Hard start when warm and Scanmaster Q's

[matt94z]

My 87 GN has been hard to start for the last few weeks once its warm. If its cold it starts right up, but once its warm it cranks for a few extra seconds and blows out a puff of raw fuel when it starts.

Now Im thinking maybe the injectors are bleeding down or theres a bad sensor somewhere. I looked at the CTS reading on the Scam-master last time I started it warm and it was at 98 deg. Thats after the car sat for about 2 hours. It usually stays between 180 and 200 when driving, so Im guessing the CTS is reading correctly then.

My next question is what the F are all the readings on the Scanmaster and what should they be at on a good running engine? I would like to compare all my readings to make sure everything is reading correctly.

Thanks, Matt

 

[matt94z]

Just realized this might be the wrong section to post my questions in... I'll make a new thread.

 

[grocerygetter]

what's the IAC value?

 

[matt94z]

Im not sure, I'll heck tomorrow. But The BL is 150 @ idle... so Im guessing I have some vac leaks? I already fixed a bunch of leaks, but Im gonna have to just replace all the hoses. Does the BL monitor everything after the MAF? Because my I/C couplers are pretty old. I just ordered new ones.

Also what do should the IAT read? Is the value displayed equal to the actual temperature?

 

[matt94z]

Ok, my IAC value at idle is from 29 to 39 and at one point after driving for a while it was 19 @ idle. At cruising speeds its in the 50's.

My O2 is all over the place... but mostly in the high 300's to 400's @ idle.

BL is 150 @ idle

INT is 128 @ idle

I dont know what half of these readings are and what they should be at, so the Scanmaster is pretty much in chineese to me.

Im sure I still have some vac leaks, Im going to replace all the hoses and intake gaskets next week when I get a day off.

 

[TurboBob]

hard starting could be a lot of things, but lets look into a couple things.

Vaccuum leaks are the biggest cause of high BL at idle, the places to look are all of the vacuum lines (of course), the PCV valve, and the vacuum tubing that feeds the AC vent controls, they are thin black plastic lines that are close to the windshield on the passenger side.

An old O2 sensor could be the cause, it might be getting lazy at idle. One way to check is to watch the BL reading as you stop. The O2 sensor will still be hot from driving, so the BLM will drop, then rise again as the sensor cools off. A heated O2 sensor makes this issue go away.

Leaks around the EGR valve are another common source, as well as worn throttle shaft seals.

On the warm restart, leaky injectors will usually cause one cylinder to misfire more than the others, you can shut the car off after letting it run badly for 10-15 seconds, and the bad cylinder will have a colder header pipe. A fuel pressure gauge is an easy way to tell if you need to try this.

Also, if its just not enough air getting to the engine during warm cranking, holding the gas pedal down slightly may help it start. If this does help, cleaning the IAC passages may improve the situation, or just getting into the habit of starting it this way....

Bob

 

[matt94z]

I just put a 20k mile T-body on, NO leaky seals, New PCV valve, hose and grommet, and a new TPS, IACV...etc. Also, i disconnected the EGR valve vac line. And I replaced the O2 with a new Bosch one about a month ago.


On the way to work the BL was @ 145 @ idle and IAC was @ 49.

 

[TurboBob]

what chip is in the car? If you have valve cover breathers, it lets air into the engine without going thru the MAF. This makes the BLM go up.

Most aftermarket chips have the settings tweaked to counteract this.

At any rate, 145 is not uncommon, and if the driveability is ok, then you don't really need to worry about it.

If the IAC is that high at idle, (AC and defroster off) then adjusting the throttle stop screw to open the throttle blade a little (and then resetting the TPS) may help the starting.

Bob

 

[matt94z]

I got a chip from Stagemonster.. cant remember which one it is. Also I do have a breather in place of the oil fill tube.