Robert Henriksen

I'm still trying to eradicate these stupid Check Engine light occurences. I just got done replacing my plugs & plug wires (all of them), and also have new distributor caps & rotors. OEM air filter. I screw the gas cap on securely, 4-5 clicks when tightening it down after fillups.

Where I seem to be able to repro the light coming on is a) at the track, and b) when cruising on the street at steady throttle at ~3,500+ rpms.

I just ran down to the dealership & had them print out the fault codes, which are linked below. If anyone can give me some ideas, I'd definitely appreciate it! The one thing the mechanic said when I explained that steady cruising at higher RPMs seemed to trigger it, was that the cylinders were running lean - for some reason.

<a href="http://www.houstontc.net/robert/misfires/" target="_blank">http://www.houstontc.net/robert/misfires/</a>

Steve Weiner-Rennsport Systems

Robert:

This will take some local detective work to find and resolve,.........

Here are some things that will cause these codes; if you replaced plugs & wires, then you have already addressed some of the root causes.

1) Faulty plugs

2) Faulty plug wires

3) Faulty plug connectors or any arcing

4) Arcing or cracked caps & rotors; cap resistance per connector should be .8-1.2K. Rotor resistance should be 1K. These MUST be seated correctly, too.

5) Any loose connections; distributor, coils, crank sensor, etc.

6) Coil problems: Resistance between term 1 & 15 at 68 deg F should be .4-.6 ohms. Resistance between 1 & 4 should be 5.0-7.2K

7) Check your fuel pressure at the rails!!!

8) Check and measure fuel volume

9) Check each injectors's connector and the harness. This can also cause those cylinders to go lean and trgger a misfire.

10) Check for any air leaks all over the intake manifold, especially the runners. Vacuum leaks will play hell with mixtures!

At 3500 and part throttle, you are in a lean portion of the fuel maps,...............

Hope this helps, you have some work to do.

MG993

Robert,

As I am not an expert, but i will give you my version of the same problem and the fix!

My check engine light would also come on around 3500rmp and the error codes alway showed as a misfire in a different cylinder. I replaced plugs, wires, cap and still the light went on.

I had two dealerships check the car. The final conclusion was that the DME was bad or the Dual Mass Flywheel was warped. It turned out to be a bad DME. Not a cheep item, but the light has not reappeared since the repacement.

I hope that helps and good luck. The second Dealership said that they are seeing a lot more of this occuring.

Myles

Robert Henriksen

[quote]Originally posted by MG993:
<strong>It turned out to be a bad DME. Not a cheep item, but the light has not reappeared since the repacement.

I hope that helps and good luck. The second Dealership said that they are seeing a lot more of this occuring.

Myles</strong><hr></blockquote>

You are just TRYING to get me to upgrade to a Steve Weiner (tm) DME special!! ;-) I'll show this to my wife, that'll do it! 'Honey, really, I've gotta replace the computer anyway...'

thanks for the info, I'll keep this in mind. Too bad it's such a project to extract the DME, I'd just swap with a friend to test this theory.

Robert Henriksen

thanks Steve, I'll check out all the ones above I'll be able to puzzle through w/o being a danger to myself or the car! Maybe get some help from a shop w. the fuel pressure/volume issues.

Maybe I'll get lucky & need a new DME :-)

Flying Finn

Steve,

What's the 'best' rpm (minumum wear & tear but still not too low, I don't want to get build ups either) when cruising steadily, let's say speeds at 30-40mph (city) & 65-85 mph (highway)?

Thanks a lot!

Flying Finn

MG993

If I only would have known, I would have upgraded to Weiner(tm) DME. I don't have to worry about the wife because I have "Car Fund" and she has a "Clothes and Jewelery Fund". Good Luck.

Steve Weiner-Rennsport Systems

Myles:

LOL...its good to set funds aside for the important things in life and an upgraded DME is one of them,..... Its quite worthwhile!!!

