dpeak

Hey guys, I just recently resurrected my great FD project after a long winter and am having a bit of trouble. It is a 93 auto with absolutely no mods.
-When driving the car at ANY rpm it will backfire and bog down when given just a
little gas.
-I have to accelerate very moderately until it clears up, sometimes it wont.
Needless to say, when I go WOT, all I get is backfires/bogging down.
-Occasionally, I can let of the throttle when it starts popping and when I hit the
accelerator again, it will run perfect and goes like a scalded monkey.

All vac hoses are in good shape and routed correctly, no cracks in y pipe /intercooler hoses, tps is correctly set, reset ecu, recently changed plugs/fuel filter/air filter and running on shell 93 gas.

Any ideas on what might be causing this?

lexidic

sounds like its running way rich, do u have a boost gauge/ boost reading?

J.S.J

This sounds like a typical ignition problem, likely cause a plug wire which could be "ajar" at the plug or coil, secondly could be a defective plug or wire. If you installed new plugs to correct the problem I would think they are OK and the wires are on tight since you were attempting to solve your problem. This then would lean to the wires or one wire likely. I would make sure all the plugs have adequate gaps / are not damaged at installation (cracked porcelain), wires are making contact with plug and coil electrode for sure. IF the ignition system is in good order the backfiring would then likely be a lean mixture but my feelings are it sounds more like ignition. Not complicated just plugs/wires/ not ignition module or etc. Now this just my opinion as a tune up and drive-ability tech.

FDNewbie

iTrader: (10)

When was the last time you changed the fuel filter and the spark plugs? I had the EXACT same symptoms in my FB, and the plugs were bad (had flooded recently real badly) and it was on the original fuel filter . Changed 'em, and the prob. disappeared.

skunks

have you tried to reset your ecu? do this by disconnectiong neg side of battery and steeping on brake pedel for a while. then reconnect and it should be reset.

jeremyb

Do you have an aftermarket ecu? A/R gauge and WBo2?

Jeremy

dpeak

The car is bone stock and has no mods/upgrades/add ons etc. The fuel filter and plugs have less than 100miles on them.

DGblk93

Go back and check the small vac. hose that runs to the MAP sensor. Under the hood, drivers side, little black 'box' that is supposed to have a hose coming out. The symptoms sound like it popped off.

DGblk93

...it will run perfect and goes like a scalded monkey...

FDNewbie

iTrader: (10)

The box is labeled "Boost Sensor" IIRC

DGblk93

Guess I coulda gone and looked
Off topic - but I'm busy doing the 99 taillight poorboy conversion today.

FDNewbie

iTrader: (10)

Oh I didn't check...I just remember because I had a panic attack once, thought I had blown my motor, posted about it, and someone was like CHECK THE MAP SENSOR! lol. I was confused where it was, because it said "Boost sensor" (figured it was something else). Never forgot since then

J.S.J

Reading the above and your first post again, I still don't see or here you remove the plugs and wires and inspect them for flaws. If you did great if not I would. I would not bother with the trailing plugs now, stick with the leading plugs and all the wires. Remember the leading ignition system is a waist spark system so likely the coil is OK and since the trailing plugs likely would not make the car run that bad the coils are likely fine. I still say rule out the plug/wires and there respective connections. A wire ajar or one thats defective ether burnt or where a plug wire boot has a hole or a carbon track will act up under load and as the load decreases the system will begin working good again. Surely it could be something else but the most likely problem is the above.

Sickass7

Funny, my initials are JSJ (Jeffery Scott Johnson) lol. Sorry about getting off topic, just noticed that. I had the same prob, 93 auto also. My problem was some oil being blown through the intercooler-through the TB and into the engine-and fouling the plugs.

dpeak

Thanks for the help everyone. MAP sensor checks out ok and the intake elbow/throttle body has very little oil in it. The car only smokes a little at startup so I dont think oil is blowing through . Anyway, I looked at the plug wires and saw the words AUTOLITE, shook my head and ordered some MSD's. They should be in on friday. Didn't get a chance to confirm that this is the problem but I'm sick as a dog and just figured it would be best to change them anyway. I'll post up the results this week. 1 more tidbit: the car will rev up fine sitting still, the problem only shows up whle driving.

dpeak

Replaced wires today and checked plugs, no problems at all. Coils were spec. The car ran really good for a few minutes and it started the bogging and popping again. It took a lot longer than usual this time. It is strange, it only acts up after the car is warmed up really good. If I let the car sit a half hour or so, it will run lke crazy for a minute or 2, then it f's up. I've seen coils act up only when hot b4, just not sure with these. Can anyone lend some more advice? I know it is getting boost b/c I can hear the BOV woosh when I let off the gas

dpeak

bump

rzograbian

it might be the tps that is out of wack.. check the connector that goes to it and see if its plugged in. then, check the sensor itsself... it there is soething wrong with it, disconnect the battery and press on the brake pedal to reset the ecu and see what happens...

-Roman

dpeak

Finally fixed it!!!!!!!!!!! First off, I would like to tell all of you thanks for the advice and saving me big $$$ on mechanic bills.
Test drove it today and it was doing the usual snap/crackle/pop as I was remembering the happy 10 minutes it ran perfect right after the spark plug wires were changed. I popped the hood and noticed the clamp was loose on the intake elbow pipe rinning from the intercooler and the pipe was pushed back a little. Tightened it back up, took er for a spin and she ran perfect! Guess it was the plug wires after all and just forgot to tighten that clamp up when we changed them. I know you all will probably flame me for being tarded, but at least it's fixed now.

FDNewbie

iTrader: (10)

You know what? I'll take endless flammage and being called a 'tard, and a $40 fix (new wires) ANYDAY over coming up w/ the diagnosis of something major and costly

Congrats on fixing it...I know the feeling. Now go out there, and beat the crap outta her...make all that effort worthwhile!