pulled the coils completely out of the car. Checked for resistance again.

Terminals 1 and 15 are still showing 1.4-1.5 ohms on both coils.

Terminals 1 and 4 are now showing 6.1 k-ohms on both coils.

The primary resistance (1/15) is double what the WSM is calling for. Very odd that both would be showing the same.

 

Just checked a good coil from the '84 Euro. It also has a resistance of 1.5 ohms between terminal 1 and 15. I think this verifies the coils are good.

 

Checked resistance on the coil wires that hook to the distributor. Both wires had the same resistance.

 

There has not been any work done on the car in several months. Last thing was installed the Porken s300 chips. It does have the correct regulator and spark plugs. It has been running fine for several months.

My nephew was driving it at the time it started running rough. He said the car was at about 1/8 tank of gas and it just started to act up as he was pulling into the gas station. He filled the car up with gas and the car has been running rough ever since. I was thinking bad gas at first, but he said it started before filling up. The gas tank was removed a couple years ago and was thoroughly cleaned. A new filter and sock was installed after that.

 

If you pull the coils one at a time, this will help you track down which cyls are not firing. This will do two things. One, it will ensure you don't have to needlessly open you motor again since you will have verified an electrical issue. Two, it will tell you how to start trouble shooting. IF you know which cyls are not firing you can look at those cyl only. Verify spark. Verify fuel. Seems you likely have an issue caused on the fuel side when chips were changed but it will be easy to verify spark on those cyls one you find out which ones are not firing. (or you can do it the hard way and verify spark on each one) It is likely that this is not an internal problem. Check the easy stuff first.

 

I have already checked for spark on every plug. All plugs were firing. The only question now is whether or not it is weak spark or not.

I put two new ground cables between the coil bracket and the engine on the drivers side and the coil bracket and the engine lifting eye on the passenger side. It did not make any difference when I started the car again.

I will go ahead and unplug one amplifer at a time to see if I can narrow it down to a specific bank.

 

Just pulled one plug off the amplifers at a time while idling. Each time I pulled a plug the car immediately died. This tells me they are both working.

 

Is there anyway to check the O2 sensor to verify it is working properly?

I was thinking of possibly draining all the gas and starting over, just in case it was bad gas he had gotten and just thought it was running rough when he pulled in to get gas. What do you think?

I am just about out of ideas except for swapping the Porken chips, regulator and plugs back to stock.

Looking for more ideas...

 

Also, the Porken chips have been installed and running daily for over 3 months without any issues, just in case anyone assume I just swapped them in.

 

What about a clogged cat? It still has the stock converters on it. Anyone know how to check this?

 

You should be able to use a backpressure gauge, although a standard pressure gauge might work, albeit much less accurate. You should be able to remove the O2 sensor and use that as your test port for backpressure. Backpressure spec is generally no more than 1PSI of backpressure.

Alternatively, you can do (sort of) the reverse and check manifold vacuum. It will be lower when reving the motor and won't be as "bouncy" on the gauge if there is an obvious restriction such as a plugged cat. However, this method is less isolating and less accurate. The accuracy of detecting a clogged cat through manifold vacuum readings at idle and high idle is reduced since it relies on you having a perfectly functioning intake/vacuum/ventilation system...

 

found some info on Rennlist from John Speake about the o2 sensor. I unlugged the sensor and then unhooked the battery ground to reset the computers. Hooked it all back up and started teh car. John's old posts indicates this puts the computer in a "safe mode" and should run better if the o2 sensor was bad. No change in the running of my car. On to the next idea...

 

I think resetting the computers only happens on the S4 and later. I don't think our early LH get reset.

The easiest thing to do for testing the O2 is just unplug it at the CE panel and see if it makes a difference in how the car runs.

Do a search on here about how to measure voltage on the O2 to see if it is in spec. There should be a few threads, with some discussion of the limitations of a regular voltmeter in measuring it.

Matt

 

What Matt said. Unplug the O2 sensor to test.


EZ-F and LH2.2 don't get constant battery voltage, and have no adaptive O2 sensor programming or memory to store it. Turn off the key, wait four seconds for the MAF burn-off cycle, and there will be no power to the ECUs.


You may have done this already but, unplug and reseat the EZ and LH connectors. If they are not firmly in place, there can be strange running.

As a last resort, try removing the LH EPROM from the socket which S300s chips come installed in, and install the EPROM directly into the board socket. Be very careful of the fragile EPROM pins.

 

Did you check the distributor caps, my 86.5 had one cap that looked like new but had a failed pin in the centre, resulting in some but weak spark.