I have a 86 US model that has run very strong for years but after sitting for the better part of a year it idles very poorly if at all. I get black smoke out of the tailpipe and it gets a little better if I stay on the throttle. I have done all of the recomended checks. I did the complete valley service, I had the MAF rebuilt, I installed a fuel pressure gauge and I get about 30psi at idle. I have checked for vacuum leaks and found none to account for the poor performance.

I am thinking that one or both of my control units may be deffective. I did install an authority chip set just before parking the for that year and maybe that is the problem. I don't want to cause an alarm but I don't know what else to check. Before I spend the money on rebuilding I was hoping that maybe someone in Washington DC area knew of a parts car or a shop that I could do a hot swapp to prove if mine are any good. Any help would be appreciated.

 

Coolant sensor (Temp II)?

 

I had the same symptoms on my 88 and a new narrow band O2 sensor fixed it right up. One symptom I had that you could check for is if I disconnected, then re-connected, the battery the problem would go away for a short time. Once I put the new O2 sensor in it was fine!

 

I cleaned the terminals on the tempII sensor last night with no improvement. As far as the O2 sensor, is there anyway to check to see if it is working properly without replacing it? One thing that I forgot to mention is that while the car sat for that year the battery would go dead and I would charge it for long periods of time without disconnecting it from the car. I read that could do serious harm to the control units. Any thought?

 

Yea I've heard that the charging can hurt the cars computer.
As for testing the O2 sensor, I don't know what values you might read on a meter nor how to simulate the conditions it's supposed to read to be able to test it...sorry.

One thing though, I was told the reason mine would work temporarily after each time I disconnected the battery was because the computer would start up and use some default setting before it would let the faulty sensor start to cause it problems so try the old disconnect the negative battery strap for a minute, re-connect it, then go for a ride to see if it starts to run normal. If it does you have at least re-created the conditions I had that a new sensor fixed the running rich situation for me....
I think in my case, after each battery disconnect, the computer saw no O2 sensor signal at start up so it used the default mix, then the sensor would somehow send some bad signal, maybe after warming up, and the computer tried to use that data to adjust the mix and it ended up being way too rich...long trail of black smoke rich....spotty soot on the driveway rich! With the new sensor and monitoring the air fuel mix on a good gauge it runs at a very consistent 14.x at cruise.

 

"Search" is your friend. Clean terminals is good, but you need to know what the temp II is sending and you need to know if it is getting to the terminals on the two computers. A simple multimeter can do that, but for the O2 you need a multimeter that can compute average. The O2 should be continually ranging upwards as the exh temp increases. Sorry I can't remember the numbers. It's on here somewhere.

 

Electronik Repair's website has a procedure for testing Temp II.

www.electronikrepair.com/wst_page9.html

 

Simple stuff--

Soot from the tailpie is a sign of unburned fuel. Hmmm. Pull some plugs and see what they look like. Wet from fuel? You may have a spark problem. Black soot means a rich problem.

Engines miss and spew soot when they have vacuum leaks, have ignition wires crossed, have injection harness leads inadvertently grounded. Any of these would come under 'things I might have screwed up while the intake was off'. Start with that simple stuff, and double-check your work with hoses and wires.

I usually fine that cars that ran OK before I worked on them, and develop problems after I work on them... It's usually my working on them that caused the new problems. So I review what I did and usually find what I did wrong. And hope there was no consequential damage done!

 

Let me start by saying thanks to all of you for your helpful responses. I am going back into the operating room this evening and I will give you guys and update as to the results. I will be checking for any new responses however so keep them coming.

When I purchased the car it would barely move under it's own power. But with all of the information I gathered from Rennlist, I was able to breath life back into the old girl. Lets see if it can happen again. Stay tuned!

 

Well, the shark has been given life again. The problem turned out to be the LH control unit. After checking all of the usual things like MAF (rebuilt), TempII (within specs), ISV (replaced), Fuel Damper (good vacuum and no leaks), Installed FP gauge, O2 Sensor (replaced) and going over the entire engine with the vacuum pump only to find nothing. The thing that gave it away was that I could never get the LH unit to reset by disconnecting the battery.

My advice to anyone willing to listen would be to find someone in your area and swap things like MAF and LH units and pay attention to things like no response from known test proceedures because believe it or not these cars do actually have some logic built into them. Good luck!!

 

Remove your MAF. Clean the terminals with a product called "Deoxit", and then make sure that your MAF connector is sound. Make sure the terminals on the MAF are clean [no green crud], and that the rubber above the connector is in good shape. If the rubber above this connector is bad, then wrap the thing in about a meter of electrical tape after you clean the contacts! This connector's corroded contacts can cause your car to run rich [been there], and if the rubber boots on top of said connector are not perfect, then make sure they are water-tight via black electrical tape and a whole buch of rubber cement. Trust me, this is a HUGE issue on these cars!

N!

 

Congrats on getting it going, weird that these LH brains can "sort" of work.