I have a stock 89 iroc 5.7 that has hard starting problems. I've already tracked down the maf as being the problem. The iroc starts and stalls unless I tap the gas pedal. If I disconnect the maf it starts way better without stalling, but runs rough. So I went to autozone and bought a cardone part #74-4712. I installed it and the car starts the same. So I remove the maf from the throttle body with the harness still connected. The car starts without tapping the gas pedal, no stalling, and runs way better. Thinking the maf is defective I go back and exchange it. I install it and the car behaves the same way unless I remove it without disconnecting the harness. I need help, please.
Are all maf sensors the same? I read somwhere that the maf part #74-4712 is made for 86-87 irocs and part #55877 are made for 88-89.
I dont have the original so I dont know what it had originally. The maf that I replaced, I left that one at autozone, not thinking of checking part number.
Thanks,

 

Did you check all the housings for cracks or leaks? Also check the relays, one could be stuck on. Those pinch clamps on our front air dam dont look all that great for keeping a tight seal but that shouldn't be too much of a problem since it is before the MAF.

I got this problem right now too, but haven't got around to getting a replacement MAF yet. And getting code 34 when plugged in and getting code 33 unplugged. Starts and stalls when plugged in and runs better when unplugged. I got a spare ECM and swapped it out too and same thing.

So I am interested to see how it turns out.

 

Thanks for replying Zepher. I still haven't found what is wrong with my car. Yes, I did check for cracks and didn't find any. After getting tired and not finding anything wrong I took the car to two different mechanics and they couldn't find anything either.

Thanks,
P.s. keep me posted if you find something.

 

Zepher86z28 try disconnecting the cts sensor. My car started and ran great. Now I have to find out what's wrong...cts, wiring or ecm.

 

How ?
Have you done the MAF diagnostic tests from the service manual ?
Alot more to the MAF circuit and operation than just the unit itself

http://www.chevythunder.com/maf_code_33.htm
http://www.chevythunder.com/maf_code_34.htm
http://www.chevythunder.com/maf_code_36.htm

 

My CTS was replaced a few years ago when i broke it trying to wrench something off. No my problem is a code 33, I am getting voltage on "D" connector on the MAF sensor, I replaced the burn off relay with a good ac delco one and still getting the problem. According to the flow chart everything else is good. I also took a closer look at my maf power relay I got from napa and according to another thread there should be resistors in it but there is none (source: https://www.thirdgen.org/forums/tpi/...nces-they.html) So I am currently waiting for them to come in along with another burn off relay. It takes a week to come up from the states, so I been playing the waiting game. *also mechanics now a days arent too much help unless they are familiar with TPI. I got my service manual and that help out a lot, for $50 it is priceless, when ever someone else works on the car i throw that in with it too, really helped out the guy swapping my rear end gears!!!

 

http://api.viglink.com/api/click?for...13719320327356

 

I dont know if that will help me, I do have a 122 ecm and I tried the 168 ecm too, the 122 ecm give me a code 33 and the 168 ecm gives me a code 33,36. and the car already has the Hypertech Thermo Master chip too. I do have the ability to burn chips but i have yet to sit down and learn everything, I had enough troubles getting Tuner RT pro to connect to my ecm.

 

Zepher, mechanics I've been too here in my town dont understand tpi either. I noticied that when i start disconnecting sensor's the car will start without having to press on the gas pedal. So I can rule the maf out as being the culprit.

 

any luck figuring out that code 33, I am having the same problem, I have gone through the gm troubleshooting chart to where it says my problem is a faulty MAF so I change it and still have the problem. Checked all grounds, ducting, vacuum, relays, the only thing I can figure is the ECM! Please get back to me if you find your problem I could use the help!

 

Sorry for not posting sooner, but had work related issues. Now that I have some free time I checked my car again. I replaced oil pressure sender ( oil was leaking from it) and also replaced the pigtail. I start up the iroc and she starts on the first try without me pressing on gas. The idle is still rough and rpm jumps from 650 to 700, but didn't have have that much trouble starting her. I notice that the knock sensor connector is broken so I replace it along with the pigtail. As soon I try to start her (initial start cold motor) I have a hard time and have to press on gas pedal to keep her from stalling. I wait for engine to cool down again, disconnect knock sensor and she starts right up. I can unplug maf, tps, cts etc., one at the time on first start of the day and she fires up. When all sensors are connected thats when I have trouble starting her. Limp mode? ECM is bad? What do you guy's think? I'm leaning towards ecm.

Thanks,
Gerry

Parts installed
Fuel pump about three years old (fuel pressure is good, took iroc to two seperate mechanics)
bosch III's from South Bay
spark plugs, wires, rotor, and cap
iac, tps, o2, knock, oil pressure sender, maf
ecm (autozone cardone)
pigtails to sensors are new

 

Sorry, I forgot that fuel pump relay, maf power, and maf burn off relay's also new.

Thanks,
Gerry

 

Have you checked your intake manifold vacuum? A vacuum leak can cause the code 33.

 

I got my relays from NAPA also.BUT as you have noticed ,you have to double check to see if it has all the required internal components. my burn off relay from NAPA is for a Cadillac rad fan
for instance

 

Thanks for replies. Last time I checked I couldn't find any vacuum leaks, but I wouldn't hurt to check again. I need to get my hands on a manual. Again thanks.