I finally hit on the problem; MAP sensor is the culprit. The only sensor I had not changed. Thanks for the suggestions to solve my problem. G.S.

56 VIC  Gene Stoehr Sr.

Oh, well you can plug a laptop in. You don't have to use the built in wireless. Also, the majority of laptops do not use an outside source, like a cell phone or satellite internet. They use a wireless source from within your home or a local source like a restaurant.


Lawrenceville, GA

Charlie, Knock sensor has been replaced, Plug wires 8MM are good, total rebuilt distributor. Haven't done the MAP sensor yet. Will try that next. What I meant on the laptaop was it will not get any reception from an outside source in the house. I would be able to use the program from the truck in the house but any other signal you would have to outside to use the laptop. G.S.

56 VIC  Gene Stoehr Sr.

Make sure the initial timing is set correctly, just to be sure it is not causing some issue. Like I said, on my Firebird, it should be 0 with the brown wire disconnected. Consult your manual and set it accordingly. It may be fine at 6 but for now, everything needs to be at the specification to help eliminate variables while troubleshooting.

I did not notice that you replaced your plug wires. Mine developed a miss a couple years ago and it was bad plug wires.

Aside from that, I don't really know. I think the only sensors you haven't replaced are the knock sensor, map sensor, and distributor pickup. The map sensor will probably be the easiest to replace. A test you might try there is to simply disconnect and plug the hose to see if there is any change. If it is working properly it should run even worse. If there is no change, then it might be the problem. Make sure the hose is good, too.

Many times a vacuum leak can be a little more difficult to detect because the fuel injection will compensate for it. If that leak is in the map sensor hose or possibly even one teed into it, it will caues problems.

I don't understand why a laptop won't work. Are you saying that if you press the on button, it will not turn on if it's in your house??


Lawrenceville, GA

Charlie, That initial timing change was me I had move it from 10 degrees. Today I installed a new electronic spark control module. Engine started cold as it had before. Running rich and a little rough. I had the timing light on it and the timing mark was well advanced I am guessing a good 30 degrees. I unhooked the computer wire on timing and I got 6 degrees. So i'm seeing advance in open loop running. When the engine got hot and into closed loop I saw no change. Still would not idle without feathering accelerator pedal and would go down on WOT. No change with ESCM part. This truck was a smooth runner before this happened. Good start up cold, great idle, when the air was put on the RPMS would pick up to compensate for the extra load on engine. My box of good parts is filling up. You may wonder why I have not taken you advice. I live in a inground home. Cell phones do not work here nor do laptops. It would work on the truck but not inside the house. So I will keep buying parts sooner, probably later I will hit the right one. Any suggestions on what to buy next? Thanks G.S.

56 VIC  Gene Stoehr Sr.

6 degrees now, but 10 degrees before, and no change when you disconnect the wire. It does sound like something funky is going on with the timing.

The engine will keep running with that wire disconnected. It will run pretty badly, but it will run.


Lawrenceville, GA

I found the single brown wire on the firewall hid behind a bundle of wires in the engine bay. It was a single diconnect wire and I diconnected it. It made no difference in engine timing disconnected or hooked up. Timing set at 6 degrees BTDC. It revved up hot the same way. Would go down on WOT and had to shut back to keep running. There was about 6 more degrees advance revved up, for a total of 12 degrees brown wire hooked up or not. Computer is not advancing the timing! The idle was a little better probably because I put in a new IAC valve. While it was idling I unhooked the electronic spark control. It ran just the same and the timing stay as I mentioned earlier. Should the engine keep running with the ESC disconnected? Thanks G.S.

56 VIC  Gene Stoehr Sr.

My '94 burb has a brown wire under the dash in the neighborhood of the glove compartment that you disconnect to set the timing.

  Dennis in Lititz PA

Charlie & Sundance 241, I had a good temperature sensor so I put that in today. The engine started up after the 3rd try cold. I can't see what it is doing during cranking as I live alone. I'll try to get a buddy over to take a look at that. I also loosen and retighten the ground wire at the thermostat housing. I have a good cone spray of fuel both injectors on cold start open loop. Nothing changed on close loop. Would not rev up hot so today I had the SFluid ready and as it started to die I gave it a shot and the motor picked up with the throttle blades opened up. I still see a gas spray on each injector during this time but it is apparently not enough for the engine to rev up? Today it did not want to idle hot without feathering the throttle to keep it running. I can't see that I have a sensor under the intake. Nothing in the drawings show a sensor. Also I have yet to find the brown wire to take the computer out of the basic timing setting. I am looking at the 10 degrees BTDC with the computer in play. Charlie I may buy that laptop yet!!! I have attached a picture of the truck taken in 2003. It still looks nearly that good with 180,000 miles on the spedo. G.S.

56 VIC  Gene Stoehr Sr.

Rudder,
Since you have good pressure and it's running rich, I would not suspect the regulator. Have you been able to observe the injector spray pattern when it starts to act up?

On my Firebird, when you check timing, there is a plug on a brown wire that you disconnect that takes the computer control out of the equation. With that wire disconnected, static timing is 0. When it's plugged back in, the computer sets the timing. I imagine your truck is similar and if 10 is static, it may be contributing to the problem at least. Check your shop manual.

Since you plan to keep the truck, investing in the proper tools will be worthwhile. You should be able to find everything you need for under $300.00. Just like you need screw drivers and wrenches for an older vehicle, a computer and logging software are necessary for an electronically controlled vehicle. Just think about how much time and money you have already spent with guesses that haven't fixed the problem. I can't guarantee that the laptop and software will help you in this instance but it has come through for me so many times. Like I said, everything else being equal, I take modern (or newer, anyway) electronics over clunky old carbs and points. I've found it much easier to diagnose, but you have to have the right tools.

I don't know about sensors under the manifold. I can tell you positively, my '88 305 has no sensor under the manifold.


Lawrenceville, GA