Topic: Electrical Problem ?

[LANCER]

I can not get my engine to run smooth. It has a hesatation. The problem is speratic. This is a total rebuilt engine. When it is running it sounds great but the engine acts like there is a ignition problem. It studders alittle. I have new plugs, wires. cap, rotor, and I even installed a MSD 6A box to see if that would help but it solved nothing. When I check compresstion all check at 135 to 142 and for some reason #7 only has 127. Can this be my problem? The problems seems to be ignition but I may be wrong. Please send any suggestion my way. I have to get this on the road soon before summer is goen and it goes back into storage. Thanks

[jjr]

 Did you try "checking" the new plug wires?

 Maybe you got a bad one. I'd check 'em and while
checking move 'em around a bit...

 Joe R

[dfred]

sounds like a similar problem I have been chasing, idles ok but misses sometimes,  I tried new plugs, 2 sets of wires, and finally just took it to the dealer.  they had it for a while , and told me they are pretty sure my problem is a worn cam.  probably a worn lobe. had valve cover off and said one of the valves isnt opening up enough.  kinda makes sense, I guess, but then I am no mechanic either.  they wanted 1400 to put in new cam and lifters. I said thanks for your time and brought the car back home. for that price, I will probably just have the engine rebuilt soon.

[LANCER]

I have checked the wire for resistence and they checked good and have went threw 3 sets of plugs. The engine is a complete rebuild and it has doen it since the first start up. It is there most of the time but leaves for a few seconds and then come back. I hope nothing happened to the cam but nothing would surprise me. Thanks for the input.

[jjr]

 Your compression check tells me that the cam and valves are most
likely ok. A monitored vacuum gauge may help your diagnosis, but
I think you're probably on the right track with ignition.

 I'm wondering about the ignition module. I have had partial failures
of these all so very important little buggers before.

 In days gone by tune up shops would put your ignition patterns
up on an oscilloscope and look at each cylinder's firing line. Something
like that would flush out your troubles in a heartbeat.

 Maybe you could find someone with a handheld unit and check each
plugs firing line separate, that'll work too. Fluke makes those.

 Joe R

[Joker (§ir£Ğragon)]

127 lbs of compression is a little low, but it's within 10 of the next higher one so it seems sensible to look for other, "simpler" problems. I think you're on the right track too. Joe's right about the module. Used to be mechanics would say that they would either work or not. Now-a-days we know better. Does it get worse with temperature? Another place to look is the wires inside the distributor. Sometimes they get brittle and the insulation comes off. This can cause different issues like simple shorting to arcing within the distributor.

[miketransamkid]

Another plus to owning your own Sun Engine analyzer. either module or pick up coil.

[ta78w72]

You keep saying ignition....but I generally don't associate a hesitation or stutter with ignition.

When does the car do this?  When it's cold, hot?  Does it hesitate when you began to accelerate? or when you put the engine under pressure?  Is it the same cold or hot?

I've never had a partial problem with an ignition module, nor have I ever had a pick up coil go out.  So, those things wouldn't even come to mind with the symptoms you have.  I'm not saying those things couldn't be the problem, but I would suspect a whole lot of other things before those.

Could be your vacuum lines...could be an air leak at the carb...what carb are you running?

If you have a rebuilt engine....why would #7 be so low? 

Get a service manual from Brett....there are three or four pages on diagnosing these types of problems.

[Joker (§ir£Ğragon)]

Weak spark can cause a hesitation or stumble. So can arcing of the spark under load both within the cap as well as along the plug wires. Weak spark can be simply be caused by bad wires or modules can have issues that will cause the spark to be weak. They are also temperature sensative. The grease under the module helps with the heat issue, but it's not perfect and if the module does start to break down then it takes less heat to affect it. (Just as an example there was a recall in the ealy '90s on the Civics and in the mid '90s on the 300ZX because the module would act up when the car got up to normal operating temperature.) The low compression in the #7 cylinder could somply be caused by the rings or a valve that didn't seat quite right. You're right, it very well could be something vacuum or carburetor related. But I think they would be more consistant than Lancer's "spuratic" problem as he describes it.

[ta78w72]

It appears that he has replaced all the ignition parts...although he doesn't mention the module.  The grease under the module allows the heat to dissipate a little better off the module...and I bet a lot of people skip that step.  I'm not sure what he means when he says it's sporadic.  Does it hesitate when it's idling?  Is it missing when it's idling....does it do it when the engine is hot...or cold...or does it matter?

I think if I had a rebuilt engine with one cylinder that much lower than the others....I want something done about it.  I think I'd diagnose that first.  He should be able to tell if it's rings or not pretty easily.  That would bother the heck out of me.  It's like getting the car painted and finding a hair in the paint.