RMC030

I need some help on a very strange problem! This may take some time to explain. I have a 1988 Trans Am. Originally the car was 5.0 throttle body/automatic. I pulled that motor and trans and put a 5.7 tuned port injected motor and converted to a 5 speed.

The engine: rebuilt 82 to 92 5.7, .30 over flat top pistons roller lifters little beefier cam. Only change to the heads were stainless valves. All sensors were replaced with new. The injection system is from a 1989 T/A. Motorcraft 24 lb/hr injectors (as recomended by Ed Wright) Stock throttle body. Stock ignition.

Electrical: The wire harness, ECM, 5 speed, and everything to convert to 5 speed came from a 1988 GTA 5.0 TPI. The harness is equipped with a cold start injector, but my intake does not have one. I had the chip made by Ed Wright Automotive in Oklahoma. All the specs for the engine were sent to them and they made a chip. They removed the VASTS pass key, set the fans to come on at 180 with a 160 thermostat. A high volume fuel pump was installed in the tank. A new 5.7 Mass Air Flow sensor was installed. Both fans were wired to come on at the same time for better cooling.

Problem: After all of this the car runs perfect when it is cold. When the car reaches temperature, after about 10 minutes of run time, it begins to break up at top end of each gear. By this I mean it feels like it is starving for fuel at half throttle and above. When the car cools down for a while and it is started again, it will run great until it warms up. I documented all the scanner numbers during the problem and sent the chip and numbers back to Ed Wright. What they did to the chip I do not know because they did not send me any paper work when it was shipped back. Problem still exists.

Trouble shooting: I deal with a shop in my town that is well versed in GM performance cars, from muscle cars all the way up to late model TPI. Fuel pressure was checked- no problem. Ignition was also checked- no problem. Oxygen sensor (new)- no problem. Several sensors were disconnected and the problem was still there.

Overview: The problem is not there when car is cold. Problem is there when car is at temp. Problem is not there at idle. Could a bad Coolant Temperater Switch (CTS) located on the front of the Intake manifold cause this problem?
I NEED HELP !!!!!!!!!!!!!!!!!!!

bulletboy29

Does it have an ignition control module? That's what it sounds like. They are hard to test if they are only acting up when the engine is warm.

I had a similar problem recently and it turned out to be low fuel pressure, but mine has a carb.

CTS is a cheap thing to replace, so it couldn't hurt to try.

What about EGR valve? I don't have any experience with TPI, so I'm just throwing out everything that people told me could be wrong with my car.

CaysE

Ignition timing? Maybe bad gas? Getting any codes? What sensors were disconnected?

RMC030

The ignition module is new and good. I clamped off the return fuel line to boost the fuel pressure and the problem was still there. The EGR is new and good. The timing is fine, runs good at idle and when it is cold. Gas wouls be all the time not an intermittin problem. As for the sensors, I disconnected the CTS but the problem was still there. I don't know if it was because there was no signal going to the computer. According to the TPI Swapper's Guide, the CTS controls the fuel delivery at differant temperatures. Being that this is a fuel/ temp related problem, I am going to get a CTS and try it.

Hopefully this works!!!!!!!

87Formula4bbl

Try another ignition module. If the car acts the same way with both (new) modules then you can probably pretty much rule it out. Otherwise I'd say there's still a chance your 'new' one could be flaky.

ridecamro

sounds like your ecm isn't advaning your timing. check your knock sensor. it could keep retarding the timing if it thinks it hears a knock. also if the igntions mod. isn't getting the signal to the ecm your running in base mode. which isn't good. check all the conectors. try a diffren't ignition nod. and check the knock sesnor

Air_Adam

Did you get a knock sensor for a 5.7? If you took a knock sensor from a 5.0, then you have the wrong one.

greezemonkey

iTrader: (14)

Try putting the est in by-pass mode, this will pull all of your advance out, it may run sluggish but this will be a start to find out if the ignition system is to blame. It really sounds as if you have Too much advance, have you checked the total timing with an advance style timing light? Realisticaly you could get away with 40-42 total with decent fuel. anymore timing will start the miss fire and poor running. The only reason I can guess why it does not do it cold is the engine just isn`t detonating at the cooler temps.

