Take a breath. Do an extensive search for vacuum leaks, and make sure you dropped the distributor in right.
85 GT intermittent miss at highway speed
- Thread starter rwordenjr
- Start date
I realize that this is an unpopular opinion but I think your issues lie in air/fuel delivery.
I'd really like for some of the old guys on here to look at your spark plug images and give their thoughts. I think you're running right on the cusp of tripping a lean code.
Do you have any dyno shops in your area where you could pay for a pull and get all the AFR and RPM data?
I'd really like for some of the old guys on here to look at your spark plug images and give their thoughts. I think you're running right on the cusp of tripping a lean code.
Do you have any dyno shops in your area where you could pay for a pull and get all the AFR and RPM data?
Unfortunately not. I’ll have to see where nearest one is but it’s going to be at least 2-3 hrs away each way. I did change the fuel filter yesterday and ran a bottle of fuel system cleaner on empty tank through system. Will report back once I try with another new tfi. The reason I changed diz quick yesterday is the car throwing a code now… 18c. That’s loss of tach signal/spout ground issue. That’s same code I got few weeks ago when I installed a new tfi and the car would stall out fast. I installed another tfi (one currently installed) and the code went away and car ran fine except my intermittent miss issue
You can do a search in the 5oh section about modern TFIs. It is not uncommon to purchase 3 at the same time and get 2 bad ones right out of the box these days.
85 Auto's have the CFI and to my knowledge are roller blocks with a flat tappet cam. So I am not sure about the firing order and I am not sure if the TFI module is a one year only but I am leaning towards it doesn't matter. Pulled this from a thread over on the Corral:
Basically speaking, the TFI module uses the PIP (profile ignition pickup) generated waveform from inside the distributor to fire the ignition coil. The PIP signal consists of a series of pulses generated by a magnetic shutter wheel, essentially like a magnetic trigger output on an older HEI or duraspark style ignition.
The PIP signal is also sent to the ECM and it's waveform contains a shorter pulse which indicates where the engine is in firing order. When the ECM detects the cam position pulse, it sends back a SPOUT signal, which the TFI then uses to adjust the spark timing based on engine requirements. The ECM also uses this signal to fire the fuel injectors in correct sequence.
If the SPOUT signal from the ECM is absent (i.e. when the SPOUT connector is pulled to set base timing), the TFI module fires the coil only at a fixed time based on the PIP signal alone (also known as "locked out" timing) - the ECM no longer controls ignition timing in this case.
Do some research and verify.
Basically speaking, the TFI module uses the PIP (profile ignition pickup) generated waveform from inside the distributor to fire the ignition coil. The PIP signal consists of a series of pulses generated by a magnetic shutter wheel, essentially like a magnetic trigger output on an older HEI or duraspark style ignition.
The PIP signal is also sent to the ECM and it's waveform contains a shorter pulse which indicates where the engine is in firing order. When the ECM detects the cam position pulse, it sends back a SPOUT signal, which the TFI then uses to adjust the spark timing based on engine requirements. The ECM also uses this signal to fire the fuel injectors in correct sequence.
If the SPOUT signal from the ECM is absent (i.e. when the SPOUT connector is pulled to set base timing), the TFI module fires the coil only at a fixed time based on the PIP signal alone (also known as "locked out" timing) - the ECM no longer controls ignition timing in this case.
Do some research and verify.
Somebody that has so much car knowledge and so little else to do that he accumulates in excess of 4800 posts.
Check continuity between spout connector and EEC and ground and the connector. PiP and TFI can both cause this code as well.
Yea it has 2 lol. It was the stock fuel filter that I replaced yesterday tooQuestion:
Does this CFI have injectors? Like what... 2? I'll bet they've never been serviced.
Well, I be a young'n with only bout 2800Somebody that has so much car knowledge and so little else to do that he accumulates in excess of 4800 posts.
After Unleaded gas came to be ( you wanted an old guy) most spark plugs started looking like they were burning leaner or cleaner...
The rust on the plugs and the worn electrode would make me replace them...
First start on my dodge motor did not go well.... Part of it was attributed to some of the engine paint being left on the plugs and possibly grounding out the spark.. I replace them before the second attempt to start a few days later.... The rust might be contributing to some grounding or poor grounding..
The wider gap contributed to this lean burn look also.. Spark plug gaps were mostly 030 back in the day...
The rust on the plugs and the worn electrode would make me replace them...
First start on my dodge motor did not go well.... Part of it was attributed to some of the engine paint being left on the plugs and possibly grounding out the spark.. I replace them before the second attempt to start a few days later.... The rust might be contributing to some grounding or poor grounding..
The wider gap contributed to this lean burn look also.. Spark plug gaps were mostly 030 back in the day...
another distributor installed… tach jumps in park and when put in drive can tell it’s missing bad
View: https://youtube.com/shorts/YhVywoUMyaU?si=9ko9urPuK5swpyMu
View: https://youtube.com/shorts/YhVywoUMyaU?si=9ko9urPuK5swpyMu
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