Ok, somethimes that doesn't work all that well because the coils might have a short in it which would explain why sometimes it runs, other times not. You hit a small bump, it runs like ****, hit another, now it runs. A rotary tech at a Mazda dealer told me sometimes the coils test out ok but because there was no other option, he changed the coil (I believe primary), car ran great. So it was the coil even though it checked out ok. I'm having similar problems, my coils checked ok with the ohm meter but I have a feeling its one or all of them thats my problem. I mean think about the basics for a motor to run; air, fuel, spark energy, and then eliminate variables. Your getting close to proper fuel pressure readings, an interior fuel pressure gauge could tell you fuel pressure during acceleration, which would help to determine if maybe you're running to rich, like the MAP sensor is bad. I think you can't burn the fuel provided so it's fouling your plugs making it look lke you're running rich. Did you say you changed the MAP sensor or checked it? Also, check crank angle sensors.

 

I changed the MAP sensor and the crank angle sensor was checked a few months ago. I see what you are saying, but get this, the last few times I drove it, it was running bad the whole time, which would mean that the coils(if that was the problem) should be showing some sign of the problem now. I'm not trying to argue or anything, I just thought that since I never had any high rpm problems that the coils were probably ok. I can't really go replacing everything on here.

 

Yeah, thats what i'm having, higher rpm problems. How's your wiring harness? Check the connectors to the coils and wiring. Begining to sound electrical. Although the rotary tech said that the coils checked out ok even though the primary was faulty. What year is your car? Is it on the original motor?

 

93 with 20k on a mazda reman. My wiring harness in general looks like ***, but I'm not sure what to be looking for. I'd love to put a new on in, but that would cost way to much, and if that wasn't the problem then I'd be totally screwed.

 

When I put my new motor in, I had to suck it up and buy a new harness (like $1000). I also have a 93. It's on it's fifth motor (this is my 1st motor). Being how hot FD's run and its a 93, could be somewhere in the wiring. Purchase the shop manuals and start troubleshooting the wiring. These cars are sweet but man are they a pain in the ****. Good luck! Keep at it, you'll find the gremlin. I'm about ready to start buying one coil at a time, starting with the primary. If that doesn't work, at least I'll have one less variable to wonder about and I'll have new coils that generate good spark energy (also going with HKS twin power coil thing). Again, good luck!

 

Thanks, if the majority of the folks on here think it's the wiring I'll buy one. I found one in the parts section for $205.

 

Where exactly is the parts section?

 

It will be interesting so see what the answer to this is. I too have the "fuel cut" type of thing when launching. Its weird, Its like I let totally off the gas for a sec then it just goes..

Made me look like a moron at the strip. First time it happened I was REALLY worred. Next time I was kinda pissed so I just stayed on it. Nose went up, came down, went right back up. Still beat that bastard trash talking 'stang

 

It might be a fuel injector that sticks intermittently. Unfortunately, you might need new injectors to test the theory. I am not sure the problem would show up on the test bench -- it might be heat related.

-Max

 

Pcola

..clean your grounds
...make sure your intake is free and clear ..left a rag on the intake at one time with same results
....possibility your intake hoses collapsing? have heard this before
.....adjust your air screw for your idle probs ?
......intake hoses on tight ?
.......sticky injectors ? run some redline inj cleaner on your tank
........any chance the vac lines got crossed during the tiewrap job?

sorry if this is obvious...
good luck

 

I am going out on a limb here but try changing your 02 sensor and water tempeture sensor. If the water tempeture sensor is repaired you might as well replace it anyway.

 

Here's a far shot. Check the rubber seals at the fuel injectors. If you are sucking air, the vacuum would drop. You would think that you go lean though. I would change them while you have them exposed anyway. They are only a couple of bucks.

Also, the wiring harness being brittle can cause cracks and various "gremlins" due to short circuiting and grounding unintentionally. My bet is your harness is getting bad.

Tim
Tim

 

Jake, I was talking about the parts section of the forum. It's at the bottom of the list of forums.

Max, if I sent them off to RC engineering, would they be able to catch/fix that.

amp, the vacuum hoses are alll right.

