GT88Yota

I am getting the following codes from my check engine light when I place a jumper in the connector box.

42 (Vehicle Speed Sensor)
51 (Switch Signal)

For some background info this is an 88 4x4 Deluxe Extra Cab with a 22-REC. It has about 160K on it and I just finished replaced the cylinder head (cracked) and the timing chain/guides. I set the timing to 5 deg BTDC as per the Haynes manual I have and installed new plug/rotor/wires/dist cap/knock sensor/oil pres sensor/water temp sensor. When I took it out for a test drive it seems to have very little power. I know it?s a 4-banger but it should be able to at least get out of its own way. I initially thought it was a clogged catalytic converter but I cut it off and it runs better but still leaves a lot to be desired.

The vacuum hoses look are a mess as the previous owner appeared to have moved some things around and the layout of my engine is different from every picture I have seen. It appears as though 1 or 2 of the VSV?s are damaged and will need to be replaced.


My question is what do the codes mean and any suggestions for the lack of power?


Thanks!






UPDATE: #3 cylinder is running rich, see below for more details

GT88Yota

update:

A number of the vacuum lines were in the wrong spot so after correcting that and resetting the timing it runs great, as long as there is no load on it. So it still runs like crap on the road.

Any ideas?

Targetnut

If the light is not actually on then I would suggest clearing the codes by removing the EFI fuse in the underhood fuse panel for about a minute and then drive it and then check the codes to see if one or both even returned.

the switch signal means that the TPS is not reading closed throttle and/or the A/C switch is on. You cannot accurately adjust the timing while this code is on. Obviously you'll have to fix this, and set the timing correctly before you can get a good evaluation of the performance.

The vehicle speed sensor should not have a significant impact on the driveability I belive that your truck has a speedo cable and the sensor is in the speedometer.

GT88Yota

You are correct, the light does NOT come on when driving but when I put the jumper in the see if I was getting any codes those are what popped up. I did pull the fuses (stop and EFI) before the last test drive but only for about 30 seconds. I'm going to go try it again, this time for 3-5min and see what happens.

As far as the TPS, do I need to replace it or does it need to be adjusted? Also, how do I "turn off" the A/C switch?

Thanks.

Targetnut

The TPS is adjustable and if it out of adjustment then you can get that code. Usually they end up being out of adjustment because someone adjusts the throttle stop in an ill fated attempt at adjusting the Idle. The throttle is set at the factory and does not ever need to be adjusted. Idle speed is adjusted using the Idle air bypass screw on the top of the throttle housing.

Unfortunately we all get our trucks without knowing what all may have been done to them before. So in most instances it may be better to just start at the beginiing and set all of the basic adjustments as the first thing we do.

GT88Yota

I replaced the TPS with one off a 22-REC equipped Celica. I noticed when I was at the junkyard yesterday looking for a set of injectors that 89 4Runners with the 3.0 had the same TPS as on my '88 Pickup so I pulled it off and noticed that the return spring failed to return the TPS to zero. The Celica TPS appears to have a much stronger spring and after installation and adjustment I no longer get the 51 (Switch Signal) code.

I still have the VSS signal even after pulling just about every fuse and the battery for half a day.

After installation of the new TPS I reset the timing, it was a few degrees off and the truck runs (marginally) better on the road but still lacks power.

Could the coil have gone bad and possibly not sending enough power to the plugs?

GT88Yota

any ideas?

Yotapup

You may just have a wiring issue. The code will not clear if a wire is broke or disconnected. just went through this with my O2 Sensor.
Trace out your wiring to the VSS.

GT88Yota

Do you know where the VSS is on a pickup? I couldn't find a location in the Haynes manual I have and I do not know what I'm looking for.

timebandit

You cauld have set the timing totaly wrong if the TPS is broken and code 51- switch is there. Ignore the speed sensor for now. Put a vacuum gauge on the intake. Should be pulling 20-22" at idle unlees the chain is off a tooth.
I dont think the codes are "the" problem. Dumb question but, you checked the compression after the head went back on? Set the valve clearance hot? None of those vacuum hoses are ˟˟˟˟˟˟ with the EGR valve right?

GT88Yota

I replaced the TPS and no longer get that code. No I have not checked the compression yet, I figured it was a brand new head and it shouldn't be a problem. Also, I have not set the valve clearance hot. I'll check all the vacuum.

The truck is at my parents house, I'll be back there not this weekend but the next and I'll go over all those things.

What effect would the EGR be having on it?

Thanks.

timebandit

UUUUHHH. You have to set the valves hot. PITA. Can't run it with the cover off either. VSS location depends on the year. Either on the tranny where the cable should be or inside the gauge cluster in the early years. Don't worry about that right now. Make sure the EGR is not on when it should NOT bet. DON'T ASSUME ANYTHING. Double check every thing. Including compression and running on all four. Reset those valves. Check the vacuum to see if you still have any valve problem's.

Targetnut

If you are concerned about the EGR just disconnect it and see if it makes a difference. If it does then you'll need to focus some attention there. If it does not then reconnect and look elsewhere.

When you timing is set correctly where is your distributor turned to? is it near the adjustment limit?

When in doubt it is best to start at the beginning with a compression test. You can chase your tail in circles indefinitley if you have a basic compression problem and you are looking at the ignition and fuel system.

GT88Yota

Timebandit: So I have to warm it up then pop the valve cover off and set the clearance? Why is it a PITA?

Targetnut: If I remember correctly yes the distributor is close to its adjustment limit BUT the truck is 30miles away at the moment so I can't check until next weekend.



Thanks for all the help, I'll start at the beginning, work through it and let you know how it goes.

Targetnut

If the distributor is close to maxed out to get the timing set properly it could be an indicator that the cam timing is off a tooth.

timebandit

PITA to work on anything that's red hot, man.

timebandit

If the distrubitor is off 1 tooth that's about 8 degrees of error!!
If the timing chaing is off a tooth it might run without bending any valves if it is retarted. But I am not sure on that one. Compression should be ~175PSI on all.

GT88Yota

OK, the valves are adjusted and the distributor is about in the middle of it's adjustment range. I also checked the compression and I don't remember the numbers exactly but they were well within spec.


New problems: #3 cylinder is running way rich (determined by condition of spark plug) so I think there is an issue with either that injector or the wiring. My best guess is that the #3 injector is stuck "open" and dumping a ton of fuel in thus starving the other cylinders which would explain the lack of power under load. So, I pulled them and shipped to Cruzin' Performance to have them cleaned and balanced. I figured for $14/injector plus shipping is a lot cheaper then a new injector. Also, a 18yr old engine with 160K has seen a lot of fuel so the injectors could very well be gummed up.


Once I get the injectors back and installed I'll post the results.

GT88Yota

I got the test results back from Cruzin Performance and they all appeared to be working perfectly with a slight increase in flow after they were cleaned. Any ideas why one cylinder would be running rich?

GT88Yota

bump...


any ideas why the #3 cylinder is running rich?