So I'm running into a problem once the car reaches operating temp. After reaching operating temp and I shut the car off for 30-60mins, it takes 2-4 times to re-start the car. Upon attempted start-up, it will stumble and die until finally it stumbles and corrects itself to get running. The engine temp is around 160* when this problem happens.

This started after I had the car tuned by Geoff at EPS here in Baton Rouge. I drove the car there on a mail order tune from Frost, swapped out the injectors to new 36lb @ 58psi injectors from Fuel Injector Connection and then had a street and dyno tune. So the only variables are the tune and new injectors.

Initially the car would have a problem starting at all times and Geoff adjusted the tables which corrected cold start-up, but I still have the warm engine start-up problem. Car idles and drives fine.

Car has:
TSP 228R cam
LT's
New Plugs and Wires
New fuel filter
New 02 sensors
Cleaned MAF

Dyno graphs show perfect fuel at WOT across the board, strong tq curve, and HP

I'm going back Tuesday to have Geoff try one more thing before I start throwing parts at the car... Any input?

 

Without having more info on what the tune really looks like, my best guess is a combination of RAF tables, MAF/ VE, After start Enrichment, or Startup Airflow.

Hard to say without scanning though... Its not a very large cam though, so it should be able to be tuned to a fairly trouble free setup...

 

Yes I'm ignorant when it comes to tuning, I'm just trying to get some ideas I can mention to my tuner. I don't have an idea as to whether its a mechanical problem (i.e. leaky injector, fuel pressure) or its in the tune. I would say its in the tune since the car was running fine before and the injectors are new, but Geoff is highly touted on various sites so I'm unsure. Hopefully he can resolve it.

Question: Would it be possible to keep the care in open loop at 0% throttle during all start-ups? Since the problem seems to occur with warm start-ups only, I assume if I prevent it from entering closed loop at warm start-ups it would solve the problem...? Again, I'm not very knowledgeable with the PCM so if this idea sounds ridiculous please correct me lol

 

Did your problem start, after you cleaned the maf ???

 

No that was cleaned before I brought it to the tuner

 

Are there codes coming up! I had some trouble like that! It was the maf !B0101

 

OK when the car is 1st started the ECM runs in "open loop "mode and the 02's are not being used until they warm up--
When the eng is dead cold the coolant temp has to reach apprx 140* before it switches to "closed loop" and then the 02's are fueling the eng and making adjustments to the fuel via the fuel trims to achieve a stoich AFR of 14.68-1 ( part throttle only)
AFTER the eng is warm and started above 140* the ECM uses a timer usually it waits only about 20 seconds before it switches to "closed loop"
With a cam and most importantly LT headers the fueling becomes rich in open loop --just the nature of the beast-- To compensate for this richness you have to trick the ECM to run leaner in open loop by commanding a much leaner AFR in the "open loop normal table" of your tune-----This is the table the ECM uses to command fuel during all start ups
Typically On a stock tune the ECM asks for a rich mixture at all starts anyway --something like 13.0---14.2 ----On my 98 with hds/cam LT's I had to "ask' or command a start up fuel of 16.10 in order to get the fuel back to somewhat stock AFR at start up
But don't worry it's really not that lean even though you are commanding an AFR of 16.10 what you're actually ending up with is an AFR similar to stock 13.0-14.2
This is all due to your mods --Again the LT's are the biggest reason
Only make the open loop adjustments in the start up fueling area of the OL normal table and at the appropriate coolant temps (20-65 KPA)

 

My issue...2019 stingray....also after warmed-up.....90% it is fine. I’m having trouble getting GM or dealership to doing anything until complete failure. Hasn’t failed to start but it will stumble 3 times once in a while.