Car is running very bad - need help!

5.0L Miata · Aug 21, 2007

Hey All,

I just installed Edelbrock Performer RPM aluminum heads, comp cams push rods, aluminum adjustable (stud mounted) rockers, and an Explorer Upper and Lower intake on my otherwise stock 88 5.0L H.O.

The engine is all back together and will start, but is running REALLY bad! This was my first time ever doing head gaskets, valve adjustment, etc. but I think I have everything together correctly.

The car will start but idles very rough and wants to stall. The exhaust also smells pretty bad. I figured it was a timing problem, so I hooked up my timing light to see where I was at, only to find that my timing light is only getting a signal from 4 of my 8 plug wires.

Plug wires, plugs, cap, and rotor are all new. Dizzy and coil are original from 88.

So a couple of questions then:

1) If my Dizzy was off 180 degress, would my car even start? I'm thinking it wouldn't as it would spark when the piston is at the bottom...therefore no compression or air. If it wouldn't start, then I can just focus on ignition...if it is possible that it would start then I may have to look into my dizzy install.

2) If a coil was going bad it would still give a spark to all 8 cylinders correct? Is a symptom of a bad distributor that it only distributes spark to certain cylinders? What else would lead to lack of spark on certain cylinder but not others?

I have triple checked my plug wire connections...any thoughts are very much appreciated!

Thanks.

cenok is family · Aug 21, 2007

is the motor still speed density? are you using the correct firing order? and yes the motor will start if its 180* out. when i rebuilt my motor, i was using the NON HO firing order AND i was 180 out, it ran, but ran like total a$$. from what it sounds, i'm gonna say that you stabbed the dizzy incorrectly.

5.0L Miata · Aug 21, 2007

Yes the engine is still SD and is using a stock cam. Firing order is correct.

I guess the only way to check that my distributor is out 180 degrees is to pull the plug in #1 and have the wife crank it until I feel compression. If the rotor does not line up to #1 on the dizzy then I'm out 180...this correct?

This does not explain why I have no spark signal on 4 cylinders though...or does it?

jrichker · Aug 21, 2007

Putting the distributor back in is fairly simple. Pull #1 sparkplug, put your finger in the sparkplug hole, crank the engine until you feel compression. Then line up the TDC mark on the balancer with the pointer on the engine block.

The distributor starts out with the #1 plug wire lined up at about 12:00 with you facing it. Align the rotor to about 11:00, since it will turn clockwise as it slides into place.

Align the distributor rotor up with the #1 position marked on the cap, slide the distributor down into the block, (you may have to wiggle the rotor slightly to get the gear to engage) and then note where the rotor is pointing. If it still lines up with #1 position on the cap, install the clamp and bolt. If not, pull it out and turn 1 tooth forwards or backwards and try again. Put the #1 spark plug back in and tighten it down, put the clamp on the distributor, but don't tighten it too much, as you will have to move the distributor to set the timing. Note that if it doesn't align perfectly with #1 position, you can turn the distributor until it does. The only problem is that if you are too far one way or the other, you can't turn the distributor enough to get the 10-14 degree optimum timing range.

At this point hook up all the wires, get out the timing light and start the engine. Set the timing where your car runs best. Don't forget to disconnect the SPOUT jumper connector when you set the timing, and plug it back in when you finish.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

5.0L Miata · Aug 21, 2007

Cool, I followed these steps when putting the distributor in last time...but perhaps I am off?

If I pull the valve cover and look at the rockers, they should both be even with each other (both valves closed) when at TDC correct?

I guess I'll pull the upper intake and the valve cover and double check that I am indeed at TDC on #1 and double check my dizzy placement.

If all checks out I'll be back to trouble shoot some more. I still don't understand why my timing light would not pick up a signal from 4 of 8 cylinders even if the dizzy is off 180 degrees?!

jrichker · Aug 21, 2007

Use an Ohmmeter to check the resistance of the spark plug wires. You should see about 2000 ohms per foot of length. A 2 foot long wire would be 4000 ohms, a 3 foot long wire would be 6000 ohms. The values are +/- 20%, so don't get excited if you are out of spec. Less resistance is always good.

Speciality wires like some of the Taylor & Accel wire sets have a spiral wound metal core conductor and read about 40-60 ohms per foot.

5.0L Miata · Aug 21, 2007

Can do, but the wires have only about 3,000 miles on them and they worked fine before the rebuild in June.

HISSIN50 · Aug 21, 2007

Also, if using an inductive timing light to check for spark on each plug wire, be sure the arrow on the inductive pick-up was pointing the right direction. Since 4 wires didnt work, I'm wondering if this could have been the case (you'd have had to flip the clamp around for one bank vs the other).

This won't help with the car's performance but might explain some things. JRichker will know better than I do, but I dont think a car will even idle on 4 out of 8 cylinders.

Good luck.

cenok is family · Aug 21, 2007

i was always under the impression that if you upgrade the heads, cam and/or intake, (pretty much anything that'll flow more air or fuel) you would have to switch to mass air or have your SD computer reprogrammed. maybe someone will chime in with more detail on this? that could be the problem as well. Just throwing some ideas at ya. Not too sure on the spark issue though. Good luck!

5.0L Miata · Aug 21, 2007

cenok is family said:
i was always under the impression that if you upgrade the heads, cam and/or intake, (pretty much anything that'll flow more air or fuel) you would have to switch to mass air or have your SD computer reprogrammed. maybe someone will chime in with more detail on this? that could be the problem as well. Just throwing some ideas at ya. Not too sure on the spark issue though. Good luck!

My understanding (after much research) is that SD cars can take heads, intake, TB, pullies, etc. without any problem. The problems start when you mess with the cam, and I'm running a stock one. Someone please chim in if my assumption is not correct.

5.0L Miata · Aug 21, 2007

HISSIN50 said:
Also, if using an inductive timing light to check for spark on each plug wire, be sure the arrow on the inductive pick-up was pointing the right direction. Since 4 wires didnt work, I'm wondering if this could have been the case (you'd have had to flip the clamp around for one bank vs the other).

This won't help with the car's performance but might explain some things. JRichker will know better than I do, but I dont think a car will even idle on 4 out of 8 cylinders.

Good luck.

Very good tip on the timing light...this is my first time using one so I don't really have any experience with it. I will re-read the owners manual and make sure I'm using it correctly. This may resolve my ignition conerns and lead me straight to the dizzy being out 180 degrees.

Will let you know.

Aliate X · Aug 21, 2007

same thing happened to me first time i did a hci swap, turned out i adjusted the valves too tight. Would not idle without giving it gas and ran PIG rich. very very very easy to over tighten them.

Just read through more of your post, ill bet $100 your valves are too tight.

If the dizzy is out 180 degrees it will not start, it will backfire when you crank it.

5.0L Miata · Aug 21, 2007

Ok, I have spark and I've re-checked that the dizzy is correct. Had the wife crank the car while my finger was in the #1 spark plug hole. Each time I felt a blast of air the dizzy rotor was pointed at #1 and the block pointer lined up with 0 degrees on the balancer.

So with tightening the rockers too much...how would I have done this? I followed the instructions which said 1/4 to 1/2 turn of socket for each after I'm at zero lash. I was closer to 1/2 I guess...I also finger tightened them until I could not move the pushrod by hand.

What should my correct proceedure be?

Aliate X · Aug 21, 2007

I did the same thing, then my friend came over and redid them for me and the car started right up, just do looser than whatever your doing, do a 3/8th of a turn then if your doing 1/4 now or less. Its hard to explain over the computer.

5.0L Miata · Aug 21, 2007

Ok, I'll give it a shot.

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