I have a 355 TPI AL heads,mild cam,full headers,26lb injectors,Th350 with gear vendor OD. While dataloging with Datamaster I give it wot when it gets to 3200-4000 rpm it cuts out like chugg chugg when I keep my foot on the floor, and gives wild readings like o tps,255 L term,32 retard, 10 map, 255mph with no speedometer hooked at those spots in the datalog I can run it up to 100mph in 3rd at 35% tps no chugging and strong, but wot it poops out. Can anybody help me to figure it out? can send datalog if you can read datamaster for $8 730 ecm. no codes! 8k on new rebuild. Thank you Mike

 

One thing I would check (then experts can comment) is if your TPS is faulty. You say you can run to 100MPH at 35% TPS but not at 100% TPS and get a TPS reading of 0 at WOT!

Use a digatal Volt Meter and probe IIRC blue wire pin B middle of TPS sensor and read voltage, key on, engine off. Should read about .54 volts closed and close to 5 volts open. Those readings are not as important as... Open throttle slowly and watch reading rise, smoothly and steadly, no jumps or glitches or dead spots which would indacate a faulty TPS sensor. HTH!

 

Not running out of fuel at WOT are ya? whats injector DC?

 

I checked my tps and the wot voltage only went to 3.6volts. it increased smooth and it never dropped off. could it still be bad, it's should go to 5volts? I did some more data runs and when i let off the gas the map goes as low as 10 that high vacuum a? any more ideas would be great. where is the big time ECM guy BOB?

 

If your logging setup normally shows readings that make sense, making this an intermittent problem, I would first ensure that you have all the necessary grounds intact, clean & tight.

I need 4.5v to call a TPS good.

 

He's probably waiting for us little guys to help work out the bugs first!

I'd have to agree with xch3no2. Since this is a conversion running good, gotta find which wire is the ground for this circuit. Actually just clean paint under all grounds associated with the EFI system. System grounded to block, right? If anything is grounded to body then really need good body to engine ground strap. Lots of ground issues on old car EFI conversions. Charging system too but that is usually causing idle issues because old car charging system won't keep over 12 volts at idle...

Something not right with TPS if you are not closer to 4.5 volt WOT? What is idle TPS voltage? What is reference voltage? Reference voltage should be right at 5 volt.

Deceleration vacuum to 10 MAP kpa is high but possible under right conditions and not an issue.

 

Mine always went to .5 to 4.5 V. Mine is not adjustable. Is OP adjustable?

 

I pulled the connector off the tps to check ohms it read 7 k ohms closed and 2.7 k ohms at wot. rechecked voltage read .52 volts closed and 3.7 volts wot, also checked the tb butterfly blades and they open fully. checked refrence voltage full 5 volts. could it be starving it of gas at wot TB but the ECM is only getting 3.7 volts from the tps? hard to test wot for too long (police) without going back to te dino $$$ I would like to be sure the tps is bad before putting out $70 + with no fix!

 

looks like a bad TPS. Test off car! http://www.youtube.com/watch?v=IsX5q3jBeBQ

 

Yup what Ronny said. Easy to check, just pull it off, leave wiring plug in, key on, engine off.

Something is wrong with TPS... and even new not that much money... not sure how it would effect fueling with your ECM because some set at startup to 0% and WOT should be 100%, voltage is another reading, but yours is wrong? I've never seen that before?

 

Mine is non adjustable but prior was so but only for idle. If you want to go cheap get one from JY.

 

I'm not looking for cheap, made in USA would be nice!? This is my daily driver and the wife expects it to be ready for long road trip this summer.. correct part numbers for quility parts for a 1991 TPI . The wiring is out of a 1991 camaro , the TPI is also 1991 oem harness, all the charging system is also new for 1991 camaro, yes it is a 1955 chevy I've replaced with all new sensors except the tps and the map , and replaced the map last week because I thought it was causing the cutting out at wot. did put a lot of ground wire to every thing know it can be a problem with the ECM. always can add more.

 

The only way to tell is to replace it . I've looked for the new oem part numbers but can't find them . most sites can't find a tps for 1991? I would like to know I'm putting a good part on? do you know where I can find one? thanks for your help Mike

 

Just walk into NAPA with the TPS...

