ycmike

Trying to find the cause of a misfire on a 1986 22RE. Engine was Just rebuilt. Engine had 250,000 miles and a blown head gasket before the rebuild. Now after the rebuild, when engine is cold it runs fine from idle to 3,000+ RPM.

But, let engine warm up until coolant temperature is 160+ F degrees and:
-At idle, the engine still runs fine with almost no detectable misfire
-As the RPM is increased a misfire is noticed
-I can hear the misfire and also watch the engine shake or jerk each time the misfire occurs
-The misfire frequency increases with RPM and at greater than 2,500 RPM the engine sounds really bad and the engine is misfiring so much it is shaking a lot

I'm doing this with the engine under no load. In neutral. Truck Parked.

When the vacuum line to the EGR Valve's diaphram is disconnected, the misfire is dramatically reduced. It is not completely eliminated, but the engine runs much better.

The ECU does not give any codes. With "T" jumpered the CEL flashes once, pauses, flashes once, etc showing no codes.

Since removing the EGR vacuum line helped reduce the misfires, I tested the EGR Modulator Valve according to the FSM and it failed one of the FSM tests so I replaced it using a new Totoya part. There was no change in the way the engine runs with the new modulator valve.

I then replaced the EGR Valve with a new Toyota part - no change.

Taking a reading of direct intake vacuum it is steady at 21 inches when idling hot or cold.

The vacuum is from 19 to 20 inches when at steady but higher RPM. This seems a little concerning since I thought the vacuum should be slightly more than idle vacuum at higher RPMs while holding a steady throttle.
Maybe a plugged exhaust?

I've double checked that all vacuum lines are connected correctly, I've looked for vacuum leaks and blocked off the Brake booster, Power steering idle up circuit, and PCV hoses one at a time at the air plenum with no change.

The timing is adjusted to 5 degrees BTC with "T" jumpered.

I also did the following before reinstalling the rebuilt engine:
-Throughly cleaned the Throttle body (with TPS removed so it would not get damaged from the cleaner).
-Throughly cleaned the Intake manifold and the Air Plenum of all carbon
-Adjusted the TPS according to the FSM (resistance tests) and rechecked the settings.
-Checked the Air inlet tube from the AFM to TB for cracks/leaks - it looks good and I do not see any cracks or problems
-Injectors were cleaned and flow tested. New filters installed along with seals and o-rings
-Installed new Fuel filter - Wix
-Installed new Air Filter - Toyota
-Installed new spark plugs - Toyota (NGK)
-Installed new plug wires - Aftermarket
-Installed new Thermostat - Toyota
-Installed new Hoses - Gates
-Installed new Radiator - Aftermarket
-Installed new Water Pump - Toyota
-Installed new Belts - Toyota

I plan to check all other vacuum hoses connected to the air plenum. I think the only thing left is the Air Control Valve.

I also plan to check the injectors with a stethoscope to see if they all seem to be firing.

My best guess at this point is an injector not firing, vacuum leak I've yet to find, or the exhaust is partially plugged.

Any advice?

tinkertoy

And you set the plug gaps at??????? Just checking.

ycmike

No problem. Appreciate the feedback, I'm looking for anything I might have missed. I set the plug gap at .031"

I also checked the distributir air gap and it was right in the middle of the range per the FSM. Don't recall now, but I think that was .008".

Tonight I had some time and I listened to each injector using a stethoscope. Each one had a definite tick, tick, tick and each one would increase/decrease frequency with engine RPM so they seem to be firing ok. Since I had them cleaned and flow tested, I'm assuming that they are working correctly since I can hear them ticking.

I also pulled each plug wire one at a time while it was running and each one causes the engine to run rougher and drop some rpm. The spark is jumping a large gap for each wire. And it doesn't feel very good to get bit by 20,000 volts.

I plugged the Air control valve at the throttle body and there was no change. I don't think there is any other vacuum source I haven't plugged.

Suspecting there might be a plugged exhaust, I dropped the cat and tested again running the RPM up and again the engine has the same miss.

It definitely still rruns ok when the engine is cold and then develops the miss once it warms up.

whokrz

This happened on my girlfriends 4runner replacing the cap, rotor and the napa brand plug wires with ngk did the trick.

thook

I assume the valves are adjusted correctly?

- coolant temp sensor
- fuel pressure regulator
- airflow meter

I'd check those. Maybe a compression test, as well.

ycmike

At first, I thougt this was an ignition problem. In the past, I've had a couple wires go bad on this engine and this time it seemed very similar however, the misfire gets very bad above 2500 rpm and it seems like its multiple cylinders misfiring. I've now had two sets of spark plugs, wires, cap, and rotor on the engine and there have been no changes to the way it runs.

ycmike

I'm going to recheck the valve adjustment and TPS.

I'll also check the AFM.

I'll need to get a fuel pressure gauge/test setup before I can check the fuel pressure. Unless there is a way to check it without one.

thook

The FPR is mechanical/vacuum actuated and works very simply. There's an internal diaphragm and that's almost always the way it goes bad, if it does. If the diaphragm springs a leak, the regulator won't be able to maintain pressure in the fuel rails. So, the way to check that is to pull the vacuum line off and see if there's any signs of fuel. Engine vacuum will suck the fuel through it.

If the valve clearance, TPS, and FPR check out fine and if it comes to testing the AFM, post up and I'll provide a link or two on a good way to check it that's not covered very well in the FSM, per se. It can test fine for all static positions, but still be bad along the measuring plate circuit.

