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Hesitation when cold

5K views 12 replies 2 participants last post by  1slosix 
#1 · (Edited)
Ok guys, I have been looking around the forum but I can't seem to find anyone else with this problem so I will just open a new thread. Ok I own a 97 mustang v6 with a CAI only. A week or two ago I noticed that the car started to hesitate or bogs down while it was cold even if I waited a minute or two for it to warm up. Once the car warmed up and I mean when it gets to normal temp range it would stop shaking and hesitating so much. It still seems to hesitate while its running at a constant speed and more in slower speeds then higher but not nearly as bad as it does while its cold. My brother works for a public utility board at the mechanic section and he brought home the computer they use at work to test the car and the results would come out as oxygen sensors bad and misfires on 1 and 4 pistons. So he told me it could be the coil pack. I went ahead and bought MSD street fire coil pack with MSD 8.5mm super conductors with NGK iridium sparkplugs to go along with the coil pack. (I thought since I'm there might as well upgrade a little :D) So after all was said and done I went to turn on the car and drive it and it seemed like it got fixed so I left it as is. (This upgrade was done today in the morning by the way) As I was coming home from work about an hour ago it started to do the same exact thing. I should also mention that it seems like there is loss in power on take off hot or cold even on the acceleration. I was thinking that it might be either the fuel pump relay or the IAC but I am just spit balling here. Any suggestions are more the welcome and fast suggestions even more so. Thanks in advance. Sorry about the book I wrote.
 
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#2 ·
clogged cats...that'll explain the hesitation and power loss...they can't really do their job when they're cold and if the warm up cats (two smaller cats) aren't working right either that'll make it have cold start issues. it would also help explain the codes you got for the o2 sensor...was it a real o2 sensor code or something like "catalyst effeciency below threshold bank (1 or 2 or both)
 
#3 ·
Actually I took off the cats along time ago when one of them blew a hole. I just decided to take both off and run a straight pipe all the way to the mufflers. And if I remember correctly the O2s where just jumping from lean to rich. The computer we used is a 1500 dollar comp so it was able to give us real time diagnostics.
 
#6 ·
OK guys here are the codes the comp spat out that day we did the diagnostics:
- p0136-O2 sensor circuit B1S2
- p0141-O2s Heater Fault B1S2
- P1151-HO2s B2S1 SW Point Indicates Lean
- P1152-Lack of HO2s B2S1 Indicates Rich
- P1443 EVAP Purge Valve Malfunction

Now, I know that the last one is just a valve that purges some kind of build up and I know that if this malfunctions it doesn't really effect anything. Its the other codes that worries me and I know that it keeps pointing to the O2 sensors however I just have this gut feeling that its not the O2's but another sensor that is failing somewhere else. I don't know but this problem is becoming really fu**** annoying at this point and if anyone can prove other wise that its the O2's are at fault I will gladly cough up another 100 bucks for them I just want to make sure before I get them. Thanks
 
#7 ·
both o2 codes are for the passenger side downstream...however that is only a monitor which keeps track of the cats...other issues that can throw those codes include intake or exhaust leak

the third o2 code however is the driver side upstream...which like i said earlier is the sensor that helps tell the computer how to mix the air/fuel
 
#11 ·
buy two spark plug non foulers that'll fit the o2 bungs...now drill a hole in the bottom of them (1/2")...unbolt the o2s from the bungs...screw in the non foulers...screw the o2s into the other end of the non foulers...in most cases this will fool the comp into thinking the cats are there and working
 
#12 ·
Interesting I will try that. Thanks a bunch man.

---------- Post added at 07:40 PM ---------- Previous post was at 07:09 PM ----------

One more question before I try this method which is a whole lot cheaper. The hole that I need to drill goes on the O2 side of the non fouler or the exhaust side?
 
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