loud exhaust pops when cold undrivable until norm temp reached
The first start of a morning I get a lot random loud pops out of the exhaust, if I touch the gas it just coughs & pops even more, I can't even back out of the driveway without it dying until it is near operating temperature. There is no way I would try to drive it in traffic the way it is. Once it warms up it drives pretty okay, fat as a pig but it moves under its own power.
To make it even more fun - I have not been able to get the Data Logging feature of the hand held to save anything. There has been nothing new written to memory since April of 2017 which is when I bought the entire package. I know it has saved basic things like the idle RPM so it may just be I can't view it when plugged into my PC. I've seen people mention a software update in the forums, is this a thing I should take care of?
The short questions are: Any opinions on why does it run like dog matter when it is cold & Do I need a software update?
and a bonus question - The RPMs shown on the display are pretty erratic, jumps around from 740ish to 900ish the goal is 800 RPM. could this be a potential symptom/cause of my issues.
What I have:
A stock AF GM crate 350 that has maybe 7,000 mile. My timing is dead on 12 deg BTC with a pretty new Accel HEI distributor. GO Street 400 HP with the Fuel Command sump style fuel pump.
What I’ve recently done:
I just installed a new O2 sensor with really good quality exhaust gaskets. Replaced the temp sensor with AC 2134396. Unthreaded the blue tach wire and ran directly from the distributor to the unit. The tack wire is sleeved full length, with braided shielding and added a ground to the shielding. The blue wire is nowhere near any plug wire or alternator wires. Added a ground from the base of the unit to the battery and confirmed continuity. Put air pressure to the exhaust and hit every gasket & weld with dish soap, no leaks found. Checked & tightened anything to do with vacuum a couple of times over. I recently went through all of the AIC adjustment steps (front & rear) to get the AIC to flicker between 3 – 10. That helped with driving once it is warmed up, but everything cold is just useless.
Thank you for any help or pointers in the generally right direction.
What is your A/F ratio when running cold? Almost sounds like the unit is dumping too much fuel & it's igniting in-the-exhaust.
Yep, that's probably it. When I had loud popping in the exhaust it was running way too rich, which makes sense that it would be more pronounced when cold, since the fitech leans up during warming up. Mine was running too rich because I had a leak at the O2 sensor, throwing off it's reading in thinking it was too lean, dumping more fuel in to compensate. I found my leak by hooking up my vacuum to blow air into the exhaust that I duct taped to the end of the pipe to seal it, and using spray bottle with soapy water in it. Right around the O2, bubbles were forming from the air blowing bubbles out the leak. I welded those holes up, and it's been running great ever since.
Sorry it took me so long to post an update, I'd lost my UN/PW to the forum and just found it buried under random debris.
It turns out most of my problems were due to the back 2 injectors not squirting. one was jammed-up the other seems to have failed for whatever reason. Replaced those 2 injectors and it has made a world of difference. I can drive! still shows its ass when cold but it's way better than it was, just need to figure out the tuning, I think.
Late update - I'm an idiot and have bad luck. That new distributor turns out to have the lightest cent adv springs I've ever seen in use. Poor bastards timing was so far advanced off idol that I can't figure out how it actually ran. and shame on me for for thinking initial timing without an adjustable light would get me close enough. That and I found a crack in the vacuum bib on the manifold for the vacuum line into the cabin. Between the timing and the vacuum leak, it is acting a lot better, still not there but I might stand a chance of getting right next time i fiddle with it.