Need GM Specific Help with my 97 Lasaber

[JohnBrowning]

It has a code for multiple cylinder mis-fires and is idleing really rough. If it is Park or Nuetral it runs fine but the second you put it in gear it barely runs at idle. Off idle it runs like a top and has all kinds of power right to redline.It has a normaly asperated 3.8V6.

This is waht has been replaced in the lasty 18,000 miles:

Plugs
Wires
Ignition Module
Idle Air Control
TPS
Upper Intake Manifold
lower Intake Gaskets
Tensioner
Houses
IC Harness
Crank and Cam postion harness

Any ideas welcome.

 

[nel]

John,

This may or may not be helpful, because it's been years since I worked on the engine control systems of those cars. At a minimum, have the code scanned and see if it's related to your problem. This car, like many GM cars, uses an idle control algorithm called PID (proportional, integral, derivative) where it uses the engine speed and changes to that speed to determine how to move the idle air control stepper motor. There is an input as to whether the car is in park or drive. It's possible that your park/neutral switch isn't working or not connected properly. If that's the case, the engine doesn't know if it's in gear or not and when that changes. Putting it in gear adds a load on the engine, and the idle control algorithm has to compensate. If everything is working, it knows that things has changed and instantly tells the motor where it needs to be. Try this: After the engine is idling properly in gear, put it into Park. If it is the park/neutral switch, the engine rpm will flare and stay high before coming down. Good luck.

 

[T-Keith]

A lot of stuff replaced, was this in search of fixing the problem? Are the misfires all on one cylinder, or random? Has this car been in for a recall on the fuel pressure regulator?

 

[lght11]

Hi

I bought a LSS with a Series II in it 2 years ago.

Is there anyway I can check to see if it had the recall done by previous owner?

 

[T-Keith]

You may be able to tell by calling the dealer and having them run your VIN. I didn't notice anything different on the new FPR.

 

[JohnBrowning]

T-Keith, No those items were replaced as they went bad. The car was bought off my grandmothers estate and it was all OEM with 109,000 miles when I got! I replaced the plugs,wires and pcv as routine maintence everything else as it went bad.

This car has been a money and time pit since I bought it. It is just falling apart. Frandma took excellent car of it and did not abuse it. It is just wearing out. The engine runs too good off idle and has great throttle responce and power for it to be anything major.

As far as I can tell it has not had any work done to it underwaranty to the engine or trans.

 

[Shaman]

quote:

---

Originally posted by JohnBrowning:
T-Keith, No those items were replaced as they went bad. The car was bought off my grandmothers estate and it was all OEM with 109,000 miles when I got! I replaced the plugs,wires and pcv as routine maintence everything else as it went bad.

This car has been a money and time pit since I bought it. It is just falling apart. Frandma took excellent car of it and did not abuse it. It is just wearing out. The engine runs too good off idle and has great throttle responce and power for it to be anything major.

As far as I can tell it has not had any work done to it underwaranty to the engine or trans.

---

Have you checked the MAF for corrosion, or the front o2?

 

[Schmoe]

Try this, replace the coil packs. Had a similar problem on my Cutlass.

 

[iceberg]

I see you replaced the cam crank and IC harness what about the sensors? My brothers lesabre would not idle unless you held the gas and I threw on a IAC valve from napa for $35 he also needed the crank sensor replaced. I guess you need a special tool to do that had a guy charged him $50 to install crank sensor.

 

[JohnBrowning]

I have stayed away from the crank sensor becasue of the cost of the SNap-On tool for it. I also am not getting a Crank sensor code. Some one mentioned the PNS switch so I am going to try it. I found one for $20 adn it is easy to get too.

 

[T-Keith]

One of these days I'll have to take pictures of how to align the crankshaft sensor without the special tool.

Your right though I wouldn't change it without a code.

The three things that I could think of would be:
Fuel pressure regulator
Plug wires
vacuum leak

Pull the vacuum line off the regulator and look for fuel. Check all the plugs for a wet or black one. Listen for a vacuum leak, or if possible check with a vacuum pump.

-T

 

[JTK]

JB, have you had a look at the EGR valve? EGR valve pintle could be stuck open, causing A/F ratio issues at idle. I hate random misfire codes. Could be a bunch of stuff

!
G/luck!
Joel

 

[Brett Miller]

Bad coil packs caused the same problem on my parents Lesabre a few years ago.

 

[JohnBrowning]

Not ever haveing been a Tech at an American make dealership I knew I should avoid a high ,illage doemstic product!!! I should stuck to what I know!!! Oh well! It runs so well off idle!! I just do not want the wife stranded some place!

 

[brianl703]

A leaking injector could cause a rough idle (so can a bad electrical connection to one of the injectors). I'd check the fuel pressure at idle, make sure it is within specification, and then check that the fuel pressure holds for at least 5 minutes after shutting off the engine.

Vacuum leaks also can cause a rough idle, and with that in mind, what is the reading for long-term fuel trim at idle on this vehicle, if your scantool can read it? Does the long-term fuel trim reading drop as you open the throttle? (EDIT: This engine has a MAF sensor so vacuum leakrs will really screw things up compared to engines with a MAP sensor!)

Did you replace the fuel injector o-rings when you had the upper intake manifold off?

Oh, is the check engine light flashing when it's running really rough? That means that the computer is detecting misfires right then.

[ January 22, 2005, 07:36 PM: Message edited by: brianl703 ]

 

[T-Keith]

John your experience is definately the exeption and not the norm. 150,000 is nothing for the 3800, I've owned several over 150,000 and none has required any major work. I would ask why all the items have been replaced, but I don't feel it would benefit your problem.

-T

 

[97Astro]

Do you have an SES light on? If so, what are the codes in the order they appear when read. The first code is the first place to check. The codes will be in the form of P1870 (A transmission slip code). Once you have all the codes, you can do a search on the net for ODBII codes where you will find some defination of the problem. If you don't have a code reader, Autozone stores will read the codes for free. Just have a paper and pen so you can write them down as they are read. They will also tell you the defination of the code. Hope this helps.