95 Lumina, rough idle when cold
Question:
It could be your plug wires. Here’s what happens. As they age, the insulation develops tiny cracks. On cool damp mornings, moisture collects in the cracks and reduces the spark to the plugs. After the engine warms up, the moisture is driven off allowing the engine to run normally. Dean – Hide quoted text — Show quoted text – > Hi, > My 1995 3.4L Lumina idles rough when cold, with an accompanying > check engine light. > Runs great however when warmed up after 10 minutes, and the engine > light then extinguishes. > The auto mechanic gave me no guarantee’s that his diagnostic equipment > will truly find the problem. I first suspected the EGR valve failed, but > was told that these units rarely fail. I thought that maybe the idle air > control motor may have failed, but not sure. When I did a resistance > check, per Chiltons, the motor failed, when I checked a new part I got > the same resistance values as the IAC that I thought was failed. > Up to date I have cleaned EGR valve, blown out exhaust port( with engine > running), and replaced gaskets on the EGR valve, also cleaned carbon > deposits off of the IAC motor, none of those task’s seamed to help. I > have noticed though, that when ever I have finished one of the previous > cleaning tasks, the car seems to operate normally, I thought that maybe > when disconnecting the negative battery cable was part of the help. I am > just plain lost! > I hate to just shotgun problems. > Any thoughts or ideas are greatly welcome!!! > Thank You very much in advance for any help!
Response:
I had somewhat along the same problem you did with a 87 Buick Century. I replaced the Air Charge Temp Sensor and that solved my problem. Good Luck Gary – Hide quoted text — Show quoted text ->Hi, > My 1995 3.4L Lumina idles rough when cold, with an accompanying >check engine light. >Runs great however when warmed up after 10 minutes, and the engine >light then extinguishes. >The auto mechanic gave me no guarantee’s that his diagnostic equipment >will truly find the problem. I first suspected the EGR valve failed, but >was told that these units rarely fail. I thought that maybe the idle air >control motor may have failed, but not sure. When I did a resistance >check, per Chiltons, the motor failed, when I checked a new part I got >the same resistance values as the IAC that I thought was failed. >Up to date I have cleaned EGR valve, blown out exhaust port( with engine >running), and replaced gaskets on the EGR valve, also cleaned carbon >deposits off of the IAC motor, none of those task’s seamed to help. I >have noticed though, that when ever I have finished one of the previous >cleaning tasks, the car seems to operate normally, I thought that maybe >when disconnecting the negative battery cable was part of the help. I am >just plain lost! >I hate to just shotgun problems. >Any thoughts or ideas are greatly welcome!!! >Thank You very much in advance for any help!
Response:
>etc.) and all looks OK, the next step is to find what electronic control >module (ECM) error codes correspond to the check engine light being on. >The codes can be seen with a scan tool or by shorting two pins on the >assembly line diagnostic connector and reading the long/short blinking >sequences of the check engine light. The Chilton’s manual explains how to
Although this is very true, that it’s necessary to see what the ECM has to say, it’s not possible to accomplish this via the paperclip and flashing Check Engine Light method. The 1995 is an ODB2 compliant car…you need a proper scanner to get the codes. Either way, it’s worth paying someone to get the codes, and then fix the exact cause of the problem, rather then guessing. — Mark – Oshawa, Ontario, Canada Chevy Astro / GMC Safari Message Board! Click Below! http://pub37.ezboard.com/bchevyastroandgmcsafari
Response:
> Hi, > My 1995 3.4L Lumina idles rough when cold, with an accompanying > check engine light. > Runs great however when warmed up after 10 minutes, and the engine > light then extinguishes.
Well, if the check engine light is on, then there should be a code registered in historical memory. My gut says it’s a temp sensor is shifted, but not totally failed, just out of the normal range when cold. — HogDr SENS BS#123 HD Dealer Technician at your service…… My Employer’s site: http://www.wishd.com My site: http://www.execpc.com/~patrickz/patricksite.htm
Response:
> Hi, > My 1995 3.4L Lumina idles rough when cold, with an accompanying > check engine light.
Hello, I have a 1991 Lumina Z-34. To parrot automotive guru Pat Goss, after you’ve checked everything under the hood (belts, hoses, wiring, etc.) and all looks OK, the next step is to find what electronic control module (ECM) error codes correspond to the check engine light being on. The codes can be seen with a scan tool or by shorting two pins on the assembly line diagnostic connector and reading the long/short blinking sequences of the check engine light. The Chilton’s manual explains how to do this. For each error code there is a procedure that must be followed in order to remedy the situation. That info is also in the Chilton’s. Keep in mind that error codes are stored in the ECM memory in the sequence in which they occur. There can be old codes leftover from another incident that could have been months ago. The usual approach is to pull the ECM fuse to clear all old error codes. You can alternatively disconnect and reconnect the vehicle battery but you will lose the radio time and station presets. Good luck. Sincerely, Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337
