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mechanical diagnosis

3K views 30 replies 6 participants last post by  Zaman 
#1 ·
I've got a riddle out there for all you mechanical guru's. About a week ago, my car started having problems when I accelerated too much. It felt like cylinders weren't firing. But it would clear up as soon as I hit around 4k rpm. The problem got worse and worse, and finally just died. The engine cranks, but won't turn over. (Oddly, the tach doesn't move when you crank it.) I checked the entire fuel line and injectors, which were fine. I replaced the distributor rotor, cleaned the cap terminals, and changed the plugs, but can't get it to fire. The plugs are firing, and when you take them out of the head, and ground them to the top of it, flames blow out of each of the spark plug holes, indicating that they're strong enough to ignite the gas mist.

My only thought now is that the fuel mixture is too rich to ignite.

Anyone have any thoughts?
 
#2 ·
have you checked your ecu for codes? 1st thing you should have done. 2nd thing i would do is check my map sensor and map vaccum line. you seem to be getting everything you need to run, spark/fuel you must be getting air so check your map.
 
#4 ·
I don't have a compression guage, but when I put my hand over the throttle body, I can feel the vacuum, and when I put it over the spark plug hole (removed) , it's building up pressure.

I tried disconnecting the map sensors, but it still didn't crank.

Yes, it cranks just as fast as it usually does. It's not a weak battery.

I got it back from the service center today for a diagnostic. They told me that I was getting a weak spark. I'm using an MSD cap and coil, which has worked fine for the past 2 years. It's possible that they just never charged the battery after all that cranking, and that's why it had a weak spark. Is there a way to determine how strong or weak the spark is?
 
#5 ·
wait it does or doesnt crank which is it? 2nd of you plug or pull the map sensor line you are guarenteed (sp) that the car wont run 1 bit. if the map goes bad the ecu has nothing to run off of. pull your buddies map sensor vaccum line and see what happens.

if the cap and rotor at 2yrs old i would replace those but it doesnt sound like just a spark problem, you said you are getting spark. if it was to weak to jump the gap under compression then that would be a cause.
 
#6 ·
It cranks, but it doesn't fire. (the starter works.) My mechanic told me that it should start without the map sensor, so I might have eliminated it too prematurely.

As far as the map sensor line, what do you mean? Are you referring to some sort of vacuum tube, or the electrical cable that runs to the map sensor (which is what I removed) ?

I've already replaced the rotor, and I sanded down the cap terminals. I don't think that's the problem, because the first time the car completely stalled, I changed the rotor and sanded the terminals, and the car started up beautifully. It ran great too, all the way around the block, before it died. It hasn't started since, and the cap and rotor look just as good as new.

89 IROC Z said:
wait it does or doesnt crank which is it? 2nd of you plug or pull the map sensor line you are guarenteed (sp) that the car wont run 1 bit. if the map goes bad the ecu has nothing to run off of. pull your buddies map sensor vaccum line and see what happens.

if the cap and rotor at 2yrs old i would replace those but it doesnt sound like just a spark problem, you said you are getting spark. if it was to weak to jump the gap under compression then that would be a cause.
 
#7 ·
blase said:


I've already replaced the rotor, and I sanded down the cap terminals. I don't think that's the problem, because the first time the car completely stalled, I changed the rotor and sanded the terminals, and the car started up beautifully. It ran great too, all the way around the block, before it died. It hasn't started since, and the cap and rotor look just as good as new.

don't sand the terminals TOO far down where u don't have any contact of the rotor and cap...
have u tried diabling your fuel system and spray starting fluid or wd-40 into the intake manifold?
 
#8 ·
taz77 said:


don't sand the terminals TOO far down where u don't have any contact of the rotor and cap...
have u tried diabling your fuel system and spray starting fluid or wd-40 into the intake manifold?
I've considered that maybe I sanded them too much, but that wouldn't explain why it worked well for 5 minutes before it finally died. Either way, I'm replacing the entire distributor and everything after it.

I tried disabling the fuel system and spraying starter in it, but nothing happened.
 
#9 ·
i will assume you understand speed density and dont need a tutorial to that end. basicly the map gets its info from a vaccum line running to the tb or manifold, if the map goes bad or the vaccum line or electrical connection goes bad or is grounded it will feed the ecu bad info and cause a code or simply run poorly or stall completely.

now a car can run for a short time without the map on some models not all (havent tested every model SD came on so i couldnt tell you if yours should or should not run). but at any rate it wouldnt run forever.

did you check the ecu for codes? i still havent seen anything about codes or lack of. 2nd thing check the map vaccum line and electrical connection, if the vaccum is cracked car wont work or work poorly. if you have a buddy with a similar car pull his vaccum line and see what happens, if his dies we maybe going in the right direction. you can swap your map with his and see if that cures the problem. it sounds like you either have a completely shot cap/rotor/wires/open ground or a map problem.
 
