I have a 1991 TA TPI 305 w/5 speed.

It is modified with:

SLP headers and 3" exhaust
Crane Cam
SLP intake runners
SLP air foil
SLP High Performance chip
Crane roller rockers
TPIS big mouth intake
Accel 23# injectors
AFPR set at 47 psi
Racetronix high flow/pressure fuel pump and wiring harness
New fuel filter
All new ignition items (wires, cap, rotor, etc)
Jacob's Pro Street Ignition

The car is very fast and responsive except at WOT.

At WOT the car jumps and hesitates. Right before WOT everything is fine.

What could be causing this?

I am going to put my stock chip back in to see if the advanced timing is a problem or maybe something else with the chip?

I already put the ignition back to the stock coil and it didn't make a difference so it is not my Jacob's Ignition.

I am thinking that I need to get into some PROM burning and have began reading the basics.

What should I begin to change in the programing to help with my problem?

IAC
Injector Constant
WOT tables


Thanks for any suggestions.

 

Before I even went there I would be sure that you are not running out of fuel.Filter need changed? Pump going bad?

 

Please read my post????

I mention what I have changed already, including these two items.

What I have been told so far is that I am bogging down because I am running too rich for now before the supercharger goes on.

I was advised to change the prom settings for the injector constant.

Just wanted someone to confirm that hesitation and stumbling at WOT could be caused by running too rich.

Any other ideas or suggestions?

 

Anyone else??

 

Did you check your fuel pressure?

Make sure you dont have any vacume leaks and that all your plugs and plug wires are ok! Sometimes you can have a miss and not feel it until you really get into it!

 

Fuel pressure is fine now that I have the Racetronix set up.

Note that I have excellent response and accelleration till about 97% WOT. At full it goes to sh t.

I am thinking that it is too rich with the 23# injectors and I need to program a new chip to compensate.

Just wanted some experiences on running too rich at WOT and seeing if others have had this problem

Looks like just me.

 

Dead spot in TPS? Its cheap....change it and see.......

 

Good suggestions. Please keep them coming.

But in reply to your suggestion. I checked the TPS with my autoxray scan tool. TPS volts increase smoothly throughout position of throttle.

 

I read your post but you need to understand that it is not very common to get a rich misfire unless your ignition system is to weak or your plug gap is too big.
Make a wot pass and turn off car while in WOT and pull a plug.
Is it very black and wet?
The TPS is a good place to check also like mentioned ,what is voltage showing at WOT?
have you ever checked fuel pressure at WOT while this occurs?
What your base timing set at? whats your scan tool showing
under WOT spark adv?

 

Thanks for the ideas. I will do some runs and look at these things.

Will update after I get the information.

 

Here are some values from a previous run.

TPS volts at WOT = 4.27 V

Base Timing = 16.8 deg

WOT Spark Adv. = 22.7 deg w/ 1 deg knock retard

BLM = 128

INT = 128

MAP = 4.76 V

O2 Sensor = 876 mv

Fuel Pressure at 50 psi w/ stock failing pump

My fuel pump was going out as the fuel pressure would drop at WOT. I thought this was the problem, but it still does it with the new high flow pump, hot wire kit, and fuel filter????

Does this tell you anything???

Looks OK to me???

 

Man you are running a pretty high FP!! I think I would have tuned that sucker from like 45 or a little lower!

I guess everything looks ok from here, but we would really need to see the scan file and or an export from it!

 

his fuel pressure isnt high at all especially with a high flow pump to support it....stock is alittle over 40.....i got mine set at 55 with the stock injectors and the car performs amazingly....w/sportsman2heads and 502/510 lift 224/230cam, 1.6 rockers, 52mm t.b.,shortys to a 3 inch catback slp runners

unfortunatly with a stock chip

 

Actually I am running 40 psi now with my new high pressure Walbro pump and still have the same stumbling/hesitation problem.

I also have a periodic problem with the idle just dying off till the engine kills. But if I start it and give her some pedal (not WOT) the car just takes right off with no hesitation???

I am really thinking that my WOT tables need to be modified with my current set up.

Also my idle tables.

I will post the AutoXray files shortly.

Thanks.

 

I have some new observations with the hesitation and stumbling problem.

I found that if I am in second gear and gradually increase the pedal angle before going into WOT then the problem does not occur. So what is happening is that I am not going into WOT untill I am at about 4000 RPM.

So what it is looking like is that by going WOT at too low of an RPM then I am putting too much fuel in then what is needed and causing the engine to stumble. By waiting till the higher RPM to go into WOT, the rich fuel mixture can be tolerated better and does not cause the problem.

So it looks like if I change the injector constant to produce less fuel the problem my be solved.

Opinions?

 

Maybe take some fuel out of the VE tables!

 

Yes. I think I will go that route and see what happens.

I am going to install my supercharger over the holidays and will begin tuning after that.

I am sure that this will open another can of worms.

 

I would suggest fixing the problem you have before you proceed with the blower install!

 

just a thought here whats the wot a/f ratio at ? or more correctly how the PE vs RPM table filled out. with stock injector they might have hads to push it up to very rich in a/f calculation term. but with more fuel flow that could be way to much fuel.

