Hi guys,

My 89 GT is still running on 4 cyl. with the green ezk relay light on. Over the last week I have switched dist. caps, coil wires, coils, and ignition final stages from side to side. Also replaced the drivers side exhaust temp sensor. No luck on isolating the cause of the fault yet.
The car runs fine for about 20 seconds, then the ezk relay green light comes on and goes to 4 cyl. mode. I guess next step is to check and replace plug wires-they are not originals, but aftermarket brand (magnacore? installed by PO's). Any other ideas? This is getting frustrating! Luckily this is a "weekend toy" and not daily driver.

Thanks,

Jim R.

 

One very common cause is a failure in a fuel injector. What the car is responding to is a difference in block temperature from side to side. The sensors are at the second cyllinder from the rear on both sides. You may have an injector that's bad or a bad electrical connection to an injector. The circuits control the two middle injectors on one side and the two outer ones on the opposite side.
The way I found my problem was to detach an injector wire and start the car. If it went from 7 cyllinders to barely running on three cyllinders the injector OPPOSITE that one was not the problem. The goal is to unhook your INJECTORS one by one until the car runs on SIX cyllinders. The injector OPPOSITE the one you just unhooked will be the problem and neither circuit will be turned off because the temps will be the same on both sides.
CAUTION: DO NOT PULL THE SPARK PLUG WIRES TO DIAGNOSE THE PROBLEM!! YOU DON'T WANT FUEL POURING INTO A NON FIRING CYLLINDER!!
HTH.

 

Well. Crap.

Quote:

I guess next step is to check and replace plug wires-they are not originals, but aftermarket brand (magnacore? installed by PO's). Any other ideas?

Since all the components seem to resist pointing you at the problem I think you are on the right track with 'wires.' No necessarily just the plug wires though. I'd start at the plug wires and use a timing light - or something - to see if any of them 'go dark' coincident with the start of limp home. Based upon that point the finger at the plug wires or jump across the motor to the harness connecting the EGT sensors. You have - I assume - made sure those two connections behind the block are tight. Either spark is truly going away, or the signal from the EGT is getting messed with. Maybe pull the plugs and see what they story they tell too.

Good luck. This is starting to sound similar to my Great Hall Sensor Hunt - at least in terms of hair-pulling level.

 

Thanks Ernest. I'll try that out-nice trick! I had the injectors tested,cleaned and balanced a month ago, and they had been working well up until now. Hopefully this will be an easy fix-if I wanted a 4 cyl I would have bought a 944.

Jim R.

 

I'll bet you've got a loose connection on one of your injectors. (Don't ask me how I know).

 

Dave,
I rechecked the EGT sensor connection tonight behind the head after switching coils-connected and tight. Definitely ready to start pulling out hair at this point. I plan to pull the plugs and check wires as well as checking the injectors next.

Jim R.

 

Hmmm... Occam's Razor.

... Starting to lean Ernest's way...

 

Jim,
It is possible to bypass the protection relay, in order that you can run the engine to find the fault............

Regards

 

What happens if the protection relay itself is faulty? Does it sit there in silence .... or can it trigger a circuit (II, green in your case) shutdown?
Could be worthwhile to look at/clean it's connector.

 

This is of no help to you, but I had the relay come on tonight and the car go into limp mode. This was on a lazy drive home after a day at an open road race hitting speeds of 155 or so. I pulled over, turned off the ignition, restarted and drove another 200 miles home with no further incidents. Weird. Now, I did a thorough check of the timing belt last week, which involves removing the distributor caps. I will check plug wire seating first.

 

John,
How would I bypass the relay? Is it possible The ezk relay or the computers (lh or ezk) could be causing this? I also replaced the eprom in the ezk with factory chip-took out an autothority set. Any thoughts are greatly appreciated.

Thanks,
Jim R.

 

And you took out the non-factory chip in the LH too?

 

Dave,
The chip in the LH was the factory chip. One of the PO's had only the ezk chip in the car. I don't know why, DR has the chip now and is checking the serial number with autothority. That chip was probably causing the ping which led to intake R&R. It is possible it was a poor install, a replaced LH, or just ???

Jim R.

 

Hi Jim,
I doubt the Autothority chip had anything to do with the protection relay problem.

To bypass the Ignition protection relay, Fit a link from terminal 87 (Vbat from the LH relay) to both terminals A1 and A2.which are the two banks of injectors positive feed.

Then also link AL to ign switched Vbat to force it into cat mode.

Regards,

John

 

Ah! So that was you!