Low RPMs bucking

[XfireZ51]

Originally Posted by MuRCieLaGo

Good idea

RECAP

Problem: low rpm bucking, especially when cold. Stalling at red lights (restarts like a charm). Got codes 55 and 64 once, erased them and they never came back. Also experienced a strange knocking/rattling noise, which went away on its own.

-Electrically tested the injectors, hot. Got between 17.3 and 17.9 ohms everywhere.
-Spark plugs changed.
-Fuel pumps removed, visual inspection done: nothing was wrong.
-Fuel pressure tested. Idle: 41 psi, FP1: 46 psi, FP2: 48 psi.
-Fuel filter changed.

Receiving two NGK NTK o2 sensors tomorrow.

I was curious as to what mods may have been done prior to all this.

[MuRCieLaGo]

Originally Posted by XfireZ51

I was curious as to what mods may have been done prior to all this.

Mods:

-Marc Haibeck's chip
-OBX headers
-Magnaflow resonator
-Borla catback

[XfireZ51]

Originally Posted by MuRCieLaGo

Mods:

-Marc Haibeck's chip
-OBX headers
-Magnaflow resonator
-Borla catback

So is that when the motor started to misbehave?

[Paul Workman]

Originally Posted by MuRCieLaGo

So...

1. Change both o2 sensors.
2. Remove plenum and check for that connector.

Should I check something else while the plenum is removed?

Well, obviously there's no time like the present (plenum off) to inspect everything and replace as necessary:

• vacuum circuit, SPT actuators,
• all electrical connections**,
• hoses and clamps,
• inspect/refresh starter solenoid contacts as needed,
• inspect/clean the drain tube (under and at the back of the starter)
• port matching.

**NOTE: When inspecting electrical connectors, be doubly certain NOT to accidentally misalign any pins as you reassemble them. And, due to the delicate nature and number of pins be especially attentive when reinstalling the long DIS connector; the one with the little bolt/hold-down screw in the center. (Ask me how I know...)

[MuRCieLaGo]

Originally Posted by XfireZ51

So is that when the motor started to misbehave?

No, I'm having the problems since I bought the car (before the mods).

Just removed plenum this morning. One of the DIS connector pin was BARELY bent, so I straightened it.

No change at all.

I inspected pretty much everything you mentionned Paul...

Gonna get my o2 sensors changed on a lift friday morning.

[Paul Workman]

Originally Posted by MuRCieLaGo

No, I'm having the problems since I bought the car (before the mods).

Just removed plenum this morning. One of the DIS connector pin was BARELY bent, so I straightened it.

No change at all.

I inspected pretty much everything you mentionned Paul...

Gonna get my o2 sensors changed on a lift friday morning.

Well, I betcha you wish now you had installed those lateral bungs on the collectors like "someone" suggested, huh?

This whole episode screams for data-logging! I feel some of your frustration at this simple issue dragging on. And, (please forgive me if I'm wrong) I feel more frustration if you haven't data-logged it yet so we could maybe see what is going on when it 'bucks'. (There are some slick programs, e.g., Tunercat, etc., you can download to a laptop. With the appropriate cabling you can watch in real time everything going and often spot the issue in just a few minutes of actual driving!

No worries. When you finally nail it, you'll forget about all the trials and tribulation. And! You'll prolly know a lot more about the car than many do: nothing like hands-on experience, right?

Hope you can put this to bed pretty soon.

[MuRCieLaGo]

Originally Posted by Paul Workman

Well, I betcha you wish now you had installed those lateral bungs on the collectors like "someone" suggested, huh?

Correct me if I'm wrong, but this whole episode screams for data-logging! I feel some of your frustration at this simple issue dragging on, and feel more frustration that (please forgive me if I'm wrong) you haven't data-logged it yet so we could maybe see what is going on when it 'bucks'. (There are some slick programs, e.g., Tunercat, etc., you can download to a laptop and with the appropriate cabling you can watch in real time everything going. And, sometimes that is the only way one can efficiently zero-in on what the problem is. Just sayin, buddy.