As for checking pressure in general, you would need a guage, but not necessary for simply checking the regulator status.

ycmike

Thanks for the clarification on the FPR. I did pull the vacuum line on the FPR last night while the engine was running (idle). No fuel detected in hose or FPR. And the engine RPM changed just slightly when the line was removed. Plugging the end of the vacuum line with my finger and it seemed to have full manifold (strong) vacuum at idle.

I will be using the FSM for checking the AFM and I also found links from another post here to a site that describes checking the AFM and the TPS. I'll print these out and use them as well:
http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

BTW, I've search this site, Pirate4x4, ih8mud, and other general google searches for a solution to this problem and have found several promising threads but either they end up going a totally different direction and end up not helping my situation or they never posted their solution if they found one.

I keep thinking I'm overlooking something very simple or have made some stupid mistake...

thook

Well, run a compression test and make sure you're rings are doing their thing right........that is if you aren't already sure you installed them right; ring order, ring gap, blah, blah. If the compression readings aren't correct, that's where I'd start looking. Rule it out, eh.

ycmike

The TPS resistance and AFM resistance tests looked fine to me. I also did the sweep tests on teh TPS and it looked fine as well:

TPS:
0.00" VTA - E2 680 ohm
0.022" IDL - E2 20 ohm
0.033" IDL - E2 Open
WOT VTA - E2 4.98k ohm
Vcc - E2 6.73k ohm

AFM:
E2 - Vs 300 ohm
E2 - Vc 180 ohm
E2 - Vb 280 ohm
E2 - Tha 2.03k ohm @ 70 F
E1 - Fc Open when fully closed
Short with any position except closed
E2 - Vs The resistance varied between 300 and just under 1000 ohms so this looked good as well.

ycmike

The long block was assembled by the shop that did the machine work. If I get time this weekend, I'll run a leak down.

Other than that, I can start diagnosis at the ECU to see if I might have a wiring issue from ECU to the TPS, AFM, etc

I'm running out of ideas and I'll need to move on to some other things soon. I may be taking the truck to a shop and have it checked out. At least have a tail pipe sniffer done to see what the emissions and A/F ratio looks like.

thook

Yeah........time waits for no man and life keeps calling us to other things, doesn't it?

Checking at the ECU is definitely a good idea. Good luck.

Oh, if you want, run a forum search under "AFM testing" using my name. I have/had a thread going on about my crazy learning process on trying to figure out the reason for a long time code 5 on my 22re. The AFM was the problem. There's some other info, but I'll have to find it later today, if you're interested.

ycmike

If possible, could someone provide vacuum readings from the "E" and "R" ports of their throttle body? I would like to know what vacuum readings you have from idle to 3000 rpm. Perhaps in steps of 500 rpm - for instance - idle, 1500, 2000, 2500, 3000.

I would like readings from an '86 22re but I think '85 to '89 should be same/similar.

I'm trying to confirm at what RPM the vacuum is developed and how much vacuum.

Tests should be done right at the throttle body ports.

Thanks in advance if you can test and provide results.

thook

Sorry, Mike. I don't have the tool for it.

ycmike

Plugs look clean but they are new and the engine has been sun very little. My thought in looking at them was that they looked like they were running hot but I'm not an expert and again, the engine had about 30 minutes on it when I took them out and looked.

I'm thinking now the prpblem is a lean misfire. It runs ok when its in open loop warm up but then when the temperature comes up to operating range, the ECU switches to closed loop and the A/F ratio is leaned out and my guess is that it is being leaned out too much.

I unplugged the O2 and the misfiring was reduced quite a bit, same as if I disable the EGR. Perhaps the O2 is bad. I didn't have time tonight but I will run the O2 test and see what I get. I'm really thinking that its getting too little fuel or too much air.

I still want to veriy the valve lash but I'll have to do that this weekend. No time today or tomorrow.

ycmike

see post above

The AFM temp sensor seems to be working ok. The resistance was within range for air temp.

The BVSV for the EGR is working correctly. No vacuum when cold and vacuum after warm up.

I haven't checked the coolant sensor. I'm not sure how much this affects the A/F ratio after warmup. I'll look at the test procedures and see what it takes to check it out..

ycmike

Readjusted valves - nothing unusual found - no change in the way it runs
Rechecked timing - right on the money
Replaced Oxygen Sensor with a direct fit, Denso brand. - no change.

ycmike

The engine continues to run the same:
Runs good when cold.
"Cold" is when the coolant temps are below about 160 degrees F. (According to aftermarket gauge I added)

Once coolant temps are in the normal range ("normal" operating temps of 190 to 200 degreed F) the engine still runs ok at idle or up to about 2000 RPM.
Engine starts to develop a miss above 2000 RPM.
At 2500 rpm and higher, the engine has a very bad, constant misfire.

At normal operating temps:
With the Oxygen sensor unplugged, the engine runs much better >2500 RPM,
or
with the EGR vacuum disconnected, the engine runs much better at >2500 RPM.

Suspect engine is running lean in closed loop mode. Don't know why.

No CEL codes. (verified that the CEL does work)

thook

Did you ever get the compression test done? How long ago was the motor rebuilt? IOW, have the rings been able to seat properly?

Other things to look at would be fuel pressure, fuel pressure up valve (the switching valve inline with the regulator), and run a sweep test on the AFM.

https://www.yotatech.com/forums/f116...esting-146662/

Unless you've already run the test as illustrated on Roger Brown's site????