1996 Camaro Z98.

Well recently I have been having some stumbling issues at low rpms especially on the highway in 6th gear, and when just cruising around town. So I have been doing a lot of research and figured that it might be the EGR valve (I was throwing a code for P0420- Which I didnt care too much about, I dont care if my cats aren't cleaning the air enough, and I didn't think this would be causing my problem). Well I went to autozone to buy another EGR Valve today. When I got home I reached back to discover the vac line going to the EGR valve wasn't even connected. So I connected it and test drove it. It didn't solve my stumbling issue. So I got home and replaced the valve. It still did not solve my issue. So I did some more research and thought it may be the TPS. So I replaced that, and it still didn't solve my problem. So I ran my SES light and discovered a P0400 code. Do you think that my new EGR valve is bad? I have hooker shortie headers but both cats still in. So I doubt its due to lack of pressure.

What do you guys think?

 

The code indicates the MAP sensor isn't showing the required change in manifold pressure when the EGR valve is cycled. Generally due to no, or low exhaust gas flow. Manifold could be plugged, exhaust system may not produce adequate back pressure, EGR valve may not be opening when the PCM attempts to operate the EGR vacuum solenoid. Have you verified the vacuum path from the manifold to the EGR vacuum solenoid? Although you reconnected the line from the solenoid to the EGR valve, it is possibly cracked? Is it possible the EGR vacuum solenoid is sticking closed? Probably need to check the system with a small hand-held vacuum pump like a Mi-T-Vac.

 

Yeah I checked and inspected the vac lines going to the solenoid. They looked good and fit firmly. I am going to take the EGR line going to the header off to clean the ports on the manifold and make sure its tightly connected to the header tomorrow. I had a new solenoid transferred to the autozone near my house in case i needed to buy that as well. I'm hoping not, even though its only 21 bucks.

 

probably the egr valve.

 

Well I hate to think its that since its brand new but i'm going to see.

 

As described above, the pressure in the intake manifold must change when the EGR is cycled. If the port in the manifold has debris build up not allowing the EGR plunger to fully close, that would account for your stumbling and the code. Since the valve never really closes, the engine won't run correctly and the pressure never changes.

So did you clean the port thoroughly ?

 

I cleaned the port very well. At first I was getting a lot of grim out of it. I cleaned it until the rag came out clean.

 

I cleared the codes last night and drove to work today with no codes but still a stumbling issue.

 

Ok updates. I'm not longer throwing a code for the P0400. I'm still having stumbling issues.

I checked the fuel pressure today. Not on its 41ish, and running its around 38 or a hair less. At WOT is 47ish. So i'm thinking its not a fuel Problem.

I inspected the MAF and all the conductors are intact and look good.

The opti is only acouple months old and was installed by a GM dealer. I called them up and told them this has only been happening since they installed the MAF and they said to bring it by on monday for them to take a look at it.

 

Ok well the car hasn't thrown the P0400 code but threw a PO100 code tonight. I was thinking that my stumbling problem could be MAF related. So i'm going to check the pigtail tomorrow to make sure that it is receiving appropriate voltage. If it is, i'm gonna go ahead and attempt to clean the MAF and if it isn't, i'm going to make sure the Ground on the PCM is good. If it is, i'm going to order and new pigtail and start splicing.

 

P0100 usually sets when the signal from the MAF doesn't change for a period of time. Check for 12V on the pink wire in the harness.

 

Well I took it too the dealership because they just replaced my opti back in july, and I wanted to make sure it had nothing to do with that. It turns out that its a cly #7 misfire. The plug wire was just a little melted. So I replaced the plug (the threads were f-ed) and wire as well. I put a ceramic boot on the plug with a heat resistant sock. So its running smooth again. I spent, 87 dollars that I didn't have to replacing the EGR and TPS. However, I'm glad that I did, the car just passed 101k last week. The items in there were stock.

I haven't thrown a code for the MAF again. I think that i'm going to check the voltage on the wires again.