my brother has an 88iroc that runs great, but since he has had it, it has bucked from 35-45mph when it drops into overdrive. we have replaced the tranny, and put a 4th gen rear in it in preperation for the 383 in the machine shop.i also replace the ignition control module just cause i had an extra one and thought i would give it a try. i would sure love to solve this problem for him before we put this engine in and before he gets back from military training.

 

Either ignition, or inadequate fuel delivery.

If it's ignition, put new cap, rotor, plugs, & wires on it. All that will transfer over to a 383, for which you wouldn't want to run old stuff anyway.

If it's fuel delivery, get a set of Frod 19 lb/hr injectors off eBay, the yellow-orange thin-body ones like these http://cgi.ebay.com/ebaymotors/FORD-...em220200272211 You can pick em up SO CHEEP, and they're SO EASY to re-sell, that it's not worth even taking the chance that the crappy Multecs in there now, are accidentally still any good.

 

why do you want to shift into overdrive at 35mph? it is probably bogging the engine down.

 

I forgot it had a complete tuneup right after he bought it. and its an automatic 305tpi i really don't think its bogging it down. ive owned three 3rd gens and one was a v-6 all were autos and none of them did this

 

I am having the exact same problem and can't pin it down! I have changed the plugs, wires, distributor cap and rotor, fuel filter, and ran some high octane boost and it still does it. I am running out of ideas. It like gets really jerky right? like forward and backwards?

 

did u change the torque converter when you did the trans? maybe the torque converter clutch is shot?

 

It got brand new everything, including torque converter i think it has 2200 or 2400 stall

 

Right; it's not the transmission, or anything TO DO WITH the transmission. Dead end line of questioning.

It's a driveability problem. Ignition or fuel.

 

you're right, it is a driveabillity problem.....with a factory tune, the torque convertor locks up at roughly 35mph, if it is going into overdrive at 35mph as well, he is prolly only turning 1200rpms. in overdrive with the tc locked up at 45mph i am only turning 1350-1400rpms with 3.42 rear and 25.7" diameter tire. with the stock 3.27 that was in my car it would be even lower. the tuning isn't gonna provide the fuel to pull that heavy car at that low of an rpm.

 

im having difficulty understanding how it could be an ignition or fuel problem if its only occuring while shifting into OD. if it was ignition or fuel wouldnt it occur from a takeoff also, i would imagine that would put more of a load on the engine than shifting into OD

 

In overdrive, you've got the least mechanical advantage driving the rear wheels, so the load on the engine is highest. That means that if any of your ignition or fuel delivery components aren't up to scratch (my money's on ignition), you'll be misfiring. In addition, the torque converter clutch is locked up in overdrive, so you don't have the slippage in the torque converter to soften the blow and hide the problem.

 

I had an 87 chevrolet truck that did the same thing. My buddy unplugged the plug on the driver side of the transmission, and this stopped the jerking, I dont know if this hurt the transmission because I sold the truck about a month later but it stopped it for a month anyways

 

I am more inclined to think it is an ignition or fuel problem too. i just don't have a starting point. with it having a tune up with control module and as well as it runs in every other situation i just don't know were to start.

 

Since I am having the same problem and you have seen what I have tried so far in an earlier post. I have new fuel injectors on the way so I will let you know how those do

 

Yeah, I had a 84 Cutlass ciera that did the same thing in O/D. It wast the TQ lockup switch. I unplugged it from the trans and it stopped the jerking.

I dont know if your switch is setup the same, but it might be worth looking at.

 

If i run it in drive it does fine, but as soon as i put it OD it bucks back and forth. and its only in that speed range so i really don't think its tranny related. especially since thats a totally diff tranny.

 

Well the cutlass had the same symptoms. It was fine in drive, it only jerked in OD.

Not really a big deal to just unplug the trans for a short trip just to rule it out.
I could be wrong, but it would be a easy test.

 

It's not the transmission. Unplugging it won't tell anything about the problem that isn't already known; which is, it's a driveability problem, either a weak spark, or a lean condition, that renders the engine unable to cope with the added load on it at light throttle that the TCC puts on it.

If you'd like to actually fix it, you should quit messing around with the transmission, and diagnose why the motor is unhappy.

 

Well I do want it fixed, hence my post. I also stated I don't think it is a tranny problam either but i don't want to be rude to anyone willing to offer any suggestions. I just don't have a place to start with. everything that i can think of has already been tried

 

What happened when you threw out the crappy injectors and put in some good ones?

What's the fuel pressure WHILE IT'S DOING IT? That is, while driving down the road during the malfunction, NOT while sitting in the driveway idling. Duct-tape the gauge to the windshield or something.

 

Ohm out plug wires/check plugs, but I'm guessing you already tried that? Fuel pressure?

Tell us what you've tried so we won't have to guess?

 

Right, I can see you don't; on the other hand, people seem to want to send you down that left turn.

You REALLY REALLY REALLY should try the Bosch injectors. People who rebuild injectors, won't even bother with Multecs, they say they're not worth the effort or money. You absolutely WILL NOT believe the difference. Try them. They're cheeep and easy. High probability of fixing the problem. If you don't like them you can re-sell them. What's not to like?

 

I think i'll try replacing the injectors since we were going to replace those with the new engine anyway. if i put in bigger injectors on the mighty 305 will it mess anything up

 

Same "nominal" size.... 19 lb/hr

Did you click on the link I gave you yet, and read through the applications listed?

The Bosch ones just WORK better. Better in every way.

 

I don't see any link. but I am willing to click one

 

It's in the VERY FIRST reply. Hiding. Right after the words "like these".

Starts out http://..... Click there.

 

Yeah the ones in the first post those ones? I bought them lol. Sorry but like I have said I am having the exact same problem and am running out of things to try. When I get them and put them in I will let you all know how it goes. Anyone know how difficult this is going to be to install them? I am thinking I am going to have to take off the Plennum and everything?

 

The most complicated thing about installing injectors is making sure you lube the seals and don't pinch them when installing
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WOW sofakingdom I'm a big blind idiot. thanks for the link

 

I don't think those will work with his 383 cause he is planning on pumping out 400+hp. Is there an injector that would run the 305 and the 383.

 

No; of course not.

A 383 takes 30% more fuel to run at any given RPM than a 305, all else being equal. That means the injectors need to be that much different in flow.

I think he might be surprised at what those Bosch injectors will support.

And like I said, they're SO CHEEEEP, and in sufficient demand, that he can buy them, try them, and if he doesn't like them re-sell them. What's to lose?

Yeah I know how it goes with things like that link.... I'm kind of dumb and slow myself, and don't pay near enough attention (sometimes it charges me too much I think), so I miss things that way too....

 

Hey camarod24 did those injectors fix the problem? i haven't replaced my brothers yet because he wrecked his car. so i have to get the car driveable before i can do anything to it.

 

Mine had the same prob and my culprit was the computer. used to buck and jump round 35, may or may not be the same problem with yours.

 

I had this exact problem. And I mean EXACT. I did so much work during my rebuild that it became difficult to pinpoint the problem. Turns out that my new torque converter was NOT the problem.
Somehow I swapped 2 of the plug wires around when I changed the plugs. I swapped 4 and 6. Couldn't feel or hear anything wrong until the car hit OD. As soon as it did that, direct line between trans and engine, it felt like I was on a quarter operated vibrating bed.
It's a simple check. Won't cost you anything but 5 minutes.
Bottom-line......dead miss due to swapped plug wires for me.