High Idle 1991 Toyota Pickup

[Dick Altman]

When I turn on the A/C on my 1991 Toyota Pickup the idle picks way up. When it's off, if idles normally. What's up?

 

[Dick Altman]

OK, I got a response that told me how to adjust the idle with the A/C on so that worked.
Bought a timing light, jumped out E1 & TC1 and timing was way off. So I got that done.
Biggest problem now is a tingley, metallic sound in the top end which I hear when I come off idle to say, 2000 RPM and when I back off. I'm wondering if it's the timing chain/guide issue. But two important factors to consider are that, although this is a 1991, it has than 44K miles. Secondly, it sat for around three years and when the mechanic pulled the pan it was sludge city. Since he cleaned everything and put in a new oil pump, I've driven it about 40 miles. Should I just run it and see if it clears up? A friend recommended marvel Mystery Oil as a product that would clean up the top end if it was added to the oil. Thoughts?

 

[tbplus10]

Unfortunately your noise could be about anything in the top
Marvel oil is a great addative, Ive used it to quiet lots of engine noises.
A silicone addative can sometimes do the same thing too. end.
A mechanics stethescope might help isolate some of the noise.

 

[BuffaloBill]

OK, I got a response that told me how to adjust the idle with the A/C on so that worked.
Bought a timing light, jumped out E1 & TC1 and timing was way off. So I got that done.
Biggest problem now is a tingley, metallic sound in the top end which I hear when I come off idle to say, 2000 RPM and when I back off. I'm wondering if it's the timing chain/guide issue. But two important factors to consider are that, although this is a 1991, it has than 44K miles. Secondly, it sat for around three years and when the mechanic pulled the pan it was sludge city. Since he cleaned everything and put in a new oil pump, I've driven it about 40 miles. Should I just run it and see if it clears up? A friend recommended marvel Mystery Oil as a product that would clean up the top end if it was added to the oil. Thoughts?

It sounds like you performed the truck's first oil change. I pray you don't have clogged oil galleys and resulting bearing damage but it sounds like there is. MMO is a good product but it's not magic. It's best used as an oil additive for vehicles that take old school oil. Best of luck.

 

[toyotafan]

I had that happen to me in a Ford 5.0 in the 90's. Oil pump broke on me, full of sludge from the previous owner.