a TBI to TPI conversion. If it really way a TPI SD harness, then you need to do a few changes. First, find the C207 near the ECM, locate pins K (BRN dash side) and D (GRY engine side). These need to connect. Next locate the buffer box in the same vicinity, it will be either yellow or cream colored. Unplug it, bend a length of wire into the shape of a U and insert into pins C&F

This process changes how the VSS signal is sent to the cluster. TBI ECMs were too dumb to understand the raw VSS data so an external buffer box was used to change the signal into something cruise, cluster and ECM could all understand. SD TPI ECMs were fully capable of decoding the VSS data, so there was no buffer box. The steps above are a work around of the box

Cruise is a direct connection. Find pin P (RED engine side) and the C209 (tiny black 4 pin connector in the same vicinity but more towards the pass kick panel. Pin A (RED) is VSS signal to cruise. These need to connect

Horn is not related to the conversion, but just for GP, see if they're plugged in. Drivers side battery tray behind the fender. Single DK GRN wire feeds both

Overheating is a cooling problem, not electrical. Ensure both fans operate and the front air dam is in place. Wouldnt hurt to check the coolant level, low coolant is pretty frustrating

Backfiring could be anything, basic maintenance would help greatly

Trbomike

Thanks for the advice. The backfiring/popping only occurs at 1500 - 1800 RPMs regardless of gear.

dereklicon

I would do a compression test, then check timing, then check for intake leaks....

TPI is a real pain to work with and not really worth it in the end anymore.

I had a similar issue and I ran circles around this thing. Ended up being a blown headgasket between pistons 4 & 6 causing idle issues. I didnt know what it was until I removed the heads.

Trbomike

Thanks for the input.

Freakazoid

C207 near the ECM is this the plug that is somewhat clear? if it is then there is no wires on either side on pins K & D

Pocket

iTrader: (24)

Thats right and in that case, youll need to run an external wire for the speedo