Attempting to destroy my idle lumpiness

[Trstno1]

Hey guys -

I have been asking questions in other threads attempting to get my engine idle lumpiness gone. Though I think at this point I should start a new thread in order to cover the things I have already tried in order to finally get at the root of this problem once and for all.

Ok, so when I first purchased the car the engine never really ran very good. At first it was a high idle. That led me down the road of getting my lambda system working properly again. I replaced the WUR(which was frozen), FV wiring (which was shoddy at best), the O2 sensor, and the lambda ecu. Now I can state that the lambda system works, and my idle is where it should be at 775 or roundabout. Once the idle was fixed I noticed a lumpiness in the motor that would vibrate the engine and by extension the rest of the car while at idle.

When I posed questions then, the advise I got was that it was probably fuel related. So I conducted a spray pattern test with all injectors in jars and sure enough I had a couple that really were not doing all that great. So I ended up sending them into Hervey for cleaning. I got them back, tested them, they seemed better than before, so I re-installed them. Unfortunately the lumpiness remained. Next people asked if I conducted a compression test on all cylinders, so I did. All of the cylinders were in a nominal state with the exception of cylinder #1 which was just a little lower than the others. When I posted the cylinder readings mostly everyone thought they were acceptable readings and should not be causing the lumpiness(dead cylinder). So I replaced all spark plugs and made sure to identically gap them to a gap setting that was given in another post somewhere here. I also replaced the cap/rotor, spark plug wires, and the coil. The lumpiness remained.

Next I was told that it could be vacuum leaks. I made a fog machine and smoked the motor and found absolutely zero leaks. But just incase, I replaced all vacuum lines and ensured operation of vacuum solenoid, vacuum advance on the distributer, and changed all gaskets around the/under the intake manifold while I was cleaning the VOD. The lumpiness remained.....

So while I have been on another thread attempting to figure out TDC #1 cylinder to ensure that my timing is correct something occurred to me. when I replaced the rotor on the distributer I'm sure that I manually rotated the engine the TDC mark on the crankshaft pulley and also made sure the front of the rotor was facing the correct cylinder (#1), but what I didn't know what that the crankshaft pulley has two notches in it. Is there a chance I lined things up to the #6 cylinder notch on the crankshaft pulley and set the rotor to point at the #1 cylinder? Is that even possible? Would the car even run that way? The only reason I ask is when I was checking my timing with a timing light it showed at about 12 degrees. So I loosened the nut holding the distributer and rotated it until I got 13 degrees but I noticed that the distributer was rotated almost as far counter clockwise as the adjustment would allow. Is this normal or should that adjustment be somewhere in the middle when properly set? Also, how the heck to you tell which notch on the crankshaft pulley is which? #1 or #6 TDC? I guess I am a little confused.

Also, I have not done a valve adjustment. I was planning on tackling that this winter. I just assumed that prior to doing that I should probably make sure that the timing is set correctly first. What am I missing here guys? I am not a mechanic by any means but I have done all the work to my car myself and am learning along the way. I just feel like I'm missing something. I will attach a video to see what you guys think.

https://youtu.be/49za2OAyBuc

As always your help is always appreciated.

Thanks

[DMCMW Dave]

Have you ever compared it to another DeLorean? Are you sure you aren't complaining about odd-fire characteristics?

[Trstno1]

Have you ever compared it to another DeLorean? Are you sure you aren't complaining about odd-fire characteristics?

Thats a great question! Unfortunately I'm in Anchorage, Alaska and haven't seen any other Deloreans running to compare. Man, I would sure love to.

Does your D's engine vibrate the car at idle? Have others that you have seen through the years do so?

I guess I just thought that the stumble/lumpiness was the result of something that needed fixing, not that it could be normal. Is it?

[DMC-Ron]

My car has a "rhythmic" idle; it hunts a bit with the RPM varying +- 25. It runs fine, just not a super smooth idle such as on my Toyota vehicles. Other DeLoreans I saw at the Tech session seemed the same so I assumed it was normal. Since you've looked at all the usual suspects consider that the odd idle might be amplified if you have a loose engine mount. You probably have new ones, but wouldn't hurt to see if they are doing OK. If they're not new, consider doing the crowbar test to check for separation.

Ron

[Trstno1]

My car has a "rhythmic" idle; it hunts a bit with the RPM varying +- 25. It runs fine, just not a super smooth idle such as on my Toyota vehicles. Other DeLoreans I saw at the Tech session seemed the same so I assumed it was normal. Since you've looked at all the usual suspects consider that the odd idle might be amplified if you have a loose engine mount. You probably have new ones, but wouldn't hurt to see if they are doing OK. If they're not new, consider doing the crowbar test to check for separation.

Ron

Good idea. I have not done the crowbar test yet.

[dmruschell]

If you set the distributor 180 degrees out (timed it with #6 instead of #1), the engine would not run. The proper distributor adjustment usually puts it pretty far to one side of the adjustment. The distributor being one tooth off will usually mean it can't be properly adjusted within the given range.

The engine appears to be idling as smooth as can be expected. Both of our DeLoreans have performance cams, so they're jumping all around the engine compartment at idle. Yours seems to be fine.

Do a valve adjustment, since some valve clatter can be heard in the video, but keep in mind some clatter is to be expected by design, so it may be fine. At least then you will have done just about everything to be sure your engine is in great running condition (and it's free, assuming you have feeler gauges).

[Trstno1]

If you set the distributor 180 degrees out (timed it with #6 instead of #1), the engine would not run. The proper distributor adjustment usually puts it pretty far to one side of the adjustment. The distributor being one tooth off will usually mean it can't be properly adjusted within the given range.

The engine appears to be idling as smooth as can be expected. Both of our DeLoreans have performance cams, so they're jumping all around the engine compartment at idle. Yours seems to be fine.

Do a valve adjustment, since some valve clatter can be heard in the video, but keep in mind some clatter is to be expected by design, so it may be fine. At least then you will have done just about everything to be sure your engine is in great running condition (and it's free, assuming you have feeler gauges).

Awesome! Exactly what I wanted to hear. Thanks for clearing that up. I'll just do the valve adjustment and move on to other things.

Thanks!

[David T]

A perfect Delorean will have an idle that hunts. Noticeable because you can hear the frequency valve change pitch. if you do not have the stock cams it will hunt even more. Before touching any valves measure them all paying special notice to cylinder #1.

[Trstno1]

A perfect Delorean will have an idle that hunts. Noticeable because you can hear the frequency valve change pitch. if you do not have the stock cams it will hunt even more. Before touching any valves measure them all paying special notice to cylinder #1.

Will do, thanks for the response. It may be a good time to pull the valve covers to do the valve adjustment and clean up the valve covers.

[David T]

The valves are supposed to be checked every 30,000 miles. No hydraulic lifters in the PRV. At that service you would replace the O2 sensor, tune the car up, check the mixture adjustment and reset the Lambda counter.