Misses only after 70 MPH
Thread Starter
Intermediate
Joined: Feb 2002
Posts: 42
Likes: 0
From: Woodbridge VA
Misses only after 70 MPH
My 88 is missing only after I reach 70MPH, I thought that it was spark related however Chevy said that my car was trying to revert back into OD, not spark. Tranmission guys say that that's not true and couldn't find anything wrong with the tranny. I was thinking more on the lines of Vaccum since it only happens at high RPM. Please help because I'm running out of options. Fuel, timing, spark, injector,tranny or what.
[Modified by szukrider, 5:17 AM 3/10/2002]
[Modified by szukrider, 5:17 AM 3/10/2002]
Burning Brakes
Joined: May 2001
Posts: 873
Likes: 0
From: Dallas Texas tx
Re: Misses only after 70 MPH (szukrider)
Well my first opti-spark did that at high speeds. BUT since you do not have an opti year car I would start with the little things... change the spark plug and wires. Then see if that will fix the issus.
Burning Brakes
Joined: Sep 2000
Posts: 1,199
Likes: 1
From: NewCastle IN. USA
Re: Misses only after 70 MPH (szukrider)
could be something as simple as a sparkplug going weak under load. did you have a tune up done? (plugs, wires, cap, rotor, air filter) a coil or ignition module could be going out.
vacume problems affect idle mostly.
fuel: it could be the fuel filter. been changed lately? If it was the pump it would fall on its face at high rpm's.
Try some fuel injector cleaner ( its recommended every so often anyway).
Could be the gas your running too, is it old? or did you get it some where different? what octane? low octane can be a problem on motors with high mileage.
vacume problems affect idle mostly.
fuel: it could be the fuel filter. been changed lately? If it was the pump it would fall on its face at high rpm's.
Try some fuel injector cleaner ( its recommended every so often anyway).
Could be the gas your running too, is it old? or did you get it some where different? what octane? low octane can be a problem on motors with high mileage.
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
Re: Misses only after 70 MPH (szukrider)
Is it only at WOT?
If so, it may not be missing per se. The majority of L98's with moderate mileage will go into limp home from knock sensor counts at WOT around 3000-4500 RPM ( causes black smoke from exhaust and loss of power until you let off the gas.
There are a lot of fixes for that including replacing timing controllers and knock sensors.
Also, if you do have hi mileage...could be a number of worn components, valve springs very likely ( they are weak to start with and the roller lifters weight cause them to be inadequate at high rpm's...especiallywhen they have 50-100K miles. )
I'm sure a few other things could be problems too...so all I can say is good luck!
If so, it may not be missing per se. The majority of L98's with moderate mileage will go into limp home from knock sensor counts at WOT around 3000-4500 RPM ( causes black smoke from exhaust and loss of power until you let off the gas.
There are a lot of fixes for that including replacing timing controllers and knock sensors.
Also, if you do have hi mileage...could be a number of worn components, valve springs very likely ( they are weak to start with and the roller lifters weight cause them to be inadequate at high rpm's...especiallywhen they have 50-100K miles. )
I'm sure a few other things could be problems too...so all I can say is good luck!
Thread Starter
Intermediate
Joined: Feb 2002
Posts: 42
Likes: 0
From: Woodbridge VA
Re: Misses only after 70 MPH (ol,RJ)
I have not changed the fuel filter in a while, but I put injector cleaner maybe twice a month, I'm going to change it anyway....I only rn 93 octane, the wires and plugs have been replaced and alos the Distro cap, modules rotor but I will check and see if theres has been any burning going on...thanks
