1999 suburban miss

[wjcbps]

my 130,000 '99 suburban 5.7l at 4x4 is missing badly in cylinders #5 &#7. the dealer replaced the cap,rotor,plugs,and wires. compression test is normal.did drop and balance test on injectors-normal. replaced upper and lower intake gaskets. removed valve cover -rockers,springs appear normal.inspected distributor appears normal to look at.dealer wants to remove head to check guides(would compression be normal with bad guides?)any help?

[777stickman]

On my '98 Sub K2500 7.4 I had a miss pulling a hill. When I changed the intake gaskets I found some of the injector wiring under the upper plenum rubbed bare. Repaired that and have not had a problem since. Don't know if the injector wiring for the 5.7 is the same.

Compression test would not show worn valve guides since both valves are closed on the compression stroke. Worn valve guides will increase oil consumption.

Compression test on each cylinder will give you great info as to the condition of the rings, valves and gaskets.

Another thing to look at are the spark plugs. They should all be a tan color indicating proper combustion. If #5 & 7 are misfiring they need to be looked at closer for oil fouling, lack of spark or lack of fuel.

Also #5 & 7 are next to each other on the drivers side. A compression check would show if the head gasket has failed between those two cylinders.

Lots of info and hope it helps.............Steve

[wafrederick]

Did you inspect the distribitor gear real closely?I did one last week and could not find the miss and it was a worn out distribitor gear.Look for shiny spots.

[maxwedge]

How does the distr. gear create a miss, by moving the rotor off the its firing position on the dist cap,? Is this common on these engines, thanks for info.

[wafrederick]

THis one I did to was a 1997 GMC 2500 that my father bought from a car auction.Luckily had a distribitor on hand and robbed a gear off it.It is a common problem and the gear is about $75.00.