Re: Exhaust changes causes problems
 

And?

Re: Exhaust changes causes problems
 

Yes,the primary could be performing poorly,you also have to remember the secondary Feul Pump will kick on at a certain throttle point.
I would then also try what Jeff said,take the secondary FP fuse out and try again,should have the stumble all the time if it's the primary.
If it turns out you do need FP just get one from a 1996 Chevy Truck 2500 the one with 454ci big block.
Pete

Re: Exhaust changes causes problems
 

I'l add to this some injectors can Ohm out good but could leak like a fire hose.
To check this without a pressure gauge turn ignition to the on position and do a visual or have someone else keep an eye on the injectors while you turn ignition on.


Pete

Re: Exhaust changes causes problems
 

Pete,

That was my point. Having replaced injectors in August doesn't eliminate them as a problem. Thanks for clarifying that even ohming out injectors may not be enough. Wouldn't there be a gas smell if the injectors were leaking or plugs showing raw fuel?

Re: Exhaust changes causes problems
 

I haven't smelled any gas smells. I am in no position to not listen to all of you all's sugestions. I was hoping that I could elimenate the injectors as a possible problem being they are new, but obviously I can't. I just want to get this thing figured out.

Re: Exhaust changes causes problems
 

Correct, just because they spec out in ohms, does not mean there is a issue with them being stuck open or closed or dribbling. I've had a few like that.

Re: Exhaust changes causes problems
 

Roger,have you done anything else to the car recently besides exhaust.

The symptoms you describe sound like bad spark plug wires,spark plugs or injectors.

You know what's funny is half the guys on here, had the car in front of them or took it for a test drive would figure it out in a second.

Pete

Re: Exhaust changes causes problems
 

I know, that's what is killing me. The injectors and spark plugs were changed in August. The spark plug wires were not changed.

The best I can describe it is:

As I step on the gas there is a little hesitation.
As the car speeds up it seems to catch back up and perform correctly until 3rd gear around 4500rpms it jerks (like there is no fuel) then continues to accelerate.

I don't know how better to describe it. When the power key is off, the car shakes and hesitates as I step on the gas. It seems like when the key is on, it makes the car drive better but it seems its just masking the real problem.

I don't know, now I am confusing myself.:o

Re: Exhaust changes causes problems
 

Were the injectors replaced or were they cleaned?

Re: Exhaust changes causes problems
 

I had them replaced with the Accel injectors.

Re: Exhaust changes causes problems
 

ok, just grasping at straws since the car isn't in front of me.

Wonder if they put the injectors in correctly, meaning they used the top indent for the c clip.

I would start looking at spark. This is when a scan tool is handy. Just makes it all the easier when you can see fuel trims, knock counts and 02 fluctuations.

Re: Exhaust changes causes problems
 

I just have ordered the Helms maual, no scan tool. Should I go ahead and get the fuel gauge and check that or does it not sound like a fuel issue?

Re: Exhaust changes causes problems
 

Roger,if you have a digital camera take pictures.
Close up of what Jeff mentioned the injectors,unplug a primary and take a close up.

I would change the Wires.

Pete

Re: Exhaust changes causes problems
 

Problem is I have never taken the plenum off. I had the other work done and can't afford ($) to take it back to the guy right now. I guess I could try a plenum removal.

Re: Exhaust changes causes problems
 

Plenum not hard after you've done it once. Actually, it's not hard the first time, but a little scary since you don't want to mess anything up.

Get your tools together, the Helms manual, and a WARM place to work and you're all set.

btw, where in Georgia are you?

George
1990 #2957 black/black

Re: Exhaust changes causes problems
 

roger, i think jeff has apicture guide on plenum removal, but not totally sure . I ampositive he could guide you through it . the process is alot easier than you might think . you just have to go slowly and make sure you remove all 4 electrical connectors that are under the plenum 2 from the front and 2-3 from the back 3 if one includes the map sensor . you dont have to seperate the throttle body from the plenum. it comes off in one big piece . but the decision to do it is up to you .is there anyone close that could help this nice guy out ?