#10 ·
First off, I completely forgot to thank you for your help in all this. Having said that, I've determined that it's not the map sensor. I swapped it out today with no luck. You confused me with the map vacuum line, simply because my car doesn't have one. The map sits right on top of the TB, with no vacuum line between them.

I haven't checked the ECU for codes, cause I'm an idiot, and I work full time, and haven't read about how to do it yet. I'll be researching the matter immediately after this.

If I can find someone local to switch ECU's with, I can make sure mine isn't fried, and install my new AEM EMS without worry of frying it too. Then I can just hook it up to the laptop and figure out what's wrong. (I'm concerned about the ECU because the tach doesn't move when I crank the car. Am I right in relating those together?)

Tomorrow, I pick up the new distributor.

89 IROC Z said:
i will assume you understand speed density and dont need a tutorial to that end. basicly the map gets its info from a vaccum line running to the tb or manifold, if the map goes bad or the vaccum line or electrical connection goes bad or is grounded it will feed the ecu bad info and cause a code or simply run poorly or stall completely.

now a car can run for a short time without the map on some models not all (havent tested every model SD came on so i couldnt tell you if yours should or should not run). but at any rate it wouldnt run forever.

did you check the ecu for codes? i still havent seen anything about codes or lack of. 2nd thing check the map vaccum line and electrical connection, if the vaccum is cracked car wont work or work poorly. if you have a buddy with a similar car pull his vaccum line and see what happens, if his dies we maybe going in the right direction. you can swap your map with his and see if that cures the problem. it sounds like you either have a completely shot cap/rotor/wires/open ground or a map problem.
 
#12 ·
It's a 95 integra LS.

It's getting fuel for sure. Injectors are working fine, I pulled the whole fuel rail out and watched them mist out clouds of gasoline. I even replaced the fuel pump. When I removed the exhaust manifold, I could see the unburned fuel mist being pumped out of the cylinders.


taz77 said:


i forgot to ask u.. what kinda car do u have (if that matters at all later on)...

are u getting fuel to the cylinders at all?
 
#14 ·
i would probably have the timing checked then... make sure the timing belt hasn't jumped a notch or something... or make sure you're getting the proper spark at the proper time.

other than that, i'm outta ideas.
 
#15 ·
taz77 said:
i would probably have the timing checked then... make sure the timing belt hasn't jumped a notch or something... or make sure you're getting the proper spark at the proper time.

other than that, i'm outta ideas.
I'm not quite sure how to check the timing belt. It has the same tension on each side of the belt, but I don't know what else to do to check it.

I think I've narrowed it down to the distributor though. When I realized that the tach didn't move when I cranked the car, I found a diagram of the tach circuit in my haynes manual, and it traces straight to the distributor.

My only problem is that I can't find any integras in any of the local junkyards. Thousands of american cars, hundreds of toyotas, nissans, and Mazdas, but not a single acura. ( I guess we bury our dead.)
 
#16 ·
BREAKTHROUGH! (or breakdown...)

It occurred to me today that I REMOVED the distributor from the car when I replaced the rotor, and I never considered that I had retarded or advanced the ignition timing when I reinstalled it.

So starting from the dead center mount, I slowly rotated the distributor itself counter clockwise a mm at a time, while my brother cranked the engine. Nothing happened. So I returned to dead center, and begun rotating it clockwise a mm at a time. At about 3/4 of it's final limit, the tach started jumping around again. I kept rotating it, to about 7/8 of it's final limit. When my brother cranked it this time, it started firing, for about 2-3 seconds, but ran really badly, and smoke (or gas vapor, some white cloudish stuff) started pouring out of the throttle body, and from underneath the valve cover. I got scared, and told him to quit.

Sooo.. who wants to comment on this one?
 
#17 ·
so smoke came out the tb? well something is totally wacked then. timing or cam timing, the dist is run right off the intake cam so check the cam timing and make sure it lines up. there is a pointer on the timing belt cover and a mark on the pulley and a mark on each cam. i forget the exact line up as far as cam to crank markings, but take #1 cylinder to tdc and see if everything is lining up. if you have a haynes look under valve adjustment or valve lash adjustment and it will give you the run down on valve adjust and taking the engine to tdc.
 
#18 ·
Here's what I think is happening, tell me if you agree or disagree with any of it.

