Surging idle and stalling after rebuild. HELP!!!

[JoshCampbell55]

Hey all, I have a 98 1500 with a 350 that had 90k miles on it. We just rebuilt the motor; same crank, bored .030 over, new cam and lifters with a 110 degree lobe center, the MPFI fuel injection we just installed, with new plugs/wires/cap. Anyways so I have the CRP123 scanner which we used to set the timing to 0 degrees on the distributor (which we are using the original one that was in the motor, the gear is not worn on it at all) and we are getting a massive surging and stalling idle; the retard on the scanner stays between 0 and .03 degrees so I know it isn't that.. We had thought it to be the IAC valve so I cleaned it up and it helped a little but not much, so I went and bought a new one and installed it with no luck. I've been reading to change out the Crank Sensor but I don't want to go just throwing parts at it like I have been so I wanted to ask you guys first.

I'm stumped here and really need some help, if anyone could give me some advice I really need it. The CEL is off and there are no codes to scan for but I want to say we got the code ONCE for Crank Sensor Circuit High Input but we haven't gotten it again.

[EDIT] I forgot to mention I've sprayed starting fluid all around the upper/lower intakes and there was no change so I don't think its a vacuum leak.

 

[JoshCampbell55]

Hey guys I didn't mention that the truck runs absolutely fine when not in park if it doesn't die before I get it to that point

 

[jrollings]

Find anything? Only thing I can think of is iac or tps but that's just throwing something out there.

 

[Countryboy38]

Possible tps also im sure you know this but when setting timing on those of fuel injected you have that brown wire you got to hookup. And maybe check your fuel pressure?

 

[JoshCampbell55]

Find anything? Only thing I can think of is iac or tps but that's just throwing something out there.

We changed out the IAC and TPS with no changes, I also changed knock sensor and crank positioning sensor as well as the Coolant Temperature Sensor (the one on the upper intake) with no changes. These were going to have to be replaced eventually anyways so I went ahead and did it now just incase. I called Chet Herbert cams and told them my situation and they said the ECU definitely needs to be flashed for the new cam. On Wed I called up Black Bear and ordered a tuned ECU which was shipped out today so I should get it either tomorrow or Monday (I'm only about 3 hours from them.) I'll let you guys know what happens!

Possible tps also im sure you know this but when setting timing on those of fuel injected you have that brown wire you got to hookup. And maybe check your fuel pressure?

Which brown wire? Is this the one with the MPFI spider? Yea we thought fuel pressure too, we had just replaced the fuel pump right before the engine went out but I checked it anyways and it was 60 psi and stays up after you turn the key off.

Mine is the Vortec 5.7 L31

Thanks for the replies, I'll let you know what happens after I get the new ECU from Black Bear!

 

[JoshCampbell55]

Just to update, I replaced all of the sensors as mentioned in the previous post and installed the new ECU from Black Bear. Truck runs fine now but on the occasional start-up it will jump to 2000 RPMs then idle real low around 500. Any ideas?

 

[90W7]

I know a bad MAF sensor will cause a rolling/ surging idle and won't throw a code. I've done a handful of 3.1, and 3.4 engines that have had the same problem.

I'd almost bet that's your problem.

Sent from my throttle body injected galaxy note3

 

[JoshCampbell55]

I know a bad MAF sensor will cause a rolling/ surging idle and won't throw a code. I've done a handful of 3.1, and 3.4 engines that have had the same problem.

I'd almost bet that's your problem.

Sent from my throttle body injected galaxy note3

Thanks for the info, I might pick up the Delphi from Rock Auto.

How can I test the one I have?

 

[JoshCampbell55]

I did the test on the MAF found here http://easyautodiagnostics.com/misc-index/maf-sensor-test-basics-1

Tests 1 and 2 it passed, but when I went to probe the middle wire it read out 0 volts at idle, and all the way up to 4000 RPMs. I unplugged the MAF at idle and there was no change in operation, still surging idle. I drove it up to put gas in it and it stalled quite a few times unless I kept my left foot on the brake and right on the gas. On the way back it stalled, I turned it back on and it had absolutely no power, it chugged and chugged no matter how much the throttle opened it wouldn't go passed 10mph.

When I hooked up the scanner to get the g/s MAF reading at 3500 RPMs it only read 28 g/s. Is this a normal reading or is my MAF sensor bad?

[EDIT] there also is no CEL

 

[90W7]

What is the grams per second at idle?