I'm new to this forum so thanks in advance for any info.

Background:

Recently underwent a 305 to 350 swap. Went with a jasper class 1 motor. Replaced the prom with a jet stage 1 (trying to keep it pretty much stock for now to make sure I've got all the bugs worked out). After the swap, I was getting a code 32 and have since replaced the egr and the code did not return. I am not getting any codes now. I have also replaced the 305 injectors with the correct ones (350) and the knock sensor. I checked the base timing and set it to 0 BTDC. New fuel filter. I just finished cleaning the IAC and checking all the vacume lines.

The problem:

The engine runs smooth at idle and accelerates (WOT) fine. However, at slow acceleration and steady cruising speeds (e.g. 50) I can feel it surging. It is as if when I let off the accelerator (to try and maintain speed), that is when it starts happening. At speeds over 20 MPH, it is just annoying and at 70 I can't tell one way or another. At speeds under 20 (like moving up at a light), it will almost stall the motor.

As a test, I rev'd the motor in park, when I back off the accelerator, the surging is still noticable (guess it's not the tranny).

I'm stumped - any ideas would really be appreciated.

Thanks in advance!

 

Ive had that same problem as well as many other people who use the ecm with the stock code along with a different engine/setup. Im not entirely sure why it does it but its probably due to erratic vacuum signal from aftermarket cams with lower then stock LSA's and/or possibly from very low BLMs at low engine speeds causing erratic A/F mixture. Search around, im sure its been covered before in this or another forum.

 

OK - Just replaced the IAC and TPS - Still the same problem. Got a Fuel Pressure tester - running between 13 and 14 lbs at idle. Took the Trottle Body off and cleaned the living bjesus out of it. Seems a little better, but still surging at just off idle and at constant (low) speeds.

I finally got my WinALDL cable built and did some checking while at idle tonight. The "Rich Flag" seems to be on more than off and the BLM is at 115?

Is this beast running to rich? I realize that I need to do some logging while driving around, but does a 115 BLM at idle sound right?

Thanks in advance,

Spark

 

OK, I now have the base idle set correctly and the rich at idle seems to have gone away (at least for now).

Surging problem continues...

Question: I replaced the EGR from the 305 with one from Auto Zone. They wanted to know what the number was off the original OEM valve was. Because this was a 305 to 350 upgrade, I had no idea what the correct EGR was for this vehicle and pretty much had to guess - they gave me one of those "punch the washer into the valve" type EGRs and the code that the ECM was throwing did go away. Is it possible that I don't have an EGR that is correct for this engine (wrong washer) installed? Can I bypass the EGR all together by taking off the vacume line - just to see if the problem is with the EGR? Will the computer try to compensate for this condition and negate the test? This surging thing is driving me nuts!

Also, could it be the MAP sensor? I've replaced just about everything else - Is it possible to test the MAP sensor? How?

Thanks again,

Spark_man

 

you know, I just found out yesterday that my Fuel pressure regulator is crapping out, have you checked yours lately?

I'm having the same problems and have yet to change the FPR, I don't know if that will fix it or not. I too did an engine swap and such..

 

How did you determine that the FPR was bad or going? As I've said, I did put a tester on it and it was reading between 13 and 14 psi.

Spark_man

 

Thanks for all the help fellas!

Well, since I got no response to my last, I went ahead and yanked the vacum line off the EGR. Voila` - she purrs like a kitten - no stutter, no surge...NOW WHAT?

EGR=New - but still could be a problem - Auto Zone crapola.

EGR Solenoid = Tested per the Haynes manual and passed.

Map Sensor = Worked on the 305?

Which/Where do I go from here?

 

i was just browsing through the topics i am having somewhat the same problem i have a 350 engine and it idles fine at first then when i am driving i put in into nuetral(5 spd) and the idle surges form 1000rpms to 1800rpms it is real annoying one thing i forgot to add was the washer under the egr valve?? just wondering if this is my prblem? but i think you could delete the egr valve mode off the computer!sorry probably no help i just waant this engine to run right!...update me what you have since done..thanks a million!...

 

well, since the egr closes without a vacuum signal to it then the egr valve probably isnt the problem. Hook a vacuum gauge up to the line that connects the solenoid up to the egr valve and see what readings you get. there should be zero vacuum signal coming from the line at idle but at higher loads the solenoid should open and deliver vacuum signal. If it gives vacuum all teh time then it is defective or leaking.

 

I have the numbers off my stock 350 I just replaced it yesterday, I think it MAY make a difference. If you need the stock number off of my EGR please email me sky@skyscomputers.com , and I will get you those numbers. They gave me one with the washers too, and I didnt use a washer beecause the stock orfice was bigger than any washer they included.

When I went to get the EGR their were two that belonged to that 350 So I had them pull out both, and there was a huge difference in diaphram size. I had to measure mine to find out which EGR wa the right one.

Like i say if you need the numbers, and the size measurem,ents let me know. My 350 is a 94 TBI

If you Email me ill respond quickly, here I might not see the post.

LMK..let me know

 

115 blm means you're very rich, optimal is 128, stock computer will read down to 112. That'll cause a lot of bogging in the low rpms.

 

Winaldl is showing my blm counts as low as 88 at idle and sometimes under 112 while under load. What does this mean? Other than the obvious I need chip work and run way rich when cruising ...

 

My truck was doing the exact same thing.

I believe that there is a sensor to detect IF egr is present, but not how much is there. Code 32 going away only tells you that EG is present in the intake - but not necessarily in the correct quantity.

You are on the right track with the orfice washers. I was able to determine for sure that EGR was the problem by throwing a golf tee in the vac line between the egr solenoid and the egr valve. The surging problem disappeared altogether and so did my gas mileage. I then systematically started at the biggest orfice washer on the egr valve and swapped in smaller and smaller orfice washers until the problem went away altogether. It still very subtly bogs abit, but barely noticeable - not enough for me to want to swap in the smallest orfice washer.

EGR systems are really sensitive to modifications since exhaust backpressure is so critical to that system.