I think there's a problem with the distributor thats resulting in a weak spark. It's strong enough to ignite gas at normal air pressure, but it's not strong enough to ignite under compression. So when I was advancing the timing by rotating the distributor, I was actually moving AWAY from the correct timing, but I was also igniting the cylinder before it had been put under compression, which allowed it to combust. Of course the timing was completely off, so it was just escaping from whatever valve was open at the time.

The only thing I can't explain is why the tach started moving again when I advanced it so much.

89 IROC Z said:
so smoke came out the tb? well something is totally wacked then. timing or cam timing, the dist is run right off the intake cam so check the cam timing and make sure it lines up. there is a pointer on the timing belt cover and a mark on the pulley and a mark on each cam. i forget the exact line up as far as cam to crank markings, but take #1 cylinder to tdc and see if everything is lining up. if you have a haynes look under valve adjustment or valve lash adjustment and it will give you the run down on valve adjust and taking the engine to tdc.
 
#19 ·
i had been waiting to hear how it went after you replace the cap/rotor/wires and plugs, plus a possible coil swap but i havent seen that yet. i dont know if i agree, even a weak spark will usually still start the car and even if the dist timing is off a few degrees a motor will normally start. it is possible that the gas was simply escaping as you said but unlikely, normaly a dristibutor doesnt have that wide a range of advance/retard room to ignite when a valve was wide open. the timing should only advance a couple degrees either way for a total swing of around 12 degrees or so (guessing havent checked) but you get the idea. so unless the distributor was on upside down (unlikely) or the wires where connected to the wrong terminals i dont see that happening.

i dont know your mechanical skills and dont want to see you get in to far to the point of no return. try swapping ingition components for known good units, cap/rotor/wires and check the cam timing to be sure everything is lining up correctly, also get your dist in the middle of the road as far as timing say straight up when you try and start the motor.

a shop will always say weak spark or bad plugs/wires any time they check a car, its like a rule (tune up) even if the plugs are good it needs plugs. if it comes down to it, take it to a dealer and have then run a real diagnostic on the car. this will give you a for sure no questions asked answer to the problem for about $45. and you do not have to have them fix it, you can take the list and fix the car yourself. i have done this when i had a major sensor meltdown and lost 5 sensors at once, hard to narrow down that way. but the dealer has the proper more expensive equipment to run a good dianostic and find the real problem. they normally give you a list of repairs and prices, mine was $1800 which i spent maybe $200 on sensors and was good to go. of course they included plugs & wires even though mine where good and listed a weak spark. weak spark can be wires, cap&rotor or all three, its a general repair really meaning lets milk'm or sell the tune up.
 
#20 ·
If you took the distributor out you probably are out of time.
Atleast thats my guess. What I would do is line your motor to TDC on the #1 Cylinder. Then take off your distributor cap and see if the rotor is pointing to the #1 plug wire. Before you do any diagnostic stuff make absolutely sure your motor is in time. I know what your saying about your tach not working, but dont worry about it. If your engine is not even trying to start the tach wont jump. If your getting it close enough to were its jumping and your engine sounds like it wants to start you most likely have a timing issue. Your car should be throwwing a code. If you go to the integra forum I think they have a code FAQ, it should answer your questions.

I had a similar problem with a Mitsubishi MightyMax engine. I rebuilt the whole thing and when I stared it, it wouldnt run. I played with the timing and got it to finally cran,k but it ran like shit. I finally had to start over from scratch. I pulled the distributor out, lined the engine up to TDC on #1, and placed the distributor back in the correct way and it ran fine from then out.

BTW you said your spark was not hot enough right? I had this problem too. My car was getting spark, but not enough for it to run. Ofcourse my problem was inside the distributor(not a honda - subaru)but it could be from many things. Look and see what the spark looks like. I cant remember but I think a white spark is bad and a blueish spark is good.
Let us know what hapens.
 
#22 ·
I checked the ECU for codes by shorting the black and brown wires on the green plug, next to the ECU, and only got a solid check engine light.

Well, bad ECU it is, I guess? I'm just wondering what caused it. Do ECU's just go for no reason? I'm going to be replacing it with my AEM EMS ($1400) and I don't want to fry it too, if it's a short or something. Any ideas?
 
#23 ·
Is it at all possible that a bad distributor would disrupt the ECU electrical circuit, and cause it to throw a bad ECU code?
 
#25 ·
Lord Accord said:
Did you do everything right? Sounds like to didnt do something you were supposed to to get the code to flash.
double check the steps to doing it and try it again and see what happens.
According to what I read, you're supposed to short the black and brown wires on the green service plug, and then turn the key to the ON position. I did it 4 times, checking the paperclip each time, and only got a solid check engine light. Is this in fact the correct process?
 
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