4spd924

True...What size?The classic 9/16? A little but I am done now.lol.

MHT

look for a really big air leak. The AFM signal is used at idle, if it wasn't the mixture adjust screw would have no effect. The screw alters the size of a by-pass around the barn door so that for a given total air flow you can alter the amount the door deflects. As you screw the plug in you make the bypass smaller, the door opens farther and the mixture gets richer. The output voltage from the AFM at idle should be in the .3 to .5 volt range.

StupEd05

hmm... I guess it could be a vacuum leak. So your saying the engine is getting enough air elsewhere to idle, so when the AFM is plugged in it is either seeing no barn door activity or an error so far off the DME knows something is wrong and thus cuts injectors/spark. I think I see.

Danno

Check the output of the AFM at the DME itself. Tap into the #7 line (small green/red-stripe wire) and measure +voltage (use anything for ground). Turn key to ON and have assistant manually open the flapper-door by hand and move it from fully-closed to fully-open. Readout on multimeter should be steady, starting from 0.25v at fully closed to about 7.75v or so fully open. There shouldn't be any spot where it drops out or spikes.

I suspect there may be a short in the AFM wires. Have you tested your TPS open & close switches?

StupEd05

I did that test directly on the AFM a couple weeks ago and didnt spike or dropout anything noticeable. I did not however check it at the DME. It's currently at ImagineAuto and Kasper and Ben are thinking its almost definitely an electrical issue. They are brainstorming and will attack it on Monday. Ben said everyone around there is baffled (im so surprised that my car has brought SO much frustration and agony to so many people across the U.S.), but Ben said Stephen thinks he will have it figured out in fairly short order. He said my O2 sensor is shot and they THINK my Temp sensor MIGHT be bad, but he said there is no way those could be causing this particular problem (or atleast they dont think so). He also replaced some of my grounds for me too eliminate those completely.

StupEd05

Ok Ok, I think there might have been some miscommunication on the symptoms between me and my wrench, BUT the good news is that they have found the problem!!!! It lies in the speed/ref sensors. Turns out those sensors are grounded through the DME. The ground wire to those sensors is bad. This problem must have occured with a PO (or caused by a PO) and fixed 'well' with electrical tape. They temporarily grounded the sensors to a different ground (prolly just the engine or chassis) and he said it fired up perfectly and ran fine. The bad news is that Stephen thinks to do it the right way would end up being close to 6 hours of work. Im assuming that would involve removal of the engine bay wiring harness, not sure though as I have not found out the specifics yet. Im thinking it would end up being something I can do so that is the route it appears to be going.

I'm so glad I decided to take it to the shop as I can gaurentee I would have given up long before even thinking of looking at that. Stephen Kasper is my hero.

I dont really understand how the DME 'grounds' these wires, and would it be wise to ground through the chassis in a 'professional' manner (i.e. NOT using tape!) and not cause problems??? I want to make sure it is a quality job, yet still considered proper.

Zero10

Hmm, on those sensors, the connectors are notorious for going bad. They tend to corrode inside. Honestly, you could cut out the connectors, and just solder the wires together, and it should be fine, unless you ever need to change them. However, I have never tried this.

It sounds like the ground wire to the sensors is broken?... I thought they grounded through the bracket they were mounted on, but I never verified that.

StupEd05

I thought they did too, but I guess not. Because of the fact that the power has to go to the sensor and return with a reading they prolly just grounded all the sensors that go into the DME at the DME. The main thing I am concerned about is if NOT grounding it through the DME is bad???

At this point it looks like I will be pulling the whole engine bay wiring harness and replacing it with one from a parts car.

Charlotte944

If the ground for the Spped and Reference sensors is open in the harness I would think it would be a fairly easy job to solder the wires and then use some heat shrink tubing to protect the repair.

BTW: Pulling the DME harness is a piece of cake. Just drop the DME, unplug the harness, pull the gromet through the firewall, and then pull the rest of the harness into the engine bay. After that you unplug the injectors, AFM, Aux Air Valve, DME temps sensor and so forth. Be sure to mark the speed and reference sensor connectors BEFORE you disconnect them, or the engine will not start after the repair is completed. The good part is, if you do get the sensors backwards you just need to swap them around.

StupEd05

Yeah, that is prolly the plan. I will see if Ben and Stephen think its possible to solder it and limp it home. Then again I still havent seen the damage, so it might be the whole ground wire is shot. The harness swap shouldn't be too bad at all. Karl said it would prolly be a 3 hour max job and it sounds pretty easy. Ben said the reason Stephen thought 6 hours is because he planned on pulling the harness apart and just replacing any wires that were bad. But a whole harness replacement sounds easier for me.

meanmaroon951

Position and speed sensors?

StupEd05

Anyone got an engine bay wiring harness from an early car??? If so, I will buy it!!!