I've had a few problems lately with my 93 VE 5spd.

I had a miss or 2, so by pulling coil plugs I determined the 2 front cylinders closest to the front of the engine made no change in how it runs or sounds. I pulled the coils and found them to have substantial cracks, so I replace them.

It runs much better, however their is still 1 miss, a lack of power and doesn't want to rev near as quick and easy as normal. The gas mileage also got worse. I track it down to the middle rear cylinder. Unplugging coils on all other cylinders makes the idle drop then the computer smooths it out in a couple seconds. This rear cylinder being unplugged has no effect. So I switch some coils around, that I know to work and no change.

I am getting voltage at the coil plug. I pull all the plugs. The fronts all look a little lean, look 2 lean to me. The rears are a little rich, I'd say twice as dark as the fronts. The center cylinder plug was dry of gas but had a black oil deposit on the electrode. It seems like an injector.

So I pull the upper manifold to get the injectors, no problem. Well the ports for the rear bank all have a thin layer of black gassey soot, while the fronts are a clean golden color. How is this possible, the lower intake is the same with the "colors" stopping to show the shiny clean alum right before the intake splits into each cylinder?

Normally this car runs strong, even when I had a bad coil in the front, but I was getting some pinging so I started looking into things. This motor is completely rebuilt and has around 15K on it now. Nothing major done just some mild porting/clean up work. Lots of time balancing. A Fidanza flywheel, new 94 VTC's and that's it. At first it had no power and I knew the cam timing was off, so back to the builder. After setting to TDC the cam position sensor was reset and it started and ran good. It pulls to the rev limiter very smooth and quick. But after sitting overnight or 8 hrs or so, starting it I get a clacking sound, that sounds more like timing chain movement more than VTC's.

Here are the issues in summary;
After sitting the clacking noise.
The uneven mixture front to rear.
The injectors, all except the rear center (dead cylinder) look suprisingly clean. The inlet screens and 4 spray holes are clean. The rear center injector 4 hole spray area is dirty and you can't really see the spray holes. So I am replacing this one.

Could the bad rear cylinder cause the computer to adjust mixture to compensate causing the other 2 rears to be rich, as well as the intake ports? With the back being rich the O2 feedback would be to lean it out. Could this cause the front to lean out while keeping the back rich?

The PCV system is intact, new hoses and looks to be very clean, so I don't think it's a blow by issue.

All vacumn lines are new and it holds a steady 18 at idle. I'm almost certain they are all connected to the right places comparing to the pictures I took before I took the car apart before the motor rebuild.

I was thinking the front may be lean due to the ECU cutting fuel due to the coils not firing?

Could this be a cam timing issue, meaning the front or rear bank being off a tooth?

I'm lost and apologize for this novel. I just really want to fix this especially on a basically new motor. The uneven mixture has me concerned.

Now is the time, I have the upper mani off so and have the injectors ready to reinstall. If I need to pull the valve covers for a timing issue I want to do it now.

Thanks a lot
Matt

 

these cars do not have the ability to lean out a specific bank of cylinders. There is only 1 o2 sensor that sniffs all the cylinders at once.
when the motor was "rebuilt" were all the timing pieces replaced? including the VTCs? or was it all just checked and put back in?
when the motor was installed were new hose put in for the vacuum and fuel lines?

 

Yes, everything was replaced, hoses, including fuel.

The ECU can detect a misfire, does it compensate for that in any way?

That's why I don't understand how the rear could be so different from the front. Especially in the intake before there is fuel or oil. Normally the only reason I see black runners in an intake is a bad turbo or blowby. I have no turbo and the PCV system is clean with a working valve.

Actually in a post below about a VE engine swap he shows photos; this lower intake looks very similiar to mine color wise. http://i176.photobucket.com/albums/w...4/DSC_0271.jpg (I don't know how to embed the pic here)

The VTC are new as are the chain and tensioners.

Would it even run well if the timing was off between front and rear banks? I mean this car with this current motor a few months ago was close real close to my stock mustang 5L especially from a roll. And it was averaging 27 mpg cruising 80mph on my 30 minute commute. I can't imagine it would run that well and be silky smooth if it were a timing issue/chain jumping.

As you can see, I'm hoping it's not timing. Multiple cams and chains are not my strong point.

I really appriciate your help.
Matt

 

well is it possible that the chain is a tooth on one bank? maybe if the chain had ever been removed for any reason previously.. i know it's a long shot but if one is absolutely certain that the front and rear banks are behaving differently... then who knows.