RMC030

CTS was replaced, a tiny bit better but still there. When I ran the car hard at one point it almost died at full throttle. I'm looking into the ignition module next. The nock sensor is for a 5.7. I have a full schedule this week and weekend during the day, so I might be able to look at it more one night. In the mean time keep thinking, Thanks!

tom3

I understand everything is new or nearly so, but I'm wondering if the valve springs are up to the task with the roller cam? Seems like you've covered about everthing else.

RMC030

I would think the valves would be an issue all the time not just when the temp is at 180 degrees. When the car is first started and cold it does not have any problem. I ordered a module and will pick it up on Friday.

mw66nova

iTrader: (13)

what are the specs on the cam? is it possible that you are actually giving the motor too much fuel? i would suggest slapping the stock injectors in it and putting the return line back on it. sometimes these little gremlins are staring you right in the face. try the simple stuff.

if the motor is lean, it will gerenally run hot(ter).

black89ws6

try changing your fuel filter.

JeffW

what was the original motor i think you said it was a tbi, does the feul pump match for the tpi? don't tpi need a high pressure pump. what is a tbi pump rated for .

just a thought

jeff

Red Devil

Oh I'll jump in with a WAG too. Coil or the O2 may want a change. With all those new parts and it having problems only at temp... :shrug:

bulletboy29

The problem I had sounds very similar to yours even though mine is carbed. In the morning it would go thru the gears good when it was cold. When it warmed up, it started doing what you describe. It turned out to be low fuel pressure. I guess the low pressure was causing vapor lock. I don't even want to say how much money I put into this car trying to trouble shoot. I had already put on new fuel pump and filter, so I didn't think it could possibly be low fuel pressure. The installation of an electric pusher pump back by the tank solved my problem.

I know you have a different setup than me, but don't rule out low fuel pressure just because it only does it when the engine is warm.

RMC030

I changed the fuel pump. I had a mechanic check the fuel pressure and he said it was good. I am putting in the new GM ignition module tonight and we'll see what happens. I may put the stock injectors back in if this does not work. I put in the LB/HR that Ed Wright automotive recomended. I'm working up a nice amount of cash trying to troubleshoot this problem.

Items replaced:
(1) Coolant Temp Sensor
(2) Fuel Pump-- both were high volume for TPI
(3) Ed Wright Chip sent back for service
(4) Fuel filter was replaced

Items Checked:
(1) Timing
(2) Fuel Pressure
(3) ECM swapped out with a new G.M. for testing
(4) Oxygen sensor swapped out for testing
(5) Return Line was clamped then reopened
(6) Coil was swapped for testing

Every thing else is new from the engine swap 08/24/04. Still searching for an answer.

Red Devil

I think it's time to datalog the car.

JP86SS

iTrader: (1)

Red Devil is right, One datalog will easily give you the answers on what to look for. Not that Ed Write's chip is bad or anything, it's just not tuned with your car and could be a little off at the high end where the VE's and spark tables are hard to tune without having the exact car combination.
Get a $35 cable( or build one), download TTS datamaster or Craig Moates software and see what is happening. These alot of info on the DIY PROM board.
IMO, You could be guessing and changing parts for a long time.
The system will show you how it's running, use the tools that are "built in" just for these types of issues.
JP

Dragroc

Make sure that the Throttle position sensor is adjusted correctly. I know that some of them aren't able to be adjusted according to the years, but you might have to take a dremel tool to it to slot it out so it can be adjusted. This is what I had to do when I got a 58mm Holley TB.

RMC030

Okay! I checked the fuel pressure and it dropps off from 40 lbs to 10 lbs when the car acts up. It could be the fuel pump relay. I clamped off the return line and then ran the car. Same problem. So I would tend to think the relay is bad. I replaced the fuel pump and still had the problem. It also only happens when the vehicle gets to temperature. I'll find out tonight!!!!!!!!!!

