i just did a 305>>350 swap in my bird, everything is running fine but the car is stalling on me almost every time i try to back out of a parking spot.... the idle seems a little low about 500 rpm sometimes, and other times normal at about 900. my guesses are:

1) im using the same 305 injectors.
2) fuel pump... only the people i bought it from had changed it recently (about 10 months ago)
3)the gas tank needs to be boiled because theres crap in it
4) the MAF sensor is bad or not calibrated (i've tried 2 and they give me the same results)

any help would be greatly appreciated, thanks a lot

 

If you are still useing the 305 injestors that is probably part of your problem. 305's came with 19# injectors 350's I believe came with 20# injectors thus allowing more fuel into the engine. Basical right now you are leaning your engine out.... I've heard that if you get an adjustable fuel pressure regulator and bump up the pressure this will help. Some one correct me if I'M WRONG.

 

Try the relays if you think it is MAF related. Will it stall with the MAF unplugged?

 

about the injectors, ill look into that.... and the MAF sensor, ill unplug it tomorrow and see if it makes a difference...... anything else i should try? thanks!! :hail:

 

does this also happen when the engine is warmed up and in closed loop? or just when you first start the car, with a cold engine? even if the motor is already hot, the ecm will still wait for a programmed amount of time before switching from open to closed loop. If the car doesn't suffer this problem when in closed loop, I think it would be pretty safe to say that you've gotta do some tuning of the ecm to bump up the amount of PW; specifically in the low rpm/low load area.

 

Check ground strap from engine to firewall.

 

Check for vaccum leaks since you replaced gaskets in a engine swap.

 

grounds are fine, seals and vaccum is fine..... i unplugged the MAF sensor and the car seemed to run the same way..... no difference at all. does this mean the MAF sensor has to be calibrated or changed? if so, how do i do this? or where can i find out? thanks a lot!!

 

The question is, did it stall going into gear while the MAF was unplugged?

 

haha i didnt try it...... but the idle was still not perfect, just like when it is plugged in...

 

With 87 Camaro with 305 to 350 swap. Anymore ideas out there. I was thinking that an adjustable FPR would be a good step and then adjust the FP until integrator on the SCAN Tool would run back around 128 like it is supposed to. This I assume would help correct the fueling issues.

If the O2 sensor is unpluged in this case (make the ECM stay in open loop) the engine will no longer stall when it is put in gear. But it has reduced part throttle and low speed drivablilty. This makes sense as the closed loop would allow the ECM to tune somewhat to the 350 even though it thinks it still is a 305.

At idle the computer seems to be chasing its tail when in closed loop. kinda of unstable up and down and commonly stalling when pulled into gear (auto).

Am I on the right track....????

 

yes you are, i unplugged the MAF sensor and the car seems to be idling a lot better, and not stalling when put into gear.... i havent actually driven it around yet with it unplugged, but i drove it to the front of my house and it seemed fine, not stalling what so ever, and the idle seemed fine..... can i just run the car with the MAF sensor unplugged since its running a hell of a lot better???

 

Sure.

It just won't run very good. Your MAF sensor tells your computer how much air is entering your engine and can thus demand more/less fuel out of the injectors (via a smaller/larger pulse width) at differing RPMs and loads.

What year 305 ECU/harness are you using, and what year 350? I'm assuming its an L98 from an LB9?

The L98 350tpi motors ran 22# injectors by the way. It *DOES* make a difference, but you should still be able to run a 350 on a 305 comupter. Granted the injectors are smaller, but the ECU still has the 19# injector constant, so it will still know how much fuel to put in. However, the 19#'rs may be running at too high of a duty cycle and not providing enough fuel. I don't know how close to maxing out the 19#'s are from the factory in the 305s.

Larger injectors would help, but you would need a chip burned for them. Raising fuel pressure can fix the problem, but it will usually make you run pig rich on one end of the spectrum.

Have you checked and adjusted your IAC (idle air control) and TPS (throttle position sensor) voltage? Could possibly be related to one of those, and they only take a few minutes to test and adjust. The procedure is in the Technical Articles on this site.

If you decide to go bigger injectors, I can burn a chip for ya pretty cheap so the ECU knows what's going on. PM me if you decide to go this route.

 

Ok Chief, hit the relays now. It's probably only one that's bad, but I like replaceing both. I then test the old ones and keep the good one (if one is) for diagnostics.

 

send a picture to where the relay is for the maf, or let me know where that wire runs into the harness..... theres a lot of relays ;x thanks

 

Courtesy of my buddy in the pop can helmet:



This is on a t/a. HTH.

 

thanks a lot man, big help

 

No prob. But thank Vader, I always hijack his stuff (like above).

 

hahaha
i think it was the freggin fuel filter HAHA it was broken and REALLY old. so i dont think the car was getting pressure when it was initially started. PROBLEM SOLVED thanks a lot for your help guys

 

There's been a mistake here. The four wire relay with ORG, ORG, BLK, DK BLU wires is the MAF Burn Off relay. Info from Chilton's and I just replaced mine. MAF Power relay (Can't see wires in picture) has 5 wires BLK/WHT, RED, TAN/WHT, ORG, and DK BLU. Best to go with wiring than location. Can be mounted in any of the three spots if your harness will reach.