Hello!

Im completely out of ideas... I have an 86 tpi that has developed a misfire/backfire while in drive only after it warms up.

When I start it, it runs perfect, but as soon as its warmed up the car pops and misfires under load and at idle but only in drive...as soon as I put it back in park its back to normal idle with no backfire or popping.

TPS tests out fine, I replaced the coolant temp sensor, all plugs were just out and good, plug wire order verified and correct. Cap/Rotor/wires/ignition module/Distributor have less than 2000 miles on them, brand new O2 sensor.

Thoughts? Please?

 

when this happened too me it was my ignition control module, when u replaced it did u put that dielectric grease on the metal under side of it?

 

Unfortunately I didnt replace it myself..it was replaced by a shop when I blew out my ecu and ign module.. Any way to tell if they did? Check for residue?

 

if there was not put on I know they can burn up pretty quick, easiest was is pull off the distrubter cap and under the rotor its held down with 2 screws, back them off and u should be able to see or feel some goop under there, depends what they used it could be clear or white

 

Ok, sounds like a good place to start..I figure it has to be something electrical/sensor related since it only does it in drive or reverse and not in drive/neutral.
And to be honest, I wouldnt be surprised if I open that up tomorrow and no grease from that shop.

Thanks for the tips!

 

Some easy tests.
Fuel psi test while driving and run the car with the hood open in the complete darkness an look for arcing plug wires.
If you run K&N filters, when was the last time you cleaned the MAF ?

 

Thank you for all the input, I will be doing all of the above saturday and hopefully I get to the bottom of this!

 

Just on the off chance someone comes across this with similar problems, I replaced the MAF Burn off Relay and MAF Power relay (same relay) and the issue has cleared up..There is a learning curve once the MAF Sensor kicks back in though I think...I have had it die out a couple times when you let it fall to idle after acceleration but its evening out now and dying much less with a much better idle.

Thank you so much for all the advice! It really helped me to narrow it down. Love this site!

 

i too have a 86 TPI car and the MAF relays are NOT the same. here are the GM part #s. burn off 10094701. power #10067925. and quoting from my FSM as to popping ,backfiring.loose wiring connector @ the MAF ,loose broken air duct,bad ign coil,valves sticking /loose, EGR fault,bad ign system,fuel pressure too low,too far advanced ign timing,proper routing of spark plug wires. i hope that helps .hit me up if you still have problems