What makes your car lose its tune?
09-10-2010, 07:53 PM
#1
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What makes your car lose its tune? for some reason, my car runs fine. then after it is ran for a few minutes, i've noticed that the skip shift, throttle response, and oil pressure all changes. Once it starts acting up, the skip shift comes on. My car starts to hunt when i stop. I got the car tuned and it's fine at idle, it cranks up and goes right at it's idle point when cold. My pcm is just sitting in the engine bay. Could it be a bad pcm? It's been that way since i bought the car. It's like the tune get's ignored after some point when it warms up. HELP!!
09-10-2010, 08:55 PM
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oh wow... that sounds bad but i dont know awhole lot but i have a 98 that has some funny acting stuff... my oil pressure goes up and down a lil bit when idleing ... and when i try a hot start the car doesnt wanna fire up until i push the gas down a lil bit. Then it fires right up and holds its idle good
09-10-2010, 09:19 PM
#3
for some reason, my car runs fine. then after it is ran for a few minutes, i've noticed that the skip shift, throttle response, and oil pressure all changes. Once it starts acting up, the skip shift comes on. My car starts to hunt when i stop. I got the car tuned and it's fine at idle, it cranks up and goes right at it's idle point when cold. My pcm is just sitting in the engine bay. Could it be a bad pcm? It's been that way since i bought the car. It's like the tune get's ignored after some point when it warms up. HELP!!
About 5 months ago my PCM to Engine block ground wire came loose and fried my PCM in the process. When I popped the two PCM caps off the PCM I saw a bunch of burnt pins.
Anyway.....I had to get a new PCM and fix the ground wire. Luckily my tuner from back in 2002 saved my tune and was able to just load it up and send it to me. I put the new PCM in, fixed the ground wire........and HOLY ****......every single gremlin for the prior two years was GONE. 100% NEW RUNNING engine. It ran perfect, idled, cold start, warmed up running, everything....fixed. Very unexpected but it fixed everything.
It was my PCM for the prior two years that was on its way out...........and I remember a couple guys on here telling me back then when the issues started to get a new PCM.....I wish I would have listened back then.
Oh...one other thing I forgot to mention....the PCM 2-3 years ago totally took my MAF out of the system. I could unplug it totally and the engine would start up and run without it. It still sucked at cold start till it was warmed up, but the MAF was 100% disabled by the PCM. I even tried new MAFs a few times. When the new PCM went in, it was back and making my cold starts perfect. I could just start my car now and instantly put it in reverse, pull out of the driveway and leave. Before for those approx. 2-3 years....no way I could put it in reverse, it would stall every time. It surged and idled like crap till it was warm. For 2-3 years I literally had to wait about 2 minutes till I could drive away. Or I would have to pedal it to keep it alive to pull away right away. The new PCM fixed a few things that were unexplainable to everyone.
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Last edited by LS6427; 09-10-2010 at 10:30 PM.
09-10-2010, 10:29 PM
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wow i need to do that with my car then... or ask the tuner to put a real tune on my pcm... or if i need to buy a new one... hopefully when i get it retuned he can hook it up where it doesnt do that weird start thing during warm starts... and maybe the oil pressure will not go crazy sometimes
09-10-2010, 11:16 PM
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and possibly ANOTHER thing to buy... lol. I was told pcm a few times before. It's got to be the problem. Thanks. It was something i figured but doubted because i'm an idiot lol
09-10-2010, 11:27 PM
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hey bud dont worry i am completely retarded about anything with these cars... but if you give me a manual i can take it apart and put it back together 500 times... thats just how i am lol
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09-11-2010, 03:48 PM
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too bad i just moved 14 hours away lol. can another tuner do it or does it have to be the original tuner since he burnt it in and more than likely has it locked out for anyone else?
09-11-2010, 11:14 PM
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the issue is present no matter the weather. Wouldn't the weather seals a condition issue? That oil pressure sender is a thought. Where is it located? The pressure is fine when cold. Sit's at 40 cold 55-60 while driving. Doesn't start dropping to 30 at idle until that imfamous period when everything else goes to crap. My pcm has no case. I know it's supposed to be enclosed but it's just sitting in the bay banging around. That has to cause something...
09-13-2010, 08:49 PM
#18
You should wait til everything goes to hell again.....have a scanner or Tech II ready, then pull over with the engine still running. Pop the hood and grab the wiring harness that comes directly out of the PCM and move it around, just lean into it and oull on it in all directions. Do it as far down the harness as you can reach and also do it right near the PCM. See if that does anything or if anything shows up on the scanner. Even pick the PCM up and shake it some, tilt it, etc..... Grab the two pop top wiring harnesses on the top of the PCM and move them around too.
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