Re: Exhaust changes causes problems
 

I live in Cartersville. I wanted to maybe watch plenum removal a couple of times before I tried, but looks like that won't be the case.

Re: Exhaust changes causes problems
 

Its not really involoved, you can do it. Links here to help you out. Take your time, observe and go slowly.

Re: Exhaust changes causes problems
 

Ok guys, I checked the fuel presure. Here is what I found:

With key on(no engine on) - 46# about 20 minutes later 30#

With key on(no engine on and seconary fuse pulled) - 48# 20 minutes 36#

WIth the engine on - 44# at idle car off presure at 44# for 20 minutes

I don't know what any of this means.
Does any of it make sense?

Re: Exhaust changes causes problems
 

Roger,

Data indicates the problem is probably not with the fuel pumps.

Few questions:
1. Did you ever change the fuel filter?
2. Did you ever experience any of these symptoms, before installing the new exhaust system?
3. Have you pulled the stored codes?
4. Are you getting any warning lights on the display?

Re: Exhaust changes causes problems
 

1. The fuel filter was changed back in August.
2. There were a couple of times that the car did hesitate, but I just thought it was the nature of the beast. One thing I thought of is that the car is more prone to act up if there is another person in the car with me. I can't imagine another 180lbs would cause any problems. Just trying to give all the info I have.
3. I don't have a scan tool.
4. I have not had any lights come on except the service ride control. It comes on if I let the car idle for a while, but goes away when I start driving.

I am going to show my extreme ignorance now - I paid close attention when I started the car the last time. There was a vacume type sound and I felt a lot of air under the left coolant conector. After a couple of minutes the sound went away and the air flow did too. This is probably normal and I should know it, but I just thought I would mention it.

Again, let me thank all of you who are trying to help. I really appreciate it.:worship:

Re: Exhaust changes causes problems
 

Hi Roger - I found this link for removing the plenum in another post:

http://www.bcvettes.org/

Look under "How To"

Good luck

Scott

Re: Exhaust changes causes problems
 

The vacuum noise is the air injection system. I would not expect you to be feeling any air other than what is coming off the serp belt system and power steering pulley right in that area.

Re: Exhaust changes causes problems
 

If the air I was feeling is coming from the serp belt or power steering pulley would it go away after a couple of minutes or would it be there the whole time the engine is on?

It is a very noticable amount of air flow.

Re: Exhaust changes causes problems
 

Thanks Scott. I looked it over. I don't feel quite as scared as I was before. I think with a step by step guide I can pull it off. The only problem is I don't really know what I am looking for under the plenum.

I drove the car this evening and actually had it backfire on me. I drove it around for a while to let it warm up and it drove fine. After it warmed up I gave it a few WOT. A couple of times it drove great. One time it backfired in 1st at 5500 rpms, then drove like it was turbocharged through 3rd. I am so confused.

Re: Exhaust changes causes problems
 

It should not go away if it's coming from the belt and pulley. I'll give you a call in a few mintures Roger.

Re: Exhaust changes causes problems
 

Jeff,

Please give me a call when you get a chance. Do you still have my number?

Re: Exhaust changes causes problems
 

Sounds a lot like my Z.

Replace the 02 sensors. Easy and cheap to do. Also check the TPS with VOM.

Re: Exhaust changes causes problems
 

My Helms manual should be here next week. I hope it will describe how to do what you have suggested.

I plan on taking the plenum off and will more than likely change the plugs and the plug wires. I have a set of the AC Delco plug wires. Should I go with the NGK plugs? :icon_scra

Another question: Any chance my ECM is the problem. Seems like I read before that a couple of guys had a simular problem that replacing the ECM fixed.

Re: Exhaust changes causes problems
 

My Helms manual should be here next week. I hope it will describe how to do what you have suggested.

