Missing 3.4

[grandprixgtp_91]

RE: re missing 3.4

ok, the icms from canadian tire work ok, ive used one, i would still rather a gm one. when you did your crank sensor did you use a gm one? if not i would go back and get one. also take off your connector and make sure its not corroded or bent, i had the same probelm and i had a code 42, and it was my wire , it got jacked somehow changing the crank sensor, but it didnt happen until a few months later. check that out

Jake

[GTP091]

missing 3.4

That's Genious! I just read your post and now Im going to have to go wake up my car and do some soldering to check out your fix. When I replaced my crank sensor I pulled the wire completely out of the car and used new auto wire (im a car geek so I bought matching colors) and bought a new standard sensor plug harness. It had black and yellow wires on the new harness so I just assumed they were correct; and it did start after it hadn't.

Im going to try this and if it works Im gonna be right pissed. I spent $1000 on redoing the timing and about 1200-1300 on new 3 new sensors, coils, plug wires, 2 ICMS and even the IAc valve. If this works My engine will run near perfect as it won't have any old sensors on it. I almost bid on a new engine form ebay I was getting so frustrated. Check this out if you want a brand new 3.4. I could have bought a new engine for what I paid to have mine not running right.

http://cgi.ebay.com/ebaymotors/GM-3-4L-DOHC-Engine-NEW-3-4_W0QQcmdZViewItemQQcategoryZ33615QQitemZ8017202605QQrdZ1QQsspagenameZWDVW

I also read through your site on your fiero I like those cars light and fast they look like little ferrari's. Awesome job.

How much of a pain is bolting that getrag 284 to your 3.4?? I have a line on a 284 and I wan to do a manual swap in my car.

[Juglenaut]

RE: missing 3.4

The CPS is non polarized so it does not matter what way it is hooked in, however it may be just a fluke that switching wires helped..Also impedence has a factor with pulsating wave forms, twisting the wires is like creating a capacitor and a inductor. Leading to a certain value I rather not figure out, anyway in terms a certain frequency may or may not like the way a wire is twisted in with current traveling one direction, but reverse it and it may pass easy in both wires.

Core wire diameter, insulation thickness, air separation all play a factor on matching impedence. capacitors couple AC and pulsating DC with phase offset, inductors decouple AC and pass DC, a plusating DC wave form will be deminished depending on the duration of the peak and frequency, basically the duty cycle of the pulsating DC will be deminished. There is a equation but just don't feel upto it today.

[ltlfrari]

re missing 3.4

GTP091. The tranny is an Issuzu not an Getrag. It just bolted straight up. dust shield was off a little (one hole needed streching) but otherwise no problems.

Juglenaut. I agree the CPS is non polarized (AC signal) which is why I never bothered about it before but I found an article (on the megasquirt web site) that indicated the ICM only triggers on the negative going edge of the signal. That WOULD make the ICM sensitive to the polarity of the wires since the cycling of the signal is based on the crank cuttouts and those are fixed of course.
Not saying you may not be right and that it wasn't something stupid but I'd done these wires a couple of times, same way each time, twisted them, covered them in foil to suppress interference, earthed the foil, rerouted them, you name it, nothing worked. All I did was swap the polarity overand it worked. For me that is proof that in my case at least the problem was in the wiring polarity. I also suspect that when I first did the wiring this problem was what probably fried my original ignition module although I have no proof.

[Juglenaut]

RE: re missing 3.4

Negative edge triggerd is the point where the peak positive begins to drop, positive edge triggered is the point where the peak stops to rise. Both signals coming off the induction are in phase and the same polarity unless rectified, or pulled low or pulled high. When the magnetic flux drops the charge goes in both wires and since the cps is non-polar the polarity is the same. If one of the wires is internally grounded then the pulse is pulled high, if one of the wires is hot then the pulse is pulled down. Charge comes from the inductor, does travel back however that doesn't induce a negative. A negative going wave is positive in respect to ground, so a grounded ICM can use either. In a sense yes the ICM polarizes the form, but can be externally manipulated to get whatever wave form it needs.

If the wires are longer, used different type even slightly will cause the impedence not to match right and will pulse undefined.

On a 12volt negative ground system, you technically can't have a negative wave going below 0 volt, because it is positive in respect to ground.

wire must be twisted 9 times per foot, using stock wire. A 3.4L ICM is not referenced to ground, so the only reason the wires connection would come into play is because of the reluctor and the 24x cps spark reference that the PCM uses.

[ltlfrari]

You win, too complicated for me. The article I read said it triggers on negative going edge at the zero crossover point. I'm assuming the ICM biases the input signal above zero volts so it can detect that. Basically I still stand by my statement that I think the polarity is important.
My wires have been orig length, longer, shorter, twisted, earthed, deep fat fried even (joke). Even now they are much longer then the originals. not saying all the stuff you described will not influence the signal but I think you are making it too complicated, well for us mere mortals anyway.
Anyay, whatever the cause, all I know is I swapped the wires over and it works, and it GTP091 swaps his and his works I shall be vindicated and if not I accept that you may be correct and I was just lucky.

[GTP091]

I went out to my car cave today and did as ltlfrari suggested. I soldered the yellow to the black wire and the yellow to the black. After reinstalling the battery I turned it over and here's what happened.

it fired, started, idled up to 1200 rpm, then back down to 950 rpm and purred as I stared in disbelief. At that point I was still extremely skeptical so I gave it some gas and it revved up to the cut off at 3500 RPM. no missing no backfiring, no stuttering, no sluggish response. I forgot how responsive these engines are. But it's fixed!! damn crank sensor wiring.

POWER!! I love it. This was the problem the whole time. To bad I spent nearly $2000 throwing parts at it just to spend about 2 cents on solder. There goes my rim and tire fund until spring.

And what really sucks is its winter now and I have to put it back to bed for 5 months. (my 2001 4X4 dakota is a much better vehicle in the winter - it doesn't have cold leather seats).

Thanks for all the help though especially ltlfrari.

When I want to do a manual swap Im sure you guys will hear from me...

And if you want a new engine go to ebay and search for : GM 3.4L DOHC Engine NEW 3.4 - Im currently winning it and I don't need it now that mine is fine. Bid quick!!

[ltlfrari]

re missing 3.4

I rest my case .......................

Man am I glad for you that it worked out. And I have to thank you for putting my on the right track in the first place.

My little Fiero is now on the road, passed inspection and emmissions today.

Dave

http://www.ltlfrari.com