When searching the scrap yards, keep an eye out for this...


On the last couple years for the cast iron L4, GM revised the tray that holds the DIS brick together. As you can see, they added quite a few small fins to the perimiter. This is a significant boost to the surface area of the tray and should help the PIM stay cooler.

The car I got that one from was a 90-91 I think.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurasic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

Is there a P/N stamped into it???

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Notchbacks RULE

"Let a man drive a Fiero and he'll own one.
Teach a man to fix a Fiero and he'll own eight....errr...nine."

Wasn't that I could see. I'll look at some of my other photos and see if maybe they caught more detail than I did. With that camera, it's entirely possible.

89 thru 91 Vin U engines.

It fits the R motors just fine. I put it on yesterday when I was cleaning up the brick after that F'ing coolant fitting O ring quit. If had time, I'd have cleaned it more but a short soak with some wheel cleaner got the worst of it. As it is it looks better than the plain tray.

It has to cool the PIM at least a little better. Anything has to help. There are a couple ideas I have to help block transfer of heat from the block to the plate but I just don't have the tools to test them.

I looked at the images I have... top and bottom. I don't see any number. There is only one flat area that I don't have an image of and that is unlikely to have anything cast into it. (The in small side area with no fins.) It could have had an inked number but that would have been gone years ago.

I'll be interested in hearing if it helps on the stalling when the engine gets to warm operating temp. My 88 4 cyl, auto has me looking seriously at the 4.9 sitting on a dolly in the garage. Stalling really pisses me off.

quote Originally posted by theogre: It fits the R motors just fine. I put it on yesterday when I was cleaning up the brick after that F'ing coolant fitting O ring quit. If had time, I'd have cleaned it more but a short soak with some wheel cleaner got the worst of it. As it is it looks better than the plain tray. It has to cool the PIM at least a little better. Anything has to help. There are a couple ideas I have to help block transfer of heat from the block to the plate but I just don't have the tools to test them. I looked at the images I have... top and bottom. I don't see any number. There is only one flat area that I don't have an image of and that is unlikely to have anything cast into it. (The in small side area with no fins.) It could have had an inked number but that would have been gone years ago.

How about a 'thermal conductive compound' like is used under the ignition control module.

quote Originally posted by Fierobruiser: How about a 'thermal conductive compound' like is used under the ignition control module.

I do that automatically. The only pain is that the PIM is so large you have to spread the stuff fairly thin over the area. You can't glob some in the middle and let it ooz. It won't spread that way and may be a risk of stressing the PIM.

You can use any sort of compound you want. Besides helping cool, most should also help block corrosion since many have Silicone oil in them. I just use the basic white compound since it is cheap and you need a fair amount of it. I doubt stuff like Artic Silver would make a big dif in this case anyway. I'm looking more toward small alterations to block/reduce transmission of heat from the block.

1. I thought about insulating the bottom of the Plate from the block. However... The plate also carries the CPS and sets CPS to Crank clearance. This means I'd have to mill the plate to accept an insulator such as Phenolic washers. Lacking tools time and money to be bothered... leading to #2...

2. Chamfer the holes on the block face of the plate to reduce metal to metal contact. Not as good maybe as an insulator but better than nothing and can be done with a Dremell.

3. Use insulation, likely phenolic, washers under the bolt heads. This requires no alteration to anything beyond adding the washers. Unfortunately I don't have any Phenolic sheet or washers around to try it.

The more heat your cut from the block, the better the plate can cool the PIM.

quote Originally posted by Brian Lamberts: I'll be interested in hearing if it helps on the stalling when the engine gets to warm operating temp. My 88 4 cyl, auto has me looking seriously at the 4.9 sitting on a dolly in the garage. Stalling really pisses me off.

It might. Can't say for sure.

Stalling when hot can be allot of things. You'll also want to read the ECM heat note in my cave. Maybe even leave one of the grates off the console to allow max air flow to the ECM. I'm guessing you already saw the notes on hot stalling and the Transmission's TCC solenoid. If not unplug the electrical connector on the front of your transmission.

If you really think it is the ignition, use a GM/ACDelco PIM and OEM type coils.

Standard/BlueStreak PIM aren't too bad if you can't get a GM one. I've used those in the past. They have been ok.

Accel coils are crap. Even if MSD coils are actually better, you don't need them. DIS is already far higher power than HEI and plenty of others.

[This message has been edited by theogre (edited 07-28-2006).]

I'm going to have to get after the stalling issue. It doesn't seem to be the standard TCC problem as it doesn't stall on the deceleration. Generally it will attempt to stall when the engine is cool w/ the A/C running, then as it gets warm it doesn't stall, but once it's warmed up to operating temp it stalls with the A/C on when starting out from a stop. Also sometimes stalls when trying to start out on an incline--with the A/C off.

The last time I pulled the codes, it had set a code for the timing being off. But as it's DIS, adjusting the timing is out of my hands.

Unfortunately, my 4 cyl 88 is the only car I own with working A/C. And we've been a bit of an extended heat wave here, so working on anything outside has been just too uncomfortable. Supposed to cool down into the upper 80's this weekend, so I can get after checking the ignition out. I have a new crank sensor to install, it wouldn't surprise me if a couple of new coil packs would make a big difference. (Car has 110,000 mi. on it and the coil packs could be weakened by age.)

I'll check out the write up in the cave. Thanks

[This message has been edited by Brian Lamberts (edited 07-28-2006).]

On the stalling and other issues....

Check the heater fitting on the bottom of the manifold. I recently found mine leaking just a tiny amount. So small it was hard to know it was even leaking. Leakage from the fitting easly gets on the ignition. Coolant, even with just moisture from the air is conductive and will leach power from the coils even if it doesn't flat short them.

If you have even a small doubt about that fitting, replace it.

Some thoughts on your ideas about reducing the heat transfer from the engine block to the plate and thus the PIM.

If insulators/washers are added between the plate and the block, it will move the CPS away from the crank by the thickness of the insulators. However, if the same insulators are also added between the CPS and the plate, then it will move the CPS back toward the block by the same amount. Thus no net change in CPS to crank spacing. Now I just need to find appropriate insulating material.

If insulating washers are added between the block and the plate and between the plate and the bolt heads, then the plate is no longer grounded to the block by the bolts. If I understand the wiring correctly, this is not a problem because the ground for the DIS comes from one of the wiring connections to the PIM. Correct? Should the plate also be grounded for shielding purposes?

I wonder if most of the heat transfer is from direct contact with the engine block or from the radiant heat from the block. Would a thin aluminum shield between the block and the plate help much?

I will probably try the washers on the plate while I wait to get a new PIM. This is a good time to experiment since my current Auto-Tune brand PIM appears to die when it gets hot. After the car runs for about 20 minutes it dies. Then the tach reads zero when trying to start. Coils are cold, plate is hot, and block is hotter but not overheating (temp gage on the line between 100 and 220). Let it sit for a while to cool off and it will start and run fine, until it warms up again.