 

Exactly Funstick.

That is why I am going to see what happens with the SC install. It may be that the higher air flow from the SC will fix the rich problem I am having now with normal aspiration.

I appreciate your comments Poorboy8. I will just test drive it with the sc on to see if the problem persists. If so, I can remove the drive belt and tune from there.

But I suspect that the entire problem is from a rich condition caused by the upgrades as recommended for the sc and still running normal aspiration.

I will update. Got the parts layed out as we speak.

 

I still stand by what I say.....I guess I just figure it's better to try and fix the problem before you go adding another potential one

On the other hand I agree with funstick and think that the blower will definately want more fuel.

Definately keep us up to date, I'm interested in seeing what happens!

 

Thanks for the support. I will be cautious.

I am installing a kit that was custom made for list member Willie.

Am running though some trial and error fitting the intercooler tubing right now. Cut one of the Damn hoses too short so I need to try to find a local replacement.

Fun though.

Am excited to see the outcome. Looking for a 400 HP little 305!!!

Keep you posted.

Also see the post under power added named twin intercooler started by Willie.

 

yeah I remember you from over there, I've been one of the guys WAITING for the out come of this setup, because I have been toying with the idea of a blower sometime soon maybe!

 

I have been working with a PROM programmer from www.pcmforless.com

His name is Alvin and he is very familar with the programming of our 3rd gen cars. :hail:

He initially took the modifications information done on the car and sent me a first run prom. I provided him (through email) data using TTS software collected with my laptop. He then reprogrammed the prom file and sent it to me via email. I burned the program into the prom using pocket programmer II.

We went through this process about 6 times. But now I have a prom that gives the car perfect start up idle, very sensitive accelleration and incredible power at WOT!!!

I highly recommend his services. He is friendly and motivated.

We exchanged files this last weekend. He would take less than an hour to send me a new prom file from the time I sent the data.

Hope this helps other list members.

 

Wow that is great, although I dont understand why you wouldnt just go ahead and get the Tuner cat software and start doing some programming on your own. It sounds like you have everything except tuner cat and or winbin or whatever.

 

Would you happen to know what the fix was for your initial problem? The hesitation and stumbling at WOT. Was it what you were thinking, too rich?

RBob.

 

ttt

 

Yes I believe it was the problem. Once I added the supercharger and gave it more air the problem is gone.

I do plan on learning how to program my own chips that is why I bought the pocket programmer. But since the car is my daily driver, I wanted to get it tuned right away.

This was actually a good first experience. Although I did not create the program, I went throught all of the other steps. As of collecting data and burning the prom. Fun stuff!

 

OK thanks for the update. Nothig wrong with taking the ECM programming/tuning stuff one step at a time. Can be overwhelming otherwise.

Are you planning to go with a 2 bar MAP & some boosted code? (IE: $58).

RBob.

 

Yea. But I need to read up on it.

Do you know of any good tech sources or threads?

Thanks.

 

RBob,

Pardon my ignorance, but the $58 code is Turbo Grand Prix (6 cyl) correct? Does this mean that if you change the cylinder select it will run a V8? I've been wondering about that for a while. Somehow I didn't think it would work with spark advance being calculated with a 90* in the formula somewhere. Again maybe it's just my inexperience but don't V6's fire on 60* intervals?

I'm not questioning you, just trying to learn as you are far more advanced with this stuff than I'll ever be. I just wished you used the '730 as that is what I have. I try to adapt your '747 info to my '730 with varying results. Thanks.

Regards,
Gary Anderson

 

I think my post dropped off the face of the earth or something. Try this link:

http://www.diy-efi.org/gmecm/ecm_info/1227749/

Don't miss the P4 doc.

RBob.

 

You guys' have to spend more time wearing out the search feature and the archives.

The TGP is $8F, the $58 mask is SyTy and Sunbird/Grand am.

Most masks handle the differences between 4, 6, & 8 cylinder engines. It is a cal parameter. Some don't calc an airflow term properly (always zero) when set to an 8 cyl.

RBob.

 

Thanks RBob,

Now I got some good reading to do.

What kind of projects do you have going???

 

LOL, projects? Way too many. The short list is I'm halfway to having the Elky w/EFI. Running a '747 for ignition w/carb at the moment. Fuel return line is in, surge tank built. Have another (fresh) engine waiting for warmer weather with a TBI on top. Gonna' use the old carb for a flower pot!

Helping someone else out with an EFI conversion on a '68. First was going to be TBI, then LT1 intake, now he is going with a port injected Torker intake & '727. Heck, he's doing the mechanicals, so doesn't matter to me. Once he bolts something on top I'll do the ECM side .

With winter having set in here I've been busy with code, that and school. Inside stuff. As they say, getting ready for the spring thaw.

RBob.

 

Hec. I just came from outside to install the latest chip I burned new code to!

I am in Louisiana. It gets cold here. But cold for us is 30's !!!

Right now it is sweater weather. Winters are mild but summers are brutal!!!

Keep warm.

Nice chatting with ya!