ReefShark

Does your model have dual distributors? My belt broke on mine and I limped home on 4 cylinders. Might check your distributor belt if you have duals.

WallyP

A mechanic's stethoscope is a very useful tool. Should be available at your local auto parts store, or Harbor Freight. You can use any long rod (wood dowel, screwdriver, etc.) in a pinch. Using any of these to listen to the injectors will quickly tell you whether or not they are clicking.

One note - Bill is correct on the wiring for the injectors for this car, but on the later cars, the injectors and the ignition systems match - same two cylinders on each bank.

Landseer

You can show all kinds of spark activity with timing light or individual sparkplug flasher.

And the car will still run terribly, on four cylinders (sorta).

Happened to us on 87 S4 on a BR Pkway outing. I checked for spark at coils and plugs along the side of the road. Kept lighting up the flasher. But, later found, issue ultimately was arcing coil and sparkplug wires. There was always enough "spark" to flash the detector pretty well, not enough to run the car though. Charles Payne went through a tank of gas just limping home 60 miles. Dangerous situation in retrospect, we should have had it towed. At home, at night, we finally saw the evidence of arcing.

So, you are thorough clearly and may have already ruled out this situation, if so, good.

Polish inside the two coils. Change the coil wires if not new. Change the sparkplug wires.

Also, if not done, pull the distrib caps and carefully clean inside.



Bill, is it that the positives to the injectors are segregated by bank, and the switched ground is a common circuit, so that they batch fire?

Shark Attack

I had this issue on an 86, all 4 injectors on the one side were clogged. What lead up to this? was the car sitting?

Flormat

I have been able to do some testing time permitting. With the car at idle I can feel the injectors click with a long screw driver touching them. There is absolutely no change when I pull the wires off the spark plugs while running. I did this one at a time and cylinders 5-8 gave no response. Pulling the wire off the plug on cylinders 2 & 3 killed the engine, it chugged heavily for a couple seconds and quit. Wire off plugs in cylinders 1 & 4 was not a very noticeable difference, I think it may have ran slightly rougher but not sure. With the fluctuating idle and popping intake it is difficult to tell if it was the cylinders or just fluctuating engine speed.
Yes, the car was sitting prior to this. You think maybe new injectors are in order? Cap and rotors are new.

SQLGuy

There still seems to be some missing information here. You're getting no power from the 5-8 bank, but you are getting spark, and the plugs look wet?

Is it possible to flood one bank? Have you tried a test light or Noid light on the injectors? It would be interesting to hear how such a light looks on the 1-4 bank versus on the 5-8 bank.

Bill Ball

Seeing no effect from pulling a plug wire does not mean there is lack of ignition if per chance that cylinder is not getting fuel.

If the injector solenoids are clicking, then I suppose the injectors could be plugged as Kyle found. With a "dead" cylinder, like your 5-8, if the spark plugs are not wet, then that cylinder is not getting fuel.

daveo90s4

I reckon: If you have spark to all the leads on one bank then that rules out coils (they fire two per bank). If the plugs are wet and you can hear the injectors pulsing this (probably) rules out fuel. If you have compression that rules out holes in every piston, burnt valves in every cylinder, etc. I think that then leaves two simple things: plugs are stuffed and / or plug wires are swapped around.

I hope it ends up being this simple.

Koenig-Specials 928

Does this model year (86.5) have the IMS where the LH sends the engine into four cylinder mode due to a difference in cylinder temperatures? If yes, should Flormat check the LED light on the relay near the LH/EZK? Or disregard comment if this model does not have the IMS

SQLGuy

No. That wasn't added until '89, IIRC.

Bill Ball

Correct, no IMS. I'm interested if the spark plugs on the "dead" cylinders are wet or dry.

If they are dry, in lieu of a noid light, I would pull the electrical plug to the injector on one of the dead holes just to verify they are actually getting a signal. The vibration he is picking up with his screwdriver should stop when that plug is pulled.

WallyP

The '86 should have two pressure dampeners and one pressure regulator, and the fuel pressure should be the same on both fuel rails.

If there is sufficient pressure to run four cylinders, the pressure should be the same for all eight. If the injectors on 5-8 are clicking, and there is fuel pressure, there should be fuel being injected.

If the timing light shows regular flashing on each of the eight cylinders, the ignition systems should be working.

If your reports are correct on all of the above, then you have lost air, compression, or timing on those four cylinders. If there has been no work on the engine since it ran perfectly, the plug wires should be correct. If the plug wires are off (loss of timing), you will lose power on those cylinders even with spark and fuel.

If the timing chain on that side has failed (loss of timing), you will have no power on those four cylinders. If the timing belt sprocket has failed but is still turning so that the belt is OK (unlikely), you will have no power.

A compression check will tell you if you have cam problems.

Having someone else check the plug wires might be useful.

dr bob

Since you are into this a bit already, you may want to pull the two top timing belt covers off and verify that you still have good cam timing at the gears. Stupid stuff happens sometimes, including the bely jumping if there's backfire from a cylinder. With the discussiion including intake popping, I'd verify the cam timing early. If nothing else, it will rule out one major possibility. As Wally advises above, a compression check will help identify problems like this. Odd numbers on just one side are a symptom of a jumped cam drive.

Bill Ball

He claims compression of 165 in the original post with no details (they can't all be 165). I presume he checked the "dead" bank.

GregBBRD

Bill:

Still a very logical thing to think about.