Here we go again.....more TPI woes

[mobileortho]

I'm really starting to get tired of this! The truck just doesn't run worth #$A*#!
It won't accellerate over 20mph or so, it sputters & backfires but it starts & idles fine. Ive changed the fuel pump & filter, checked the vac to the map sensor & timing so what gives? There are no codes showing, could it be a bad ECU?

[fabguy]

This info probably won't help becaue i dont know anything about that setup but just wanted to share it with you,
I remember when my buddy installed a TPI in his 59 vette he had a similar problem and it was his mass airflow sensor I believe. I couldn't tell you what it looked like I just remember him talking about it to me and how frustrated he was.
I hope you get your situation fixed soon so the frustration will be behind you.
Posted via Mobile Device

[1project2many]

It helps to get a laptop with scan software or a scantool to view engine data.

The ecm could be bad. Try tapping on the case with the handle of a screwdriver while the engine's idling. If the engine stumbles or stalls then the ecm is bad. Don't tap hard enough to leave marks.

Will the engine rev up when it's not under load? What's the fuel pressure when this is happening? What's the spark doing? Contamination in the cap or wrong plug wiring can cause this. What's the throttle position sensor read when it happens? Coolant temp? MAP voltage?

Trying to diagnose without a tool to view ecm data can be tough.

[kevin59]

i has simular issues with my vette, idled fine, i went thru fuel system-new pump, filter, cleaned fuel rails out, cleand maf, replaced plug wires, plugs, coil, replaced some sensors, still had sputtering on acceleration.the last thing i didnt want it to be was fuel injectors, but i replaced them and thatwas the problem.

[65Ch3v3LL3]

Grab a 5.3 LS motor out the junkyard for $500 and get rid of the TPI. You will have more power and better gas mileage. Problem solved!

[crossfire84]

Originally Posted by 65Ch3v3LL3

Grab a 5.3 LS motor out the junkyard for $500 and get rid of the TPI. You will have more power and better gas mileage. Problem solved!

replies like this do not help the poster,

so, i had the same problem, the temp censor failed and caused the ecm to think the coolant temp was 20 outside and caused the ecm to flood the engine above idle. replaced it and did an oil change and life is good. hope this helps.

[roger55]

I think I would remove the injectors and take them to a shop and have them checked out / reconditioned.. Some trial and error here but it can't hurt to make sure they are all good and clean anyway.

I'm in the process of putting a 305 TPI in my '57 right now so I'll be interested to see how this issue ends up for you.

I still have a love for these engines.

[_Ogre]

first thing i would do is check your fuel pressure at idle and wot
not sure what your tpi needs for fuel pressure
my ramjet needs 45 psi and does the same thing when the fuel pressure goes down
starts fine, idles fine and works fair at partial throttle with 15 psi, just no go in it
oriellys has the free rental of the pressure gauges

[roger55]

Originally Posted by _Ogre

first thing i would do is check your fuel pressure at idle and wot
not sure what your tpi needs for fuel pressure
my ramjet needs 45 psi and does the same thing when the fuel pressure goes down
starts fine, idles fine and works fair at partial throttle with 15 psi, just no go in it
oriellys has the free rental of the pressure gauges

Oh yeah. What he said first. Then what I said.

[mobileortho]

You know, I was having similar problems when I had a carb & I thought it qas fuel flow. It would idle fine, then spit & sputter & eventually die when I drove it. It would be hard to start afterwards and usually required a jump. It was around this time I started the TPI swap, but the truck sat for awhile because I was relocating to VA. I thought I'd figured that problem out when I discovered that the wire from the starter to the alternator was fried. I don't have the hard starting problem but it still seems like it's fuel starved. Confused!

[_Ogre]

what pump are you using?
did you check the fuel pressure?

[Coupeguy2001]

sounds like a fuel filter that is almost plugged.

check the throttle position sensor. voltage should be .54 volts at idle. with engine off, key on, go from idle to max throttle and your volts should go to around 5 volts

[roger55]

Originally Posted by Coupeguy2001

sounds like a fuel filter that is almost plugged.

That would show up on the pressure gauge.

