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.

Sean94Z

Did you check for exhaust leaks in the header gasket? How about leaking at the y-pipe connection. ANY leak will cause your O2 sensors to read off and then cause the PCM to run richer..

How about vacuum leaks? Have you hooked up a vacuum gauge? What kind of vacuum are you seeing?

--Sean

Fastbird93

I don't have any exhaust leaks, and can't find any vacuum leaks. I'm pulling about 15 in hg of vacuum at idle after playing with the closed TPS spark advance table some.

I just can't seem to find anything at all.

OneFlyn95z28

93 , Raising the fuel PR was like shooting your self in the foot. you just added even more fuel(litraly) to your problem.

At this point the best and cheapest thing for you to so is get tune cat for your car and a chip burner. the tune is rich and needs to be addressed.

SVO injextors make the problem even worse. you see the SVO injector resonds completely different to fuel pressure changes then our stock injectors. As much as people would like you to think you can just toss them in reset the injector constant and go you can not.

To run a SVO injector properly you need to rewrite the ENTIRE fuel table. Like I said some will argue but I know for a fact I am right and have tuned them a time or two my self. If you just change the constant and injects volts you will always get a fuel curve like you have now or had before. It will be rich at idle and fine on top or fine at idle and lean on top. No free ride.

Some will tell you all kinds of band aids but in truth you need a real tunner to build a file for you or build it your self

Good luck on your project man and may it turn out good!

rskrause

Ramdom thoughts: Hook up a wide band and see if it is really rich, just to be sure. Did it run right before the work? Sure there's no exhaust leak? If it's really rich and there are no mechanical problems like an exhaust leak or electrical problems like bad O2 sensors than it needs drastic retuning. Your combo is not as drastic as mine, but if you saw my tune you would see what I mean when I say "give it what it wants, not what you think it needs". My displacement is set at 60ci/cyl and my base FP is at 55psi. That's what it took to get it to run right.

Rich Krause

Fastbird93

I have Tunercat and a Chip Burner already. Been burning my own chips for a while, getting tunes emailed from PCM For Less.

I only raised the pressure as a test because of what Jay Fisher told me about the injectors not seeing enough pressure for the pintle to fully open. Aparrently not the case with me.

The car ran fine before the H/C work, and immediately thereafter ran fine says Joe. I'm thinking I've had some sort of mechaincal failure in that short time between the two dyno sessions.

One thing that was brought up to me was the EVAP Canister Purge system, and the possibility of the valve sticking open. It was said that the stuck open valve would dump a disgusting amount of fuel into the system. Thoughts???? It's something that I've thought of but did'nt think would play into the problem.

Hot Rod Hawk

Ya know Rich is correct you should check again with wideband o2.
Another thing ya might want to do is a emisions sniffer test paying attention to the hydocarbon count. Lean running tune will stink, burn your eyes, and kinda make you think rich but its not....
HC count will be very high if lean.
For a 94 LT1, I belive 120 is the max recomended HC count.
just my .0000025671 cents

Eric Bryant

On my car, running the stock fuel pressure regulator and the red-top 30 PPH SVOs, I had to bump up the injector constant to something insane like 35 lb/hr to get my BLMs in line (sorry I can't remember the exact number - I don't have LT1_edit on this PC). That's stock MAF with the stock MAF tables, etc. - nothing in there that would tend to throw things way off. That's just my experience with the matter. Oh, and that's also running revised injector offset tables. My tune off frickin' everywhere when running lower injector constant values. Obviously, you need to progress very slowly when making this sort of a radical change, but it got the job done on my car. You said that changes in the injector constant aren't really resulting in significant changes in the BLMs, which I take as a sign that you haven't gone far enough yet.

Once I got the injector constant figured out, all those little changed I'd be making to the tune prior to figuring out the real problem really paid off, and the car just flat-out ran great.

The fact that you blew out an oil seal after taking a dyno pull with a lean tune worries me just a bit. If I were you, I'd think that doing a compression or leakdown check would be a good place to start. I'm not saying that you broke something internally, but it should would be nice to know that for sure before sinking any more time and money into it. If you've got a cylinder leaking-down, it's not going to be possible to tune around that.

Oh, and get a better fuel pump if you're dropping fuel pressure on the high end. You won't be able to get a consistant WOT AFR by simply trying to compensate in the PCM tune, and eventually the motor will suffer.

Sean94Z

Your car is a 93, so, it is Speed Density right? What do your VE tables look like? I might try getting something like VEMaster and running it a few times on your car, just to see if anything changes..

Either that, or make some DRASTIC changes to the VE tables to see if something changes for better or worse, then go from there..

--Sean

Chris B

FWIW fuel pressure will hold the pintle *closed* - it's the electric current that opens it. Ford also rates the SVO's at ~2.7 bar (~39psi) so I would submit that the spray pattern would be just fine there (it is).




Swap the o2 sensors from side to side and see if the problem follows the sensor, or stays on the side.

If it stays on the side then it could be

Exhaust leak
Localized vacuum leak
Coolant/oil control problem

If it follows the o2 then you have a problematic sensor. Swap them both out. Also I noticed you have a 93 - if you have longtube headers and haven't converted to heated O2 sensors this would be a good time. You can just get a 3-wire heated bosch sensor - run the signal wire just like your stock wire, ground out the heater (-), and relay the heater (+) to acc.

If your sensors are dying, esp. on a single side, it is 95% a coolant control problem on that side (read: headgasket).


Also blowing out seals on the dyno, as was mentioned earlier, sounds like massive blow-by to me. I would definitely do leakdown/compression test.

Fastbird93

Ok, the O2's are brand new and look fine.

I haven't done a leakdown test, mainly because I don't have the gauges for it. I'm hoping that the seal that blew out was an anomaly rather than something bad.

The car runs fine. Outstanding at part throttle, and once the initial stumble happens when I goose it into WOT, it runs like a raped ape all the way to redline. It's just at the initial fast throttle tip in where the load up affects it.

If I was indeed getting the blow by and a cylinder leaking down enough to affect the motor like I've been seeing with my idle testing, it shouldn't run damn near perfect everywhere else in the powerband.

I'm still going to back up my tuner because of how the car performed the first time on the dyno. When the second tune came in, all he did was add some fuel up top. But the car was rich across the board, indicating some other problem being present.

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....

got_hp?

hmm........thats the first ive read of that......im just about to purchase some ford motorsports 42lb injectors (those are svo right?), so im glad you posted that..........what type should i get instead?

LiT1_up

Hope this will help.

http://www.noid.org/~lj/PCM%20Tutorial/SplitBLMinfo.htm

Fastbird93

Interesting read. I'm not so sure that could be the cause of my problem since I'm NOT reading a split at idle anymore. After putting the new AFPR, Both of my LTerms, or BLM's, were dead on with each other while plummeting to 108. The only reason I got the split was when I reset the injector constant to a higher rating to see what would happen.

In either case, my split isn't what was described. My split is just a few, plus or minus from about 7, both to the rich side. I don't have a rich/lean split.