I have an 86 IROC and it hesitates when first started. If you try to give it gas it just hesitates pretty bad but if I let it warm up it goes away alot but still has a slight hesitation. Could it be that the timing is off? Vacuum leak? Would a bad MAF relay cause that? Thanks for any help!

 

Well if your not getting a service engine soon light on then consider your sensors OK.

If you car has alot of miles or hard miles it could be a brittle vacume hose gone bad or your timing chain could have a good amount of slack in it. A little advance might help.

 

I got the SES light on and was told it was a code 34 MAF sensor but replaced that and its still on. Would a bad ECM cause that?

 

try unplugging the + on your batterie then hooking it back up to reset the cpu... ive had this happen to me before ran like **** after replacing a sensor then reset the cpu and my problem went away

 

Z28 monster is correct.. Anytime your ecm senses a bad sensor even though the light go's out the ecm still has the ses code set.
You are suppost to disconnect your battery for 10 to 15 seconds after you replace a bad sensor to clear the code from the ecm's memory .Then drive it.

 

I've already done that many times but it still stays on. My luck I have another sensor going bad. All Vacuum hoses look good. Only things left I could think of is timing off or bad O2 sensor.

 

Mike how did you find out you had a code 34.. you can test your ecm for codes set with a paper clip and your ignition turned to the on position to pull any codes from the ecm have you tried that yet?

 

I found out by having it tested by a friend who works at Autozone. By putting the new MAF on there it runs alot better just has that hesitation at first start up. No I havent tried doing that cuz I'm not too sure exactly where the paper clip goes. I mean I know how to count the blinks and all but like I said not too sure where the paper clip goes.

 

place your ignition forward to the acessories position.
you know where to test and run diagnostics under your dash.
bend a medium sized paper clip and stick one end into the corner top right hole and the other into the hole next to it .

your fans should come on instantly
then you get a code 1 2 (3)times then every code after that is a bad sensor that your ecm has stored ...

 

the hesitation you speak of is a common problem for many of us. my car hesitates and pops thru the intake when it is cold, but when it warms up, it goes away. there was a post on it a few weeks ago but no one had any answers.

one thing to check if you are getting the maf code is make sure the ground wires on the back of each cylinder head is good, clean, and tight. then you may want to replace the maf power and burnoff relays as well just to be safe.

 

Well my fan is hooked up to run all the time. I'll try the paper clip sometime today hopefully. I'll also check the ground wires behind both cylinder heads to see what they look like. As for the relays how can you tell which sensor is which cuz they all look alike? I have the haynes manual but it doesnt do any good when the sensors arent where the say they are I mean I know where there located just figuring out which is which. I think the guy who had it before me that did the swap didnt know much about what he was doing.