9silverbird8

iTrader: (19)

I pulled my intake today to replace the oil pressure sensor. No big deal, I've done it a few other times. Put everything back together, torqued everything down, double checked all the connections and fired it up. Everything seemed okay, but then I noticed the car would buck if I let off the throttle a bit and then tried to ease back into it. So i stop at a stop sign for a second to chill and try to think what may be going on. All of a sudden idle drops to about 500-600 acts like its gonna die and then recovers. Its now not idling steady at all, just kinda hunting all over for it. Theres no leaks, I've checked all over, and vaccum never fluctuates with the idle.

Only thing I can think of is that I had the injectors swapped and scaled, but no tuning was done because I was leaking oil from the oil pressure sensor. Would untuned injectors cause any of this? I didn't notice any problems at all driving the 40 miles home from the shop. I also have a scanner if theres anything specific I should look for.

Thoughts? Ideas? Suggestions? All appreciated.

9silverbird8

iTrader: (19)

anyone?

Syxx613

iTrader: (8)

if youve got a scanner just start reading ur info off of the data stream line. pay attention to ur MAF, TPS, IAC, LT/ST fuel trims, pretty much anything that will affect the cars driveability.

9silverbird8

iTrader: (19)

I just logged a full clip. The problem is I'm new to the tuning stuff. I don't really know what to look for, I mean I don't know what would be an out of ordinary reading even if I were looking right at it.

*98Formula*

iTrader: (2)

Check to see if your oil pressure is jumping around when it starts doing this. I had this happen to me before to. Also did you reset the ecm at all. Try resetting the ecm and see if that helps as I am not a tuning expert but I think your problem lies elsewhere. You pulled the intake and I would start there.

LS1Aggie09

iTrader: (25)

mine did that two different times when i have pulled the battery and restarted...but i drove it each time it did that for about 10 to 20 minutes ( it was doing that the whole time i would stop) and then i stopped and restarted it back at my house, and she was fine...doubt if that has anything to do with what yours is doing, but i think mine was just the computers readjusting...i would guess if your still does it after 3 or so trips, its something electrical with the computer

9silverbird8

iTrader: (19)

I haven't reset the ecm. Ive taken it out twice now, hoping that the computer was just trying to relearn, but that doesn't look like thats the case, it should've relearned after 30 miles. Its just baffling because I know I put everything back together correctly. The number of times I've done it recently, its almost second nature to put that MF on. *sigh maybe ill just pull it and put another intake install notch on my belt.

Phoenix 5.7

iTrader: (7)

could ur map sensor be loose, or leaking? or maybe the vacume line? idk if that would cause that, but im thinking about what a intake install might affect

9silverbird8

iTrader: (19)

Thats is exactly what is throwing me. If it were leaking somewhere it would just plain idle rough and low right? But it idles fine sometimes, then it just drops off the table for a minute and recovers. Im gonna end up taking the damn thing apart again..

g00se99

whats your maf look like? my car was doing prety much what yours is, so I check around and finally looked at my maf and there was this piece of rubber clogging part of the sensor, took it out and fixed my prob

Farmer2

iTrader: (168)

I would start with a complete idle relearn procedure and then go from there.

Perform the following procedure to return the learned idle to the correct position:

Automatic Transmission:
1 Turn off the ignition
2 Restore the PCM battery feed
3 Turn Off the AC controls
4 Set the parking brake and block the drive wheels
5 Start the engine
6 Allow the engine coolant temperature to reach 176 degrees F
7 Shift the transmission selector into the drive range
8 Allow the engine to idle for 5 minutes
9 Turn on the AC controls (Omit for 2000-02 model)
10 Allow the engine to idle for 5 minutes (Omit for 2000-02 model)
11 Shift the transmission selector into Park
12 Allow the engine to idle for 5 minutes (Omit for 2000-02 model)
13 Turn off the AC controls (Omit for 2000-02 model)
14 Allow the engine to idle for 5 minutes
15 Turn off the engine for 15 seconds

Manual Transmission:
1 Turn Off the ignition
2 Restore the PCM battery feed
3 Turn Off the AC controls
4 Set the parking brake and block the drive wheels
5 Transmission in neutral
6 Start the engine
7 Allow the engine coolant temperature to reach 176 degrees F
8 Turn on the AC controls (Omit for 2000-02 model)
9 Allow the engine to idle for 5 minutes (Omit for 2000-02 model)
10 Turn off the AC controls (Omit for 2000-02 model)
11 Allow the engine to idle for 5 minutes
12 Turn off the engine for 15 seconds

9silverbird8

iTrader: (19)

Right on farmer, Ill definitely try that before I go pulling the intake again.

*98Formula*

iTrader: (2)

Try unplugging your maf and driving the car around easy. I wouldn't beat on it with the maf unplugged but try that and see if it goes away. Something may have damaged the maf while it was being put on and taken off. The ecm takes alot longer than 30 miles to relearn things. It takes about 200 miles to do most of it and I think it is like 3-4 warm starts and 4-5 cold starts or something like that. Unplug your maf and try that if that doesn't work do the idle relearn procedure. Also do you put new intake gaskets on. Mine has an intake leak and it runs fine. But if I reset the ecm it takes like a month before it will find its stupid idle. And it will perform like yours does for a few days to.

TopFlite

Any news with the idle surge?

9silverbird8

iTrader: (19)

Not yet. Gonna try some of the stuff mentioned in here when I get off work today.

9silverbird8

iTrader: (19)

Well, I tried the idle relearn procedure.....nothin'. Pulled the MAF to see if anything was on it in it or anything else out of the ordinary.....nothin'. Checked all vaccuum sources (again)......nothin'.

Unless anyone has any other ideas, or thinks it could actually be the injectors, I'm gonna pull the MF intake check and reinstall everything again tomorrow.

LS1Aggie09

iTrader: (25)

Mine didn't reset for 140 to 150 miles on my computer...

houresp4

This may not be your problem, But I have a 1938 Chev Street Rod and had some problems like yours. I have a 98 LS1 in my ride and was at a show when rpm surged then dropped back, then ran rough after that. Put on computer and show coil, PCM, Plug wires. I bought PCM but did not know which one was bad. Then learned a little trick. Put a crayon mark on the headers where each cyl is and start car then check to see if all are melted, in my case one cyl did not melt changed the PCM and bingo fixed the problem. As I said this may not be your problem but is good to know.