Fastbird93

Ok, this is going to be long, so bear with me.

Back in August, I finally got my car back from Joe Prince, having had done a head and cam package consisting of JPR heads, 224/230 112* XE cam, 30# SVO injectors, Accel 300+ ignition, Pro Magnum 1.6 rockers, vented opti swap with a cloyes true roller, and a mezier electric water pump.

The first time on the dyno, August 12th, the car just ripped, says Joe. I have the sheet. 375/363 SAE at the wheels. Tune was a little lean up top, from about 4200 RPM on. Alvin@PCMForLess is doing the tuning. Unfortunately, when on the dyno, the car blew out an oil seal on the front of the motor. Turned out to be the opti seal, but the front had to come off and go back on. The crank seal was also replaced. During this time of maintenance, Alvin did me another tune, a little more rich up top.

We put the second chip in, and head back to the dyno. This was the first time I had driven the car since all the work was done. I immediately noticed a fast throttle movement "stumble" was present. Joe said he never noticed it before. On the dyno, we pulled 364/353. Air Fuel ratio was a sickening 10.5 at 2800 leaning to 13.0 at 6000. Something was amiss.

Fast forward to October. I got home from a six week deployment, and dove right in. I was through working with Joe at this point, on my own. I swapped the following over the course of the next 3 months: Opti, Plugs, Wires, Coil, did the ICM spacing mod, Oxygen Sensors, EGR valve, Fuel Filter, MAP sensor, and adjusted my TPS to a more friendly .74 at idle, down from a .92. Nothing was helping. I started using TTS Datamaster at this time also. After everything was swapped, I could finally get some good datamaster readings.

What's happening is that after running for approximately one minute, my right side Oxygen sensor mV would start climbing. It would move from 450 up to about 650 or so. Once the PCM swapped over into closed loop is when the real problem because readily aparrent. My right LTerms would bottom out at 108, and the left side would be in the mid 11X range. The STerms for the right would dive to 1 and the left would drive to the 40-70 range.

I spoke with Jay Fisher, of Jay Fisher Pontiac in Elmer NJ, and he asked about my fuel pressure. I told him it was 38 PSI at idle and 46 PSI at WOT (vacuum line removed). He said that's too low, even for the SVO's and I need to bump it up. What he explained to me was that if a fuel injector isn't getting enough pressure, the pintle won't open all the way, causing a stream of fuel to be injected into the airstream, instead of an atomized fuel spray. "Pissing" he called it.

So, I get a Hypertech AFPR. Set the pressure to 47 PSI with the vacuum line off, 41 vacuum line connected at idle. NO HELP. I put datamaster back on it today as it was the first time for the car being run after the new AFPR. One thing of note here is that with my stock regulator, the fuel system pressure would bleed to zero within six hours of shutdown. Almost 24 hours after installing the Hypertech and pressurizing the system, there was still 12 PSI of pressure in the fuel system. One fuel pump note, I get a pressure drop during acceleration, which is out of specs, but I'm not concerned too much with it because pressure is fine at idle and that's where I'm diagnosing this problem.

I ran the same tune as before, and as soon as the car got into closed loop, you could watch the STerms for both sides start driving down, then the LTerms for both sides drove down to 108. The Sterms stopped at 60 on the left and 74 on the right when the car jumped back into open loop for a second. After coming back into closed, they were reset back to 128 and immediately started driving down again, and the LTerms were stil bottomed out at 108.

Next, I tried a tune with the injector constants set up higher to try to lean out the car. The right LTerm only went down to 116 and the STerm went lean to about 132, but the Left side LTerm drove to 108 and Sterm went to about 68.

Now, about the tune, Alvin knows what he's doing, I have full faith in that. He has the car tune set up with the injector constants set at 27.9, even though they're SVO 30# and rated at 31.68 on a GM system. When I played with the constants, I set it to 31.68, and it made almost no difference.

So, I'm at the end here. I can't find any reason for my car to be running so rich. I believe my stumble/hesitation problem to be a secondary reaction to too much fuel being dumped into the picture. When the stumble/hesitation happens, it's a "pfft pffft pffft" kind of noise, like when someone is really out of tune while working on the dyno.

I'm lost, and about fed up. Six months, a lot of dollars, and I can't find anything wrong.

If anyone could offer any ideas, tips or assistance I'd be greatly appreciative. I'm posting this here because I keep getting the "it's the opti" or "check your plugs and wires" over in LT1 tech.

Thanks for your time everyone.