FF:

I like to cruise these engines in the 2500-3700 range. IMHO, anything below 2500 is kinda lugging them although they will pull very nicely from those RPM's. I've not done any scientific studies nor measurements but the cars that display the least amount of carbon buildups and and running issues are ones that are driven rather aggressively and their owners use Techron or LubroMoly on a regular basis.

As a side note, the cars that we have installed close-ratio gearsets also don't seem to suffer the ill effects from carbon buildups either.

Must have something to do with how these cars are driven.

Jeff 993TT

[quote]Originally posted by Robert Henriksen:
<strong>
Too bad it's such a project to extract the DME, I'd just swap with a friend to test this theory.</strong><hr></blockquote>

Taking out the DME is not too bad, really. I've been able to take it out and put it back in less than 1 hour.

However, the first time, you will need a dremel to cut off a few "blind" bolts. After you get it out, replace them with regular 10MM head bolts. The first time will be longer with all this trickery.

If you have a friend with a factory DME, you won't have to bother with the immobolizer reporgramming issues and should be able to swap between cars easily. When I upgraded my ECU to the factory Turbo S ecu ( from another car ), I didn't have to reprogram the immobolizer. I've had another confirmed report of this as well.

However, if you have the ECU reprogrammed, ie from Steve, FVD, et all, you have several options.
a) Have them disable the immobolizer, or use a "universal" immob code, which causes a light to stay on your dash all the time
b) Have the dealer reprogram the immob codes back into the new ECU. Costs about $100 if there are no issues that come up.


Hope this helps.

Jeff

Curtis - '97 Targa

Hi Robert,
You are experiencing the exact same symptoms that I am. I've also taken most of the same steps to correct that you have.

The only other possible cause that I've heard regards a slightly warped flywheel that causes the sensor to indicate a misfire.

I'm pursuing a DME replacement. I'm trying to convince the dealer to do it for free because it is emission related. We'll see....

Curtis

Flying Finn

Thanks Steve!

I should be fine then, I've had similar thoughts. When I'm cruising about 40, then I sometimes drive under 2500 (about 2100). But usually I like to keep rpm's around 2500-3500. It's just that if I'm driving about 60-70, and with 4th gear rpm's are around 4500 (can't check it now <img src="graemlins/yltype.gif" border="0" alt="[typing]" /> ) and with steady speed, I fiqured I'm running too lean? (that's not goo either).

And of course, I like to 'stretch her legs' (rpm's 4500 to red line) at least once a week so that she can do what se was meant to do. I do these same things with my old timer too (-75, 2.7 liter 911), I believe there's not much carbon buildups there!

Thanks again!

Matt Vaughan

Robert, if it comes down to it, I can pull my "Weiner Special" for ya for the test. But we of course must sign a contract prior saying that after the testing concludes, I get my DME back!!!


-Matt

Robert Henriksen

[quote]Originally posted by Matt Vaughan:
<strong>Robert, if it comes down to it, I can pull my "Weiner Special" for ya for the test. But we of course must sign a contract prior saying that after the testing concludes, I get my DME back!!!


-Matt</strong><hr></blockquote>

But then how will you CATCH me to get it back?! <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Speaking of which, how did you handle the immobilizer issue that Jeff mentioned above - universal code, or dealer reprogramming? If the latter, does that mean I'd just use your keyfob during the testing? (SHORT test, yeah, that's the ticket...)

Matt Vaughan

[quote]Originally posted by Robert Henriksen:
<strong>

But then how will you CATCH me to get it back?! <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Speaking of which, how did you handle the immobilizer issue that Jeff mentioned above - universal code, or dealer reprogramming? If the latter, does that mean I'd just use your keyfob during the testing? (SHORT test, yeah, that's the ticket...)</strong><hr></blockquote>

<img src="graemlins/oops.gif" border="0" alt="[oops]" />

I'm pretty sure Steve did no modification to the imobilizer, so I'd imagine a good lock-unlock of the doors should work fine.


-Matt