I put a another tbi 350 engine in, was running great for two weeks now starts surging

[Tyree]

I dropped this engine in truck and was running fine for about two weeks. I then washed my truck then started it the next day and now it starts to surge at idle up at down. I previously had a surging problem caused by my previous map sensor being wired up incorrectly. I worked all those bugs out and this engine was going great till after I washed the truck. I cannot detect any vacuum leaks from any of the known sources of vacuum. Anbody have any ideas on this.? TPS, IAC, MAP, fuel pump Etc.. all working correctly. I m suspecting something got wet, some wire, somewhere but I could be biased because of previous problems so don't want to say that is the cause just a thought. I attached a log. An help on this would be appreciated.
Thanks Tyree

[damanx]

I'm throwing a guess here, but looking at the log, I don't see the o2 sensor doing anything other than being stuck at about 440mv.

[Tyree]

Thank for the reply damax, does anybody know what is an expected proper reading from a one wire o2 sensor at idle.? I will check this today.
Thanks Tyree

[Tyree]

Does any body have a .xdl log file of a known good running 5.7 so that I may compare my values in my log against a known good running engine.? That would be a great help. Thanks to all in the forums

[Tyree]

I just swapped another o2 sensor. Same result. Any other ideas out there?

[damanx]

here is a log I made a while back. If you select the monitor function during the playback, you can see the o2 sensor swing "high" and "low"

[damanx]

I just ran your log again and about time 4:29, you get a Code 34 "Map Low" error. Maybe something going on with the connector or the map sensor?

[Tyree]

on that map thing, That was me disconnecting the map sensor for a minute looking around for problems. Thanks for the reply I will check and compare. Phantom problem is repeatable and went from running great to running like crap. Thanks again

[Tyree]

Thanks for that log. Does anybody have a log of good running 5.7 from start in open loop until it warms up to idle and closed loop. This is when it starts happening in my truck as soon as it goes to closed loop, it surges small up and down and then idles like crap till it dies. Thanks again to all

[Tyree]

I decided to swap out egr valve with another one I had laying around. I ran the engine again and it ran much better. I will have to test drive and keep doing more logs. I revved this one up a few times during log. Does anybody know what normal idle rpm's are for a 1990 5.7? I attached the log so if anybody can watch it and let me know if they see anything strange. But it seemed to be running better.

[damanx]

I always forget the egr valve. I'm not running one.