Hello everyone,

I am having lots of problems with my TPI motor, It is very hard to start and when it does it runs poorly and backfires.. I just noticed today that the temperature gauge is not working. went to look for the temp gauge and found that the cable is no longer there I think it got disconnected and melted or got caught on something... What color should it be and where should it be coming out to the engine bay? Also could that missing wire be the problem does the ICU uses that temp sensor on the drivers side of the engine or the one below the throttle body?

The wire going to the 02 sensor has a shield that is completely melted as well I have to go under the car tomorrow to check that and maybe replace the sensor and cable going to it... I just ordered an extension for the o2 sensor cable so I can router away from my headers

Any help would be appreciated... thank you!

 

The gauge is operated by a sender next to spark plug cyl 1 but is not needed for the computer.
Under your throttle body is the coolant temp sensor for the computer.
But there are a few things that can lead to poor running.
Coolant temperature sensor
Bad o2 Sensor or exhaust leaks
Vacuum leaks
Bad fuel pressure regulator under the plenum
Bad fuel injectors

Maybe start to check for leaks and the cts and o2 sensor

 

Thank you Mick, I will check that.. after the backfires I hear a exhaust leak but that was not there before... I am afraid that the o2 sensor cable is damaged the plastic shield / conduit is all melted around it. I have a new 02 server and extension arrivng today or tomorrow going to replace that and try to find the temp gauge sensor wire... do you know what color it is?

 

Make sure your spark plug wires are in the right spot on Dist cap and also make sure rotor and cap and spark plugs look good and make sure rotor points to #1 plug at correct time and after all the is verified check timing of car. this all assumes your gas is good, along with the rest of your fuel system components.

 

Thank you LiquidBlue I assume it is no one touched the car and it was running good before... Gas in the tank is getting close to 6months but I always fill with recreational fuel no ethanol and add the fuel stabilizer to my cars since I don't daily drive it. I ordered a fuel pressure gauge to add to my car.

 

if you don't drive your car often, invest in a battery tender. will pay for itself. when our cars are cold started, they run in open loop until the o2 sensors get warm. that means the o2 sensor should not have an effect on cold start for about 1 min or so. you can hear the switch over, the car will idle slower once it goes into closed loop. how long has it been since your car ran good? something has obviously changed. is the distributor tight? sometimes they don't get tightened well and it could have rotated a bit, putting the engine out of timing and causing rough running and back firing.

 

Thank you LiquidBlue that rules out the o2 sensor. I was running good 2 months ago one weekend I was going to take it out for a drive and it started to back fire and run poorly... I checked all the spark plug cables, checked already if the distributor was loose it is not loose. Not sure if it is good or not, but I always disconnect the battery both poles when I park my cars and know I wont use it for a couple of days, I have the quick disconnect terminals.

I bought a FiTech TPI ecu last year after I had problems with this car, it would die while driving mostly at stop signs/red lights. I replaced the coil and another sensor next to the coil that I broke while replacing the coil dont remember the name of the sensor and the car was perfect so I never installed the FiTech, if I can't figure out the problem in the next couple of days I will most likely start the FiTech Install this weekend! Do you guys have any feedback on FiTech TPI?

 

it only rules out 02 sensor during cold start. after it goes into closed loop, o2 sensor could be one of the problems. battery will still sulfate even if disconnected from the car.

 

How long have you owned the car and do you know the condition of spark plugs, wires and ignition timing? I know all three are huge culprets with backfires.When my plugs were bad and my ignition timing was off, my car backfired. I think Ignition Timing might be your main issue.

I would get the 02 Sensor fixed for sure though. When my 02 sensor was missing (scumbag tire shop removed it and welded a hole shut in my header collecter), my car would frequently stall out when braking hard before it was warmed up. Also had a sporadic idle when first started.
Both a bad 02 sensor as well as bad plugs/ignition can contribute to running poorly and backfire.

These videos should help with ignition timing:

 

Thank you Vinscully50, I replaced the plugs / cables / cap and rotor when I got the car 5 years ago... But my cars idle a lot sometimes I dont take them out because they are behind other cars that I am working on etc... I will replace the spark plugs anyway and check the timing thanks for the links...

 

I would just check the timing first and see what that does. Should be at least 6* BTC. I know sitting can cause problems but usually just running odd (stalling out, not smooth idle) until warmed up. Backfiring almost always seems to be ignition related.
I would focus on the timing and O2 sensor first.

 

Got I will check that first. Thank you for your help!