97WRAITH

I thought I read that you are going to change your fuel pump.Did you do this.Can any of your good friends let you try there know good opti? Just a thought.

Rob.

WhoBetter?

you've got all that money from working in the military, why don't you just forget about it and get a new car. I'll tell you right now with my job I don't have that kind of time to **** around and waste nor would I throw money by dumping it in a 93 car.

Fastbird93

Haven't done the fuel pump yet, mainly because the need hasn't arisen. I'm not getting any erroneous fuel readings off of it except for the pressure drop at light throttle acceleration. BUT I'm not even driving it. The diagnosing I'm doing is in my garage, just idling, and the problem is present. There's no pump lag or anything I can see.

And whobetter, I have no need to buy another car, even if it is faster. I'm happy with what I have and that's all that matters. The car is paid off, and I don't have to worry about full coverage insurance or anything of the like. It's strictly a toy, and it occupies my time.

Thanks for the help though.

MentalCaseOne

When did you last checked all the hoses, valves etc etc that connect to your Evaporative Canister located nicely way back there by your fuel tank?

I've heard that it has the potential to spit all kinds of fuel into your intake manifold when the valve sticks open. There is something about the Canister cracking up but I cant recall it now.. The chiltons book has some instructions on how to check the system.


Try it. Worse that can happen is that you make sure its properly working.


Marvin

brokenz

Man that was alot of reading. You still got your factory injectors handy? If so then try swapping them out. See what happens. It won't cost you anything atleast. Also you may wanna try just switching sides (left bank to the right side and right bank to the left side) with the injectors your running. See if this problem switches sides.
I'm thinking injectors cause your running those SVO's. You wouldn't be the first person in the world to have problems with new injectors. You can't imagine (well actually you can) the problems I had with a brand new set of Accels.

Fastbird93

That's something I haven't checked yet, the EVAP canister system. That thought occured to me, but I did'nt think it would be that pertinant enough to the system to cause such a load up. I'll give that a shot this weekend.

As for the injectors, the thought occured to me. Definitely not a sticking open injector, because the car fires right up almost instantaneously. If I do end up getting to the dealership with it, I'm probably going to have a flow test done on the squirters.

Back to the EVAP Canister system, I did notice that I was getting an excess of fuel vapor in the manifold. Could it really be so bad as to flood my system like that?? As for the purge valve and sticking open, we are talking about the valve on the side of the intake manifold right? I have a Chiltons and a 93 Servoce Manual, so having a look should be no problem. Thanks!

TraceZ

Hmmmm

During the first dyno run it ran properly, right?


The you redid the program to make it richer at WOT, right?


now you have problems??

Logic would conclude the last thing that changed (the program) is causing the problem. I'm not saying the guy didn't know what he was doing. Maybe he just made a mistake?

Do you still have the old chip that you can pop in and try?

EDS Z28

Does the engine go into closed loop after the required 3-4 minute warmup after starting it? If it does go into closed loop, which it should, the air fuel should be close to 14.7:1, no where near 10:1.
Running it this rich all the time will ruin the cat converter, if you have one.

Fastbird93

It's NOT the tune, because we've run the first chip again. I'm pretty convinced that whatever failure I've got is coincidental with the first opti removal situation between the chips.

It's not a 10.5 at idle, that was just the WOT portion of it.

I thought about the cat being clogged, but have pulled and checked a few times and it's fine. No worries anyway, because if I clog it I'm just going to move to an ORP anyway.

joeSS97

I bet you have checked...but are you positive there isnt an exhaust leak?

Fastbird93

Yup. Besides, wouldn't an exhaust leak show a lean condition by too much oxygen being in the mixture??? I'm having an issue of too much fuel being in the mixture.

Fastbird93

I found one thing to give a shot: EVAP CANISTER PURGE SOLENOID VALVE

From the text in service manual: If the solenoid valve is open, or is not receiving power, the canister can purge to the intake manifold at the incorrect time. This can allow extra fuel during warm up, which can cause rough or unstable idle. I wonder.....looks like I'll be swapping solenoid's between cars tomorrow....

MattysTA

here are my thoughts.


1 bad pcm. regardless of the tune if the pcm quad drivers are bad it will keep doing what its doing no matter what tune you have in it.

2. do you have cats? i had a similar problem to youres but it was on the passenger side only and it turns out that my right cat is clogged. hope this helps.... good luck

brokenz

I still say swap the injectors from one side to the other. It should take less than an hour to do and if the split still favors the same side then you know that it isn't an injector issue. Atleast from that standpoint. If it changes sides then the problem become pretty obvious.