Cybermind

Hi Guys,

Well, after years of reliable driving, it finally happened. I was accelerating on a highway on-ramp yesterday when the engine started losing power, and finally stalled. I had time to pull over on the side of the highway. I restarted it and it started up right away and ran fine. I immediately pulled the codes and I got the following:

58 - SDM U1016 H
B0 - RFA U1016 H

Those were the only codes it showed. The car then drove fine all the way home. However, as I pulled up to my drive way, it began idling rough like it wanted to stall again. It didn't though.

I need to point out that the engine began running weird a couple of weeks ago when I re-installed my Volant twin cone CAI. I did experience a reduction of rpms (almost-stall) for the first couple of days. But I chalked it up to the computer getting used to the increase of air in the intake. I did not get any codes at the time.

So, do you guys think that the above codes were thrown as a result of the stall or are they the cause of the stall?

I re-installed my OEM airbox yesterday and went for a quick drive. It drove fine with absolutely no issues but I'm still worried. It was frightening, to say the least, when I stalled yesterday. I almost got hit by a semi truck that was behind me as I pulled over.

Any help would be greatly appreciated.

PS: all car ground points are perfectly clean and tight. Car has barely seen rain and is always stored in a humidity-controlled and heated garage. So corrosion is not an issue.

Cybermind

Forgot to mention; my engine and tune is completely stock. Also, I know that the U10xx series codes should not cause a stall...........correct?
Could a contaminated MAF cause the stall that I experienced?

moespeeds

Make sure you don't have an intake leak behind the MAF. This will cause the car to stall when moving at low rpms, such as rolling up to stop lights and taking off ramps.

Listen for whistling at the intake while someone revs the engine, then take some brake cleaner and spray all around the intake connections while at idle. If RPMs increase, it's sucking in brake cleaner (and air).

Cybermind

Thanks for the advice! I will look for air leaks in the intake connections. I'll report back with the results.

Bill Curlee

You had a seat module comms error "U" series code so,, on the hunt to do something to help you, I recommend that you try this.

As remote as it may seem, I have seen Serial Data Buss issues cause my 02 ZO6 not run. I could crank the engine but it would not start and run until I fixed the drivers door connector issue.

Recommend that you unbolt your drivers seat and carefully examine the seat connector. Look at the wires and also the female pins in the connector. Make sure that they are NOT bent and spread apart or corroded and the wires are not damaged.

NEXT: Pop out the rubber accordion tubes between the doors and door frames. Pull the door wiring harnesses up and out of the hole in the A pillar. Disconnect the POWER plug and see if any of the female pins are bent and spread apart. There is a toung in the femal pin that makes positive contact with the male pin. If it is bent down, that needs to be fixed. Bend it back up so that it makes better contact with the male pin.

Poor connections in any of those plugs can and will cause hate and discontent on the serial data buss, The poor connection causes the door module/s and or seat module to turn ON & OFF rapidly and that causes the serial data buss to shut down and cause NO COMMS issues between modules.

Hey,, its FREE , Its QUICK and its EASY and it may solve the issue.

Hope this solves your issue.

Bill

Cybermind

Thanks Bill,

I will definitely add that to the things to check. I will keep everyone posted on the outcome.

Cybermind

So, after going back to the stock air box everything appears to be back to normal. I performed the following checks:
1) Checked for any air leaks. I did not find any. To be sure, I performed a vacuum test and I got a steady/ healthy 20 in.Hg. No problems there.
2) Checked all connections, and wiring looms at the various areas as recommended. Everything was clean and tight. No chaffed wires or loose/ corroded connections.
3) Just to be safe, I re-cleaned my MAF with CRC MAF cleaner.

I went for a very spirited drive yesterday trying to reproduce the problem I encountered on Wednesday and I could not. The idle is super smooth and there was absolutely no more engine hesitation. The car actually felt more peppy with the stock air box.

I'm gonna chalk this up to a bad aftermarket CAI install causing an air leak somewhere after the MAF or simply the oil from the air filters having somehow contaminated my MAF.

Thanks guys for your help!

Cybermind

It happened again!! I stalled on the highway two times yesterday. Again, the car started up easily as if nothing happened. No codes set. I am so disappointed and stumped. It appears to only happen at higher, constant speeds.

My wife doesn't even want to ride in it anymore. I don't blame her.

Any other recommendations or ideas?

Bill Curlee

For you to NOT see any DTCs when this is happening, the PCM thinks its getting a normal shutdown. If the engine was having a sensor problem you would normaly see a DTC/s

So, have you ever cleaned or replaced your ignition switch?? If it were me, that would be the very next place I would go. If you clean nd service it Its a free repir. Give it a try. If you dont feel you cn do the clening, just replace the switch:

-C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html

Hope it solves your issue.

