85 IROCNROLL

I have a 85 iroc that has a 350 out of a truck. Came stock with a 305 tpi. They took all the tuned port and stuff and put it on the 350. Ok, now I just recently got this car on a trade and brought it home on a trailer. I new it didnt run good when i got it but thought maybe a tune up would help. Well i have replaced cap, rotor, plugs, wires, ignition module, and the pick-up coil. Got it started and no change. Has a really bad miss and when you drive it down the road it has no power at all. Wont even spin the tires. Air filters are clean. Once again i am stumped. Any ideas?

five7kid

iTrader: (14)

In order to run properly it needs air, fuel, compression, and spark at the right time in the right quantity.

Did you check timing? It won't cause a miss, but will cause poor power.

Are you sure the spark plug wires are on in the right place? A couple of wires crossed will definitely cause a miss.

Have you done a compression check?

Is the SES light coming on? If so, have you checked for trouble codes?

85 IROCNROLL

Yeah the check engine light is on but i did not check the codes yet. Would the car run if the dizzy was 180 degrees out? Tried to set the timing with a timing light but the marks were not at tdc where they are supposed to be. So i got the motor at tdc by sticking a sharpy in the #1 cylinder and turned the motor over by hand and then made a mark on the harmonic balancer and tried to set it that way. Its just an estimate though so cant really get it exact. When I rev the engine the timing moves alot and when i let it idle it goes back to tdc. Is that normal?

ninetyone

iTrader: (2)

Sounds like a bad injector. You will not get any codes from this either. Get a multimeter and ohm your injectors. Set the meter to ohms and to test at 2k. Then, pull the harness off of each injector one by one and test the injectors by the two small prongs sticking up out of them. They should ohm out around 0.013-0.018 or so. If you find one at like 0.003 , then you have a dead injector. That would definately cause a miss! I just went through the same problem. This is a very common problem on our cars. Mine is a 91 350TPI. Let me know what you come up with. Later

ploegi

Does it have the original PROM from the 305 in it? If so, you just found a major part of your problem.

ninetyone

iTrader: (2)

So, did they take out the 305 and use the 305 TPI stuff? If so, then yes, it probably needs that 305 prom in the 305 computer to run properly. The computer itself does not matter. You can even use a computer out of a v6 firebird. Just as long as the prom is changed. Now, i am not sure if actual engine displacement is accounted for in the GM proms. I doubt it though. The 305 motors only came with 19 lb/hr injectors , while the 350 had 22 lb. I do not think that the computer or the prom(chip) is the problem here. If you have all 305 fuel injectors and sensors from the 305 , then you need that computer and prom you have in there.

ploegi

When the engine is cold, (and therefore NOT in closed loop) the computer runs the engine via data written into the prom. This information is going to be different for a larger displacement engine. (more cubes = needs more gas....) You have a valid point with the injector size though.

To REALLY fix it right, you need to change the PROM, and the injectors. (or, you can compensate to some extent for the too small injectors by installing an adjustable fuel pressure regulator, and ramping up fuel pressure.)

85 IROCNROLL

I was wondering about the injectors. I read some where that you can use all the 305 injectors but the computer would have to be programed to push more gas ( as long as the 350 engine was stock with no upgrades) Probably better to get the right injectors though. I would put money on it that the 305 injectors are in still in it and that would explain alot. I will get the numbers off of them and check and let you guys know.

iroc a 86 berli

check the valve lash, pop a vacum gauge on it while its missing and watch for any fluttering on the needle. this will help indicate valve problem.
the 305 injectors will lean it a bit, but should still run somewhat decent.