ok, i've got some time on my hands and i'm getting serious about finding the cause of my hard starting when cold problem.

Problem: turn key to ign, fuel pump primes, turn to run, cranks healthy, fires, stumbles, dies. crank again, fires, stumbles, dies again. I can keep it running if i give it gas. Runs great when it's warmed up. I've had this problem since i did my 350/T5 swap. got custom PROM made by tuned performance. converted sensors, ESC, all others i had to change over to 350 specific parts.

So today i hooked the car up to my computer and took some live data with tunerpro RT. i'm going to share 4 screen shots with you. based on what i saw on the live data when the car was warming up i have a few ideas. Please tell me what you think:

1) MAF sensor: when car is off or not running, it reads 23. When running at operating temperature, it reads hight 6s, low 7s. My FSM says that its supposed to read between 4-7 at idle when warmed up. if it's going over 7 does it mean it's bad? no codes set. It IS kind of old. probably over 15 years old.

2) The "desired idle" speed is set to 3187. why so high? is this correct?

3) CTS and TPS are both reading correctly. CTS read coolant temp accurately. Checked TPS with ignition on and checked the voltage reading as i pushed the gas pedal all the way down slowly. voltage at idle is .57 and smoothly went up. no jumping.

4) The live data has a section that says whether the engine is running lean or rich. I noticed it runs lean at start up, but once it gets warmed up it gets rich. shouldn't it be the opposite? could this be because of the MAF sensor?

So the only thing i can see that's wrong so far is the MAF is marginally out of spec due to it's live data readings. I REALLY want to make sure it's bad because this part isn't cheap (aftermarket brands are between $180 and $250, and brand new AC delco is $450!). TPI gurus i need your help!

Also, my photo-hosting website just went down for maintenance, so i will post my data screen shots when it comes back online.

 

Screen shots. Just a heads up, I took these screen shots after 5-10 minutes of idling and then turned the car off (as you can probably tell from some of the data). i will take more screen shots tomorrow while the car is running.

also, i want to bring attention to a parameter in the 2nd picture. you will see the MAP parameter highlighted. My car does not have a MAP sensor and the value next to the parameter was changing. how can this be?

 

anyone?

 

bump

 

Are you running a 88 tune or did Tunedperformance migrate you onto a 89+? I ask as it may or may not be related to your cold start injector. If tuned did a 89 tune he would have allowed for 8 injectors to add fuel when cold. If he didn't- is your 9th injector all hooked up?

 

He migrated me to an 89+ tune, because my engine is from a 1991 corvette and doesn't have a cold start injector.

 

bump

 

bump

 

can someone at least tell me what brand of MAF sensor works good for them? should i get another bosch? new or reman? where does everyone buy their MAFs from?

 

Get a Rich Porter brand

see this thread

https://www.thirdgen.org/forums/tech...sistantly.html

 

Thanks for the suggestion! However, this isn't going to work for me because 1) there are no O'reilly auto part stores in NJ. 2) i went to their website to see if i could have on delivered and all they show is the A1 cardone garbage reman sensors. i'll do a search for rich-porter brand.

 

what's the community's consensus on Spectra brand MAFs? That's the only brand i found that sells new units. Otherwise rock auto has reman'd AC delco units. that's probably the only reman'd brand i'd trust to use.

 

bump. still need help.

 

Try a different 89-350 PROM maybe? I don't know the ECM value too well to know what to look for, nor am I very MAF versed, but that's what I would try just to rule it out.

 

So before starting for the first time today, i primed the fuel system 4 times with the key and disconnected the EST wire. The engine fired and stayed on but idled very low. about 250 RPM. kept feathering the gas pedal for a few minutes. then turned the car off, reconnected the EST wire, started up, Idled better. Does this mean the pick up coil is bad?

 

Seems kind of strange that the IAC is pegged at 160 in your screenshots. Have you verified that it is functioning correctly? It may explain your extremely low idle if it's malfunctioning. When was the last time you checked the timing?

EDIT: Scratch that, I thought it was while it was running. 160 is normal for data when the engine is off, if I remember correctly. Unless it actually is running in the screenshots.

 

yeah sorry. I have to get a screen shot when its running. also my timing is set at 8*. I'm not sure what it's set at on the chip itself. also, bought 2 brand new IACs. no change.

 

I've got a special interest in this thread since my car is having similar behavior, where it will catch and die a couple times when cold before starting. I've got a MAP, but hopefully I can get something out of the answers here. In case it's applicable, I also have working CTS and air intake temp sensors etc etc.

It does seem very strange that it was idling that low with EST disconnected. Did you read that 250 RPM from the scanner or just guess by sound? And dumb question, but good to rule everything out: You set the timing with the EST disconnected right? Have you been able to check fuel pressure while trying to start cold?

 

cool. hopefully we can help each other out.

it was idling at 250 RPM based on what the Tach was showing. Engine was bogged down real low by the sound of it too. I did this because my FSM says to do this to test the distributor pick up coil.

Yes, i timed it with the EST wire disconnected at operating temperature. Keep in mind i started the engine with the EST wire disconnected when it was stone cold. so there was no advancement.

Fuel pressure cold at first start of the day is 42 PSI. I set it there with my AFPR.

It runs great when its warmed up, it just idles low when cold. like its not getting enough fuel enrichment or idle up. i wish i had my EBL flash ECM. That's next on the list.

 

ok, so here's the data feed with key on, engine off, engine cold, didn't start it even once. Anything look out of place?

 

bump

 

no ideas, huh? i know throwing parts at a car isn't the best way to go about diagnosis, but given the info i've presented, i'm going to pick up a cheap MAF sensor and see what that does. If it fixes the problem, i'll return it and buy a better one. If it doesn't the diagnosis will continue.

Until then, tune in next time for another post of "Hard starting when cold".

 

Did you ever try a different 89 prom? It'd be easy to tell if it's in the calibration that way. I do like the ebl thought. It's way user friendly, especially compared to earlier stuff.

 

Why such a low idle? Did you set the minimum idle speed via the throttle blade stop screw? What are your IAC steps when idling?

 

No i didn't as i don't have any other proms from 89. I do still have my original 305/auto prom but i don't think it's gonna like that what with larger injectors, no AIR, no EGR No VATS, etc...As for the EBL i'm still on the market for one. Some day i'll order it.

Yes i did, Al. I'll get the IAC steps when i get the computer back on the car.


So tonight i took the car out for the first time since doing the head gaskets. Drove it all night. I tried starting it with the MAF disconnected, didn't want to start. Plugged it back in and fired up. So the MAF is good?

Again, once warmed up she ran like a champ! drove 50 miles and she used a quarter of a tank. not too bad.

Actually here's a stupid question: I disconnect the battery every time i put the car back in the garage. would this cause the hard starting?

 

Well it doesnt help. Everytime you disconnect the battery and reconnect, the computer has to relearn itself. Leave it connected and see what happens.

 

ok i'll drive it and keep it hooked up for the night and see what happens tomorrow.