ZR-1 Net Registry Forums - View Single Post - Diagnose - 2,500 rpm Stumble Miss - 1991 8k mile ZR-1

SteelBlueZR1 · 03-05-2013

Thanks everyone for the great substantive ideas and feedback. I am slammed at work, but bummed I can't find time to start doing these diagnostics... I will update when I finally get time in the next week or so. To Answer Hib's questions:

If I read the OP correctly, this car sat unused for 20 years? CORRECT, CAR DELIVERED WITH DEAD BATTERY AND NO GAS.

Does the check engine light function properly during bulb check? If so, are any codes set. NO CODES SET

Has the light ever been on then gone off? NOT SINCE REPLACING INJECTORS

My guess is this is not a secondary pump problem, but you can be sure if you run the fuel pressure tests in the Service Manual. GOING TO BORROW JIM'S AND RUN THE TESTS BEFORE REPLACING PUMPS.

I think I'd pull the intake off, then make sure all the secondary port throttles are working and that the actuators are functioning properly. THIS WAS TESTED THOROUGHLY 4,500 MILES AGO (1 YEAR), BUT WILL DO IF PUMPS NOT BAD. PLUS, WILL CHECK FOR CARBON BLOCKING SECONDARIES.

Once the engine pulls through the 2500 rpm area, how does it run up to 6500 or so? STUMBLE AT 2,500 IS INTERMITTENT, BUT CAR PULLS TO HIGHER RPMS WITH LESS VIGOR AND LESS SMOOTHLY, KINDA LIKE STARVED FOR FUEL (BUT SOMETIMES RUNS HARD WITH NO ROUGHNESS NOR STUMBLE).

I noted the car is Steel Blue Metallic. What a great color THANKS FOR THE COMPLIMENT... THAT IS WHY I BOUGHT THIS BLUE/BLUE CAR 1 OF 26 EVER MADE IN THIS COLOR SCHEME. MAKES CAR LOOK REALLY CLASSY AND UNIQUE.

03-05-2013	#17
SteelBlueZR1 Join Date: Aug 2011 Location: Evergreen, Co. Posts: 344	Re: Diagnose - 2,500 rpm Stumble Miss - 1991 8k mile ZR-1 Thanks everyone for the great substantive ideas and feedback. I am slammed at work, but bummed I can't find time to start doing these diagnostics... I will update when I finally get time in the next week or so. To Answer Hib's questions: If I read the OP correctly, this car sat unused for 20 years? CORRECT, CAR DELIVERED WITH DEAD BATTERY AND NO GAS. Does the check engine light function properly during bulb check? If so, are any codes set. NO CODES SET Has the light ever been on then gone off? NOT SINCE REPLACING INJECTORS My guess is this is not a secondary pump problem, but you can be sure if you run the fuel pressure tests in the Service Manual. GOING TO BORROW JIM'S AND RUN THE TESTS BEFORE REPLACING PUMPS. I think I'd pull the intake off, then make sure all the secondary port throttles are working and that the actuators are functioning properly. THIS WAS TESTED THOROUGHLY 4,500 MILES AGO (1 YEAR), BUT WILL DO IF PUMPS NOT BAD. PLUS, WILL CHECK FOR CARBON BLOCKING SECONDARIES. Once the engine pulls through the 2500 rpm area, how does it run up to 6500 or so? STUMBLE AT 2,500 IS INTERMITTENT, BUT CAR PULLS TO HIGHER RPMS WITH LESS VIGOR AND LESS SMOOTHLY, KINDA LIKE STARVED FOR FUEL (BUT SOMETIMES RUNS HARD WITH NO ROUGHNESS NOR STUMBLE). I noted the car is Steel Blue Metallic. What a great color THANKS FOR THE COMPLIMENT... THAT IS WHY I BOUGHT THIS BLUE/BLUE CAR 1 OF 26 EVER MADE IN THIS COLOR SCHEME. MAKES CAR LOOK REALLY CLASSY AND UNIQUE.