I'm helping a friend of my son whose '95 Z is stranded on a highway and we're trying to figure out what's going on. This car was reputed to be having loss of power problems that we've (until now) been unable to reproduce.

Local driving, highway cruising, short WOT burst (top of 2nd in a MN6), no problems, sounds, or smells.

Today while cruising had major loss of power, to the point of being unable to continue. Engine idles fine, will run up to 2500 rpm in neutral before "bogging" starts to set in.

Scanmaster shows a code 51 (EEPROM error) and a code 16. I'm thinking both of these are historical, but we can't find (I'm at work and helping via cell phone) the PCM BAT fuse. Is the '95 different from my '94 in that regard?

One time he was able to get going up into 2nd gear, but then started hearing a "squeal" and started losing power.

My guess is the cat has broken and is plugging the exhaust; does that sound reasonable or does anyone have a better idea?

TIA, and have a good one,
Mike

 

My first thought as I was reading this was that the cat was clogged..we seem to have reach the same guess.

Vacuum reading can help determine if the exhaust is closed, you should get significantly lower readings. If you do get really low readings, have the kid bang on the cat. Maybe that'll dislodge something and allow him to limp off the highway....

Good luck!

 

He got it safely parked, but is still a long way (40+ miles) from home. We'll try the hammer approach when I get off work.

Any idea on the PCM BAT fuse issue?

 

You could always try just loosening the ypipe bolts on both sides enough to let the exhaust flow out. I am not sure that it would really be a cat issue but that would surely give enough exhaust relief to let it run and get it home.

 

On a 1995 the PCM BAT fuse is under the hood and is labeled PCM (fuse #8).

 

Thx, Shoebox, we'll get under there as soon as I can meet up with the guy. The DTC 51 is a new code; it wasn't there last night.

I know the DTC is listed as a EEPROM error, but does anyone have any experience with this code?

Thanks again, and have a good one,
Mike

 

No (yet atleast), but isnt EEPROM the type of memory the ECU uses? Maybe try swapping computers?

 

Why are you going to pull the pcm batt fuse? I am just curious ---

 

Clears the codes.

 

Fred,

Got any anecdotes about DTC 51s that could shed some light? I've tried searching (both in and out of CZ28) without much success other than the EEPROM fault description.

I'm not going to be able to get to the car until tomorrow afternoon. Probably going to put it on a 2 wheel dolly to get it to my house.

Thanks for any help, and have a good one,
Mike

 

Nope.... never came across a DTC 51.

When you cleared DTC 16, did it come right back?

 

A 51 can be caused by poor connections so remove, clean and reinstall all power and ground connections.

A faulty alternator (leaking AC) onto the DC power line can cause all sorts of weird PCM problems. Very easy to test for using a DVM.

If either of those 2 don't cure the problem it's time to find someone like an Auto-value store that can reprogram the PCM. If either they can't or they do but the error comes up again. Time for another PCM.

 

Never got the chance to clear it. It was the only code showing, and since the engine was running fine (at that time) just worked on other higher priority issues on the car. Should get to it this evening after work.

Speedy, the interesting thing is that DTC 51 just showed up without doing any work in the engine compartment. One day it was fine, couldn't make anything go wrong. Next day, "dead skunk in the middle of the road".

Anyway, I'll let y'all know what we find out.

Thanks for all the help, and have a good one,
Mike

 

UPDATE:

While I was at work the guys got the car back home from 40 miles away. Max speed was around 30, car was very much down on power, Scanmaster was showing continual spark knock, EGR command was 0 the entire time, the engine was running warmer than usual, and there was a whistling sound from the engine bay.

They had cleared the codes prior to starting the trip home (thanks again, SB), and the only one that came back was a new one, code 43 (knock sensor).

So, we pulled the Y pipe and, um, "cleared" the catalytic matrix of any obstruction. No smog in our area, so we're OK there. Unfortunately, examination of the matrix showed nothing significantly wrong. We bolted everything back together, cleared the codes again, and started her up.

In short, the test drive was normal. Got the engine up to operating temperature, did another WOT run up to the top of 2nd, zero spark knock. LT fuel trims were fairly close to 128, but time will tell there. No codes, either.

I'm pretty sure the problem was excessive back pressure. The whistling I'm thinking was leakage past the EGR valve, which was dumping into the intake manifold and causing really poor performance. Hot gases could also have caused the engine to run warmer than normal.

However, I'm NOT convinced we found the real cause of the backpressure. The good thing now is that if it happens again, we'll know it's downstream of the cat and he can just loosen that connection to the catback and limp home.

I'll let you know if anything else comes up.

Thanks again for the help, and have a good one,
Mike

 

Just thought I'd close the loop with y'all. After gutting the cat I had the guy drive the car for a couple of days locally. He made one semi-cross country (about 50 miles), no problems. He then headed out to Colorado, about 700 miles to home.

Made it, no problem. Even though the cat didn't look bad, something was causing a blockage. My guess right now is that the forward brick had come loose and slid into the rear brick, causing the blockage.

In any case, I think this problem is solved.

Thanks for the thoughts and ideas, and have a good one,
Mike