TPI Starts and runs, but bogs down under power. Lost
 

Thanks for looking,
Car is a 1991 T/A GTA. 5.7L TPI.
I've been searching threads for days and performing tests you guys recommended to others and still no cigar.

The car was sitting for about a year while I was deployed to afghanistan in which time it was in a body shop, started and moved around occasionally. When I got back it was idling while I picked it up from the shop guys and it ran out of fuel. We put fuel in it, started it up (after playing with it a little) and it ran like crap, barely stayed running and had a skip.
I babied it home and cleaned the fouled plugs, it idled fine so I took it for a drive. picking up speed slowly it goes fine but as soon as you give it any gas it falls right on its face, no power, bogging, skipping etc.

A year ago I replaced: plugs, wires, cap, rotor, pickup coil, ignition module, coil, and it ran fine.

Since it stopped running correctly I: Cleaned the plugs, put new fuel in, (edit: Fuel filter), put fuel injector cleaner in... still ran like crap.

So at that point I checked fuel pressure, it was good even when I gave it throttle. So I ohm'ed the injectors and they were all over the place plus 2 of them were at 6 ohms. So I replaced all of them with southbay injectors and while I was in there replaced lower intake gaskets and added a holley afpr (set it to about 45psi for now until I can run and test it). I put everything back together, timed it to 0* and it still did the SAME thing. So I advanced the timing to 6*... still the same. No CEL codes. No noticeable skip at idle....

I don't know what else to check Thirdgen'ers... I'm lost and am in need of your help.

Thanks, Josh

Update: The car has a noticeable skip now at idle and seems to just worsen when accelerating so it doesn't seem to be isolated to a load issue now. I took out the o2 and it didnt help. Also sprayed started fluid all over the intake and found no noticeable vacuum leaks. I also checked the plugs again, they we're all black and sooted ( I cleaned them a week ago) and wet on the threads but not the heads/ electrodes. So I just ended up replacing them while I was in there. I assume the carbon fouling is just from it not running right for the time being. New spark plugs do not help. Also tested the coil and its good still and ran another fuel pressure test while accelerating and pressure holds near 40psi... any other suggestions?

Re: TPI Starts and runs, but bogs down under power. Lost
 

didn't see fuel filter on the list...just for good measure though. any codes?

Re: TPI Starts and runs, but bogs down under power. Lost
 

agree with the change the fuel filter , it could be a plugged cat as well you can take out the 02 and run it to see if that helps just dont drive it much a power brake you should know if it helps.

Re: TPI Starts and runs, but bogs down under power. Lost
 

Sorry, I replaced the fuel filter a year ago (about 10 miles) then when it didnt run right I did the fuel filter again with the new gas. Also, I have about 2000 miles on new magnaflow high flow dual cats so I wouldnt think thats the case but I will try to pull the o2 sensor anyways. Thanks.

Re: TPI Starts and runs, but bogs down under power. Lost
 

How much gas was in it while it was stored? Also, did it have fuel stabilizer added before you deployed? My cavalier sat while we were gone in '04 and it ran like crap when I got home...sticking valve. I put a HEAVY concentration of seafoam through the throttle body that helped it stop sticking.

Re: TPI Starts and runs, but bogs down under power. Lost
 

It only had a few gallons in it but like I said, it ran good before and was started periodically while I was gone. Some fuel stabilizer was in it as well. But it seems to me like the problems arose after it ran out of fuel, not 100% though...

Re: TPI Starts and runs, but bogs down under power. Lost
 

When it runs low on gas it sucks fuel from the bottom of the tank, which is where ALL the crud is. For certain change the fuel filter. Might even put some gas in there and take the fuel filter off and let it pump some gas out into a can by cycling the key switch or powering terminal G at the ALDL terminal.

Re: TPI Starts and runs, but bogs down under power. Lost
 

Thats a good way to get all the crud into the injector filter baskets

Re: TPI Starts and runs, but bogs down under power. Lost
 

I figured it sucked some stuff up which is why I changed the gas and fuel filter. And now that the fuel injectors have been replaced along with the fuel rail being cleaned out (plus I have good pressure at the rail) I cant think there would be any more gunk in the fuel system.

