'95 SES / "Limp Home" problem

Greetings fellow Aurora Junkies!

My ’95 Aurora has been throwing the SES light going into “Limp Home” mode quite often lately. There are times when the RPMs drop so low that the engine stalls. :uhoh:

The problem occurs:
1. Almost anytime I put the car in reverse…especially when cold…
2. When I’m driving at 40mph or faster and take my foot off the gas to “coast”…
3. Sometimes when I hit a bump…

Having the air on seems to increase the chance of this happening. It also seems to happen more when the car is cold, but has happened several times on the highway long after the car has reached its normal operating temperature. I find that if I cycle the ignition (not letting the engine die completely) or shut down completely, the SES clears and the car will run fine. There aren’t any other problems with the way the cars runs or handles. The car has 105, 726 miles on it. I’ve also modified my air intake box by removing the baffles and inserting a PVC cap in the “hole.”

Here are the troubleshooting steps to this point:
1. Checked the fuel pressure at the rail. I saw 50psi (normal range I hear is 48 – 55psi). I purchased a new fuel filter but haven’t installed it yet as I don’t have the “disconnect” tools for the one end.
2. I purchased and “installed” a small can of A/C compressor conditioner thinking it might be old and need a “boost.” It didn’t have any effect on the problem.
3. I pulled and cleaned each spark plug. Each looked fine with no indication of a rich or lean condition. The plugs and wires were replaced with Delco OE about 35k miles ago.
4. I pulled the FPR and checked for “sand” as mentioned in other threads. Nothing found. When I re-installed the FPR, I did slightly tear the small O-ring so I need to purchase / install a new seal kit ASAP.

I’ve spent a bit of time browsing the forum and haven’t seen anyone else mention this type of problem. So, I’m interested in any thoughts or comments on what might be causing this problem. I don’t have a scan tool and I realize it’s an important part of deciphering what’s wrong. I’m hopeful someone might have a suggestion or two that doesn’t necessarily involve the use of a scanner. Also, if there is information I’ve left out, please ask. I’ll do my best to provide the necessary “parts” of this mystery.

So…I leave myself in your capable hands. Thank you for your time reading this novel as well as any input anyone might have.

Dave
Austin, TX

try your parts stores for free use of the scan tool.. I read somewhere that autozone did this..

Unfortunately it's a '95...OBD II connector and OBD I computer. Autozone only scans ODB II computers. I was bummed!

Unfortunately it's a '95...OBD II connector and OBD I computer. Autozone only scans ODB II computers. I was bummed!


i read something about this a long time ago.. search the threads some more...

Still haven't found any information in the threads....ANYBODY?!?

Well I had a strange problem - not sure if our symptoms are precisly the same. Mine is a '95 as well. My engine would simply cease operation without warning. Sometimes it happened when moving it from park to reverse, sometimes (most often) when moving the steering wheel from the tilt-UP position to the tilt-Down position.

I did not get any warnings...no MIL illumination, nothing. When traveling at highway speeds I would cycle the ignition switch and the engine would refire. Sometimes I had to put the steering wheel in the tilt-UP position.

In any case, the long/short of this is that I finally traced the problem through the ignition relays, back to the remote keyless entry module in the trunk (it has some fancy name) and then back all the way to the ignition switch. As it turned out....this was the problem.

Now, my particular symptoms were quite binary (i.e. the engine was either ON or OFF). In your case you get the MIL illuminated and a what seems to be a loss of power. Perhaps - AND THIS IS ONLY A GUESS - there is not a complete break in the ignition circuit on your vehicle but a loss of full voltage across your ignition switch ON terminals (or something to the effect). The peculiar voltage may be what causes a CODE to registered and the MIL to be illuminated. Naturally, temperature and humidity could have an affect on the switch's contact causing you to relate the symptoms to temperature as well.

In any case, this may NOT be the answer. It may be something to consider in your diagnosis. Check the appropriate voltages associated with the ON position of your ignition switch (this is what I did) and perhaps you will discover a low voltage situation or other weak electrical connection associated with the ON position.

Just my thoughts.

Good Luck.

Here's my report back from the "front." Took it to a local servicer...they had no idea other than "there's a blockage in the exhaust system." Seems the tech dropped the exhaust system at the manifold and it had oodles of power...but not much with the system "attached." Went to Meineke for a pressue test. They said the O2 sensor was too far up on the manifold for a good test. Back to the servicer. They sent me to the dealer.

At the end of a long day...the dealer found 2 voltage supply lines to the injectors that were bad / going bad. One was held together by insulation and the other was charred pretty bad. In the process of getting the wiring harness out, he broke the TPS connector. I bought the part, he installed it for free.

So...two questions remain:

1. After I shut off the car, the TPS "clicks" for about 20 seconds. I've tried the TPS learn sequence followed by the idle learn and it's still doing it. What's next?

2. I'll search the threads but I'm curious if anyone else has replaced the resonator with a straight pipe and saw a bump in HP?

Thanks,
Dave