Cloud9...68

Soon after a track session last Friday, during which the car ran flawlessly, it developed a rough idle, and when I rev the engine, it sounds like it's misfiring pretty badly - as if it's running on three cylinders, up until about 3500 rpm, after which is smooths out. The problem started on the way home, and was worst during the stop-and-go part of the commute for the first ten minutes or so after leaving work (the track is 2.5 miles from my place of work, so I can pop over for a session during my lunch break). But then, when I got on the expressway, it abruptly smoothed out, and stayed smooth until I got back into traffic, when it started again.

I did a blink test, and got a code of 1-1-1-3-4, which, according to the documentation, is an intermittent hall sender issue. This isn't surprising, since the hall sender connectors disintegrated years ago, and I've had the whole area wrapped with electrical tape secured with zip ties for about the past five years. So, I'll definitely order a new hall sender. But what concerns me is that I thought a hall sender issue is usually manifested in a loss of power at high rpm, which is the exact opposite of what I'm experiencing, so I was wondering what else I should be checking while I wait for the new sender.

I don't think it's a balance shaft belt issue, because the belt is almost new, and a bad belt wouldn't cause a vibration/misfire to come and go. The engine is extremely smooth - it feels like it wants to rev to 8000 rpm, once I get past the misfires. I also doubt it's a vacuum leak, because it just doesn't feel like one. If feels like there's something electrical that's cutting in and out, and a vacuum leak wouldn't disappear for awhile, then come back. And I doubt it's bad gas, for the same reason. A bad ground also seems unlikely, because I recently removed the engine for a complete rebuild, and carefully inspected and cleaned all ground connections, and of course securely tightened them all when re- installing the engine.

I checked the distributor cap and rotor, and they visually look fine. I ran the engine in the dark last night to look for sparks around the plug wires, and saw no signs of stray sparks, either around the wires, or the coil. I'd love to put a Durametric on it, but I don't have one, and neither do I have a windows laptop, so getting a Durametric would be a significant investment.

Any other ideas as to things I should check? Oh, and one other question - I noticed that Paragon sells the connector that the Hall Sender plugs into, which as I understand it is the part the usually goes bad. Should I order just the connector, which costs $15, or should I go ahead and order a new sender assembly, which is about $116? I'm leaning toward replacing the whole unit, just because the car is so old, but I was wondering what experiences people have had. Thanks.

tamathumper

Fix the connector(s) at least, with the ones from Paragon or EagleDay, to keep that out of the equation, then look into your MAF, its connector, and "limp mode", which is engaged with a bad MAF around 3,000 RPMs. Google has a lot of info on the MAF issue(s).

968workaholic

+1 for the MAF sensor, if not that maybe TPS sensor

Cloud9...68

Tama,

You say limp mode is engaged with a bad MAF at about 3000 rpm? What I'm experiencing is the exact opposite - it feels like it's running on three cylinders up to about 3500 rpm, then it smooths out.

tamathumper

Sorry, I don't have my notes available, so from memory, when the DME senses the MAF is wonky, it defaults to limp mode which only allows for one or maybe two injector pulse widths. Your car is perhaps running fine with that pulse width at and above 3,500 RPMs, but this is a guess.

I'll try to find my notes from last year when I was troubleshooting my cold stutter vacuum/MAF/whatever issue that's now resolved.

Cloud9...68

Glad you were able to finally get your problem resolved - these can be a real pain. Your symptoms were similar to mine in some ways, but definitely not identical. Mine doesn't seem to be temperature-sensitive, for example. My idle is very rough, but I don't think it's the ISV, because I thoroughly cleaned it during the rebuild. And I don't think it's the TPS, because this wouldn't explain the rough idle. I'm off to the garage to poke around for loose wires and questionable connections around the various sensors...

maniaquede968

Disconect the male and female Hall sender completely from each other and your problem will probably go away. You have a short under the electrical tape.

Cloud9...68

I think I may have found the problem, and it actually has nothing to do with the hall sender. I'll try to confirm tonight, and report back. The reason I think the hall sender code may be a red herring is that when I tried jiggling the hall sender wires with the engine running, the smoothness of the idle wasn't impacted in the least.

Cloud9...68

Problem solved. I needed some body work recently, and the shop had the car for over two weeks, during which time there was a large rain storm, and I'm certain the car was outside. I put hood louvers on the car as part of the track car build (they looked so cool on Pablo Crespo's car that I couldn't resist), and rain must have dripped through the louvers and onto the valve cover, because when I inspected the spark plugs, I noticed that the spark plug holes all had water in them. I dried everything out, and went ahead and replaced the plugs, and it runs good as new now. I'm relieved that it was such a simple and inexpensive fix.

968workaholic

I love simple fixes

RajDatta

Nice troubleshooting.