2-rotor, I considered the O2 sensor, but the problem persists even while at WOT, when the computer doesn't use the O2 sensor. I'll be checking the water thermosensor after I get off work.

Thanks guys, keep it up.

 

Ok, now after a good night's rest I am SURE I know what the problem is. You either have a small slit in the hose between the intake and your MAP sensor on the firewall or the small filter that is inline between the manifold and sensor is toast. Replace the filter for (GULP) $25? at your local dealer.........yep, that's right...$25 smackers for the little sonofabitch.
Either that or you have water in your gas tank from condensation and not keeping your tank full. Add a pint of alcohol (not to you - the gas tank damn it!)
BTW - I still prefer a cashier's check, we're back to $100 and Louie is starting to twitch.

 

you guys are on the right track but i had a miserable experience with a 93 recently that seemed to originate at the wiring harness/ecu connection. i don't know if the problems(all that you described and more) were from the harness, ecu or the connector but when i repositioned the harness and tied it so that it was all stressed just so.....it ran great. good luck

 

Maybe, but not certainly. If the injector only sticks when it gets hot, they may miss the problem. But, it can't hurt to have them checked out and they may find a problem with it. Cleaning it may fix it even if they don't find a problem, too. Just be sure to use them soon after they return or they will get stuck by the cleaning fluid.

The primary tubo intake elbow sucking itself shut sounds like a good lead, too. You can get some cheap Santoprene hose from http://www.mcmaster.com/ as a replacement -- it is only like $25 for the minimum 5 ft length. Myself and several other owners have been running that stuff for years.

-Max

 

yep, i agree with RonKMiller on this one. my car was doing the exact same thing as you have explained it. The car jerks and hesitates once in awhile and when i lunch hard it seems like the fuel cut. I had the Pettit unlimited ecu too b4. I changed my fuel filter and nothing goes in to my gas tank except 100 octane. Now my car runs FINE!!!

hope this helps man.
steve

 

Possible - the rubber seals around the injectors could be f'd up when your motor was installed. Not a nice thing to check though - only check it if you are there. Redo your idle adjustment by the book. If the idle air is too low and the idle speed is set to correct the speed you will run real rich and foul your plugs - easy check.

 

Have you changed the fuel filter? this is most likely the problem.. if not start checking out your wiring..


-Zach

 

OK, I have this problem every once in a while and I've narrowed my problem down to fuel slosh because it only happens when I'm low on gas. Last week it started doing it pretty bad so I went and got some gas, problem went away immediatly!!! It's the exact same symptoms you have.

It could possibly be bad gas because I did go to a different gas station then usual the time before.

 

Ok, I put it all back together, put alcohol in the tank(and maybe a wee little in me),checked the MAP sensor's filter and hoses, which were fine(I work at a dealership and get parts for cost, haha), cranked it up and it was having the same problem. I tried fiddling with the ecu wires and that didn't help. I drove it, and it was still intermitten, but now it's only boosting 4 psi and it sounds like I'm leaking boost, almost like my air bypass valve is staying open all the time.
Something very interesting: I unplugged the L1 wire from the plug, and started it. The engine did the same thing. There is plenty of spark coming from that wire though. Why would the condition not change if the was unplugged?
I'm going back out there to check the compression again, once someone else living here shows up to give me a hand. Thanks guys.

 

Leading plugs have very little effect compared to Trailing.

 

thanks luneytune I thought it was just the opposite.

Ok, the results are in: over 120 psi on all three sides of both rotors. Could a clogged fuel filter really be causing the engine to bog this profusely?
When I had my trailing plugs out to test the compression after driving for about a half an hour and the plugs looked good. They were dark brown not black or white.

 

Lower intake manifold gasket, change 02, and check y-pipe bolts.

 

The opposite is true. Also, both leading plugs are in the same circuit, so if you pull one leading wire, you will effect the spark of both. The circuit is like this (one path through the whole thing):

Ground-----L1Plug------Coil------L2Plug------Ground

I am leaning toward fuel filter now.

-Max