This is part of my ongoing no-start saga that I posed about a couple days ago.

This is an 85 IROC with a 165 ECM conversion using a slightly modified APYP (6 speed corvette) program.

The IROC has started hard for a long time. I need to give it gas as soon as I start it and hold it at 2k rpm for a couple minutes, otherwise it'll stall, but last week it decides to no longer respond to the throttle input and would die immediately regardless of what I did.

I swapped the coil from the GTA with no change, so I consulted the helm manual. It said swap the coil, or unplug the MAF. So I go out and unplug my Wells MAF. Car starts, and responds to the throttle input. So, I shut it off and put the original 85 MAF back in (which has been in the GTA). I started the car, and was able to keep it running by playing my usual throttle game. Before the car had a chance to warm up at all, I put the Wells back on, and as before, it would start and die no matter what I did. So, I put the Bosch back on and start the car gain, and once I play my usual 2k rpm game, it idles at 800 with my scan tool showing 9 g/s for the airflow. It idles rough, but this could be due to not having the air lid on. The MAF is just hanging off the rubber boot connected to the TB.

So once it warms up I throw the wells back in. The car idles smoother and shows 9 g/s. WTF!? If the wells and the delco are showing the same thing, why is the car unable to start with the wells?

 

once i got it warmed up and idling, I threw a vacuum gauge on it and I'm pulling around 16-17" of vacuum, which seems like plenty considering my cam. I'm playing with different PROMs, and although it seems to have a small effect on starting, it's not enough of an effect for me to get all excited over.

 

i'm no expert but when it warm, both sensor work fine but when cold only the bosch maf works? that is one strange problem you have there. hmm, on the maf system what sensors are read in open loop?

did u eliminate the csi? can you smell fuel in the exhaust as a result of the no-start condition? just shooting some ideas out there.

 

Both sensors work as soon as the car is running. When I had the no-start issue, I couldn't exactly check my scan tool, but as soon as the car is running, the scan tool indicates that either one is working fine.

I have eliminated the csi, but all of my chips use the $6E definition, which is the definition designed to work with the 89 cars, which don't have the csi.

 

i too run the 89'(csi elimination) setup on my 88.' on this converison did u replace the harness + ecm or a re-pinning converson type of deal? just trying to get all the cards layed out.

 

Hey guys, I was just wondering....I have a Bosch MAF. Which one is better, does one give you more power than the other?

 

The wells unit is slightly larger and flows more air, if you aren't "MAF restricted" then there would be no reason to get the Wells unit if the Bosch is working.

 

I used the harness from an 87 TPI car, so no funny business with the wiring was necessary.

 

For the starting problem try burning a new chip.
Edit "Crank Fuel PW Multiplier vs. Ref. Pulse" Under the "arrays" tab in Winbin. The first 10 ref pulses are set to 0, reset them to .3 or .5 when looking at that array in "calculated values". This will add more fuel to your crank cycle earlier.
If you continue to have long crank times figure out weather it is usually when cold or warm. Then go to "Crank Fuel PW vs. Coolant Temp" also under arrays, and add more fuel for the temp range that is giving you problems.

Hehe, maybe you should have done the re-pin/splice from the 85 harness. I went through that (about a year ago) and have had no problems from the system as yet, other than figuring out where to add more fuel and how much.

 

Morley, I don't have long crank problems. It fires quickly. It just dies immediately after it fires.

 

Hows your fuel pressure? Is it holding? I once had a hard start delvop over time.. til one day no start.. seems the regulator carped out.

BW

 

Are you using a later ('89-up) plenum, or did you block the CSI air distribution passages under the plenum?

 

Saturn, my fuel pressure is right in the 40-45 range. After I turn the key, it bleeds off a tad faster than I'd really like to see, but not fast enough to cause a start problem.

Vader, I'm running the late style SLP runners that don't have the CSI provision, but I'm still using the stock 85 plenum. I haven't modified the CSI passages in the plenum. Shouldn't those passages be blocked off by the flat surface on the SLP runners?

 

I've heard where some people were having sealing troubles using the non CSI runners on a setup that had CSI origionally (personally they work fine for me). Might be worth a look-see next time you get it started. Start checking around the upper and lower sides of the runner around back.

Having to give it throttle to keep it running sounds like you have quite a large leak or the TPS is bogus.

 

Ok, thought it was a long crank (no gas) that made you open the throttle when cranking

 

I thought when switching from wells to bosch, you have to reset the ECM?!

 

What about injectors??