Valve adjustment then suddenly horrible mpg and power.


New Member
Had bad knocking this winter so I did a valve adjustment. First time I did it, I was in Reno, then took a trip to San Francisco to visit some family. Got 37 mpg while driving around San Fran. When I got back to Reno, the car seemed fine. When I filled up again, and drove in Reno only, I averaged about 34 mpg. About 3 days into driving, the knocking was back. Didn't get any knock in San Fran.

Did a 2nd valve adjustment. Seemed like cylinder 3 was a bit off. Redid it. Ran for 2 tanks of gas and got 33 mpg. Not only this, but after the 3rd or 4th start, the knocking returned.

Did a 3rd adjustment. Cylinder 4 seemed off, now. Went through and readjusted everything double checking and making sure things were tight. Ran for 2 tanks of gas and the car got 31 mpg. This time, the car seemed to be losing power and having idle problems where it would dip to nearly 250 rpm and feel like it was struggling to stay running, but never died.

This last adjustment, I went through and readjust everything even if the valves were spot on. Before I put everything back together, I went through and double checked everything with the feeler gauges to make sure and to make sure my bolts were tight. To be clear, I adjusted the intake side with .007 and the exhaust side with .009. Now, the car runs at about 26 mpg, I hear a slight constant "screee'ing" sound when cold during idle, and the car feels weak. I still have the random idle hunting (not every time the car comes to a stop light, but maybe 1 out of 3 times). The knocking is back, but only when really cold.

Each time I did this, I took the battery off and reset everything and drove it for two tanks of gas to make sure I wasn't getting ecu readings during its self adjustments. The engine was ice cold during each valve adjustment. I also made sure I was setting the crank in the proper position, with Cyl 1 being straight up, cyl 3 being left, cyl 4 straight down, and cyl 2 to the right.

What could be the problem here? My driving habits are nearly identical as the car is only used to grab groceries and go to work and back. I have other cars for other activities. My route is exactly the same every time. So it isn't like I'm driving more on streets vs freeway.

Before I do another valve adjustment, I was wondering if someone could help me out. I also got a timing gun so that I can adjust the timing belts. I haven't checked to see if the timing is off yet, though. I have time maybe later today once the car cools down, or maybe this weekend.