Re: TPI Starts and runs, but bogs down under power. Lost
 

Not your first day, huh?

Really tho', you're right. And I'm RIGHTER! AGAIN ;)

--------------------------------------------------------------------------------------------------------------------------------

OP - sounds like static, and especially DYNAMIC fuel pressure tests are in order. See the article I posted with dynamic test procedure (FPR response to vacuum change)

And injectors are made to be serviced.EPITOME of wrenching here..., for more FYI on Tuned Port Injection - AS GOOD AS IT GETS!
Bookmark, Sticky, and get out your notebooks yUP!!!

ed.:
That stuff is 4 years old, and ain't no wonder why it's at 8k webhits. What can I say...

It's no wonder why my LT1 got just under 33 MPG's highway ............. TUNED[WITH]PERFORMANCE ;)

ANY questions?

WRENCH OUT!!!

Re: TPI Starts and runs, but bogs down under power. Lost
 

Being in a body shop lots of dust. You check the air filter and MAF could be starving for air and running rich

Re: TPI Starts and runs, but bogs down under power. Lost
 

The car has a noticeable skip now at idle and seems to just worsen when accelerating so it doesn't seem to be isolated to a load issue now. I took out the o2 and it didnt help. Also sprayed started fluid all over the intake and found no noticeable vacuum leaks. I also checked the plugs again, they we're all black and sooted ( I cleaned them a week ago) and wet on the threads but not the heads/ electrodes. So I just ended up replacing them while I was in there. I assume the carbon fouling is just from it not running right for the time being. New spark plugs do not help. Also tested the coil and its good still and ran another fuel pressure test while accelerating and pressure holds near 40psi... any other suggestions?

Also, it is a MAP car not MAF

Re: TPI Starts and runs, but bogs down under power. Lost
 

I'm sure you have pulled off the vacuum line to the fpr to check for evidence of fuel from a torn diaphragm. The rich condition can be caused bye a bad cts located in the from of your intake manifold , bad mat or a to high of a reading on the tps or dripping injectors. A exhaust leak bye the o2 will also result in a rich condition. With out a scanner to see sensor data or tuner pro its hard to say. This is the ohms per temp for the mat and cts they are the same thermistor different locations.

Attachment 344532

Re: TPI Starts and runs, but bogs down under power. Lost
 

My 87 TPI did what yours is doing and I did all those changes you did and more. I dont recall the bad skipping though. But it did run rough and fall. It was my fuel tank. Took it off had it cleaned and restored then ran it with no problems from first startup. We did find all kinds of gunk in the bottom of that tank too and that was after doing all the filters, injectors, FPR, gaskets, etc, etc.

Re: TPI Starts and runs, but bogs down under power. Lost
 

No leak at the fuel pressure regulator, no exhaust leak, tps tests good as well as the MAP sensor. Obviously I cant test the temp sensors without a computer but I'm trying to get my hands on one now.

I put new plugs in today as I stated and the number 1 cylinder was fouled, rest looked ok. I then removed the number 1 cylinder plug after about 10 minutes of run time and it is starting to looked fouled and burnt/ blackened on one side.

I spark tested that cylinder and it has spark. also ohm'ed all 8 wires and they are good... disconnected the fuel injector on #1 and it ran even worse... not sure if #1 is the problem or its coincidence.

Re: TPI Starts and runs, but bogs down under power. Lost
 

Also, just checked the cts and mat sensors as suggested by Tuned Performance. They are both good...

Re: TPI Starts and runs, but bogs down under power. Lost
 

first off, let me say thank you for your service in Afghanistan, and welcome home. secondly, is the car MAF or speed/density sensor? i have heard of animals making homes in air cleaners when cars sit for a long period times. just a thought. figure if the car isnt getting any air and you jump on the throttle, it'll pump an exceeding amount of fuel in and bog down....just not sure how affected it would be from MAF or speed density.

