Northstar Engines and System Technical Discussion Discussion, '94 N* runs lumpy - hesitates. Any ideas? in Cadillac Engine Discussion; My '94 Concours pulls fine on hard accelleration, idles smoothly, but when just cruising along the engine seems "lumpy" or ...
My '94 Concours pulls fine on hard accelleration, idles smoothly, but when just cruising along the engine seems "lumpy" or like it hesitates while cruising regardless of cruising speed or which gear the trans is in. At first I thought it felt like the TC was going in and out of lock. but now seems more engine related. No codes. Fresh plugs. Only does this about half the time and seems unrelated to whether the engine is cool or warm or hot. Has anyone any suggestions about what I might check? THanks. Sincerely, ANdy.
Go to the search feature of the forum toolbar and type "phenolic spacer plates" into the drop down box and read the posts.
The 93/94 Northstar engines have the EGR delivery passages in the phenolic spacer plates that isolate the intake manifold from the cylinder heads and when those become plugged with carbon at high miles they can cause a maldistribution of EGR to the individual intake ports and can cause a reduction in overall EGR flow that causes a lean condition. Either could be the cause of the driveability problem. Simple fix is to clean the phenolic spacer plates.