No worries. When you finally nail it, you'll forget about all the trials and tribulation. And! You'll prolly know a lot more about the car than many do: nothing like hands-on experience, right?

Hope you can put this to bed pretty soon.

I'm thinking about taking it to the dealership. Can't they connect it to tell me what's the issue?

I still got hope for my new o2 sensors on friday though, it has been mentionned a lot of times that it could be the problem. I'd love to know how to data-log this car... But I hope I won't have to do that.

Thanks Paul!

[Paul Workman]

Originally Posted by MuRCieLaGo

I'm thinking about taking it to the dealership. Can't they connect it to tell me what's the issue?

I still got hope for my new o2 sensors on friday though, it has been mentionned a lot of times that it could be the problem. I'd love to know how to data-log this car... But I hope I won't have to do that.

Thanks Paul!

Taking it to a dealership CAN be a huge can of worms, depending on the dealership's service (manager) department. (I have an independent mechanic shop - speed shop - that I'd trust waaaay before any stealership. Anyway, regardless they have to have the right firmware for Corvette OBD-I. (Dominic or Pete or Marc might chime in with specifics far better than I can).

I have an old AutoXray scanner that I use. It is hard to explain just how simple and how efficient it is if you have the ability to hook it up and in seconds pin-point the problem(s). Unfortunately, they no longer make or support this old gem, but there are several alternatives out there that will do the job.

In any case... I believe one of the FIRST recommendations was to get that puppy scanned. That might have saved a lot of this "trial and error" stuff, and you could be enjoying the car by now. Just sayin....

[MuRCieLaGo]

Originally Posted by Paul Workman

Taking it to a dealership CAN be a huge can of worms, depending on the dealership's service (manager) department. (I have an independent mechanic shop - speed shop - that I'd trust waaaay before any stealership. Anyway, regardless they have to have the right firmware for Corvette OBD-I. (Dominic or Pete or Marc might chime in with specifics far better than I can).

I have an old AutoXray scanner that I use. It is hard to explain just how simple and how efficient it is if you have the ability to hook it up and in seconds pin-point the problem(s). Unfortunately, they no longer make or support this old gem, but there are several alternatives out there that will do the job.

In any case... I believe one of the FIRST recommendations was to get that puppy scanned. That might have saved a lot of this "trial and error" stuff, and you could be enjoying the car by now. Just sayin....

I live in a 50,000 people city and literaly nobody can help me here scanning the codes, especially the dealership. But I think I found something...

I've got a major update for you guys.

Usually, I always run the car with the heater OFF. Yesterday, I pressed AUTO and forgot to turn it OFF. The car ran pretty bad. Just look at the idle when I press the AUTO button:

https://www.youtube.com/watch?v=ZCEla2ShgF4

May I repeat:

-I had a cluster flickering problem.
-Alternator was changed 1 day before I bought the car.
-3 weeks ago, I checked the alternator voltage when the car was cold. It was 14.3V. Checked it yesterday when the car was fully warmed, it was 13.8V. I believe this is perfectly normal.
-Tensioner pulley is loose, at idle only.

I'm not sure which way to go now.

And by the way, local garage couldn't change o2 sensors, because I told you local garages can't help me. They can only work on Cavaliers and stuff like that.

[Paul Workman]

Well, my sense of it is: (1) it isn't anything too big, but (2) it is beyond your current knowledge/(ZR-1) expertise.

I hate to see anyone struggle so. I'm thinking that perhaps you should consider either taking it to someone that IS ZR-1 savvy, or paying someone that is skilled to visit your location w/ tools in hand.

If neither of these are going to work, but you have reasonable mechanical skills, then I suggest you pick someone that is knowledgeable that will be willing to work with you, off-line. By "huddling" w/ someone off-line you have better continuity of thought and the troubleshooting process and less chance of distractions - albeit in the best of intentions. Just a thought.