Jeep Strokers

I built a new stroker for my '90 Renix Cherokee. I used a '94 donor block and head and ordered Clegg's Stage 3 kit and their Stage 1 cam. I had to bore the block .040 over due to cylinder damage. I also used Ford blue fuel injectors.

After priming the oil pump and installing the distributor, it fired right up. After breaking in the cam, checking for any leaks and verifying good oil pressure, I took it out for a test drive.

It seems to run strong. Although I can't compare it to my old engine since it was only running on 5 cylinders. I did notice a couple of issues...

First, it starts out running good, but when it idles for a few seconds, the RPMs will drop and it will usually die. Suggestions?

Also, after the test drive, I noticed it was running quite a bit hotter than normal. Could be a bubble in my cooling system, but I thought I had purged them.

If this was a "regular" motor (pre-computer controlled), I would get out my timing light and check my timing as this could be the cause of both issues. But from what I read, the computer controls the timing and the distributor controls the injector timing.

Any suggestions or advice would be greatly appreciated!!!

The ECU will need to adapt to the new engine and the signals being sent by the sensors so give it more time.
A newly built engine will usually run hotter initially due to internal friction until it's broken in, so don't be too concerned unless it's running consistently at over 220*F. You may have had a pocket of air being trapped in the cooling system but now that you've run the engine once, the air will have been purged and the space taken up by coolant from the overflow reservoir during the cooldown, so you'll need to check the coolant level in the overflow reservoir and top it up.

Cheromaniac wrote:The ECU will need to adapt to the new engine and the signals being sent by the sensors so give it more time.
A newly built engine will usually run hotter initially due to internal friction until it's broken in, so don't be too concerned unless it's running consistently at over 220*F. You may have had a pocket of air being trapped in the cooling system but now that you've run the engine once, the air will have been purged and the space taken up by coolant from the overflow reservoir during the cooldown, so you'll need to check the coolant level in the overflow reservoir and top it up.

Thanks, Cheromaniac. Is the 1990 ECU a "learning" computer? I thought I read somewhere that it is all pre-programmed and cannot "learn" or be reset like the newer ECUs.

No, it's not.

Go to my Tips and Post 13 about indexing the distributor properly.

cruiser54 wrote:No, it's not.
Go to my Tips and Post 13 about indexing the distributor properly.

Already did - that's how I installed it. Actually, I printed out the entire thread with all the photos. There's a ton of great information there. Thanks a lot for all the work you put into it!

X 2 on that, distributor is key, but it has to run 50 cycles or so I think before it settles on a known set of parameters within its open ended programming, which means an almost infinite number of variations of our engine will run on the renix ecu

If its dying at idle you may need to drill a small hole in the throttle plate. But I would rule other possibilities first. Check fuel pressure, but I doubt that is the issue. Clean the IAC as well.

SilverXJ wrote:If its dying at idle you may need to drill a small hole in the throttle plate. But I would rule other possibilities first. Check fuel pressure, but I doubt that is the issue. Clean the IAC as well.

You shouldn't need to drill a hole in the throttle plate to correct a low idle/stalling issue but I agree that cleaning the IAC and the housing it sits in could solve it.

There is an idle bleed screw on the driver's side of the throttle body under a small welsh plug.

But I agree, shouldn't need to use it.

I cleaned the TB when I had the motor apart, but will double-check and re-clean IAC when I get back. Would rotating the distributor a few degrees left or right make any difference - perhaps slightly changing the FI timing?

Another issue I'm going to have to deal with is that my brakes aren't working - very hard pedal and nearly ineffective. Kinda makes me nervous taking it for a test drive. I've been having rare issues with the Bendix pump not coming on consistently. Now it's not coming on at all so I guess I will be calling the dealers hoping for that "lifetime warranty" I've been reading about. It's always something...

cruiser54 wrote:But I agree, shouldn't need to use it.

Yes, the hole or the bleed screw shouldn't be needed but it might be.

JeepFan wrote:I cleaned the TB when I had the motor apart, but will double-check and re-clean IAC when I get back. Would rotating the distributor a few degrees left or right make any difference - perhaps slightly changing the FI timing?

It might, but I doubt it would fix the stall issue. Also, make sure the throttle body bore is clean.

Another issue I'm going to have to deal with is that my brakes aren't working - very hard pedal and nearly ineffective. Kinda makes me nervous taking it for a test drive. I've been having rare issues with the Bendix pump not coming on consistently. Now it's not coming on at all so I guess I will be calling the dealers hoping for that "lifetime warranty" I've been reading about. It's always something...

I wonder if they can still get the parts for that. Personally I would ditch the Bendix system for a 95+ booster and MC.

Done the 95 to 96 booster/master cylinder upgrade. What a HUGE difference.

The 99-2004 WJ swap is supposed to be even better and is more compact. Doing that next on my wife's XJ which has 4 wheel discs.

cruiser54 wrote:Done the 95 to 96 booster/master cylinder upgrade. What a HUGE difference.
The 99-2004 WJ swap is supposed to be even better and is more compact. Doing that next on my wife's XJ which has 4 wheel discs.

I would love to get rid of that POS Bendix system, but I've got so many different projects going on right now, I'm not sure I could find the time for a full brake system swap. I hear it's 5 - 6 hours minimum. Also, where I live, junk yards for parts are hard to come by...

cruiser54 wrote:The 99-2004 WJ swap is supposed to be even better and is more compact.

Its not. Tried it on my 2000 and no difference in stopping power.

You already had a dual diaphragm booster. I have a single diaphragm booster.