mdtoren

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?

billyhoss

iTrader: (1)

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?

mdtoren

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?

billyhoss

iTrader: (1)

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

mdtoren

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!

TTOP350

iTrader: (8)

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 ?

mdtoren

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

mdtoren

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!

rusty vango

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