[Coupeguy2001]

I re-read your post. One of the things that's not monitored by the ECM is ignition. the things that are monitored are
IAC,
Throttle position,
oxygen sensor,
EGR,
temperature,
engine speed,
vehicle speed,
MAP,


Now what's left?
fuel pressure, injectors, ignition module in the dist.. plug wires, plugs, valve adjustment, base timing, vacuum leaks, fuel leaks, bad grounds, fusible links, obsrtuction of the gas tank vent. obstruction of the gas supply.
When you say the TPI is not running right,, there are other factors to consider.
Just because the TPI is the first thing on the top of the manifold does not mean that it is the culprit. Usually it means that it is the first mis-understood item on the vehicle.
If you had put any other fuel injection system on the truck and it was doing this, you would have a phone number to call. With a General Motors fuel injection, there are no tech lines to call.
This means that you have to look around and decide for yourself what's wrong. This will get you more familiar with the system, and out on the road, you can diagnose and fix whatever goes wrong.
Ok, first, I would check codes, put the fuel pressure gauge on it, leave the gauge on it and tape it to the windshield and drive it to the place where it sputters.
check plugs, check plug wires, timing, vacuum leaks.
What did you do to it last? go there and see if you overlooked something.
afterfire out the tail pipe usually means way too rich mixture. barking out the intake means there is an intake valve open when the ignition fires.
If it starts and idles fine, but won't accelerate, it would mean that there may not be enough fuel getting to the cylinders. It could point you to injectors. or vehicle speed sensor?
Good luck.

[mobileortho]

Originally Posted by kevin59

i has simular issues with my vette, idled fine, i went thru fuel system-new pump, filter, cleaned fuel rails out, cleand maf, replaced plug wires, plugs, coil, replaced some sensors, still had sputtering on acceleration.the last thing i didnt want it to be was fuel injectors, but i replaced them and that was the problem.

The injectors are new

Originally Posted by crossfire84

replies like this do not help the poster,

so, i had the same problem, the temp censor failed and caused the ecm to think the coolant temp was 20 outside and caused the ecm to flood the engine above idle. replaced it and did an oil change and life is good. hope this helps.

All new sensors

Originally Posted by _Ogre

what pump are you using?
did you check the fuel pressure?

Using an inline filter from an '89 F-150, good fuel pessure, new filter.

Originally Posted by Coupeguy2001

I re-read your post. One of the things that's not monitored by the ECM is ignition. the things that are monitored are
IAC,
Throttle position,
oxygen sensor,
EGR,
temperature,
engine speed,
vehicle speed,
MAP,


Now what's left?
fuel pressure, injectors, ignition module in the dist.. plug wires, plugs, valve adjustment, base timing, vacuum leaks, fuel leaks, bad grounds, fusible links, obsrtuction of the gas tank vent. obstruction of the gas supply.
When you say the TPI is not running right,, there are other factors to consider.
Just because the TPI is the first thing on the top of the manifold does not mean that it is the culprit. Usually it means that it is the first mis-understood item on the vehicle.
If you had put any other fuel injection system on the truck and it was doing this, you would have a phone number to call. With a General Motors fuel injection, there are no tech lines to call.
This means that you have to look around and decide for yourself what's wrong. This will get you more familiar with the system, and out on the road, you can diagnose and fix whatever goes wrong.
Ok, first, I would check codes, put the fuel pressure gauge on it, leave the gauge on it and tape it to the windshield and drive it to the place where it sputters.
check plugs, check plug wires, timing, vacuum leaks.
What did you do to it last? go there and see if you overlooked something.
afterfire out the tail pipe usually means way too rich mixture. barking out the intake means there is an intake valve open when the ignition fires.
If it starts and idles fine, but won't accelerate, it would mean that there may not be enough fuel getting to the cylinders. It could point you to injectors. or vehicle speed sensor?
Good luck.

It's not showing any codes (bad ECU?) all new sensors. Yesterday I found a broken ground strap, fixed that. Also noticed that when I put a timing light on it, I couldn't get a reading on #1 until I raised the rpms. Out of curiosity I checked the other wires and got signals on all but #6. Like #1, it registered when I raised the rpms. All the wires are new....faulty distributor?

