PCM programming / ignition timing

[Andrew F]

I have recently installed a Clifford Performance 264H cam in my '97 TJ 4.0. Does anyone know if the ignition timing can be adjusted in the factory PCM? I have a MODIS scanner (high end from Snap On) I'm still learning to use. Will it be able to adjust it? Or will I have to find an aftermarket PCM? The timing needs to be be at 4-6 BTDC. It's currently at about 8 BTDC.

 

[SteelHeadz]

The only way i can see this possible is to get a programmer. The software on the PCM cannot be re-written when it comes to ignition timing and fuel delivery even with the use of the factory scan tool. The Modis scan tool may just have the same features or if even that like off the DRB3. Google "programmer" and see if you find one that suits your application.

 

[Jester32]

The older controllers like xjs and yjs you can pull up to 8 degrees timing. But that's with obd 1. Chrysler put that in as they were bad for ping. As for your tj. I don't believe it's possible it's all controlled by computer. Should be optimum for how it's running.

 

[Jester32]

And why do you wanna pull timing. Timing is power. If your not having and detonation or pinging I would be wanting to put some timing in.

 

[Andrew F]

The Clifford cam is designed to make torque from idle. As the timing is set I don't get anything from the cam until about 2250rpm. It fights the ignition timing at startup. Once it's running it's smooth as a swiss watch (probably due to the 114 lobe centers). I only need to advance it a couple degrees. At this point it looks as though I'll have to change out the rest of the ignition system to MSD or Mallory to get any adjustment at all.

 

[Jester32]

Did you install the cam straight up. And 2 degrees in ign timing at idle won't change the torque curve that much. It being a gas engine you usually won't see a ton of torque till about 3000. Especially with a adv duration of 264. The dynamic compression will be fairly low at idle with the larger cam. A 112 lsa would have worked a bunch better but it being a efi cam that's kinda out of the picture. Although I have had good success running 110 lsa with fuel injection in the past.

 

[Andrew F]

I installed the cam straight up. It has 4 degrees advance ground into it. I'm fine leaving it for now, but future parts of this build will make the factory PCM useless and I'll have to put in a distributor with a mechanical advance anyway.

 

[Jester32]

Oh ya. Run a mega squirt. Tune everything ftom ur laptop

 

[Andrew F]

Actually, I've been looking at a Redline TBI, and an Offy manifold. I haven't really gotten to see what this motor will do as it is now since I've only put about 250 miles on it since the rebuild. I had it bored .060" over and zero decked the block. The Clifford cam kit came with bigger valve springs and the spring seats had to be machined down .100" to accomadate them. It's about 10.5:1 and still running with the stock intake (ex a K&N air filter). I may just stick an Edge Trailjammer kit on it until I can afford to do it the way I want.

 

[Andrew F]

I do have a MKIII Supra I was thinking of putting a Megasquirt in though

 

[Bounty__Hunter]

Have you increased the size of the throttle body? Installed a hotter ignition? Larger injectors?

What about an A/F ratio gauge?

 

[Jester32]

10.5:1 is pretty high for that small of a cam. I bet the PCM is pulling a ton of timing off idle from sensing knock. Can you watch total timing on your scanner while you drive it. It should begin to advance right away around 1000 rpm should be up around 15 degrees and keep climbing.

 

[Andrew F]

I'm still running the stock throttle body and injectors, an MSD Blaster 3 coil from the stock module, and MSD 8.5mm wires. I could plug in my scanner and take a recording durring regular driving and see what I get. MODIS records 30 seconds before and 2 minutes after you start the recording.

 

[Jester32]

Cool I would do that it will give you an idea if the PCM is pulling timing to correct for a prob.

 

[Andrew F]

17 degrees at 992 rpm. 31 degrees at 1984 rpm. The highest value I have is 41 degrees at 2560 rpm

 

[Jester32]

How about at higher rpms. That sounds close to correct

 

[Jester32]

And it's 8 at idle ?

 

[Andrew F]

11 degrees at 768 rpm

 

[Andrew F]

The afr graph looks a little wild, but that could be due to the narrowband O2 sensors. It does show a slightly irregular lope at idle (736-768rpm) but it sounds pretty smooth.

 

[Jester32]

The lope will more than likely be from the cam itself.