Miss around 1800-2k RPM

[M.P. Cobra Fan]

I have a miss around 1800 to 2000 RPMS. It is worse when the engine is cold. I also feel the miss alot when the A/C is running. I have replaced the plugs and all coils. The car is very mildly modded, SCT tune, intake spacer, intake and exhaust. Any ideas what could be causing it? Could a canned tune be the problem?

 

[M.P. Cobra Fan]

No Ideas?

Here is a little more info that may help. When the plugs were changed, two looked like those cylinders could be running slightly lean. I put a scan tool on the car and repiclated the problem. No misfires in any cylinder. All injectors show to operate properly. I put an ohm meter on the injectors and all injectors are a flat 18ohms.

I have seen where this could be an EGR problem or O2 sensor problem. Rear O2's are turned off. Front have never been changed, but show on the scanner to be operating. Did a manual draw on the EGR valve and it is operating. Could still be carbon buildup. I am going to try replacing the O2 sensors next and cleaning the EGR valve.

The car runs fine under WOT, and only has this hesitation between the specified RPMs under cruising.

Any other ideas?

 

[cobraetti]

I as well get a little "buck" @ 1800-2000 rpms

very slight but its there

I don't think the tune is to blame, I had it w/out my tune

 

[M.P. Cobra Fan]

From what I have seen this is a pretyt common problem, but no one seems to know exactly what it is. Damn.

 

['95yellowGT]

yeh same here ive replaced both 02 sensors as that was the initial code it was throwin but code is gone but still the problem is there....its driving me crazy

 

[M.P. Cobra Fan]

****. Someone has got to know. LOL. This is driving me crazy.

 

[V6&V8SHO]

coils?

 

[Sveet01]

When I first start up my car it will sometimes sound like it has a miss at idle--but it only misses like 3 or 4 times. Then when I first take off it kinda has a little lagging feeling around those rpms.

I just replaced all my fluids/plugs/filters this winter and it still does it.

I dunno either tbh.

After it warms up it goes away though.

 

[americanthunder]

I also have this problem and have read that after the installation of headers,or modifying the exhaust, the manifolds run cooler, slowing the response time of the o2 sensors, and to remedy this one might relocate the sensor into one of the primary tubes closer to the exhaust ports.....

 

[Jamie R.]

I used to get a slight miss and it turned out to be my dpfe sensor. I finnally got a light for it, I never knew what the miss was and eventually the light kicked on and told me what the problem was. When I took my dpfe sensor off water rolled out of it from condensation because this is part of the egr. Dont know if this is your problem but my miss would occur cruising from light to light in town under not much load and even cruising down the road after a steady speed was reached and again under very little load. I could feel the car missing and hear it missing because my bassani's are not the quietest little things:lol1: Hope you find out the problem!! Take it easy and did you check out the site I told you about.

Jamie R.
'01 Silver Cobra

 

[M.P. Cobra Fan]

Jamie,

Did you have to replace your DPFE? Or did you just clean it up?

Yeah, I checked out the site. Looks promising.

 

[M.P. Cobra Fan]

Jamie,

Is this the right one?
EGR Pressure Feedback Sensor by BWD - Part EGR155 - Advance Auto Parts

 

[IUP99snake]

I have the same problem. It's not a huge miss, but it's there. And it's a little worse when it's cold. I notice it a lot when I shift to 2nd or 3rd gear and I'm going at the right speed where the RPM's happen to be in the 1800-2K range right after I have shifted, and I'm at part throttle accelerating slowly. If the RPM's are lower when I shift into a new gar and I go through that range, I don't notice it as much. I also don't notice it as much when I give it more gas going through that RPM range.

I also noticed that it's not as bad when I don't have the blower on the car. A few weeks ago, I had to change a belt, but every place was out of stock, so I had to run the car without the blower running a short belt until the new belt was ordered.

I always thought it had something to do with the MAF, but I cleaned the MAF and it's still there. I have a blow-thru setup with the MAF in the fenderwell with about a foot of straight pipe before the MAF.

But something with the EGR makes sense. What's the DPFE Sensor, and what does it do?

Someone mentioned the 02 sensors... what if they're turned off in the tune?

Homer

 

[M.P. Cobra Fan]

Well I just changed the DPFE sensor. the improvement was immediate. I am going to drive with it for a while and see what happens, but on a cruise around the block everything seemed fine. Fingers crossed. It did have moisture in it when I removed the old one. Auto zone said that they sell a LOT of these.

IUP99snake, if you look at my above post you will see a link to the part. It sits on the back of the top half of the intake manifold. Has 2 bolts, 2 vaccuum lines on the bottom, and one plug.

 

[99Cobra_vert]

Jamie,

Is this the right one?
EGR Pressure Feedback Sensor by BWD - Part EGR155 - Advance Auto Parts

I have one in the garage with almost zero miles. If you want it, send me your address and it's yours.

edit: guess I should have read the rest of the thread first. Oh, well. Good to hear you got it fixed!

 

[M.P. Cobra Fan]

Damn, thanks for the offer. I am sure someone here is gonna jump on that offer.

 

[M.P. Cobra Fan]

Well, that did not fix the problem. It made it better, but it is still having the problem. The car seems to be bucking or stuttering.

I am going to try to block off the EGR system and turn it off in the tune. If it is the EGR that should fix the problem.

I have also heard from some folks that the alternators in the GT's are bad and cause this problem. It happened to my roommate. Same issues and once alternator changed, it was cool.

Any clues?

 

[M.P. Cobra Fan]

*update 18.3 V2.6 Chapter 4*

After searching last night I noticed that all of my rubber vacuum lines were dry rotted to the point that when squeezed started flaking away, cracking, and leaving your hands black like charcoal. So I yanked off all the rubber vacuum lines and replaced them. I also replaced the EGR gasket since I did not do that when I put the intake spacer in.

On the first drive the car was driving much worse. Bucking bad. I then reset the computer, and while I was at it cleaned all the corrosion off the negative terminals. Drove the car and it seemed to be driving much better. It still has slight bucking/jerking at the specified RPM's, but it is better then it has been.

Next up is trying to clean the EGR valve, which I did not have time to do today, and changing the fuel filter.

Any other ideas?

 

['95yellowGT]

yeh changing the fuel filter is my next step

 

[M.P. Cobra Fan]

Oh, I might add that I used my ghetto fabulous stethoscope to find a source of a ticking I have. I always figured it was the injectors. Someone told me they thought it was valve train. The valve train sounds just fine. I did find that 2 injectors on the drivers side are extremely loud compared to the other 6. The snap on scanner said all injectors were cycling properly, and the ohm meter verified that all are at 18ohms.

I might change those out to a higher flow to support future mods though.