1999 Honda Accord Mileage dropping abruptly

LALIAG

MEMBER
1999 HONDA ACCORD
4 CYL
FWD
AUTOMATIC
128,800 MILES

'99 Accord EX mileage, used to get around 28 mpg. It drifted to 25 last year. It also started struggling noticeably when going uphill. The ICM had to be changed about 3 months ago, after which the mpg went to 27 for a couple of weeks, then drifted back to 26. Last week it went to about 21.5 with local driving, and 22.5 hwy. The car still struggles at every uphill grade. It doesn't drive as effortlessly as it used to. I have to really accelerate hard when going uphill. It has gotten recommended service, and we DIY for some repairs. What should I have the shop (or ourselves) check for this problem?

1 Reply

KHLOW2008

MECHANIC
41,815 POSTS

Hi laliag,

Thank you for the donation.

The cause of the problem should be the loss of power as mentioned about the struggling to go uphill.

1. Check the throttle cable adjustment, if the cable is too slack, the throttle would not be able to open fully and constant full throttle would increase the fuel consumption.

Check the ignition timing. If the timing is retarded, loss of power would occur.

If the timing belt had been replaced prior to this occurring, recheck the installation. If it had not been replaced yet, which is overdue for your mileage, check the timing belt tension, a slack in the belt would cause the valve timings to be retarded.

Check the spark plug wires, get them ohmed and if any does not have continuity or resistance is more than 25 k ohms, replace them.