RMC030

Still there I'm at a loss!!!!!!!!! Suggestions welcomed!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

RMC030

Hello? Hello? Anyone?

Tom 400 CFI

It's not your Fuel pump rely. You can verify this by using a jumper wire in place of the relay to force the fuel pump to run all the time. Got drive it like that and see if the problem remains. If it doesn it's not the relay.

Are you saying that if you crimp your return line, you still drop to 10- PSI?

RMC030

Yes, I'm saying that I clamped off the return line and the pressure still dropped off to 10lbs. I already know it is not the relay because I bought a new one and replaced the old one. So this where I am at. Check the voltage to see if it drops. Check the connections (again it is a temperature related problem). And finally take the tank down a fourth time and install yet another pump!!!

Tom 400 CFI

If you have good voltage at the pump during one of these incidence, and you have crimped the return line, either you Have a fuel leak between your tank and your motor (obviously you don't), your fuel filter is clogged, or your new pump is junk.

Are you buying new GM pumps or aftermarket? I would only unse the Walbro 255 lph pump, personally.

RMC030

No leak. Not sure about the voltage, still have to check. Pumps on the other hand I bought after market pumps. My next pump(hopefully not needed) will be a high volume pump. What did you suggest and who has the best price????? I have used Jeggs and have always had good service with them.

mystikkal_69

iTrader: (2)

i was using aftermarket pumps oe replacements and having problems with the pump dropping pressure after the car had warmed up. i changed the pump twice with the same problem. the third time around i demanded a OEM pump (delphi or ac delco). i got a delphi and no problems since. imagine dropping the tank 3 times in the same damn week.

one thing i might suggest to replace, your fpr. is it an oem unit or aftermarket?

Tom 400 CFI

I have used the Holley 255 lph (made by Walbro) fuel pump w/great success. I got mine from Summit.

The problem is not you FPR. If it was, you'd have eliminated the problem by crimping your return line.

RMC030

Okay! I will be looking into that thanks for the help. I'll let you know how it works out.

tom3

Wondering if the problem is back at the tank. There is a plug in connector at the top of the fuel pickup unit, inside the tank, seen these get charred and cause all sorts of problems, and hard to spot too. Also, did your car have the little pulsator deal on the pump discharge? Could be bad and leaking, although not common to cause this type of problem. At least you now know it's fuel related.

RMC030

I checked with a buddy of mine and he said the pump I installed last was a Walbro 340 pump. So I will be checking the voltage next. Everyone I have talked to here has a hard time thinking the pump is bad. Most are thinking electical. We shall see!!!

RMC030

I checked the voltage on the pump and it was at 12.90 and 13.10 at idle. I hooked up a lead to the power and groung wires on the plug. I took the car for a ride and the voltage was 13.40 to 13.56. When the car acted up after it was warm the voltage was still 13.40 to 13.56. No voltage drop at all WHAT THE %@#$!!!!!

Now what do I do???Fuel pressure drops when warm and no voltage drop. I will have to check the Oil Pressure switch next, I guess!

RMC030

Did I say that everything has been replaced with new? Well if I haven't I just did!

Red Devil

Did you swap out the maf and fuel relays? I still think you ought to datalog the car. We're into guesses now.

RMC030

I replaced everything!! Datalog, with what machine? I've had it on the snap on scanner more times then off!

RMC030

anyone? anyone?

RMC030

Okay, I put an in line fuel pump in the car for testing, and the car still lost fuel pressure. I hooked the pump up with the in tank pump also. When the car was warmed up and acted up I pluged the extra pump lines into the cigarette lighter port and the car started to buck worse than it did before. I then just ran the extra pump only and the car still bucked worse than it did before. I disconnected everything and reconnected the fuel line. Why would the helper pump make matters worse????? Should the adjustible fuel regulator make a clicking?? Not that you can hear but that you can feel when touched. What is the probalility that the regulator is bad??? And finally, WHAT THE HELL IS WRONG WITH MY CAR?????????????????????????????????Somebody get me a Doctor!!!!!!!!!!!!!!

ljnowell

Maybe the pump in the tank is crapping. Sure it has voltage, but it isnt working good. When it craps, the inline pump you have may not have enough *** behind it to pull fuel through the crappy in tank pump. Just a theory.

