Howdy from the Cowboy State

Hi folks! I went to register and it said the email was already linked to an account. But I forgot the password and that would have been YEARS ago. So here I am again!

I built up a AMC 258 and have been running a GM TBI setup on it for years. It has developed some issues, low erratic idle, backfiring, and others. I recently installed a AEM wideband gauge in it and WOW what an eye opener. Super lean at idle, burn your eyes rich off idle.

Anywho, can't wait to learn more about my system and become more educated about injection and tuning!

39Ratrod

:welcome:

I like tuning with a wideband. What TBI computer are you using?

dave w

Thanks for the welcome Dave!

It is 7747 that has a chip adapter from moates and I have the Flash and Burn. I have not messed with it for years because it ran really well. Rarely opened the hood. Put I would say 50k on it with hardly a hiccup. Now it runs poorly, WOT surges and will sometimes backfire. I am beginning to think I have a hardware problem and less of a software problem. Let me ask you, if the dist is locked out, no mech or vac advance and I go to set the timing, bypass disconnected, and it is all erratic, that would be mechanical aspects causing that and not the ecm tune correct? I surges bad at idle too, and the wideband fluctuates from 18:1 (rough running) back down to say 13.5:1 and smoothes out. Would that be all fuel related or could timing be showing up via the wideband?


Thanks man!

fluctuating timing with the est bypass disconnected could be inthe mechanical part of the distributor or loose timing chain, but could be a bad ignition module. if the tune has ran properly for 50k miles chances are it is not the tune............. sounds like you need to get the ignition right before afr can ever be right.....

Quote:

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Originally Posted by skandolis

fluctuating timing with the est bypass disconnected could be inthe mechanical part of the distributor or loose timing chain, but could be a bad ignition module. if the tune has ran properly for 50k miles chances are it is not the tune............. sounds like you need to get the ignition right before afr can ever be right.....

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Alright, that's kind of what I am leaning toward. I am wondering if it isn't the chain, I have locked out a second dist, problem remained, and had the module checked at Oreillys and it was good.

So I correct in my thinking that timing can affect AFR. I guess I can see timing causing a rich condition if complete burn is not achieved, but can timing also cause the lean spikes or is that the ecm pulling fuel due to the recent enrichened state?

You guys ROCK BTW!!!!