3.8l surging

[polk383]

Hey everyone! My 95 3.8 lx t-bird which i just bought last week seems to be having a slight issue of surging between 30 mph and 50 mph. I have also noticed that it only happens when the rpm is below 1500. I have changed the plugs, wire, air, pcv, cap, and rotor. Also, put a fuel pressure gauge on it and it is fine and doesn't loose pressure after shutting it off. The only thing that I can think of at this point in time is going to be a injector is dirty. I have a local shop tomorrow morning going to run a BG injector cleaning system through it and see what comes out of it from there. I will post again tomorrow and let you guys know what comes out of it. Any thoughts let me know!!! Thanks!!!

[97Bird]

EGR valve? Check codes!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!

[coondawg6]

yassirrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr!!!!!! or slightly clogged iac valve but either way something has dirt buildup

[polk383]

thanks for the response 97Bird and coondawg6. But as i expected from the start, the injector cleaning did very little besides made it a little smoother. Codes I have checked now and nothing shows. EGR valve has been checked because when you run it without the vaccum hose on it, the car performs the same action. I doubt the IAC will cause it only because from my understanding it just regulates regulates the vaccum at idle and is big vaccum leak for the most part. maybe that will help shed a little bit of light on the subject. Also I have cleaned the MAF and the t-body now slight increase with smoothness at take off thats all so far. All the o2 voltages are fine as well. Once again any thoughts shoot them this way please!

[coondawg6]

doesnt matter if you unhook vacuum line from egr or not if carbon has built up in it or the port enough to hold the valve open that would be the problem--other words vacuum just opens and shuts the egr valve but if something has it blocked(carbon) it will not close and will give you a rough idle very similar to vacuum leak--as for iac it is idle air control valve and it does just that if you look closely at the ports the iac has a bypass hole that goes aroung the throttle plates and adjusts a pintle position to let either more or less air into motor according to operating conditions--therefore if pintle is sticking in open position(which is very common to these cars) it will be bypassing a lot of air into engine causing same symptoms as bad vacuum leak

[polk383]

Now correct me if i am wrong with thinking here but, if carbon was holding the egr open it would be consistant considering that nothing would be changing and the carbon would still be sitting holding it open. So in result would mean that it is not that due to the fact that the issue is not consistant and being that the idle is smooth anyways. It only happens between 25 and 50 mph and 1300 - 2500 rpm. Here is a highlight of the main things done: plugs, wire, air, pcv, cap, rotor, fuel filter, fuel pressure is good, no codes, ran without egr vaccum on it, O2 sensors within voltage, cleaned MAF, T-body, and had a injector cleaning done on it. Newest are that it seems to be worse under a load example having the a/c going and not getting on the gas very hard going up a hill. When it starts to act up opening the throttle all the way eliminates the problem until the rpm's drop again to the 1300 - 2500 range. Transmission doesn't shudder, shifts fine, not leaking, fluid is not burnt, no front pump noise, and is nice and reddish pink in color.

[polk383]

Well new, TPS same issue. New items occuring! Car falls flat on it's face in the rain. Checked coil it is good better than a new one actually! Well, since I am burned out on messing with this car and have spent too much time and money on this thing the dealership I bought it from seen me today and needless to say they are going to figure out what it is free of charge and fix whatever it is free of charge as well. When I find out what it is for sure (instead of playing the guessing game.) I will let you guys know! Thanks for the ideas and the help so far though!

[86tbrd3.8]

its the IAC i had an older model so things may be different but it still does the same thing....i had the same problems as you did all the same things and as soon as i changed the IAC for a new one it stopped also since it started doing this has the fuel milage dropped?