Re: TPI Starts and runs, but bogs down under power. Lost
 

Im just wondering if number one is being held open bye crud in the injector.

Re: TPI Starts and runs, but bogs down under power. Lost
 

Hi there crazyman, I'm having a similar issue with my 89 tpi. Had it running, but bogged down and stumbles at low rpm. That could be caused by a stuck egr.. Now it wont start, I'm not getting any presssure at the fuel rails but the lines leading to it are flowing. how did u clean out the fuel rails? were yours all gummed up???

Re: TPI Starts and runs, but bogs down under power. Lost
 

i dont know what the deal is but when i run my car for a while, and it gits to operating temperature, it runs awesome. but after a few miles, it falls on its face. as you can see in the video, i floor it in neutral, and it just falls on its face. when driving it, it has no power and can be a real hazard if i need to pull out and this happens when i accelerate. in the next video, its like a switch coming on, and it is right back to normal. this doesnt happen all the time, but here lately its been happening more and more.

i made a video of me flooring it in neutral so yall can see what happening. ANY advise would help.

BTW i git no codes.



this video was shot about a minute later, and it was like a light switch came on, and it was running back to normal. i couldnt floor it without redlining it, but in the video before, i had it to the floor and it just fell on its face. VERY frustrating, and i have no codes.



this is a 350 TPI, not a 305.

Re: TPI Starts and runs, but bogs down under power. Lost
 

A lot of people on this thread reported similar problems, and if anybody's case is bad it's mine. Did anyone find the source of the issue, a fix, any sort of progress?

I'm starting to think I got crud buildup somewhere in the fuel system because my car has sat in the garage for an extended hibernation. Through out that time I've started her up but have kept the gas tank very low and it has run dry on occasion.

Re: TPI Starts and runs, but bogs down under power. Lost
 

What happens when power bogs? Is it WOT or just under part throttle load does its sound loud but doesnt build rpm? Sounds like it is lean and could be fuel pressure/clogs for sure or weak injector failing under higher loads

Re: TPI Starts and runs, but bogs down under power. Lost
 

Does not build RPMs and can die when it hits that wall. A very slow acceleration while in park can build slightly higher RPMs. I Replaced the fuel filter first and then I went and checked both the IAC and TPS, both seemed fine.

Re: TPI Starts and runs, but bogs down under power. Lost
 

got mine fixed finally. 1st i had the fuel system all cleaned out, tanks and all, replaced the sending unit, and fuel pump. thats whan that problem of mine started in the 2 video's up top. now what i had to do is a pain in the *** more than anything. I had to narrow it down. so i replaced the fuel pressure regulator. then took it for a drive. on the computer it kept sayin at WOT that i was running lean. so we decided that it must be a defective fuel pump. so i had another fuel pump put in, and waa laa!! problem fixed.

Re: TPI Starts and runs, but bogs down under power. Lost
 

I had exact same issues computer said it was lean but sti at 35-38 psi idle but even when lowered inj constant to Richen it up it was linear problem so I tweaked my fuel and maf and now I have Blm where I need except final tune of lv8 192 range

So I will turn that but I am taking fuel pump back and I assume tune will still be good just tweak the inj constant back up to compensate for working better fuel pump

Re: TPI Starts and runs, but bogs down under power. Lost
 

Hey sins86, in my case the previous owner put a fuel pump for a tbi system not a tpi system causing an intermittent stalling and eventually a no start situation. In any case in order to find the problem u need to go thru entire fuel system, then air intake, then computer..... Fuel pump, check for voltage from connector, check sending unit wires and ground. Blow compressed air thru fuel lines, change fuel filter, inspect injectors test them, test fpr... If all fuel system checks out move on to air intake... Bad maf? Is the minimum air mixture set at the iac?? When u adjust timing u have to adj min air in the iac, and reset the tps to .54 volts, then drive it for 20 mins at 40 mph so the computer can relearn... If all that checks oitmove on to computer possibilities, is the vats bypassed? Is the computer sending signal to the injectors, is the ignition control module sending signal to ecm? Hope this helps

