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First Gen 4Runner inconsistent starting

I have a 1988 Toyota 4Runner (3VZE) that has an intermittent starting issue.

It typically takes several cranks before it will start. However, on very cold days it often starts on the first crank. Once it has started it runs well.

I have also noticed that after driving it, it will usually restart first crank after it’s been sitting for a little bit. However, if it sits for a few hours it goes back to the hard-starting.

While it runs good, it does run rich. I notice a gassy smell after I get home and step out of the vehicle. Also it usually billows a bit of white smoke about 30 seconds after it starts up. It goes away pretty quickly though. I have not noticed any type of coolant leaks or any other leaks.

Additionally, I checked the CEL flash codes and am getting a 51 and 52 (TPS and Knock Sensor). Not sure if those codes have anything to do with the hard starting.

I have had a couple of shops look at it, but I don’t feel they were thorough. One replaced the cold start injector and adjusted the TPS. Didn’t make much difference so I took it to another mechanic and they put a new distributor cap and rotor button, along with new plug wires. When they had the truck, it would not reproduce the problem.

One last thing to mention is that a couple of times it has been jerky while driving. It typically does not jerk, but it did today temporarily (cleared up after re-started it) and then it was bucking and jerky a couple months back, but those are the only two times I’ve noticed.

I’m not really a mechanic but it seems as if there’s a fuel problem during the start-up process. I wouldn’t think it would be fuel pump or filter because it runs well once started. I don’t know though.

Any ideas on what this could be? What should I be looking at?

I am very hopeful someone can point me in the right direction and I can get this fixed. Thank you.

TPS might be easy to diagnose and fix or replace. If it’s like the one I know from a 1984 Chevy Cavalier, it is simply a variable resistor. Hook up an ohmmeter and move the lever through its range of motion. The change in resistance should be smooth. If not, try cleaning its innards with electronics cleaner spray, or replace it with a new or good used one.

The next time the engine won’t start, turn the ignition switch on so the dash lights come on for two seconds and then turn the ignition off.

Repeat this a half dozen times and then try starting the engine.

If the engine starts right up, there’s a problem with the anti drain-back valve on the fuel pump.


Thanks Tester, I’ll definitely give that a try and report the results.

The process for testing TPS on my engine doesn’t look to difficult. I’ve never done it, but it’s worth looking into further

Wouldn’t fire up this afternoon after 2 cranks, so then I remembered what you suggested and tried it. Started right up after turning on and off 6 times.

So does this definitively mean something’s wrong with my anti drainback valve? Or is there something else I could try to confirm?

That’s how mechanics check for a faulty drain-back valve on the fuel pump.


If the key dance works and everyone who uses the truck knows about it, you may be able to go for years without needing to replace the fuel pump.

Gotcha, I’ll do it again next time and see if it has the same result. Generally speaking, is that valve difficult to replace?

That’s encouraging lol… hopefully I can fix it. I’ve been driving it 3 and a half months like this.

You have to remove the fuel pump from the gas tank to replace the valve.


As posted above the long cranking time is likely the drain back valve (fuel pump) problem. A fuel pressure hold test would confirm or disprove that theory. My Corolla is similar-era vintage (4afe engine), never had a long cranking time problem. But I did have a problem with the engine jerking during slow speed neighborhood driving. For that you first want to verify the warm idle rpm is spot on to spec. This engine just won’t perform well if the warm idle rpm is incorrect. That’s set w/an idle air bleed screw on the throttle body, on mine at least. If you discover yours is off, set it and check to see if you get the tps code again. The tps may actually already be correctly adjusted, but the computer will think there’s a problem with the tps if the warm idle rpm is set incorrectly. That could also be the cause of the jerky driving experience. Suggest to figure out and rectify the cause of the tps code before making any other guesses on the cause of the jerky-engine problem. Once you get the tps under control, and you’ve fixed the long-cranking problem, if you still have a jerky engine, you may have clogged fuel injectors. Try a bottle of fuel injector cleaner in the gas tank. That definitively helped w/my Corolla. It’s easier for a slightly clogged fuel injector to output fuel volume flow accurately at higher rates (like on the freeway) than at lower rates (like neighborhood driving).

You need to solve the knock sensor problem too, as that part helps prevent engine damage due to detonation. Could be due to an egr or ignition timing problem, but more likely the sensor or it’s connection to the computer has failed.

Thanks for the reply.

How exactly could I conduct a fuel pressure hold test? Do I need a fuel pressure gauge?

The warm idle has been a bit too high. I believe spec is 800rpm +/-50. I’ve been idling between 1000-1500.

I need to dig up the instructions for setting that screw and see if I can’t tweak it.

I’ve run a few different fuel additives: Seafoam, Techron, and currently got some Redline in the tank.

You are correct about the knock sensor. I want to tackle that as soon as I get the starting issue figured out. The knock sensor on these engines is buried in the motor unfortunately.

Any idea if it’s part of the pump itself or is it somewhere upstream? Fuel pump replacement on these Runners looks fairly simple because it’s easily accessible.

That’s much too high, and will cause all sorts of drivability problems. Adjust it to within +/- 50 rpm per spec. If you haven’t done a basic tune-up in years, good time for that. New plugs, air filter, distributor cap, plug wires, ignition rotor, set idle rpm and ignition timing. Checking valve clearances would make sense too. Checking fuel pressure is something a diy’er can do , but requires some specialty equipment and can pose a fire safety hazard, so most folks would have that done by a shop. On the 4afe engine it is measured by removing the cold start injector and placing the gauge there. If you want to try it yourself, googling will probably show you how and what you need. A factory service manual will have that info too, but will specify equipment you probably won’t have, but an auto parts store might allow you to rent. I used a product called “clean power” to clean my Corolla’s injectors, but I think that is not available in many areas. Techron is the one Ray has mentioned on the show, and folks who post here seem to think it works. Some folks here like Seafoam product too. I’ve never used either myself however.

Unfortunately toggling the ignition on and off did not work today. Had to use starting fluid to get it fired up.