rough idle while in gear

Asked by May 25, 2016 at 03:52 PM about the 1994 Ford F-150 XL SB

Question type: Maintenance & Repair

I bought a 94 ford with the straight 6 (4.9L) apparently the guy had been chasing the check engine light that was on. it has all new plugs, plug wires, cap, and catalytic converter.  Now I found out the #5 cylinder only has about 50 LBS. of pressure while the other 5 cylinders have about 150 lbs. of pressure.  I am trying to keep from doing a head job on it because I just need to make it about 8 more months.  Any ideas or suggestions?

6 Answers

Also, would this cause the rough idle while in gear?

16,600

You've answered your own question. The pressure readings of all cylinders should not be equal. But they should be within 15 percent of the highest. Since your other five cylinders read close to 150 lbs, fifteen percent of that figure is 22 lbs. No cylinder should read lower than 150 minus 22 lbs, or 128 lbs. The cylinder showing 50 lbs is dead. Hence the bad idle and loss of power.

How long do you think it will run with a dead cylinder

16,600

Who knows. How long has it had a bad idle? I would not over- stress it Definitely no interstate driving at 70 mph. Take back roads or city streets to work may be your best bet. Check your oil regularly. Raw gasoline will play havoc with oil condition.

Thanks OJ. I'm not sure how long it's been going on. I bought it like that 2 weeks ago. I haven't nor will I do interstate speeds in it. Should I continue to run 10w-30 or change to a heavier weight? I also found out today that the EGR vacuum selinoid is bad.

16,600

Stick with the oil recommended by the manufacturer. Most engine damage from lack of oil begins at startup, when all the oil is sitting in the pan with the top of the engine dry. Using heavier oil just prolongs the time needed for the pump to circulate the oil to the top upon startup.

Your Answer

Add photo

Related Questions

F-150

Looking for a Used F-150 in your area?

CarGurus has 211,804 nationwide F-150 listings starting at $1,000.

ZIP:

Search Ford F-150 Questions

Ford F-150 Experts

#1 OJ
OJ
Reputation 6,930
#2 dandyoun
dandyoun
Reputation 4,180
#3 tennisshoes
tennisshoes
Reputation 2,510
View All

Related Models For Sale

Used GMC Sierra 1500
941 Great Deals out of 62,271 listings starting at $1,395
Used Dodge Ram 1500
530 Great Deals out of 12,828 listings starting at $1,995
Used Toyota Tacoma
620 Great Deals out of 35,105 listings starting at $2,155
Used Ford Mustang
364 Great Deals out of 44,400 listings starting at $1,000
Used Ford F-250
513 listings starting at $3,500
Used Ford Explorer
939 Great Deals out of 73,806 listings starting at $750
Used Chevrolet Tahoe
778 Great Deals out of 28,448 listings starting at $1,500
Used Ford Ranger
203 Great Deals out of 6,719 listings starting at $1,450
Used Jeep Wrangler
393 Great Deals out of 19,086 listings starting at $3,000

Used Cars For Sale

2017 Ford F-150 For Sale
4 Great Deals out of 103,480 listings starting at $18,199
2016 Ford F-150 For Sale
154 Great Deals out of 41,650 listings starting at $16,995
2015 Ford F-150 For Sale
197 Great Deals out of 7,255 listings starting at $17,480
2014 Ford F-150 For Sale
431 Great Deals out of 11,725 listings starting at $10,700