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87 4Runner Rough Idle/Misfire issues

Old 07-12-2015, 01:27 PM
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87 4Runner Rough Idle/Misfire issues

So started troubleshooting this a couple weeks ago, but I haven't been able to figure this out. Here's the symptoms I had leading up to the current issue:

Warmed vehicle up and drove about 15 minutes down the road, everything was good. Turned the vehicle off and let it sit for a couple hours. After turning it back on it seemed to drive fine, as it warmed up I started getting loss of power above 3k RPM, putting down the accelerator would cause it to choke and stall out. By the time I was pulling onto my street it would stall out if I let it idle. Basically had to keep it around 2k RPM at all times otherwise it would drop too low and die.

I was able to start doing some testing a couple days later with a friend that knows a bit more about the engines:

1. Replaced distributor cap, rotor and ignition coil wire as there was carbon buildup, and corrosion/debris in the cap ignition coil wire connector. No change..
2. Compression - all ~150
2. Vacuum tested, didn't see any problems.
3. Light tested all 4 ignition lines, all spark, with no irregularity.
4. Checked timing with a Timing Light. Looks good.
5. Replaced Fuel Filter. No difference.
6. Tested resistance on MAF - all looks within spec.
7. Coolant was low, filled it up, no difference in operation. The radiator is leaking slowly from the weld points, but it's done that since i owned it, and the reservoir will never completely empty.

Current operation: Engine will fire up just fine, but misses. There's a smell of fuel, and when it runs rough it doesn't seem like it's missing any specific cylinder. I can gas it to ~1500 RPM and it evens out, with an occasional miss. 2000RPM+ it runs perfectly fine, no misses. I was able to go over 3k RPM without the engine stalling out, so I'm not sure if that issue only came about after the engine had heated up.

I'm at a bit of a loss on where to go from here, TPS? Ignition Coil?

Any help appreciated thanks.
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Old 07-17-2015, 06:01 PM
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Did some more checks today.

Inspected cold start injector. It is extremely dirty. Resistance is 4.6 ohms, seems high.
Vehicle still starts and smells like gasoline in the engine compartment with cold start injector disconnected. I would have thought the vehicle would not start if cold start injector was disconnected.

Ignition coil resistance is 1.8 ohms, this looked 3-4x as high as it should be based on the '93 FSM spec. secondary resistance was 13.6k ohms. which was in-spec.

Coolant temp sensor resistance was ~1800 ohms. I believe that's correct based on http://www.4crawler.com/4x4/CheapTri...ne_Pix/21.html

TPS resistances at closed/open checked out, but I don't have gaps for the correct mm to do the full test.

I'm going to replace the coil and go from there.
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Old 07-20-2015, 12:42 AM
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Hey man I was having very similar issues as you. For me it ended up being the ect sensor next to the cold start injector. I've been running my truck for over a month now without the cold start injector plugged in sometimes it was the only way to get the truck started up again after stalling before I fixed the ect issue. Ran great for a week...now more problems.

Good luck.
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Old 07-20-2015, 06:06 AM
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ah I guess the correct test is to pull it out and put it in cold water and verify that the resistance changes properly when it goes cold/hot. I'll try that. Also I noticed the connector housing to the ECT is busted.

Thanks montana.
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Old 10-27-2015, 06:41 PM
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Hey guys, I just got an 87 4runner and have very similar symptoms. This is an old thread I realize but was curious how your fixes turned out. Any further info that anyone has would be very helpful. Also if there was a re-direct I'm not catching I'd grateful for anyone's direction.

Thanks
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Old 11-10-2015, 02:03 PM
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Need help please

Hello I have 1987 4runner 22re it was running fine last week haven't drove it in a week. Now went to start it. It started fine then immediately started to run rough very rich sounds like it's running on less than 4 cylinders it has power there is a little gray smoke coming out. I checked the codes and code 6 and 12 pop up one of the codes might be old never clear them before they and check engine came on once but it went away so I never check it
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Old 12-08-2015, 08:12 PM
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Originally Posted by LouRadon View Post
Hey guys, I just got an 87 4runner and have very similar symptoms. This is an old thread I realize but was curious how your fixes turned out. Any further info that anyone has would be very helpful. Also if there was a re-direct I'm not catching I'd grateful for anyone's direction.

Thanks
haven't had time to fix much I've replaced the O2 sensor since I last posted, and disconnected the battery so that everything could reset, but no improvement. Probably going to take it into a shop soon and just have someone else work on it as I really need it running.
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Old 12-09-2015, 01:44 AM
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Sounds exactly like TPS symptoms (one of the most common and free to fix problems).

You definitely need a feeler gauge to check / adjust it properly. It's a worthwhile tool to have- you can also adjust your valves when needed.
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Old 12-09-2015, 07:17 AM
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TPS adjust with Reman AFM

Originally Posted by jennygirl View Post
Sounds exactly like TPS symptoms (one of the most common and free to fix problems).

You definitely need a feeler gauge to check / adjust it properly. It's a worthwhile tool to have- you can also adjust your valves when needed.
Thx for the response. Just got an A1Cardone AFM reman (one of the circuits on the previous AFM tested bad). Ohms on the reman all read in proper ranges. SOOO... time to tackle TPS. I've got the hex screw mods on standby, gotta go get a feeler gauge set but was wondering which range is best. Seems that maybe a set of like 10 or 12 that cover the ranges i need would be practical, not sure I'll ever need all 32 feelers if i get the jumbo set. ...but would that be best to have or just overkill? My TPS is def not set correctly, it was loose when i got it and i checked the idle stop screw other day, not even making contact. LOL. Sorry so much info... last question. My TPS did spec fine on ohms test BUT if i do need to replace it, will an o'reilly BWG aftermarket do well? I saw one at the store and it looked well made (seems like a straight forward and simple sensor).

Thanks again. Cheers
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Old 02-08-2016, 08:28 AM
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Took my 4runner into a mechanic a few months back, the issue ended up being the intake was pulling away from the head causing a vacuum leak. This caused it to rev up oddly at random, and was also causing the fuel smell in the engine compartment. After a new gasket and bolts (They mentioned it was actually missing a couple) everything is back working as normal.
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Old 02-08-2016, 03:11 PM
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Originally Posted by Sleaker View Post
Took my 4runner into a mechanic a few months back, the issue ended up being the intake was pulling away from the head causing a vacuum leak. This caused it to rev up oddly at random, and was also causing the fuel smell in the engine compartment. After a new gasket and bolts (They mentioned it was actually missing a couple) everything is back working as normal.
Mine idles irregularly but I'm thinking it's the timing chain guides being shot. It sounds like the chain is ticking a bit. I replaced all my vac lines and didn't get any surges when i speayed carb cleaner around to test. Tps, replaced as well.
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Old 03-26-2016, 04:12 AM
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Originally Posted by Sleaker View Post
Took my 4runner into a mechanic a few months back, the issue ended up being the intake was pulling away from the head causing a vacuum leak. This caused it to rev up oddly at random, and was also causing the fuel smell in the engine compartment. After a new gasket and bolts (They mentioned it was actually missing a couple) everything is back working as normal.
That is a legit mechanic! How much did they charge?
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