 

on the TPS voltage you gave, it that with a test meter at the sensor or what your seeing in Datamaster? did you check at both and do the 2 reading match pretty close?
i ask that because the definition file can be off a little bit and cause a sensor to not display accurately.

myself, i prefer TunerPro over Datamaster to scan with.
although i've used it, im not real familiar with TP V5.
with TunerPro 4 once you have it setup, you can go to monitors and pull up what looks like scope data.

i would think a problem with either fuel or the TPS, but with the other readings freaking out i feel its something else.
a wiring problem of some kind or maybe a problem with the ECM/chip, or possibly an ignition problem.
maybe a bad injector, the higher the duty cycle, the more current they pull.
if one or more injectors have low resistance, that will really run the current up. so check each one cold and hot for correct resistance.

under WOT, voltage requirements at the plugs goes way up. if its maxing the ignition coil out, there could be voltage from the coil feeding back thru the system causing the ECM to freak out.
im guessing you have the stock type external ignition coil.
if you pull the coil wire off the coil that goes to the cap and crank the motor over, it should be good enough to fire down the side of the coil tower to the laminations. of course you may need someone to crank it over while you watch it. you don't need to do it for very long, about 5 seconds is good.
next you can try to check for good output at the plugs. pull a wire at one of the spark plugs and
stick an old plug in it and lay it on the intake where it won't fall off when you start the motor up.
with screw driver with a GOOD PLASTIC handle, carefully and slowly lift the wire/spark plug away from the intake. make a mental note of how far away it is when the spark stops jumping.
all of the plug wires should do about the same distance.

related note, if you use a screw driver with a wood handle, odds are someone may get hurt, or something will get damaged. if your outside, you may need a new screw driver because you'll never find the old one.
and no, i have absolutely no desire to give a demonstration on that, ever again

 

The voltage was at the sensor and no they don't match the datamaster log, it's 4.7 volts at 100% tps in the datalog. while datalogging in datamaster it flashes data error but none of the readings change with the data error . proformance great except wot it cuts out. funny you mention spark, this is a 1955 chevy and the most convenent place to put the ecm harness through the fire wall was through a hole two inches above the distributor. it has a new msd coil , msd cap rotor and gm electroics oem, with 8mm wires. do you think the rf from the coil and wires could be messing with my wot because it puts out more energy at wot? thanks for your reply Mike

 

its very possible.
with the harness that close to the ignition system, your probably getting a ton of RF interference, and RF interference will do all kinds of strange things.
you can try wrapping the wiring harness where it runs near the distributor in tin foil and see if it makes a difference. i would wrap the harness under the hood out to about 2 feet away from the distributor and to at least 4 inches inside the firewall.
after you've wrapped the harness with foil, strip some wire and wrap it around the tin foil then run the wire to a good ground.
this may or may not fix your problem. but if it does make a notable difference, then you'll probably need to reroute the harness.

 

Do you have a picture of engine compartment showing the harness, distributor and coil? I may be able to spot an issue.

After I got a Mac Osiliscope I found issues with conversions that were unexplainable. Most were location of coil, coil wire in relation to harness or sensor. Distributor was never an issue, but I never ran the main loom that close to distributor... from what your saying the coil wire is almost touching the main harness?

If Denn Shah test is positive and the truck is finished to point of not wanting a new hole for harness I wonder if a set of covers from a Corvette that covered the spark plug wires and distributor I think would cure it and actually look good. Forget what years but they were chrome, cut RF noise for radio I think...

What does DataMaster say readings for TPS are key on engine off? Your still not getting correct readings at TPS with DVM?

 

I replaced the TPS made in USA ,it tested down to 0 OHMS not 26k OHMS at wot that the one I had on. I ran it all week still cut out at wot. yesterday I rerouted the data lines from 1 1/2 inch from top of coil to 7 inches it doesn't look pretty but I took it out for for a data run today on the highway got lucky(no police) lot of wot and not one time did it cut out or feel like running out of power. I'd say that RF energy is no joke when it comes data lines! I hope someone takes this problem in mind when looking for strange problem. thanks for your help guys very relieved Mike

 

 

Excuse my ignorance, what exactly are the data lines? I have a 5.3 block, LS1 cam, port and polished stock heads, with all the accessories of a 2002 Camaro SS. I am getting the same problem where it cuts out like pulses when I am on WOT so it goes-cuts-goes-cuts. There are only few times when it won't do it, but when it does I notice that the speedometer bounces like crazy when I am accelerating. I was told this could be an electromagnetic problem but I don't know where to look. By the way, my MAF only reads up to around 18 lb/m on WOT, when rev bounces off at 3800 RPM.