Base Timing Off??? Ideas???

[MazdaGreg]

Allright,

I have had a backfire/surge in my 93 Navajo for the past year. I have tried just about every piece of Fuel Injection, Ignition, Emission component i can think of. I decided i would check my base timing, and it turned out to be 14 BTDCdegrees, not the 10 BTDCit's supposed to be. And yes, i did have the SPOUT connector unplugged. I used an Inductive Advance timing light that is accurate. Any Ideas? Would a Timing Chain slip one gear, and offset the timing by 4 degrees? Any other ideas? Thanks

MazdaGreg

By the way, it has 175,000 Miles on it, if that helps

 

[dogfriend]

If you are checking with a timing light, you are checking when the number one plug fires with respect to crankshaft position. This was controlled by the distributor position on older cars; on EEC-IV Explorers it is controlled by the Ignition Control Module and Powertrain Control Module (using the signal from the Crankshaft Position Sensor). On EEC-V Explorers, the ICM is integrated into the PCM and a Camshaft Position Sensor was added so the PCM uses both the CMP and CKP signals.

The timing chain controls the timing of the valve train (opening and closing of valves) with respect to the crankshaft position. This must be set by lining up the camshaft and crankshaft sprockets correctly when installing the timing chain.

Edited to correct the first paragraph

 

[dogfriend]

Oops, I just found something that says that 91-95 (EEC-IV) Vin "X" engines don't have a Camshaft Position Sensor (96 and later Vin "X" engines do have a CMP) Dead Link Removed

I will look in my engine control book to see if I can figure out how the base timing is adjusted on your 93 when I get home.

 

[dogfriend]

Found some more info at autozone.com:
Dead Link Removed

So, the base setting is 10deg BTDC +/- 2deg. So you are 2deg out of spec. The timing is determined by the ICM using the signal it gets from the Crankshaft Position Sensor. It seems to me like one of the following components are causing the problem (listed in order of increasing $)

Crankshaft Position Sensor (maybe)

ICM Ignition Control Module (these have a tendency to go bad in Fords)

Powertrain Control Module (you don't want it to be this)

Good luck

 

[MazdaGreg]

Thanks for all of the useful information. I have tried a different Crankshaft Position Sensor, no change. Now, on the Ignition Module, is that the Coil Pack? I have tried replacing that as well, (I Just love Autozone's Return Policy) and still no change. The one thing that i have not even thought of changing ($) is the ECM. I will go check out that link when i am through replying. Thanks again for all your Help!

MazdaGreg

 

[Alec]

Really stupid question:

Have you tried just resetting the computer?

 

[MazdaGreg]

Ok, Just viewed the web-site link you sent. Very helpful. I see that the ICM is seperate from the Ignition Coil Pack. My question now is, Where is that Ignition Control Module Located?

MazdaGreg

 

[dogfriend]

Its mounted on the radiator support, on the drivers side of the engine compartment. It should be close to the SPOUT connector.

Dead Link Removed

 

[MazdaGreg]

Allright,

Here we go again. I went ahead and swapped the ICM from my dad's 4.0 Aerostar. No change. (Damn) I regret to think that i will have to try a PCM. I have found that PArtsAmerica online you can order the PCM, and then return it at a regular store. $300!!! Ouch. And of course, my Navajo is a Federal Emission, Manual, so it takes the most expensive one!!! In your honest opinion, you think that the PCM would have that type of problem, that would cause a Backfire/Buck at 1000/1400 RPM Intermittently?

By the way, concerning SPOUT connectors. IF the Spout connector is up front behind the passenger headlight, what is the Spout connector that is on the passenger side near the PCM Test connector? There's 2 on this thing, and they both look the same!

MazdaGreg

 

[dogfriend]

Are you sure that they are both SPOUT connectors? Are they on the same wires or different ones (i.e. Is the color code the same or different)?

In my Haynes manual, it says that the SPOUT connector is near the ICM on 91-95 models, near the PCM on 96 and later OHV models.

Before replacing the PCM, triple check all of the wiring, the mounting of the CKP etc, because the PCM is usually very reliable. Make sure that all ground connections look ok.

If you can't find anything else, the PCM is the unit that determines ignition timing. In my Haynes manual is this statement under Ignition timing - check

If the proper mark isn't aligned with the stationary pointer, have the PCM checked by a dealer service department or other qualified repair shop

 

[MazdaGreg]

Well, I'll tell you this. I felt like an idiot when i found the Spout near the ICM. I have not looked at the colors of the wires yet. But the one near the heater blower motor (REAR PASS Side) is exactly like the one at the ICM. So, who knows. That spout could be for something totally dfferent. The thing is, the one at the ICM is incredibly difficult to get to (behind battery, must remove to get at) So i figure that ford put in the second one for emission testing, etc. So people wouldnt have to take the battery out. But now, if that is not the case, then i've been reading the timing without the spout disconnected. bEfore i go any further, i will pull the spout at the ICM, and recheck the timing. I know that wont fix the problem of the backfire/surge, but if the timing is on, then i can move on from there. Thanks for all your help and time. I will let you know as soon as i pull timing off that thing, and tell you if it made a difference. I wonder if the 2 SPOUTS is a Mazda Thing. Maybe mazda had ford put in the second one for some reason?