1993Fast_Z

my 93 Z does this too, i checked the oil when i changed it and it was fine, no fuel contamination...it runs very rich, and from what i see, it looks like a cracked exhaust manifold...02's have never been replaced with 150 k on em, plugs etc. have been changed, and it has a miss almost like it is hitting rev limiter at 5,000 rpm, but it is only some days it does this...hopefully someone can help me....oh and yea, the oil pressure is around 50-60 psi, what are you guys running at?

DiabloGT

does anyone know how to fix this problem at all though? fo rme it was all fine after headers/exhaust, it just happened after the pcm tune, what could that have done to make me run rich?
thanks

1993Fast_Z

when then do these pcm tunes, do you think they assume you have aftermarket top end's? maybe they are cranking the fuel up on these tunes...other than that, couldnt tell you...go to the junkyard and get a stock pcm and see if it fixes it...

Honda Hunter

Let's not be quick to blame the tuners especially if it's a mail order tune. Tuning a car that's no where near you is already hard enough, then it gets a 100x's harder if you have unaddressed issues before the tune that no one was aware of. This was the case for me. I had a couple of small issues I think where getting in the way. Now I have most addressed and once I run the race fuel mixture Ill have a understanding on the last issue and what I need to do next.

Guest47904

Any time you run rich, the oil is the first thing you check. The most common way it gets there is a plug that's not firing. The injector still fires and the cylinder gets washed down. Some times called souping. This can over time be major causing cylinder and or ring damage.

Other ways it gets there is a leaky injector or a FPR that has a hole in the diaphragm.

this post is getting too long for anyone to follow. Someone needs to list the people that are having this problem and get madwolf and injuneer involved to help.

Honda Hunter
1993Fast_Z
DiabloGT
cammed_aro Z28
cmking26
MyZb383
TransAm2k4

Honda Hunter:
Why don't you get a can of octane booster rather than try to find racing fuel? Will accomplish the same thing but it's much easier to mail a can of octane booster.

1993Fast_Z:
Are you simply pointing out the problems(exhaust manifold and O2's) or are you planning on fixing them?

DiabloGT:
Get ahold of someones stock PCM (that you know works) and give it a try. Don't get one from a junkyard. Why would you waste your money on a tune, you haven't really done anything??????

Guest47904

Well with the addition of 2 more folks, we have either found that not everyone has the same cause of the problem or, the only thing common to all y'all is headers.

It would be nice to know what everyones injector pulse width is at idle AND as Injuneer pointed out a long time ago, what is the BLMs.

Honda Hunter

Well as I stated before I'm sure my problem was because of small issues that are for the most part resolved. I just need a few runs on the dyno, some race fuel and a better understanding of how to tune out low octane retard and knock sensor / spark retard and Ill be on the right track. It's gotten to the point that I may be ordering a stroker kit on the 15th so it may even be pointless to even continue with trying to figure out my current setup since I'm looking at 3 week down time for instalation and head work.

nitrous_feen

Is everyone running a 160 thermostat?, I know a few are. Mine runs rich but its from a bad adjustable fuel pressure regulator, its stuck on 45-46psi.. I thought it was vaccum but its got 16inches at the port with a new vaccum line.

DiabloGT

im running a 160 thermo, and to speedy i was curious to see if i would feel any gain, cause right now im just doing small stuff till hopefully soon i can do both bottom and top end

Injuneer

I read through this every once in a while, but there are so many different problems being posted and the thread has been hijacked by so many people with not exactly the same problem that it makes it pretty much impossible to make any sort of intelligent posts. I tried to help the guy who started the thread, but its a mess of a thread right now.

There is benefit in sharing the symptoms and modifications, and the number of people who have had their heads milled and may have an intake sealing problem is interesting.

ktg

I basically did almost all my mods at once last winter, that's when it started.
Here's a list of what I can remember that I've done since then, all with no substantial effect on the problem.
Replaced: 02 sensors, FPR, MAP seal, injector seals, fuel filter, opti, plugs, wires, all vacuum lines, aic, pvc, temp sensor in WP, new heads and lifters and all new gaskets to go with them.
The TPS and MAP seem to be reading fine in Datamaster.
Ion says he's sure that it's not a problem with the PCM and I'm sure that it's not a problem with the tune.
Fuel pressure is in normal range but bleeds to 0 in about 3 hours.
I've tried to check the injectors by pulling the fuel rail and priming the system to look for leaks but I don't have the clips on the injectors and when I prime the system, the pressure pushes one of the injectors out of the rail. 30 lb injectors should be here next week.
I did try locking the car in open loop and it runs better than in closed loop.
BTW, I didn't check my intake for straightness.

jkucz31

My car is running rich too but i just got my comp tuned and im thinking it might be plugs \. If they were misfiring would a check engine light come on and would you be able to feel it

Guest47904

No it's not from running at 46 pounds of pressure. My Aeromotive pump using a stock FPR will run up to 50 pounds in the winter. Never once had a problem with running rich with stock injectors. I find that the hotter it is, the lower the pressure is and vice versa. I attribute it to atmospheric pressure variation.

nitrous_feen

my FPR is adjustable from 30-60 and it is stuck, I have a friend with a "twin" car, we tune his at 39psi, mine is stuck and wont go any further, Ive gotta send it back for another one.

Injuneer

No SES light for misfires on your OBD-I 94. Only the 96/97 OBD-II engines have misfire detection. You should be able to feel misfires when the engine is under load.