22re missfire when warm, hard to start
 

I've read thread after thread online and usually I'm able to determine a plan of action, but need some fresh input as to what to try next. This is my first post on Yota Tech.
Vehicle is a 1987 4runner 22re with a 5speed
Here are the symptoms- It is hard to start, warm or cold, doesn't matter. It will crank crank crank for 10 seconds and slowly studder and fire up. If I mash the gas pedal while cranking, it cuts that down to like 6 seconds or so- still a long time. Hot or cold, doesn't matter. Once it is running (cold) its idles up as it is supposed and sounds near perfect, no miss, no nothing. As it warms up, a slight miss develops, and at operating temperature a pretty prevelant missfire is present. Idling, driving, basically anything under 3k rpm you can feel the miss. Most noticeable at idle. The exhaust had significant leaks in multiple spots that are currently getting repaired now.

Here is what has been done.
Plugs, Wires, Cap, Rotor, Fuel filter, seafoam treatment.

I checked over and over again for vacuum leaks to no avail.

Egr is still present.

When I disconnect the 02 sensor (all the way under the drivers seat area) there is no change at all in the engine.

No engine codes.

Where should I look next? 02 sensor? Fuel pressure regulator? Fuel pump? AFM? Throttle position sensor? Egr delete? Timing?

Thanks in advance.

Welcome to YotaTech.

Disconnecting the O2 sensor should give you an immediate code (unless you pulled it while still in open loop - engine cold). Did it?

Have you verified base ignition timing?

Have you tried a "cylinder test," where you pull plug wires one at a time (if no change, that cylinder isn't firing).

Have you put the inductive pickup of your timing light on each plug wire; the one that doesn't flash evenly might be missing.

Have you verified the fuel pump runs with key to start? (You'll need to disconnect the starter so that you can hear the pump.) If it doesn't, the fuel pump won't run until the engine starts pulling air through the VAF, which should extend cranking time as you described.

1. I cant remember, I will retry this when warm and see if it throws a code, I am about to pick the truck up in 30 min from the exhaust shop.

2. I have not verified base ignition timing, will do that.

3. The missfire isnt constant. It is more of an every 3-6 seconds studder. No matter which plug i pull, the engine loses that cyl and there is a change.

4. I have not used the inductive timing light on plug wires, ill try that as well!

5. Will also try this with the fuel pump.

Thank you for the suggestions, will report back.

you can use a paperclip jumper in the diagnostic box under the hood to bridge b+ and Fp, which will make the fuel pump run as soon as the key is switched to the "on" position. if this solves your hard start, you now have a place to resolve that issue.

your o2 sensor should not be under the seat, or near under the seat in an '87. the o2 sensor is located on the exhaust manifold, and the connector is right there in the engine bay at the driver side fender. you unplugged the seatbelt indicator.
https://cimg1.ibsrv.net/gimg/www.yot...6b7281ef44.jpg
https://cimg2.ibsrv.net/gimg/www.yot...9012dd96b4.jpg

i doubt your egr is playing any role in your hard starts, although it might play a role in the warm engine miss. you can follow the FSM directions to troubleshoot the egr and its associated vacuum switching to determine whether it is functional.

That's peculiar, as my 02 sensor is FOR SURE under my drivers seat. I followed the line up and disconnected it previously, but will baseline this again in a little while.

Thank you for the tip on the jumper for the fuel pump to run in the "on" position.

Also, my manifold does not have any sort of 02 bung.

you have a modified system. for '87 model year 22re 4runners, the o2 is attached to the manifold, with the connector exactly where i stated. this could certainly play a role in the symptoms you have; who knows whether it was modified correctly?

https://cimg3.ibsrv.net/gimg/www.yot...007da8baea.jpg
https://cimg7.ibsrv.net/gimg/www.yot...2ebe7739c3.jpg

Much appreciated, I will try these suggestions.

where is the diagnostic box supposed to be located on an 87? i only have FSM for 86 and 88. my 93 pickup had one on next the fuse box under the hood, but my 87 4Runner doesn't have one there. thanks!

At the risk of further hijacking this thread, a simple google search reveals--

https://cimg3.ibsrv.net/gimg/www.yot...de798bd30f.jpg

the picture above is for pre-1987 4runners. '87 and up utilize a diagnostic box, located along the inner fender, behind the battery, attached to the side of the fuse box. the fuse box is the L-shaped black object, the diag box is to its right with the flip top lid.

https://cimg1.ibsrv.net/gimg/www.yot...a946b74bff.jpg

His claim is his 87 doesn't have a port like the picture above.
Therefore I assumed it was pre 87 set up.

i believe the non-OP/TS asked where the box is supposed to be on an '87, not "what setup do i have?"

wally

I just thought if he doesn't have a diagnostic port on his 87, then maybe it's a late 86, my bad.