Bill

Cybermind

You know, now that you mention it, it almost feels like I shut the car off by turning the key when these stalls happen. I will definitely do as you suggest. It doesn't seem too difficult.

Thanks for your help. Greatly appreciated!

Cybermind

Just to follow up, I have now ordered a new ignition switch and a new OEM MAF sensor assembly. I will let everyone know how it turns out.

PS: I don't normally like to throw parts at a problem but I got both items for a fairly low cost. If this doesn't fix it, at least I'll have replaced items that degrade with age and I'll keep the old ones as backup.

3boystoys

Well, I've had GM cars for many years and this is generally how the crank sensor goes out. No codes till it finally fails completely, just a lot of stalls and/or no starts till if finally starts trowing codes. Only good way to tell is to ride around with a data capture scanner to see what goes away when it dies.

Cybermind

Wow, never thought of the crank sensor. But, wouldn't it be difficult to start the car? I have absolutely no problems starting and it idles perfectly. I could drive around town all day with no problems. My stalls seem to happen only at highway speeds (over 65 m/hr). That's the weird thing.

Cybermind

I had a day off yesterday so I took the time to do some troubleshooting. I verified the charging system and all was perfect. I got some live data by hooking up an OBD2 scanner and going for a drive.

I hadn't noticed it at first but the IAT was reading a temperature of 32 degrees F (0 degrees C). It was a hot sunny day yesterday (85 F). Obviously, the intake temperature sensor is not working correctly. I am assuming that it would mess with the fuel/ air ratio and cause the car to run lean and eventually stall as the intake temperature increases. This would explain why it takes a while before the car actually stalls and it did stall yesterday as I pulled up to my driveway after a 20 minute drive. The IAT reading had not gone up more than 10 degrees F.

So, I am now confident that I am narrowing it down and getting close to resolving this issue. I just have to figure out if it's a problem with the actual MAF assembly or the wiring OR an improperly working OBD2 Live data scanner. Anyway, my new MAF is on its way so I will know soon enough.

In the meantime, I will check the wiring going to the MAF. I should be reading 5 volts at the plug pins for the IAT with the ignition switch at the "ON" position. I will check that tonight.

If it turns out to be the wiring to the MAF, it would make sense because this problem began when I was experimenting with going back and forth between the stock airbox and a Volant twin cone intake. I must've partially broken the wire, plug or MAF itself during this process.

I will let you know how it turns out.

3boystoys

I've seen it both ways. Generally starts fine cold but start acting up when it gets hot. Generally gets worse and then even starting cold gets to be an issue.

Cybermind

Well guys, just thought I would keep everyone up to date on what I came up with. My problem is now solved. You will not believe it but it was simple after all. I just could not see it. I had a vacuum leak at the intake caused by a loose pcv hose. This is the small rubber hose that connects the pcv to the side of the intake manifold, right after the throttle body. It was basically installed backwards and completely loose. It was just hanging off the manifold tube. I could not see the problem with it until I felt for tightness and it basically came off in my hand.

Here is the culprit. It also appeared to be slightly deteriorated so I replaced it with a piece of fuel line. Problem solved.

Thanks everyone for all your help! Sometimes the biggest problems are caused by the tiniest things.

3boystoys

Hard to believe a PCV hose will cause an engine to DIE, I can see it running rough with the vacuum leak but not die.

Cybermind

Well.....there is an easy way to find out. Disconnect your small PCV hose going to the side of the intake and go for a drive. Just make sure you choose a road with minimal traffic or an empty parking lot for safety sake.

Fact: A vacuum leak or ingestion of unmetered air is one of the top three causes of rough idling and/or engine stalls.

What pisses me off is that I didn't see it! It's been a learning experience for me. The next time, I will look for the simplest things first. We always tend to think that there is some serious electronic issue when we have engine problems. Most of the time, this is not the case. This has cost me a new ignition switch and MAF. Oh well, at least I now have an inventory of C5 parts that will eventually need to be replaced down the road. That's a good thing.

Bill Curlee

How your car handles un metered air,,,, all depends on the state of the tune. I left the power brake booster vacuum hose disconnected by accident once and the car started OK and only ran a little rough. The loss of power brakes and the weird sucking noise was all that made it apparent there was an issue.

Cybermind

My car is completely stock. Would this make it more or less susceptible to stalling with a vacuum leak? You guys are now making me doubt that my issue is really fixed. I have been driving around with no more problems so.............I don't know. I will report back if the stall happens again.