Ok its a 3.4 from a 2.8 swap and at idle it seems to miss or im not sure if its a miss but it pudders every few seconds or so and is really anoying. the IAC valve is usally screwed in alot and i think it might be giving it too much air. Too much air makes it do what? like what do you notice when its running with too much air. But if i pull the wire off the IAC and manually unscrew it some the idle is lower and doesnt miss anymore. but i go out the next day and i have to adjust it again. what would i do to figure out what this problem is. im not sure if my TPS is adjested right either im not sure what to do. when i rev it up slowly it comes up smooth without the IAC wire on but with it on its rougher. DOnt know

 

KPT,

A little more data is going to help a bunch:

1. What year is your car?
   
2. What fuel system are you using? MPFI?
   
3. What injectors are on the engine? Original 2.8 or larger 3.1?

That will help diagnose this a little.

 

ok its a 86 MPFI with 3.4 injectors. before i left the 2.8 injectors on and had the same problem and thought that by switching the injectors would fix it. also i talked to some people yesterday and they say it seems like its running rich. well i know why, i have the tps sensor up more than normal because if i bring it down the engine will stall. so im not knowing what to do on this one


thanks...

 

When the engine is fully warmed and the O² is active, does the mixture seem to get better? You can test this in the Field Service Mode through the ALDL and SES lamp.

I'm thinking that the difference in flow rates of the injectors may not be the only problem, but that the ECM is programmed for longer injector pulses for the smaller injectors on the 2.8L engine. If that's the case, you may be into a custom EPROM or installing an FPR to adjust the fuel pressure. Incidentally, have you tested the fuel pressure?

 

when the engine is warmed up it gets alittle better. Ill be sitting at a light and the car will be running smooth and every second or so it will jerk the car not very bad be it will be enough to annoy you and you can feel it more than you can hear it. It doesnt sound like a backfire, but i it could be anything. it also pudder on a slow acceleration, if i put it to the floor it dosent seem to do anything wrong but on a normal acceleration it SUCKS!


whats this about FPR and fuel pressure. whould would that do and how do i do it??

also if i need a custom chip, is it hard to get and is it usally expensive?? or what should i do to find out why it runs bad.