Hi all, new to your forum. Looks like the best vette forum I have been to. Anyway, lifetime vette a holic.
89 vert. GM factory replacement correct crate motor with 40k miles. Engine stumbles and wont idle. Soft 44 code. So far I have checked ign. module, coil, plugs, TPS. New injectors 10k ago. All new smog components. PCV ok. No vacuum leaks. Cannont find ECM ground on back of block. Ground plug on ALDL plug shows ground. Plugs a little wet. What am I missing? IAC? New fuel pump and filter. 40 psi on fuel rail. Thanks in advance.

 

There is no factory replacement crate motor and though the ZZ4 has the same heads (updated to the '91 design), I'm pretty sure it has a little more cam in it.

I don't know what you mean by a "soft" code - they're either present or they're not. A 44 means the oxygen sensor is sensing a lean condition and that seems to be the issue you need to resolve - the ECM is adding fuel making it too rich. There are a laundry list of things to check, but essentially you need to look at anything that is letting in air after the MAF. (There's a possibility that it could be the MAF and running it with the MAF unplugged can ruleout or confirm that). More probable, there's an intake manifold or exhaust leak, but the easiest thing to look at first are the Header Check Valves. Clamp off the air pump hoses at the headers and if the engine swings normal (I'm assuming you have a scanner), then one or the other is probably broken. Usually you can tell that by looking inside, but that's not always easy with them installed, so you probably need to take them off. Before you do that, and because the motor was replaced, I'd also make sure that there is no air flowing to the headers at closed loop. It's real easy to mix up the connectors at the switching solenoid, so take off one of the header hoses and if it's got air flowing through it after closed loop, switch the connectors (or maybe they weren't plugged in in the first place?) If that doesn't do it, the solenoids are probably shot, but you'll need to make sure there isn't a short to ground on the header side. Depending on what you find, repost.

 

I dont have a OBD 1 scanner. Ran fine until last week. Went to the store, came out and the problem was in full effect. The motor has been in place since 2001. Runs the same in open or closed loop. Exhaust smells very rich. The 44 code appeared on the way home, but since has not re-lit. I have not delt with O2 sensor yet, my thinking on that was if it was O2, it would ok in open loop. I will check out aip pump system. Thanks for all input.

 

Unplugged MAF sensor. Runs fine. Did not show codes, Think i'll start by replacing relays first.

 

You can spend a lot of money replacing parts you don't need and you don't need the MAF relays based on your test. Suggest you buy a scanner instead or use a laptop with some free software - get info in Scan & Tune. It's adding too much fuel for a reason and the Code you got says the O2 is sensing it's lean. The conditions for that Code are at the extreme, but based on what you've described, the O2 is still commanding the ECM to add too much fuel. A scan will confirm that and the only thing that can trick the O2 into reporting this condition, is air that's getting in from somewhere other than the MAF.

 

Yes I want to get a scanner, where is a good place to get one? I replaced the MAF sensor and I am doing burn outs again. Runs perfect again. That was wierd because it didnt show any MAF codes. Thanks again for all input.

 

Weird - I would have expected improvement with it disconnected. As you've found out, not all problems throw codes. The ECM delivers fuel based on input from various sensors and it has no way of knowing if the input is off. Any of the Discounters provide generic scanners for a reasonable price and for basic diagnostics.