Slight hesitation at 2,000-2,500 RPM with power key on

[Vette73]

Just had the plenum and injector housings ported...

If I get into the throttle hard the car has a slight stumble at 2,500 RPM around..
I really can't classify it as a hesitation, it's like the car feels like it shuts off for a split second than it catches.......If I'm driving " normal" it really doesn't do it, just when I really lean into the gas...

Does not do it at all when the power key is turned off....Other than that the car has plenty of power and does not stumble at all at high RPM just down low like I explained...

[efnfast]

Di d you have the chip reprogrammed after the porting?

[Vette73]

Di d you have the chip reprogrammed after the porting?

Yes....I called Marc and sent him the chip...

He added more fuel to it and raised the redline to 7400 rpm..

[Hib Halverson]

Have you logged data when the problem occurs?

If so what are the O2s doing when that stumble happens?

[Vette73]

Have you logged data when the problem occurs?

If so what are the O2s doing when that stumble happens?

Hey Hib....
I guess I can run this by my mechanic...I'm not to familiar with diagnosing this..

Very new to the LT-5.....Allthough I did all the labor except for the porting when it came to the plenum and injector housings,also swapped out the coils and changed the starter....My injectors are aftermarket Accels and like I said it only does this with full power key on..

How do I check the 02s ?

Thank you..

[Hib Halverson]

Hey Hib....
(snip)
How do I check the 02s ?
(snip)

With a scan tester which can data log.

[tnova]

Same problem with my '91. Have ported plenum and aluminum flywheel as main driver for Marc's chip. Been all through the common causes; fuel pumps, secondary activation, secondary FI relay, new 02 sensors, new coils, etc., etc. Will be watching your findings.

[George Maz]

Would a Tech 1A scan tool be of service for you? If so, let me know and I'll let you borrow it. Astoria George & Me saw a pair of these 1A's selling cheap, and scooped them both.
Glad to hear you're driving the car, I just put mine away now that they've begun salting the roads.

[Vette73]

Would a Tech 1A scan tool be of service for you? If so, let me know and I'll let you borrow it. Astoria George & Me saw a pair of these 1A's selling cheap, and scooped them both.
Glad to hear you're driving the car, I just put mine away now that they've begun salting the roads.

Hey George thanks so much....
I'm going to run it by my guy first and see what he says....I think my driving days may be over for a while with this impending storm coming..

Stay safe...Will be in touch..

John ...

[Vette73]

Same problem with my '91. Have ported plenum and aluminum flywheel as main driver for Marc's chip. Been all through the common causes; fuel pumps, secondary activation, secondary FI relay, new 02 sensors, new coils, etc., etc. Will be watching your findings.

Yes Marc said to check the fuel pressure....I see you changed out your fuel pumps I presume.....Also asked me if my vacuum pump turns off after a few seconds with the key on, not the engine on....

I will run this by my guy soon and post any findings...

[Johnny5]

I heard a few members talking about this issue at Carlisle and Heibeck said to check the 02 sensors.

[Vette73]

Same problem with my '91. Have ported plenum and aluminum flywheel as main driver for Marc's chip. Been all through the common causes; fuel pumps, secondary activation, secondary FI relay, new 02 sensors, new coils, etc., etc. Will be watching your findings.

I swapped out my ignition wires today it seems to have solved the problem...I got car warm ( was 76 today in NY) and got no hesitation...

Maybe too early to tell but so far the wires seemed to help...

[lisounds]

:thumbs: Awesome simple fix