Please help me diagnose EFI problem - my long weekend is in jeopardy

[jroc]

I started a thread earlier this week like this....

I've been working on an 88' toy p/u over the winter, I finally got my saftey certificate and now it runs like crap!

When it's cold it feels as if all cylinders are not firing then hits about 3000 rpm and takes off fine. The weird thing is that once it is at tempertature (run for 15 min.) it runs great!

It has to be something simple!

Since then I've noticed that my temp. guage is acting really funny. When I first start up it runs fine, but I notice that temp guage is up at operating temp. I drive for a few minutes and it chugs, I immediately notice that the temp guage has fallen. Then it runs like crap untill operating temp is reached.

Does the temp guage signal to the ECU to cause this type of probem. My check engine light is not on and I know that it does work.

Please help, my long weekend is in jeopardy

[Shadow58]

Check your fuel injectors, replace thermostat (cheap and easy) and possibly your fuel pump.

[KToy]

clogged fuel filter. and tstat.

[jroc]

the tstat is ....thermostat?

You'll have to excuse my ignorance. This is my first Toyota (or 1 1/2). I used to have a Samari with 35's. I eventually put a drivetrain in from an 84 toy. It worked OK considering it was my 1st build and I did a lousy job on it. It's amazing how far you can get knowing next to nothing. I beat on it for a few more years untill it wasn't worth saving.

I should note that this truck sat for about a year before I picked it up. the engine had a noticable hesitation. I replaced plugs/wires/fuel filter about a month ago - checked distributer, mass air flow sensor, TPS, vacuum lines- still ran crappy. The timing was close, but I tried advancing it anyway and suddenly it ran great - for a few weeks.

Do you think that my fuel filter could be clogged already? I had only driven about 250 km's?

Also, I see people use the term running on 'safe mode' - so the ecu signals a 'generic' condition in the event of a problem? If I unplug an oxy sensor or something will it trigger 'safemode' so that I can rule out sensor problems and look at fuel delivery?

[MARSROVER]

do you have any fault codes? what is your fuel pressure. have you properly set the timing by installing the jumper first at the diagnostic panel?did you then run the procedure for setting the throttle position sensor so that it reads idle? I also have an 88 and have had some problems in the past. i ended up replacing the ignition module and the distributor.

[jroc]

Check engine light does not come on - I unplugged TPS - still didn't come on.
Unpluged MAF sensor - engine died and check engine light came on

Swiched MAF sensor with another that I had - no change

I had changed the fuel filter only three weeks ago - I think that the fuel pressure should be fine because it runs lousy at low rpms and well at high rpm. A fuel pressure problem would be opposite - good at low, crappy at high.

Marsrover, where your problems similar?

[MARSROVER]

you may still have active engine codes even though the light is not on all the time. again, start by checking your flash codes, clearing them, running the truck and then checking to see which codes came back. if you think you have a faulty ecu then get another from the junkyard and try it out. that's what i did. my problem was that when the temp would get over 70 deg's my engine would occassionaly stall when idling, or chug and sputter at all rpm's. the new ignition module, coil and distributor cured this.

[jroc]

thanks