Hi all,
New to automotive forums and i have a friend who has a problem with his 93 Tercel. 248,817 miles on the car. (the right miles, not a typo.)

Did a search but only found one thread about surging at idle. A little history first and hopefully someone will be able to help. When he advances the throttle the car has no problems, just at idle no matter whether the engine is cold or warmed up.

What's been done so far to try and fix the surging:

Changed the Throttle position sensor. (No change in surging)
Changed the Idle Air control Valve. (No change in surging)
Checked Vacuum lines and changed the ones that were cracked (no change in surging)
Was going to change or at least check the EGR valve but found out that the company that changed his oil and didn't put his oil plug in right which resulted in a seized engine bought a used one and it happened to be a canadian engine. (No EGR valve, not even bolt holes for it)
So now I'm stumped. Thought it might be the fuel filter going bad. Any thoughts about the fuel filter being the culprit?

Thanks in advance.

James

Edited: Since I've had 19 views and no responses. I guess i should have said what the book calls it, Lopes instead of surges.

Still hoping someone will have a response that will tell me what else i can check.

Thanks,

James

They got away with feeding your friend a Canadian engine after their screwup? That aside, I'll presume the loping was present before the engine swap, but he oughta get them to do it right.

Check for other vacuum leaks by spraying carb/fuel injector cleaner in and around the throttle body and intake manifold.

Check the PCV valve and clean or replace.

Check the spark plug wires, coil, cap & rotor for resistance. Clean off any oxidation on the cap/rotor terminals.

Check the spark plugs for wear, gap, and wetness or fouling.

Hopefully, this is a good start to rule out the more common issues. Hope this helps!

First off, thank you for the reply. I was starting to think no one would.

No the problem just started. He got the engine swap at 68,000 miles (Approx.) now he has over 200,000 miles on it. Too late to get them to do anything about it. Never would have known about the canadian model if it didn't start this loping and i started looking at it with the haynes manual.
I'm going over this weekend and look at it again and will try all of your suggestions.
Thanks again.