Haaklord

My 1990 3vze gets a check engine light after driving for a few minutes. Once it comes on I have reduced power and it runs slightly choppy. In the past couple weeks I have replaced the spark plugs, wires, ignition coil, distributor cap and rotor, fuel filter, did an EGR delete (light was happening before that), removed and cleaned the throttle body and tested the throttle position sensor (it works), and installed a new exhaust. There is a small exhaust leak where my new test pipe connects to the downpipe from the exhaust manifold (where my catalytic converter was cut off...).

After I put the new exhaust on I put premium in it which I forgot was dumb. That generally gives me the knock sensor issue and it gave me a starter sensor CEL issue. I put it back on regular and both went away for a while. For a bit the light would come on and the truck would struggle to stay alive while accelerating. Throttle would cut in and out and it would sometime die when at idle. Most of that issue is gone with all the new parts but it feels like it is still there just nowhere near as bad.

I'm wondering if this could be my fuel pump going bad, I have a new one but I don't want to deal with putting it in hopefully...I'm not sure if my CEL codes will be accurate since the light goes away every time I turn off the car. The truck gives me the knock sensor code whenever I check it but I think it has always given me that code whether or not I have a CEL on.

Any thoughts on what could be going on here?

2ToyGuy

Have you tried replacing the fuel filter?

Have you checked the vacuum lines? Cleaned/replaced the MAF?

Just the few ideas I got...
Pat☺

Haaklord

I did replace the fuel filter. I have lightly checked the vacuum lines while I was doing the EGR delete. I deleted the lines that were a part of the EGR/Reed value system and didn't see any cracked other lines. How else would I check them?

I haven't cleaned or replaced the MAF. In fact I never have...oops. I'll give that a try, it sounds like it could be the issue (I hope).

2ToyGuy

Some use a smoke generator, and look for smoke going into a vacuum line, whether end or length.

Others have been known to spray small amounts of carb cleaner, brake cleaner, or ether, at the ends. They listen for acceleration up from idle.

Any questionable line, replace it. The stuff isn't very expensive at all, after all. Heck, sometimes it's easiest to just buy a few feet of the stuff, and replace them all whether they need it or not. Can't hurt, after all.
You should have a diagram on the underside, left, upper corner of the hood, when it's open. If not, they are generally available on-line. Make certain that any of those EGR vacuum lines that are no longer necessary, the end on the throttle body is thoroughly capped off. Make sure the cap(s) you used is(are) good and snug, and "vacuum tight", so to speak. I hate to say it, but I've used screws in the vacuum hose in place of a cap. It works very well, it just looks very unprofessional, having the end of a vacuum line with a screw in it dangling around. I do make sure they are spot tied/zip tied down to prevent any damage to any part of the engine they might contact.

While they are slightly expensive, being "pre-formed", it's a good idea to replace the two rubber lines for the PCV system. One from the top of the PCV valve to the throttle body. The other from the throttle body to the valve cover.
Also, when you replace the valve cover gasket pull out the PCV valve, and test it. A how-to is in the FSM. Make sure you use an OEM PCV valve, not a generic store cheapie. It matters.
Why when you replace the valve cover? Because the grommet that holds the PCV into the valve cover gets brittle pretty quickly, and can break apart into little pieces, and fall down into the valve cover. If you do it with the valve cover off, those little pieces can be removed easily. Worst case, I use a pair of needle-nose pliers to pull out the the grommet, even if it's broken into chunks. Again, they are readily available.

I hope that's your trouble, and you can get your truck running properly!
Also, make sure the large air tube going to the throttle body is in good shape. Especially the flexible corner pieces, which have been known to get cracks in them. Easy enough to check: Just look into them, and flex them. Any cracks will show up as a light-leak.

I wish you all the best of luck!
Pat☺

scope103

Sure sounds like a knock sensor issue. When the ECU "loses touch" with the Knock Sensor (sometimes a bad sensor, more often a wiring issue), it dramatically retards timing (to save the engine) and throws code 52.
Using premium will cost money, but it has nothing to do with the knock sensor system. (The knock code has nothing to do with, say, excessive knocking.) I don't know what a "starter sensor CEL" is.
Well, that seems pretty diagnostic to me. I really doubt your problems have anything to do with vacuum lines or PCV valve or valve cover or VAF (you don't have a MAF), though at some point many of those items are maintenance.

I would start with replacing the knock sensor "pigtail." The knock sensor itself is incredibly tough, but once you go far enough to replace the pigtail I wouldn't argue with a new (OEM) sensor as well.

Haaklord

Isn't the pigtail a pretty simple replacement?

Haaklord

A lot of the symptoms I'm having sure sound like a dirty MAF/VAF so I'm going to give that clean a try, might as well do it either way.

scope103

Sure. If you think removing the plenum, the fuel rails, and the lower intake manifold is a simple task.

If you plan to clean the VAF don't forget:

Haaklord

Oof…yeah not exactly simple.

also thanks for the heads up, that was my exact plan…so I unplug it, and clean it from the bottom of the metal assembly then?

Haaklord

UPDATE: So on my way to Autozone to get some MAF cleaner the truck started to stutter and stall badly. I pulled over into a neighborhood and it stalled completely. Checked the CEL code and it still said 52. Fired it back up and got to Autozone, checked the MAF and saw that I had oiled the **** out of my air filter when I cleaned it recently, standing oil was in the bottom of the intake box. I replaced the filter. I also took out the EFI fuse for a few minutes to reset the ECU (a tip I had seen on another forum). Well now the truck runs perfect, no codes or anything.

I figure at some point, after new exhaust, fuel filter, or over oiling the intake, my air/fuel mixture might have gotten screwed up and the reset of the ECU seemed to start it all over. No sure but o well it runs like a dream now.