I plan on taking the plenum off and will more than likely change the plugs and the plug wires. I have a set of the AC Delco plug wires. Should I go with the NGK plugs? :icon_scra

Another question: Any chance my ECM is the problem. Seems like I read before that a couple of guys had a simular problem that replacing the ECM fixed.

Re: Exhaust changes causes problems
 

Roger, if you need a hand, let me know. I'm in north Georgia but I'm always up for traveling to help out a fellow ZRoner!

I have DIACOM and can scan your car if need be.

Re: Exhaust changes causes problems
 

Roger, if you need a hand, let me know. I'm in north Georgia but I'm always up for traveling to help out a fellow ZRoner!

I have DIACOM and can scan your car if need be.

Re: Exhaust changes causes problems
 

just thought to share . thats a really cool offer you made to him. makes me glad to see so many that go out of their way to help others here:thumbsup: :thumbsup: now if the world would only do the same.....................

Re: Exhaust changes causes problems
 

Shawn, thanks. I was hoping that you or Steve had a scan tool and would offer to help.:D

The first thing I am going to do is replace the o2 sensor. If this doesn't fix the car, I am lost and would love some help. I will drive to you if that works better, but lets see what the o2 change does.

Even if the o2 fixes the problem, I still would like to meet you and Steve.

Re: Exhaust changes causes problems
 

I posted this in another thread but it is some simple things any owner can do to help people trying to do troubleshooting from afar.

1. Compression check.
2. Run the car, park it and look at the plugs they should be uniform in appearance if not then chase fuel/spark on that cyl.
3.Take a good known plug and one cyl at a time unplug the wire, plug in the plug, lay it on the plenum and start the car. The spark should be the same on every cyl if not then you know which coil pack/wire to chase for problems.
4. There is a DIS checker and should you suspect the dis of falling apart I can lend it to you. You need some kind of a scope to look at the signals to verify its falling apart.
5. If you pull the plenum then you can check the injectors by pulling fuel rail up, crank the car and look at the spray pattern.
6. If you have a suspect cyl you can eliminate spark with step 2 and check fuel by swaping injectors from cyl to cyl, this requires pulling the plenum but you get pretty good at in with practice.
7. Listen for the vacuum pump at the left front of the car. You should hear it cycle for a couple of seconds when the key is first turned on the go quiet for at least 5-10 minutes. Both failing to pull the vacuum, on start and an continuly cycling pump signal problems that will cause what you describe.

Let us know what you find.

Tyler

Re: Exhaust changes causes problems
 

Oh, I bet I can sucker Steve into a mini-gathering! :)

Just let us know what the outcome is on the O2 sensor change. :hello:

Re: Exhaust changes causes problems
 

Changed both o2 sensors. After I changed the left one(couldn't get to the right one) the car drove pretty good. I drove it one night I guess the temperature was around low 40's. The reason I mention this is that I have now changed the right side o2 sensor and the car is still having problems. I drove it today, temp around upper 50's and it hesitated at WOTH about 20% of the time. It is driving better than before I changed the o2 sensors, but not as well as it drove before the right o2 sensor.

Could I be looking at something that is related to outside temp or am I just grasping at straws.

Any body have any dynamite?;)

Re: Exhaust changes causes problems
 

roger , let me ask a couple of ?s when you turn the key to on not star do you here the motor for the vaccume pump come on in thge right front up by the headlight . does it go on and shut off or does it cycle on and off?. did you ever get the helm manual yet ? if not you really need one it would help you alot in deducing your problems .pm me if you still need help and i will seeif i i can walk you thru some ideas to help brad

Re: Exhaust changes causes problems
 

The vaccume comes on and then goes off. I am not sure about it cycling on and off, I will check. I do have the Helms manual.

I never checked the fuel filter. Any chance there is something with that?

Re: Exhaust changes causes problems
 

could be . have you cked your fuel pressure? when i get a car the first thing i do is change all filters and fluids then i know everything is fresh . does it stumble when you first floor it or towards the top end of the rpm scale ?