Re: TPI Starts and runs, but bogs down under power. Lost
 

just a heads up, DO NOT BUY a fuel pump made in CHINA!!! EVER!! certainly not one from "airtex"

Re: TPI Starts and runs, but bogs down under power. Lost
 

i had a car that just lost a lot of power thouht the moter was about done finaly after 3 months it quit running. my fuel pump was bad and finaly went out. it was like a new car. also had a broken plug in my 88 last year ran fine dident miss or run ruff at idle or hafe throtal, but every time i steped on it then it would act up and miss.it was a very small crake. spry water over your plug wires while its running if one off them are bad it will act up

Re: TPI Starts and runs, but bogs down under power. Lost
 

I'm finally home on leave again so I'm back working on the TA in the original post. Injectors are new but my gut still points to a fuel problem. At this point I'm still just throwing parts at it but I have the tank out and I'm going to put a new pump in it. If this doesn't fix it she's going to a performance shop down the road to see the experts :) I'll keep you all updated.

Re: TPI Starts and runs, but bogs down under power. Lost
 

Fuel pump did not fix it. Off to see the Wizards

Re: TPI Starts and runs, but bogs down under power. Lost
 

I have a L98 that is doing the intermittent stumbling, no power routine. just like in the videos above.
My engine is installed in a FJ40 so I am using an external Walpro high pressure pump. I have a small two quart surge tank to insure supply of fuel to the high pressure pump. the fuel goes through a 10 micron fuel filter water separator then to the surge tank. the high pressure pump is fed by the surge tank and has a 10 micron GM style in line filter before the high pressure pump. the return line goes to the surge tank.
I am planning on replacing the fuel filter before the high pressure pump. to see if it may be the problem. I installed a pressure gauge on the fuel rail and with the vacuum line attached getting 34 psi with engine off (psi reading when the engine was running fine). I need to see what it is with engine on and at running rpm.
The fuel injectors have been replaced by Southbay Bosch injectors.
I am wondering if my problem is the FPR. it is stock. This engine sat on an engine stand from 1991 until I got it in 2012. it would not even run with the original injectors.
Also, it developed a loud clicking sound at the FPR. it did not have that sound before this problem started. that is the reason I am suspecting the FPR.
Let us know what you find on your engine.
Thanks for your service to our country!!!
Gary

Re: TPI Starts and runs, but bogs down under power. Lost
 

My New FPR fixed this issue. Had gunk in it. Bought it off eBay for 80.00 new old stock. Works great!

Re: TPI Starts and runs, but bogs down under power. Lost
 

Crazyman, did you ever determine the problem?

Re: TPI Starts and runs, but bogs down under power. Lost
 

:hmmm: did you ever find the problem?

Re: TPI Starts and runs, but bogs down under power. Lost
 

I'm interested as well. My 91 305 TPI has a similar problem but 3 injectors are bad.

Re: TPI Starts and runs, but bogs down under power. Lost
 

this just happen to my 88 GTA . In my case a relay that feeds 5volts to the maf and throttle position sensor went bad and was instead feeding them 12v. Replaced both sensors and the relay. Runs like new.

Re: TPI Starts and runs, but bogs down under power. Lost
 

What relay does that? Those should get 5 volts from the ECM internals.

Re: TPI Starts and runs, but bogs down under power. Lost
 

just went through a similar saga with my 87 t/a. i built a new motor for it and had nothing but fuel problems. turned out the pulsator was bad, i replaced the pulsator, pump, sock, sender, filter just to be sure....previously i replaced injectors and fpr to afpr
i was a big dummy though and didnt do my research and replaced the pump with a walbro high pressure pump, and put a pulsator back on. resulted in blowing out the side of the pulsator and needing tank drop again. runs good now though with a new racetronix pump

Re: TPI Starts and runs, but bogs down under power. Lost
 

anything?

Re: TPI Starts and runs, but bogs down under power. Lost