97 gmc yukon misfires at speeds over 50

[denjandav]

Does anyone know what might be causing a misfire on my 5.7l v8. I have change the plugs, wires, dist cap and ignition module but mis continues. The miss starts at steady speeds over 50 mph. If I speed up miss goes away but when my speed is steady again it begins missing again.

Any ideas

[surfing]

Hmmmmm.....did you gap the plugs to specs?? IF so, then you may need to pull'um out, and make sure none are fouled, wires are correctly seeted, ect.. .

[usscvr]

Wow! I have the same problem, although my has gotten worse with added mileage. Check out my post from USSCVR, "SES Lamp Multiple Engine Misfire." Are we having the same problem here? Have you isolated it yet?

[snr8715]

Fuel injector

[usscvr]

Wow! Glad you found your problem.... but I have throttle body injection on a 5.7 350; no fuel rails, no individual injectors - UGH! Still a problem for me... Any suggestions?

[Suburbman]

Did you finally find out what the problem was with the '97 350 misfire at speeds above 50? Was it an injector. I'm having the exact same problem, no misfire codes either.

[usscvr]

No, I haven't.... ugh! I do not have individual injectors. My Yukon has a throttle body injector system, thus no fuel rails, no individual injectors, etc. I am still at a loss. Any suggestions????

[tscholz]

How many miles on the odometer? I have seen ditributor shaft bushing worn to the point that the engine will misfire at times.

[usscvr]

It stared at around 65-70K miles. I now have 120K, and nothing has changed, no better, no worse. Honestly, I haven't done much since spending thousands on it the first few times. It appears to be more of an annoyance than anything. We've gotten used to it ~ that's not to say that what's happening is good for the vehicle; I know its not. But, we've learned to adjust our driving habits accordingly. We (my wife) loves the Yukon a lot, otherwise, or I would have gotten rid of it a long time ago.... LOL! What Ms. Honey wants, Ms. Honey gets....

[lodownlv]

you have a faulty fuel injector.. no doubt about it try running some lucas fuel injector cleaner along with spraying some carb cleaner directly into the throtle body at high rpm's then make sure u have acdelco spark plugs properly gaped at .006

[crazy202022]

check egr valve.

[usscvr]

Originally Posted by crazy202022

check egr valve.

Really? EGR? I didn't think about that. Well, I figured it was a sensor somewhere, but the EGR didn't cross my mind.

Can you tell me any quick checks for this? Or is this a dealer check?

[2000CAYukon]

Originally Posted by usscvr

Really? EGR? I didn't think about that. Well, I figured it was a sensor somewhere, but the EGR didn't cross my mind.

Can you tell me any quick checks for this? Or is this a dealer check?

The EGR valve is subject to a lot of heat and they do wear out. With your mileage, I would just replace it and make sure the passage inside the intake is not clogged (when you remove the old one you can see how it looks). Some people recommend replacing the egr solenoid at the same time.

//2000CAYukon

[lodownlv]

the egr valve wouldnt do it and if it was sticking it would throw the SES lite. whoever has this problem start with the fuel injection system bad injector or fuel pressure regulator would cause loop at high rpms and rough idle. i can assure you that its not the egr

[usscvr]

Originally Posted by lodownlv

the egr valve wouldnt do it and if it was sticking it would throw the SES lite. whoever has this problem start with the fuel injection system bad injector or fuel pressure regulator would cause loop at high rpms and rough idle. i can assure you that its not the egr

OK, if you read back in the post, you'll see that I have a throttle body fuel injection system, not individual injectors ~ so a 'bad injector' can be ruled out. However, the Fuel Pressure Regulator makes sense. Where is it located? How can I test it?

With the number of miles, changing the EGR might make sense, too. But fuel delivery has always been my concern. Where is the F.P. Regulator? Is it available aftermarket?