Yes the plug wires are correct on the cap. I dont know whether the cap and rotor are AC Delco or not and the plugs are Autolite 605. I removed all the plugs and inspected them. All appear to be of a normal greyish/brown colour, however, I did find that plug 3 wasn`t quite tight and plug 1 had a gap of 0.090. I re-checked all gaps and put everything back together. Now the misfire occurs at about 1900 and isnt bad. However tho I will have to wait till the engine is stone cold, as everytime I do something the misfire mysteriously seems to get better, then the next day the problem rears its ugly head once again. As for a scan tool that will read camshaft data, that is unfortunately on the `I Wish` list. I will post what happens tomorrow :-). I did forget to mention that when this misfire occurs, the rev counter bounces around a bit. Whether that is if any significance I dont know.

 

If the Autolite plugs are "XP605", they might be OK. AC Delco 41-993 is what came in it from the factory with a gap of .060" and it will run the best using those. To determine if a plug is causing the problem, it would need to be put on an oscilloscope to find it.

The business about the misfire changing makes me think there's a problem in the cap with crossfire. Could be a bad cap, (if it's from AZ, make a contribution to your local landfill). Could also be that camshaft retard is out of spec, or both.

Scan tools that will access camshaft retard are not cheap. Another option is: there are some software programs for lap tops that will access it, Autoenginuity is one of them. My Nephew owns a shop and uses that program, says it works well.

"...the rev counter bounces around a bit." Are you referring to the tachometer in the dash? If so, if the misfire is bad enough, you easily could notice it on the tach.

 

Having thought about it, the cap and rotor are probably BWD. I now have what could possibly seem to some as a very naive or stupid question. If the distributor is replaced, does the computer have to be `told` that it has been replaced?

I ask this because it suddenly occurred to me that I had to replace the distributor, as the one of the cap screw holes broke out in the composite base of the old one. I still have the old distributor lying around in the garage

As I said please forgive me if it a dumb question to ask.

 

Might want to install an AC Delco cap & rotor You'd be surprised the difference it makes both in performance and longevity.

As for your question: It's a question that you want the answer to, and that's not dumb, or stupid When/if the distributor is moved, removed, replaced, etc, there are two things that need to be done. First one is easy: if the check engine light is off after you install the distributor, it means that it is meshed correctly with the camshaft. If the light is on, and P1345 is in memory, the distributor is not meshed correctly with the camshaft. The second thing is that the camshaft position sensor, (inside the distributor) needs to be adjusted. It requires a scan tool capable of accessing "Camshaft retard" data stream from the sensor. The El cheapo $500 scan tools that the auto parts stores use will not access the data. The adjustment is done by slightly rotating the distributor while watching the data on the scan tool. Rotating the distributor on this engine has absolutely no effect on ignition timing. If the adjustment is out of spec, crossfire will occur inside the distributor cap, and engine misfire is guaranteed. It may or may not set a misfire DTC in memory, or turn the check engine light on. It can be off as much as ~25 degrees, (which is serious) and NOT turn the light on. Just installing the distributor correctly is not enough, camshaft retard must be checked/adjusted.

 

Let me say I`m indebted to you Captain for your help .

However I am confused when you say the distributor would need to be turned. Unless I`m missing something totally, my distrubutor is in a fixed position and can`t be turned at all. Also I will try the AC Delco parts

Again I am very grateful for your help

 

The outside diameter of the distributor base, where it fits into the intake manifold, is slightly smaller than the inside diameter of the intake manifold hole. The "slop" allows the distributor to be turned slightly, more or less on an arc. This is the adjustment for camshaft retard, (camshaft position sensor alignment). It only provides ~15 degrees of total adjustment. If the adjustment is not enough to bring it into spec, the OE hold down bracket needs to be removed from the distributor and modified, or, replace it with a SBC, (small block chevy) hold down bracket, Mr. Gasket #1009. This will make the distributor fully adjustable.

 

Finally solved the misfire problem with the simplest solution you could think of. I repaired the ORIGINAL distributor and put it back in. Problem solved. MAP sensor reconnected and the car now runs perfectly well with no misfire. All I can think of is the distributor I put in was worn completely differently or something was amiss with it.

I want to thank you Captain Hook for your help and insight into this problem.

 

Glad to help. You need to have camshaft retard checked, and adjusted if necessary. It requires a high end scan tool, and a tech that knows how to adjust camshaft retard. Replacing the distributor is only half of the job, and the chances are that cam retard is not within spec.

 

replaced cap and rotor. noticed when i canged the rotor it seemed little loose. re placed with ac delco. thightened rotor down but still seams little loose. has some play. but no up and down play. noticed under the cap it wasnt firing directly on the prongs. sel light flashes. replaced the crank snesor mechanic said he did the crank relearn. dtc p0335 was in stored codes. please help

 

Axial, (up and down) distributor shaft play of ~1/8" is OK. There should not be any radial, (side to side) play. Rotational movement of ~6 to 10 degrees is normal.


Rotor segment not pointing to the cap terminals is OK, provided there is no DTC P1345 in memory.


SES light flashing means there is an engine miss occurring that can damage the catalytic converter. P0304 is cylinder 4 and P0300 means there is more than one cylinder misfiring.


P0335 is definitely a crankshaft position sensor circuit DTC, but not necessarily the sensor itself. If the relearn was not done, misfire cylinder identification will not be accurate. Crankshaft relearn data and camshaft retard both must be correct for accurate detection and identification.