Ok so I have a 87 IROC with a TPI. Pulled the old 305 and put a new 350 in. car seems to run fine but is using a lot of fuel. calculated 10 mpg. I've got a a really expensive computer and my MAF shows 2200 g/s at idle and jumps up to 20,000 at WOT. I had a spare so i hooked it up also and it reads the same. I know that this should be 4 to 5 grams per second at idle and about 250 at WOT. Any one have any ideas as to what could cause this. I checked the relay it's getting the correct voltage and I changed the IAC because it was responding to slow. Just wanted to get ideas before i go out and buy another MAF that may not be needed.

 

update on this issue. Think I found the problem. I unplug the MAF sensor and the car died. started it back up with the sensor unplugged. My computer was still showing readings coming from the MAF sensor which was not hooked up. The way I figure it the new PROM I ordered is configed for Speed Density and the air volume is being calculated by the PROM. Any thoughts?

 

Have you done the MAF diagnostics?
http://www.chevythunder.com/maf_code_33.htm

 

I would also try to find a stock 350 chip until you can have your car tuned locally.

 

I'm not getting a code 33. The only code that it is throwing is a 45 which lead me to hook it up to my computer. The code 45 only comes on after driving it for about 10 mins and then resets it self every time I turn off the car. I figured this is due to excess fuel. That is why I started looking at the MAF. I'm just going to order a another new PROM. Cause both of my MAF sensors are working correctly but for whatever reason the g/s are really high and even when it's unplugs I'm still getting readings.

 

Tubing is tight, no vac leaks in the T-body or? Stock T-body? Base air Idle setting stock?
How much fuel are you calling excess? just a rich smell or black wet plugs?
Did you check your fuel PSI reg hose for raw fuel? Is your TPS sensor set properly .54 volts? (I think)
I'm saying to run a stock chip to help with finding the prob.
Unrelated but also run a the correct knock sensor for a 350. (I dont use one at all on my maf cars)

 

TTOP350 I've replaced or blocked off a all vacuum lines and my base idle air is set at stock along with the voltage on the TPS. My TPS sensor voltage is smooth thru WOT maxing out at about 4.7. The pressure on the fuel rail is 45 PSI. and the knock sensor is functioning or should I say it's getting voltage and I can tap it and it shows a reading on my diagnostic computer. besides it's brand new. The reason why I say excess fuel usage is because it's getting about 10 MPG on the highway. That has gone up slightly with the engine break in to about 14 MPG but smelling a lot of un-burnt fuel. I'm going to have to have one burnt as i've got 24 lbs injectors and a little bigger cam. BTW the fuel usage didn't go up until this weekend after I posted the first time.

 

It shouldn't be that bad at all.
What kind of overlap does your cam have? What are the specs? I'm guessing its not big enuff to cause this at all but I gota ask.
If you have a friend with a known good maf see if you can borrow it for a test. These mafs are a pain to work with and pricey

 

yeah it's not that big. I can't remember right off the top of my head but it's just enough to pick up the slack on the bigger injectors. you really wouldn't know. Besides the TPI's don't like bigger cam but i'm with you it should be getting batter MPG's than this. I'm hoping after I get a couple of thousand miles on it I'll see an improvement.

 

If you're still using the same prom with the 24lb injectors and the stockers were only 19, then that's an issue. Maybe not THE issue, but needs recal'd for larger injectors. If you have an adjustable FPR, trying to crank down the FP about 5psi or so and see what happens. 3-5lb's in injector size is not real small and can surely make you eat up an additional 5mpg easy. I had that same issue until I reburnt my prom and changed the injector PW to lean it out some...good luck.

 

Ok so after a long weekend I fixed this problem. I was totally off base. I found 3 wires that had been cut by the PO. They were in the wire harness next to the coil. After tracing them back to the ECM they wound up being grounds. So I grounded them off and all the problems went away. Now getting 18 MPG's on the highway and no service engine lights and the g/s are back to the normal range.