 

"well is it possible that the chain is a tooth on one bank? maybe if the chain had ever been removed for any reason previously.. i know it's a long shot but if one is absolutely certain that the front and rear banks are behaving differently... then who knows."

The chain being off a tooth is what concerns me, and which of the 3 chains?

But yeah the entire chain/timing system was replaced when I had the motor built. The CPS was not replaced.

 

if you are gonna look at the chains at all, might as well verify that the whole thing is properly in time. but i would look into other things before bothering with the chain... unless you already know how to peek at the chain and verify that it's aligned right. if you don't know how to check the chain's alignment then i would suggest looking into other possible causes because the odds of the chain being off are reasonably low (though you did say the chain and tensioners are new... which means they have been removed before)

 

If you have a cam off a tooth, you can adjust it by pulling the valve cover and removing the bolt on the end of the cam. slide the gear off the end of the cam, then pull it out of the chain and adjust. turn the cam w/ crescent wrench to line it all back up and put ti back together.

symptoms of a cam off a tooth are laggy throttle and major dips/peaks in response. I had one exhaust cam retarded a tooth a while back and it was laggy until about 36-3800rpm (when the VTCs activate or something) and then it ran like a raped ape to redline. I GOTS VTAK, YO!


As for the running slow, I would plug it all on you having a bad injector in the rear.

the intake manifold being 2 different colors is normal. the manifold spilts front and rear banks just past the throttle body. the split is horizontal, so 3 cyls on top, 3 cyls on bottom.

I bet if you pull your intake manifold, you have some oil blowby from the valve cover breathers getting into the intake. It then runs along the bottom of the intake manifold (cause it's heavier than air) and goes into only 3 cyls.

so the intake being different colors is nothing to worry about.

 

Thanks Matt, that's good to know about the intake, I can see what your saying shining a light thru it. And previously the plugs looked decent, even, but a little lean if anything. Of course the one with the dead injector was rich.

The injector in question does not have continuity at all, so that's obvious. I have 2 extra's that both sit right at 11K ohm. The rest of my injectors are also 11K ohm.

I'm considering haveing them rebuilt by RC engineering or someone, I haven't determined who and if I should definetly do this. Any advice on this?

To me my car feels a little soft on the bottom end, then it takes off right around 3500. But I'm used to driving a 280Z that is built and makes lot's of torque, also a 5L stang. Maybe this will describe it better; I can be rolling 10mph in 1st, punch it and it will light the tires up. If it's wet it will just sit and spin. It just feels weak to me leaving the line and at the bottom of second, but those gears have a wide spread. 2nd - 5th is pulls solid. This is with the dead injector and a weak coil.

 

Hmmmm...I have/had this same issue with my ve, until i grounded the vtc solenoids. Originally it was to stop some cold start up vtc clack(i wasn't looking to fix the lag under 3500rpm problem), but low and behold, the low end lag went away after grounding out the vtc's. You might want to try this just for research's sake.


My vtc's were replaced(not rebuilt) by the previous owner, and it's my guess that the shop may have done something wrong timing wise during the vtc replacement.

 

Hey Greeny, you get over by Asheville much? I see your pics below of the TN/NC area. I'm always riding around the mnt's in one of my cars, course the only thing I have that will go in the snow is my Max.

Any thoughts on dropping the $100+ to get the injectors rebuilt/flow and spray tuned? I'd rather put what looks to be a pretty clean injector in, and get it back on the road, vs waiting on the cleaning process that from what I understand could mess them up. I'd rather put the $ towards a Y pipe.

Thanks
Matt

 

If you have a good OEM injector, just put that in and run it like that. dump a bottle of BG44K injector cleaner in it and see how that does.

 

rebuilt injectors don't work on these cars, due to the way that the injectors fail in the first place, which is electrical. i have some injectors left over from previous engine work... style do you have? thumb-tab or metal ring-clip?

o and btw i'm in raleigh but might end up in boone in january.

 

Naw, i don't go to asheville much. My injectors are working fine, the issue i pointed out lies specifically in the vtc's and or timing. nearly 100% sure of this.

Don't bother with cleaning the injectors, as instructed above, just replace the suspect bad injector with current used or new injector.

 

Well I'm going to grab a new manifold gasket, some fuel line and put it back together.

I have the thumb clip connectors and I'd love to have some extra injectors If you want to work something out on them let me know.

If you come this way, email me, we have so many great roads. I don't see many Max's in good shape around here.

mattz78@hotmail.com

Matt