Low Power below 3400 rpm

[coronan]

Victim is a 87 5 speed with 4x4 and 225,000 on the clock.
I need some help trouble shooting missing power below 3400 RPM. I notice it getting on the freeway. I can get up to 70 mph in 4th no prob. I have trouble staying there in 5th.
If I rev it some more power comes In and I can hold 77mph.
Last week I read codes 6 and 11. I reset the codes and power came back for 1 or 2 trips. Today It is missing power but No Codes
TPS is 10,000 mi old; working and adjusted properly.
Trouble Shooting for Code 6 in the PDF manual…
Page FI-32: Test 1 (Pin IGT to E1) = 1 volt at idle. Test 2 (IGT to Ground) = 0.98 Volts at idle. Test 3 (E1 to Ground) = 0.3 ohms resistance. ARE THESE GOOD NUMBERS? WHAT DO I CHECK NEXT.

[timsrv]

These type issues can be hard to nail down. When was the last time you did a tune-up? If you don't know then the 1st thing to do is replace plugs, distributor cap, rotor, fuel filter, air filter, & possibly plug wires. When you check your timing you should also check to make sure the electronic advance is working. This can be accomplished by pulling the jumper from the "Check Engine Connector", then comparing timing readings with the results you got with it in. There should be a noticeable jump. Usually about an 8 deg change (12 deg BTDC with jumper in, then about 20 deg BTDC with it removed). You should also check the condition of your vacuum hoses & make sure they are all hooked up and none are cracked or broken.

Code 11 is a big hint of the TPS being bad or out of adjustment. The TPS unit for these vans is set up using continuity (not voltage). Here's a thread that deals with the throttle body. Watch the video (end of the 1st post) to see how it's set up: http://www.toyotavantech.com/forum/s...-Throttle-Body

Code 6 is usually associated with a non-running condition. My guess is it's left over from a previous issue. I would recommend clearing the codes then run it for a couple days to see if they come back.

Check the condition of your EGR components for signs of overheating. If there's damage here from excess heat that's a sure sign the cat converter is clogging up. Exhaust restrictions will have drastic negative effects on power. Good luck. Tim

[coronan]

A full tune up was about 3000 mi ago in January
Timing Chain Replaced
Compression Test = 145-150 psi
Plugs looked good. Slight adjustment on gap
New Plug Wires
New Rotor and Cap
Gap on the magnetic pickup was 0.10
(can this be rebuilt??? Or do I need a whole new distributor?)
Set timing about 15* advanced w/ out ecu jumper
(runs great on 89 oct)
In March
Fuel pressure good. (but I need to check again)
New Fuel Filter

Last Weekend
Replaced a few vacuum hoses. Cant find any vacuum leaks with carb cleaner or by ear.
Tps rings out per shim method.
Ecu has Proper Grounding
Today
Pickup coil is with in spec (172 ohms)
Ignition coil, Primary resistance = .7 ohms = BAD
Ignition coil, Primary resistance = 8.89 ohms

I've been running straight piped (no CAT) for about 6 mo.

[timsrv]

If it ran good, then not, your timing likely isn't your issue, but timing should only be set with the jumper in your "check engine connector". No real way to know where the timing is if set without the jumper as your electronic advance (if working) would influence the ignition timing. You'll need to get your timing light out to check the advance anyhow, so that will be a good time to check it with the jumper in.

It's not too unusual to see a good coil read outside the range listed in the service manual.........especially the low side. Coils are cheap, so you may wish to replace just to rule out.......but it's probably not that. So far I've been lucky enough to avoid issues with the magnetic pick-up, so I don't have much to say about that. I've never purchased a new or rebuilt distributor before either. If I have doubts about a distributor I simply swap out with one from a parts van (easiest way to troubleshoot). If you don't have that luxury it's not a bad idea to pick-up a few spare parts from the salvage yard (if you can find a van there). Tim

[Burntboot]

How long have you been hunting the low-power issue?
Were all the repairs done looking to solve this problem or is this a NEW problem, unrelated to those repairs?

As Tim noted it should either be 12 (jumper in) are about 20 (no jumper) so 15deg is wrong no matter how you look at it.
Assuming that your advance is functioning correctly you are running about 5 degrees retarded which will have a huge impact on power.
You really can't evaluate anything, until you get that issue sorted out.
BB