Red Devil

When you see 10 PSI on the guage, does the scanner show the O2 going lean?

Did you take the whole assembly from a TPI to rplace the TBI (not sure if the pick-up et al is different for the two systems)?

Look in the DYI board and search for datalog or datalogger. Most here try and use the cable to laptop and use one of a few programs, though I think most use Craig's (Moates) software. Something to just think on.

The engine breaks up, only when it reaches temp, yet you show only 10 psi on guage and no problems before you reach temp. This makes no sense because at 10 psi you'd see it at idle and I doubt you'd make any rpm without a stall.

I'll see if I can dig out a wiring schematic, or have someone post one.

That said...

Now, personally I think you should step back and start over. Deep breath break. And list entirely what you've replaced etc. I know it's frustrating, but look at the symptoms, they are kind of screwy. Maybe in a new thread with a link here so you can clear your head as you put up a new post. I think we are missing something and it will probably come to light with a new thread on your part. I'd write out the new thread in Word or something so you can come back to it and make it conscice and complete.

mystikkal_69

iTrader: (2)

well.... on my buddies LT1 it would idle fine, rev up in neutral ok, but when it was in gear with a load, it would break up around 3 grand. 10 psi on the guage. the pressure would drop even lower when the car was pushed "hard".

86BirdSE

Exhaust Restriction. Have you replaced your catalytic convertor yet?

RMC030

(1) What was the problem then with your buddies LT1? How was it corrected?

(2)At the top of this thread I listed all (I mean ALL) of the things that I did to the car. What it started out as, and what I did during the swap over.

(3)I'm a pretty meticulous type of person. That being said I made 100% sure anything I did during the build, and after would not be an issue. Granted it is not a Top Fuel Dragster, but I wanted it to perform well and still be reliable.

(4)The common denominator in this whole problem is ---
X + warm temp = fuel pressure drop
So we (I say that collectively) need to find out what (X) is!
I now know what (X) is not, and I am running out of options.

(5) My car is like the town hooker! It's been to almost every shop in town, but still leaves everyone scratching their heads.

mystikkal_69

iTrader: (2)

we replaced the fuel pump and all was good again.


did you, yourself, replace the pump or have a shop do it for you?

irocbsa

Knowing the symptoms that he is having, this is quite possibly the most retarded answer I have ever heard.

ljnowell

Actually I was thinking that maybe yours was, at least HE was trying to be helpful.

Red Devil

And there were no drivability problems until the upper RPMS? Wierd. Probably the sequential fire helps as opposed to the batch fire It would be interesting to see.

irocbsa

Please explain to me how leading someone down a completely, and obviously, incorrect path based on the given information is "helpful". That's one of the reasons that this site has been going downhill. Comments that are obviously incorrect just get thrown out there without any thought or contemplation. And then someone else jumps in to defend the ridiculous comment because "they were just trying to help". Well, here's a comment, if you have no clue or haven't even read the entire post, don't "try to help".

I'm agreeing with Red Devil here. The car needs to be datalogged. There has to be a problem in the fuel system somewhere.

ljnowell

So by flaming him, you are helping the content of this thread and fixing what is wrong with these boards?

Hmmm.

Thats the last from me, I dont want to play down to your game.

RMC030

Holy Crap! Gentlemen (and I use the term loosely) Can wee please remember who is having a problem here! I know it not all about me (well this is) but kicking each other in the nuts over who says what and to who is not going to help me look for answers! I am open to suggestions and if someone does not do their homework and read the whole post then I will still entertain their reply.

Now back to the issue at hand. If anyone knows of someone in the Northern New Jersey, or close area to, that can datalog my vehicle please let me know. If it was not such a pain in the ***** to drop the tank, I would have bought another pump and installed it already. Money, at this point is not an option. I've dumped far more money into the vehicle to get to this point, I'm sure a few more bills is not going to matter. Thankfully it is not my daily driver.