[_Ogre]

Originally Posted by mobileortho

Using an inline filter from an '89 F-150, good fuel pessure, new filter

what is good pressure? how many PSI?
efi is very pressure sensitive, if you loosen a line and have flow, that does not indicate pressure
again... the first thing i would check is your fuel pressure
you can start swapping parts but that can get expensive

[mobileortho]

Originally Posted by _Ogre

what is good pressure? how many PSI?
efi is very pressure sensitive, if you loosen a line and have flow, that does not indicate pressure
again... the first thing i would check is your fuel pressure
you can start swapping parts but that can get expensive

It's running the recommended pressure for TPI @ 43 PSI at the fuel rails.

[RootBeer 6117]

x2 on what coupeguy2001 said
I have my students go through this when we are doing engine performance, Airtex fuel pumps training has very good info for fuel pump diagnostics.

http://www.fueldst.com/FDSD/Player.html

They used to send us a hats but now we just get a certificate.

[Coupeguy2001]

It might be the distributor module Just like the earlier HEI, the module comes out with a few screws. Except this one is a 7 pin module. Wonder if you have a dirty dist. cap inside where the rotor turns. Or maybe the rotor is dirty
make sure the connectors on the dist. cap are on tight. the Pink wire is power, and the brown is tach. If you are using a Camaro setup, make sure the connectors on the coil are tight.

[1project2many]

You'd be amazed at how many people think the computer is to blame when something goes wrong with their car. If I had a dollar for every time... Well, you know how that ends. Back in the day when the TPI was brand new there were a lot of ecm failures. The most common was cold solder joints but you'd see injector drivers and quad drivers fail from time to time. The most common test was the "tap test" that I described to detect bad solder joints. These days it's much less common to see a bad ecm / pcm. In fact, you can't even get replacements through the aftermarket for many of them anymore. There's just no money to be made in offering rebuilt computers. Long story short, you probably don't have a bad ecm but if you do, the best way to find it is by diagnosing, not guessing.

No timing light on 1 and 6 is very interesting. It may be a clue or it may be a coincidence. The first problem is that you can't time it if you can't get the light to flash. I'm guessing the light flashed correctly when you first set the timing? The light flashes because it can sense the voltage change across the plug wire as the plug fires. The voltage has to be high enough for the light to sense it. If the voltage is too low the light won't flash. Some things that can cause low voltage are dirty rotor / cap as already mentioned, plug wires shorted to ground, plugs with too small a gap, carbon fouled plugs, and low compression. Of course this assumes the insulation on the wire didn't prevent the timing light clamp from seating properly.

What's interesting to me is that 1 and 6 are opposite in the firing order. It's common to see a dirty or fouled cap cause spark to leak to the cylinder on either side of the one firing and this usually causes more than one misfire. It's very uncommon to see it bleed across the cap to the opposite terminal.

Has this engine ever run right with the TPI? Did this problem start just after you did some work, or was it something that developed on it's own? What style distributor and cap are you using? Do you have something like the MSD Crab Cap, where the even wires come out one side and odd on the other? Are you running a stock cam or custom?

I would confirm the timing light is behaving badly on #s 1 and 6. I'd do a basic check of #1 plug to make sure it isn't fouled, wet, or gapped wrong. Then I'd check for spark at the end of the plug wire. You can hold it over the block but there's a good chance you'll get zapped so open an old plug to .100" (that's one hundred thousandths, about as thick as a dime), hook the plug wire to it, ground the metal part, and start the engine. If you're not getting spark at the plug you need to figure out why. If you are getting spark you could try putting the timing light clamp around the plug wire away from the spark plug and see if it flashes.

[whammer33024]

this sounds like issues people claim when the optispark distributor on an LT1 go bad. i know i've had some crazy things happen with those and they're so sensitive that they can be a pain in the ass. that's the only reason i'm leaning more towards the distributor. i know TPI is different than the LT1, just saying it sounds like a distributor problem to me

[_Ogre]

does the pressure stay constant at wot?

[mobileortho]

No, it drops. I did take care of the problems with 1 & 6 by replacing the cap & rotor.

[Highsider]

Very informative thread.
I am dusting off old info and learning new things.

[Coupeguy2001]

So is it running alright now?