ptc92rs

I dont even know where to start because the problems are everywhere. Short history: The car was originally a 305 TBI F Body. The original moron thought a TPI setup off a 350 would convert his car to a screemin deamin so armed with a pocket knife and scotch tape he began to splice in the TPI to the TBI harness. Months later frustrated with his then 1 year old '92 RS the car is sold cheaply to Sucker # 1. Many parts and much money later the car starts and runs, sort of. The car is used rarely for several years until one day along comes sucker # 2. (Me) For the last two years I have been trying to make this hybrid run right. Last fall I replaced the 305 with a freshly rebuilt 350 from a '93 Roadmaster and a new chip for a '92 Z28 350 which magically fixed most problems but I am still left with a few. Every once in a while when accelerating from a stop at WOT it just falls on its face, if I let up on the accel. it takes off but as soon as I return to WOT it falls on its face again. WHY??????? I have just about exhausted my patients and budget. ALSO... It has absolutely no power at all. A 5.0 Mustang (stock) will EAT this thing. The motor is new so it has to be computer related. I have played and played with the timing to no avail. Cant run more than about 4 Deg. base timing or I get a detonation problem. This is my first GM product and Im still figuring out the electronic sys so any HELP, Pointers, Suggestions, or otherwise would be GREAT!!!!

88 GTA

Its funny you mention it. My friend just put in a stroker motor, it too does NOT pull at WOT, but if you back off the pedel a little, it runs like a raped ape! We have not figured it out yet, but I'll let you know if we do. Please do the same for me.

dave

ptc92rs

I was thinking that maybe the TPS needs adjustment. Does anyone know the proceedure or if that would even help?

'89Formula305TPI

you should look at the 'tech central' I believe there is that particular procedure.

ArnoldBraker

Please post your solution. I have similar problem but haven't had time to work on it. I am thinking it's either fuel pressure(It's worse with more people, ie weight, in the car) and or TPS. Thanks. ~Arnold

86TpiTransAm

Ok, guys! For all of you who have just upgraded your engines and are experiencing these problems, here's the steps to check.....1. did you upgrade your injectors?? A built 350 and definitely a 383 are going to need AT LEAST 24 lb/hr injectors and an adjustable fuel pressure regulator is very advisable too! Step 2. If your car has speed density TPI and you upgraded the engine, your WOT problem COULD be caused by the chip....MAF TPI does ok with the stock chip but speed density TPI just flat blows with the stock chip if you've upgraded the engine!! Follow the steps in order....step 1 first, if this doesn't help or you've already done this then go to step 2 and get a custom chip!

(Oh yeah, black electrical tape usually works better than scotch tape!)

------------------
1986 Trans AM
305 TPI
4 Wheel Discs
9 bolt Borg Warner Rear
Completely Stock
Soon to upgrade to a 383 stroker w/TPI, Hedman Shorty Headers, 64cc Pocket Ported Worlds Product Sportsman-II heads, ported intake, comp cam, TPIS air foil, Adjustable Fuel Pressure Regulator, and 24 lb/hr SVO injectors!
Current project: Keeping my car running until I get the money for the above mentioned project! :-)

[This message has been edited by 86TpiTransAm (edited January 28, 2001).]

Bill91Z

You figure this out, you're a god...well maybe not, but I would love to hear your solution. Reason being. Had a new long block put in my 91. Same motor form GM, 305. Nothing different. Only thing I added was a complete intake from AS&M and SLP PROM. What happens??? Same thing as you. I hit 4000rpm at WOT and the car dies...I back off and bam, it will rev to 5500 no prob. I have had this car on Diacom, and everywhere that has the capabilites to diagnose and have nod no luck figuring it out. New ECM, wiring harness is mint, all sensors replaced and adjusted by me so I know they are done right. Ignition has been checked and I have run with an MSD 6al with no improvement, new distrubutor too. I would ahve to say injectors are not the problem on a mild 350, in fact it's better to run a smaller injector at a higher psi. Willie has run 19lb injectors on his blown IROC so I highly doubt you are running out of fuel. In fact, I have the same prob on my 305 and know I am not running out of injector using a stock cam and heads. Good luck

86TpiTransAm

Your problem could very well be the PROM you added!! Aftermarket proms don't do much for a car when you've upgraded the engine!! Especially a speed density car and since you have a '91 it's most likely speed density!! Could be a problem with the programming in the PROM too! Believe it or not, it's possible to get a faulty PROM!! But hey, before you go messing with all that try this....is your ignition module new?? If not, have it checked!! Also I've heard that if you get those MSD 6AL boxes wet one time they're screwed but I doubt that's your problem! Just a little food for thought!


