Tmclaren

Hello, new to the site. Hoping to get some help troubleshooting a weird problem me and my dad are having. Background on this problem is quite a long winded roller coaster to get to this point, I'll try to stick to the highlights. My dad has a 1940 chevy coupe that had a carbed 350 with a th400. He decided to put a 1992 305 tpi and 700r4 from a z28 in. I am 800 km away so he has been doing this swap more or less alone while calling for help here and there. He installed a painless harness and deleted the smog pump but left all other emission control systems intact, installed headers but followed the guidelines for proper o2 sensor placement and wiring outlined in the instructions. Modified the stock tank and installed a fuel sender with a new fuel pump. Trans was wired to work with the ecm lockup function using the correct brake switch and colum switch outlined in the instructions. I came down the first time to help him fire it And had to change a few things around and order the vats bypass. Got it running but eventually found out that the engine had a completely dead #8 cylinder. We grabbed a rebuilt shortblock and he swapped that in. So this time while i was down, we got this thing running, set base timing and adjusted the iac as well as the tps and set out for a test drive. We were cruising around running nice shifting nice, pull on to the highway and hit about 70-80 kms and it started bucking back and fourth and the engine was cutting out bad. If you let off and feather it it runs fine until you hit that speed, it will do this no matter what throttle position. As soon as you hit that speed it does it. Wot in 1st and 2nd gears no problems. This still has the vss from the th400 installed and wired to the ecm and I'm leaning towards this, they are about $250 cad shipped for the painless one with a Speedo cable out. What I'm wondering is will an incorrect vss cause something like this or is it strictly for torque converter lockup? Engine runs good but seems to be running a little rich, slight smoke at idle. Sorry for this long post, just trying to give most of the story. Would really like to help him out with this, he has had the car off the road for over a year now and just wants to get driving it.

five7kid

iTrader: (14)

Moved to TPI forum.

Vader

Did the complete '92 TPI setup get installed? Same size injectors? EGR valve?

Any error codes stored in the ECM memory?

Tmclaren

Only things that didn't get installed were the air pump and canister, other then that it is completely a stock setup with new stock injectors. Egr is installed and connected. No fault codes in the ecm.

blackoutcamaro

With the engine running try wiggling you wiring harnesses..ive had bad icms do weird stuff like that too..also had an 02 that would turn on and off at weird times and couse the engine to buck as it was cycling on to off

Tmclaren

Hey thanks for the replies. Yes tried wiggle testing and found a loose connection at the coil, fixed that and still had the same issue. The engine was installed with a brand new painless harness and i went through as much of it as i could double checking all the connections and splices. I ordered a new loaded distributor as it wasn't much more then the Icm alone. I won't be back down to do any more troubleshooting for a couple weeks. Is it better to run the heated O2 sensor even using block hugger headers? If I'm not running the air pump will that cause egr issues? Can you remove anything more from the stock setup without a chip? Also wondering about the vss, will a bad or incorrect vss cause major driveability issues? Any help is greatly appreciated.

blackoutcamaro

Im running mine without the air pump and dont have any egr issues as long as its not sticking it shouldnt be doing anything except at idle..i have good luck with heated o2 they seem to be more consistant than just the one wire o2 and they stay on at idle where the one wire o2 will cool down and turn off..i have one in the shop with a vss code in it now ill check to see if it has any drivability issues but i wanna say it mainly just locks the converter and MIGHT control iac during decel but thatd be a new one for me ive seen them run good with no vss and just a stand alone kit for lockup..keep us posted

mcgarnicle

iTrader: (14)

I had an IROC that would buck at highway speed, turned out to be a few under-performing fuel injectors. I'd ohm test them 1st cold and hot, and if they're ok (looking for 12-16ohms), pull the rail and put a little jar under each one and check spray and volume.

Tmclaren

Ok so I finally went at this thing. We had previously changed all the fuel injectors but I ohm' d them all again anyways and they were good, hot and cold. I had ordered a distributor, Southbay adjustable fuel pressure reg and new diaphragm, I also bit the bullet and ordered a vss kit from stealth solutions with the correct Speedo gears. Started by changing the reg, diaphragm and distributor. The old distributor for sure had corrosion inside, as well as the shaft was loose. These made a good improvement to idle and throttle response but still had the issue on the highway. Jacked up the car and pulled the tailgate housing, changed the gears and installed the vss. Wired it in and hit the road, problem solved we hit about 140km and watched the licence plate fly off into the ditch....oops.... finally able to drive this thing. Someone had installed an 8 pulse per revolution square wave on the trans for the previous application. The tpi engines use a 4 pulse sine wave sensor. So I'm thinking maybe it was telling the ecm it was at max road speed? Not sure if these ecms even have a speed governor. Now that everything is up and running it's time to time tune. We are running true dual exhaust and I noticed it's running a bit rich on the left bank, if your not using a crossover should you be running 2 oxygen sensors? Thank you guys for the responses.

blackoutcamaro

Theres no provisions for a second 02 just a single heated 02 placed a foot past the last port on your left bank works good..i also like to place the 02 in at an angle that allows moisture to drain off it too