Car Running Very Rich by Pete From Tennessee

[Roger]

You said the timing is at 10 degrees BTC.
Question: Do you have one of those harmonic balancers with 3 timing marks on it?

If so, did you use the center mark (the thicker of the 3) to set timing?

If that is okay then there may be an intake gasket leak. This won't throw a code.

And if you're getting MPG to brag about, have you checked the Oxygen Sensor? (You say that it is runing very rich too? Something here ain't adding up.)
Bad O2 Sensors will not necessarily give you a code.
(I don't know how to tell you to check these and I don't know the mileage on the motor or, if it's ever been changed).

What I'm getting at is by what I understand, you have a lean fuel condition. Therefore, intake gasket leak, timing too advanced, O2 sensor shot.

Does it backfire when you decelerate?
Is it just LOUD?

In which case have you checked for exhaust leaks?

[PetefromTn]

Actually  there is no backfire issues at all. The  car does surge some and has a miss feeling when you are driving but at constant RPM it smooths out somewhat still ^%!)ty but smoother.  The compression numbers were in spec for an engine of its age.  The car has around 100k OR so and I timed it off the  coil plug wire using two cylinders to take out any slop in the system.  There is definitely an exhaust leak ticking sound and when you Rev it up there is smoke from the engine bay a slight puff from the rich mixture.   I actually got a fellow sending me a used o2 sensor in the mail to make sure it is not that.  I dunno I have been all over the intake and ignition systems checking for leaks and could not find any. This ones a puzzler for me so far.   Like I said it starts right up and idles and runs and the way it drives is occasionally smoothed out sorta but never really runs right.  Frustrating thing for sure. I tore into the headlight motors over the weekend and need to order the gears  as soon as I find some cash.They look fine but one of the gears is smoked....always something right....peace

Pete

[PetefromTn]

Well guys still trying to fix this GT here.  I actually tore apart the headlight motors and am rebuilding them with some new gears. I am still trying to figure out what is wrong with the motor. Drove it around quite a bit today and it seems like it runs halfway decent at part throttle but accelerate or decelerating it misses pretty good and I noticed today that the oil pressure gauge on the cluster if that is what that is fluctuates quite a bit and when I am idling it drops down into the red quite often. Rpm makes it fluctuate rather wildly.  Not sure what is going on there. I would think if the oil pressure was that low I'd have fried the motor by now as much as I have been driving it lately.   The check engine light comes on when it drops down like that but then it goes away with some RPM after a second or two but never stays lit.  Lots of little itmes are annoying on the car but it is not terrible just barely better than terrible LOL....   makes me realize how nice the old 86 GT I used to have really was...damn I miss that car and the four speed also. Oh well any more ideas. Still waiting to receive the O2 sensor from the UPS guys and maybe that will help but I doubt it honestly. Peace

Pete

[Fierofool]

You said check engine light but do you mean low oil light?  With the gauge fluctuating, I'd check the oil pressure with a mechanical gauge to be sure exactly what pressure you really have at idle and operating temperature.  If you need to replace the pressure sending unit, I'd suggest paying the extra dollars, go to NAPA and get an Echlin or Standard brand sender.  Then check it at idle and operating temperature. 

AutoZone sells an old school mount-under-the-dash oil pressure gauge made by SunPro.  It's somewhere between 10 and 15 bucks and has the standard 1/4 NPT fitting for the end of the pressure line.  Exactly what our sending units have, so it's a direct screw in.  That gauge can come in handy for many years. 

It might be worthwhile to take a drive up or meet Derek somewhere and have him put a scanner on the car.  That should identify your rich burn and poor runability problems so you're not throwing money at it.

[Flyboy81]

I didnt have to hear you tell me that it backfired, I got to look at the car well before he got rid of it.  It did it while he had it here and I adjusted the timing which was severely retarded.  We set it up and got the timing correct and it sounds like it could be a wiped cam lobe.  They will still idle with a cam lobe half gone.  When they get to high RPM, they start to backfire, miss and carry on.  The car needs the engine pulled apart and gone through better than the last guy who said he was going to.  You've obviously have exhausted all other explanations and ideas...  The car was severely lacking in power and it had TWO mufflers on it because someone told Wes it backfired really bad and a lot and that would cure it.  It didn't and I explained all this to Wes once before.  The oil pressure can be very low and still provide enough lube at idle to keep the engine from seizing up.  That is still a good indication of detrimental internal engine wear or a bad oil pump.  You have never said what those compression numbers are and there shouldn't be any difference from age, they are either right or low.  If they are low or you have one more than 20% lower than the other, there is a problem and this could be your issue.  The car could still make good compression and have a wiped cam lobe.  The bottom line is that this engine needs to be pulled apart and gone through.  You can't just "tune up" this issue.  It would just tune the problem up, making it worse.  If you need to have someone do this, our garage specializes in Fiero repair and we can even tow it here for you.  BTW the o2 sensors are about 15 bucks at autozone, why get a used one that will probably have issues too? 

[PetefromTn]

Since I have owned the car I have never heard it backfire once. It has a bad stumble and feels like it is missing.  Other than that it idles fine albeit a Tad higher than normal and it starts right up. It is definitely down on power but again the compression checks good on all cylinders.  I am not really sure what is wrong with it and I already fixed several problems on the engine so it is not the same car you worked on really. It had a HUGE  fuel leak that I am actually amazed nobody else caught and the dusty looked like hell.  Right now I am driving it daily and if I could get it to smooth out I'd be amazed if it did not run and sound like a stock car should. I was also aware of the second muffler too and plan to cut it out here soon and stick a straight pipe in there. Managed to get the headlights rebuild last night and I want to install them and see if they work but it is pouring rain out and the shop is full of a customers project I am working on. Peace....

[Flyboy81]

Well, just hit me up if you would like us to take a look at it.  We are here to help.

[PetefromTn]

Derek,
      Honestly I would love for you to look at it but I don't think driving it up your way in its present condition would be the best idea.  It runs but it is not happy and it was bad enough driving it down here.from where I got it in that condition.  Been working on other things a lot lately and just now getting some time to tinker with the car.  It may wind up I have to pull the top end apart but I still am not sure it is not some kinda sensor problem or something stupid that I have not been able to find.  If you ever make your way down south here for anything and are in the area gimme a shout. Ill buy ya a nice steak dinner if you'll take a peek at it LOL.... Wes is supposed to be bringing his 300zx down for me to work on here soon I guess but I have not heard from him lately. Peace

Pete