------------------
1986 Trans AM
305 TPI
4 Wheel Discs
9 bolt Borg Warner Rear
Completely Stock
Soon to upgrade to a 383 stroker w/TPI, Hedman Shorty Headers, 64cc Pocket Ported Worlds Product Sportsman-II heads, ported intake, comp cam, TPIS air foil, Adjustable Fuel Pressure Regulator, and 24 lb/hr SVO injectors!
Current project: Keeping my car running until I get the money for the above mentioned project! :-)

87Z-ya

iTrader: (1)

Id have to say its a ecm/chip problem also. I have a gm 350 chip in my car and it runs ok but is well off its potential. Try setting the tps at idle with like .38v and wot right around 4.0v and see if it improves. With a hyper crap chip my car would run terrrible if wot was above 4.2v

------------------
87z 383,afr 190's, crane hyd roller(224/230-.509/.528,112 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, strange 12 bolt, tremec 5spd, , 1,3/4" slp headers.

Grim Reaper

Yeah, I would lean to a mis-matched eprom. The problem is probably a combination of the VE Tables (that control your fuel mixture) and Spark Tables. Surprisingly, it may be that your are too rich. A lot of people do some mods; crank up the fuel pressure, relocate the MAT, bypass the TB...thinking they need more fuel, when in fact they need less. If you were running lean you'd know it, as you would be hearing big time knock even with octane boost and 94 octane gas.

Amazingly, I am finding that overly rich seems to introduce "inaudible" knock (or possibly false knock, which triggers the knock sensor thus retarding the ignition and further making the performance suffer. If you encounter just a little knock, richening will help eliminate the knock. But if you are way too rich, richening seems to compound the problem. I suspect that when you are running overly rich, some of the "weaker" injectors are maxing out on the duty cycle and causing an injector imbalance.

The solution is simple, get into eprom burning...plain and simple. Bite the bullet, invest the time to learn about it, invest so money in the equipment, software and a good scan tool and never look back.

It your setup is way off, no custom eprom writer "from a distance" will be able to write you a chip that will work properly IMO. They will use a "formula" chip and if you "don't quite fit their formula" you will be SOL. You need to get "hands on"...see what your engine is telling you...learn to analyze your scan tool readings and get your air fuel mixture back in line.

Once you get your eprom more inline with the what the engine wants (even if not exactly correct), everything will start to function logically again. But right now, your engine seems to be running as if you had a 1000 CFM dual quad setup, when it really wants just a single 650.

Its funny, but with EFI, people keep thinking MORE FUEL is the answer, when it is often the problem.

JAY87GTA

I had somewhat the same problem, see if this helps. 2 years ago I put on an AFPR after reading all the mags and stuff. Everyone said, "Jack the fuel pressure to 50 and it runs great!". Well my car started to have zero pickup at higher RPM. Well I started to have a startup problem that I am sure is related to my injectors leaking down and flooding the motor. But in the process of trouble shooting I turned my fuel pressure back down to 42 and guess what, I go to pass someone now and I have to let off just as I get even otherwise I'm doing like 90mph. So I think its like Glenn said, "More fuel isn't always the answer." Hope this helps. Later

Grim Reaper

Jay, after my own experience with higher fuel pressure (compounded with other mods that added even more fuel), I concluded that shorten the pulse width by reprogramming the eprom was the ultimate solution.

I started altering my eprom with the fuel pressure as low as I could set it (it was still too rich) and eventually I started to see the results. As I DO believe in the concept of higher fuel pressure, I then increased to the level I wanted (48 psi) and readjusted the eprom again. That is when I noticed that cranking up the fuel pressure does not work in a linear fashion. I only had to make a very minor adjustment to lower MAP (high vacuum) area of the VE tables, a larger adjustment to the middle MAP values and the largest adjustment to the high MAP values.

It makes sense when you hook up a fuel pressure guage and see only a minor increase in pressure with the vacuum line connected and a major increase (and where we measure it) with the vacuum line disconnected. I've concluded that the real fuel pressure you are receiving at all vacuum ranges is more important that I previously thought.