3400 Fiero Issues.

[bandit307]

I have posted on the fiero forums, but i am not getting much response. So I figured I would try you guys as well.

So here is the issue. I have my 3400 installed into my 87 Fiero GT, It is being run by a 7730 ECM with a custom chip from sinisterperformance.

Now I have everything hooked up and have checked and double checked my wiring. The car will start if you open the throttle slightly, so I assume it is running slightly rich at start up. But once it starts you can close the throttle and it will idle fairly smooth. Once you goto give it gas it will bog out if you give it to much throttle to fast. I took the car for a little test run and it is getting no power at all, its worse then my 2.8. lol

I am guessing that it is a timing issue? The only wire that is not hooked up is the tach signal wire for the tach itself. The reason for this is i do not have pin C on the 6 pin connector to the DIS.

Here is the wiring diagram for the 7730 with DIS. http://www.fiero.nl/forum/Forum2/HTML/092393.html

And this is how I have my wiring done. I believe everything is in order, im just at a loss right now. Not to sure what to look for.

7730 Pin-Out & Description --> 3400 Connector, Color & Description
D9 - distributor reference low (ground) - blk/red -> red/blk - 3x ref low (I have tried grounding this wire at the block also)
C8 - electronic spark timing control - wht -> wht - IC Control
C9 - distributor reference signal - ppl/wht -> ppl/wht - 3x ref high
C7 - est bypass - tan/blk -> tan/blk - bypass control

[Superdave]

maybe these will help..

http://www.v6z24.com/jbodyforum/ecm-pin-out-diagrams-t99212.html

It does sound like you have a timing issue... While cranking the advance should be 9.14 degrees, as soon as it catches the ECM should advance it into the 15-20 range. Do you have the stuff to datalog?

[bandit307]

No I dont have anything to datalog. I have the software but am waiting on my usb cable for my laptop. So i was hoping i could do some trouble shooting till then.

EDIT: Great link by the way, I will check it all out tomorrow. Thank you.

[IsaacHayes]

you can add a pin for pin c for tach signal btw.

[bandit307]

I have checked and checked the wiring to the DIS, when i disconect the bypass wire the timing dose change and it runs rougher. So does that mean everything is hooked up right? It just seems everything is hooked up right. I also thought it might be a fuel issue, But i am getting consistent 55 PSI pressure. Here is a short video of whats going on. You can here it bog when I open the throttle quick. But if I bring it up slowly it will rev up to a certain RPM that im not sure of cause there is no tach right now. But it eventually starts to loose power again. I will check my trouble codes tomorrow as well and see what it says.

[bandit307]

Aftre looking at my video a few times. When i go to give it throttle and it bogs the fuel pressure goes up to 60PSI, could this be an injector issue?

[Superdave]

what did you tell the people that burnt the chip? did you let them know that you'd be running the injectors at 22.5 lb/hr?

Sounds like it might be in the tuning.. grab a picture of the chip setup that they sent you, if the prom is swappable and you are in the US i might be able to send you a good tune for a 3400 on OBD1...

[Joseph Upson]

60 psi sounds about right since base is around 56 psi, the pressure goes up with rpm because the vacuum is dropping on the regulator.

When my engine did that it was because the MAP sensor was bad and it wouldn't set a code. The engine would idle fine but cutout at part throttle because the unresponsive MAP sensor was causing the ECM to lean out the AFR.

[bandit307]

I have gotten a bit further. I had a faulty MAP sensor which i replaced and now and it runs alot better. If I open the throttle it will bog for a split second then rev right up. It still seems to struggle under load though. But after you rev off idle the engine is very responsive while its not under load. I am also now running 50psi at idle and up to 55psi during acceleration.

I do have another problem though, but im not to sure if it could be a factor of the struggle under load. I believe my TPS may not be good. I am getting good ground, steady 5V for reference but only .01V in all throttle position off the signal wire. So im under the assumption that the TPS is no longer working. This could be the issue for the slight blog from idle. But would it be the factor of the load issue?

[Superdave]

Yes, replace that too.. lol

[Guest]

no voltage from the tps means bad wiring or bad sensor. If you know the wiring is good, then replace the sensor. If the computer doesn't know what posistion the throttle is at it won't run right. In fact the stumble at initial throttle tip is an indicator that the tps is bad. Once the map tells the computer the the vacuum is changing and the computer doesn't see a difference in tps values it skips the tps so to speak to get its info from it and goes off the map sensor to keep the car running. When I had a bad tps it would run horrible at initial throttle tip in but once rolling would be ok.

Also I think 50 psi is too high. You could be dumping too much fuel at PE throttle tip in and that could cause a stumble too as its too rich. Weren't 3400's running the same 42 psi as every other 60 degree?

https://www.realfierotech.com

[hookdonspeed]

isnt there a way to jump the pins while running, and the CEL will flash slow/fast depending on what the O2 is reading?
i remember having done that before on the stock fiero ecu...

[Superdave]

Also I think 50 psi is too high. You could be dumping too much fuel at PE throttle tip in and that could cause a stumble too as its too rich. Weren't 3400's running the same 42 psi as every other 60 degree?

www.realfierotech.com

99 and older ran 43.5 PSI, 00+ ran 55P SI

[bandit307]

Ok, so now everything seems to be getting proper voltage except my knock sensor which is recieving about 4.3V in the on position (supposed to be 2.5) and my O2 sensor which seems to recieve next to nothing for valtage. So i assume its a wiring issue on the O2 sensor since it is brand new.

I can take the car out and it will drive just still seems to be lacking in power, I have got it up to 4500rpm and seems to get there fine, just really slow. lol When i have it in the shop not under load it will still do a slight stumble from idle to WOT but will then rev right up no problem. Does seem to run a little rich right off idle aswell though as I get a nice little puff of black smoke. I hope its just O2 wiring I have left. It is the heated O2 sensor from the 3400.