[thedon051586]

Hello everyone, new here and in need of some assistance. I have a 95 Jetta 2.0 5 Speed with 99,000 on the clock. My check engine light has been on since I bought the car a few months ago. If I feather the accelerator it will pick up speed fine but if I jam it hard, she falls on her face. With the weather fluctuating here in NC its cold as winter one day and hot as summer the next. That being said, I've noticed something very unusual with the car. The check engine light ONLY comes on when its cold. When its hot or even above like 65* it goes off and the car runs like the dickens. Otherwise I have this acceleration issue. I've changed IAT, CTS, checked for vacuum leaks and I'm beginning to get stumped here. I can't check the light because when I jump the wires the light just turns off, no blinking codes. Am I correct in assuming that with an aftermarket stereo it must be disconnected in order to blink the codes? I would like to pin down the issue before throwing parts I don't need at it, and any help would be appreciated!

 

[oxygen454]

I would think the problem lies in a faulty coolant sensor. The sensor may be sending incorrect readings when the engine is running cold causing the ecm to think the that the car is running at a warmer temp. This could give incorrect fuel to air ratios which would leed to poor performance.
Can you scan the ecm for codes?

 

[thedon051586]

Sorry for the late reply, with the kids being out of school, it has hampered my tinkering time with the car... That's what I thought as well so when I went to the scrapyard about a month ago I got both coolant temp sensors (one for gauge and one for ECM). I know they weren't new but I figured I'd give it a go and see what happened. Also, while I was there I got a new mass airflow sensor, well not new but you know what I mean. New to me. Anywho, put both in and now that its warm it is happening much less frequently. However, I have gotten into the habit of when starting, after the idle comes down I'll get the RPMs up a few times (like 4-5000) and it never comes on, even in the coolest of times. I am almost thinking now that it could be a TPS sensor because it acts like its not responding to throttle control. But then there's the conundrum, I don't really have the money to go out and buy every sensor, to see if this is it or that is it. To answer your question about scanning, no, I am not able to. Volkswagen in my area wants a couple hundred bucks because they claim they need to run all kinds of wires around the car (even though it has an OBDII port) so I said to heck with that. That would be a great help because then I could at least have some semblance of an idea as to where to look. Furthermore I cannot do the paperclip trick either. I have read many posts from all over that state that you have to take the radio out if it is an aftermarket stereo. Well I did that today and it does the same thing. I put the clip in pins 4 and 15 and the light just stays on and when I remove it, it goes off. The same thing it has done with the radio in. So I am kind of stumped as to how I can scan it without buying anything (OBD wire and software). That I think is the only thing that I miss about the old domestics. Stick the paperclip in and flashes out codes, no matter what.