eighty7iroc

I have 87 iroc, had an engine swap done a few summers ago. 305 to 350. Its been giving me problems since, it wont idle right. The rpms fluctuate after about 10-15 minutes of running. If your driving it through town it wants to stall at red lights. On the highway it seems to run fine but as soon as you pull off itll die. The engine light doesnt come on, nor does it read any codes on a scan tool. I replaced the IAC valve, the burn off relay, the power relay. The TPS sensor is adjusted correctly, the fuel pressure is about 41psi, and all the injectors checked out at 14.9ohms cold and 15.1 ohms hot. Today I put on a new o2 sensor. As I was putting it in I noticed a sensor right above the oil pan to the left of the oil filter, I had someone do the engine swap for me, so idk if anything is suppose to go there or not cause I cant find anything anywhere saying there is a sensor there, to me it looks like the oil pressure sender. If someone can confirm that then I will move it to where it is suppose to be, I see where they put a plug into where the sender is suppose to be above the oil filter. Thanks

cw3adkins

Well, it kind of looks like a temp sensor or something like that. My oil pressure sensor is on the drivers side of the block near the firewall; and it's probably three times larger in diameter than the one in your photo. Since you posted this in the TPI section; I'm assuming that's why you have...is the computer and prom the right ones needed for the 350 TPI? Did you get the prom reprogrammed for the 350? I would start there...? Do you have the ability to run an ALDL program logger on it?

blacksunshine'91

iTrader: (10)

Looks like an oil pressure sensor, but definitely not in the correct spot.

Fred SS

iTrader: (3)

I could be wrong, but after looking at your picture. That appears to be the fuel pump backup switch. It is a switch that closes after the oil pressure gets up to a certain ponit, maybe 8 psi or so. The purpose is to allow the fuel pump to run if the fuel pump relay fails. The fuel pump relay and fuel pump backup switch are wired in parallel. I do not think your problem is being caused by it not being hooked up.

Guest

Thats not suppose to be their. Thats a water jacked port thats normally plugged by a slug bolt/thread bolt. On the opposite side of the block in the other water jacket port is the knock sensor, it looks like a UFO. The 2 can swap side if need be i.e LT install.

eighty7iroc

Yes thats correct, it is TPI. I used the guide at tpiparts.net to buy what i needed for the swap. I bought 24lb injectors, i know theyre bigger than what stock is suppose to be, but i have a fuel pressure regulator. Bought a knock sensor and esc module for a 350. I used the stock ECM from my car. The guy that built the motor said I should be fine just buying a prom for a 350, so I bought the JET stage 2 prom PN-18705S. Was that a bad idea? Where can i find someone to reprogram a prom? No i do not have the ability to run an ALDL program logger.

eighty7iroc

As for the unknown sensor in the picture, im going to assume that its the oil pressure sensor, but i cannot find the connector that plugs into.

cw3adkins

You'll have to have a prom that is setup with the 350 parameters. I go through Sinister Performance (at gmtuners.com) for my prom reprogramming. The guy knows what he's doing and it doesn't cost an arm and a leg either. When you contact him you'll just have to let him know what ECM you have, that it's a 350 TPI swap from a 305 and you've upgraded the injectors to 24 lb, he pretty much does the rest and can send you a prom setup for what you need.

T/Aperformance

Just because your TPS sensor is set right does not mean it is not bad, Your idle its self may be adjusted to low. I would not worry about getting a new chip right now the one you have should be fine for now. It is not causing your problems.

eighty7iroc

OK, I appreciate the help.

eighty7iroc

Is there anyway to check for a bad TPS sensor? Someone told me a bad distributor could cause all this? or timing?

eighty7iroc

Is there anyway to check for a bad TPS sensor? Someone told me a bad distributor could cause all this? or timing?

rdhanded2

iTrader: (3)

Could be timing or a distributor problem. Timing can cause idle surging and stalling at lights.

T/Aperformance

You can use the same volt meter used to set the TPS sensor to check to see if its good, Hook up the volt meter and slowly operate the throttle, The # should go up evenly, If it jumps up or is uneven in anyway than it is bad.
After you check the TPS sensor out I would adjust the the throttle until the engine is Idling then reset the the TPS sensor to the correct setting. Un plug the battery then plug it back in to reset your computer. Then go for a test drive to see if that has cured your idle problem.

eighty7iroc

So I checked the tps sensor again, still set right, when giving it throttle the number evenly went up, and stopped at 4.94 volts. So thats good. Gonna check the timing tomorrow.

eighty7iroc

So a few weeks ago I was getting ready to check the timing, started up the car and it seemed to be running alot better than it did before. I shut it off cause it was about out of gas, filled up a gas can and put it in the car. Wouldnt start, the pump **** out. So this week i got a new one put in. Car starts up but when you give it gas it kinda hesitates then accelerates, definitely doesnt run the way it did before the pump went out. My fuel pressure gauge was reading about 11psi. Thinking maybe it **** out on me too, i rented a test kit from oreillys. Hooked it up, with the car on, vac line unhooked it read 0psi. Took that gauge back thinking it was broke and got a new one, same thing. Car starts, there's pressure at the schrader valve. I dont get it. Fuel filter maybe?

T/Aperformance

Your fuel filter may be bad, where did you get your fuel pump from? I replaced my fuel pump a few time from one from the local parts store, One lasted a week, one lasted only a day. Your fuel pressure at the schrader valve should be 43 psi and hold that after the engine is turned off. Anyway I ended up buying a walbor or something like that name fuel bump, 225, The good one most recommend .

eighty7iroc

I changed out the filter yesterday, still reads about 11psi, i adjusted the afpr all the way in to see if itd change and nothin. I got the fuel pump from oreillys. And i got the holley afpr on the way now.

tpi84stepside

Sounds like you may have gotten a TBI pump instead of a TPI pump.

eighty7iroc

I hope not. The one i got looks exactly like the stock one. Delphi FLO115 is the PN

T/Aperformance

If I recall that fuel pump only flows 115lph and is not the right fuel pump for a TPI You need at least a 255 lph. The walbro fuel pumps seam to be the ones that work best for our cars,

T/Aperformance

Your fuel pressure should be around 43psi at idle and hold that when you shut off the engine.